B4X JavaObject and NativeObject

B4X Booklets
B4X JavaObject NativeObject
Copyright: © 2020 Anywhere Software Edition 1.9
Last update: 2020.09.21

Table of contents 2 B4X JavaObject NativeObject
1 B4X platforms..............................................................................................................................5
2 General.........................................................................................................................................6
3 B4A JavaObject ..........................................................................................................................7
3.1 B4A JavaObject methods.....................................................................................................8
3.1.1 CreateEvent......................................................................................................................8
3.1.2 CreateEventFromUI.........................................................................................................9
3.1.3 GetField............................................................................................................................9
3.1.4 GetFielJO .........................................................................................................................9
3.1.5 InitializeArray ..................................................................................................................9
3.1.6 InitializeContext...............................................................................................................9
3.1.7 InitializeNewInstance.....................................................................................................10
3.1.8 InitializeStatic ................................................................................................................10
3.1.9 IsInitialized.....................................................................................................................10
3.1.10 RunMethod.................................................................................................................11
3.1.11 RunMethodJO ............................................................................................................12
3.1.12 SetField ......................................................................................................................12
3.2 How to use it ......................................................................................................................13
3.3 B4A examples....................................................................................................................16
3.3.1 Get B4A Context............................................................................................................16
3.3.1.1 GetB4A ..................................................................................................................16
3.3.1.2 getContext ..............................................................................................................16
3.3.2 ViewUtils .......................................................................................................................17
3.3.2.1 getParent.................................................................................................................17
3.3.2.2 getRootView ..........................................................................................................17
3.3.2.3 setRotation .............................................................................................................17
3.3.2.4 setRotationX...........................................................................................................17
3.3.2.5 setRotationY...........................................................................................................18
3.3.2.6 setPivotX................................................................................................................18
3.3.2.7 getPivotX ...............................................................................................................18
3.3.2.8 setPivotY................................................................................................................18
3.3.2.9 getPivotY ...............................................................................................................18
3.3.3 EditText Utils.................................................................................................................19
3.3.3.1 setCursorVisible.....................................................................................................19
3.3.3.2 setTextIsSelectable.................................................................................................19
3.3.3.3 setSelection ............................................................................................................19
3.3.3.4 getSelectionStart ....................................................................................................19
3.3.3.5 getSelectionEnd......................................................................................................19
3.3.3.6 getLineHeight.........................................................................................................20
3.3.3.7 getLineCount..........................................................................................................20
3.3.3.8 getHighLightColor / setHighLightColor................................................................20
3.3.3.9 GetXYCursor .........................................................................................................21
3.3.4 Label Utils......................................................................................................................22
3.3.4.1 setEllipsize .............................................................................................................22
3.3.4.2 resetEllipsize ..........................................................................................................22
3.3.4.3 setSingleLIne..........................................................................................................22
3.3.4.4 setLines ..................................................................................................................23
3.3.4.5 setMarqueeRepeat..................................................................................................23
3.3.4.6 Stop or run the horizontal scrolling........................................................................23
3.3.4.7 setShadowLayer.....................................................................................................23
4 B4J JavaObject...........................................................................................................................24
4.1 B4J JavaObjec Methods.....................................................................................................24
4.1.1 CreateEvent....................................................................................................................24
4.1.2 CreateEventFromUI.......................................................................................................26

4.1.3 GetField..........................................................................................................................26
4.1.4 GetFielJO .......................................................................................................................26
4.1.5 InitializeArray ................................................................................................................26
4.1.6 InitializeContext.............................................................................................................26
4.1.7 InitializeNewInstance.....................................................................................................27
4.1.8 InitializeStatic ................................................................................................................27
4.1.9 IsInitialized.....................................................................................................................27
4.1.10 RunMethod.................................................................................................................28
4.1.11 RunMethodJO ............................................................................................................29
4.1.12 SetField ......................................................................................................................29
4.2 How to use it ......................................................................................................................30
4.3 B4J examples .....................................................................................................................31
4.3.1 setMouseTransparent .....................................................................................................31
4.3.2 setTextAlignment...........................................................................................................31
4.3.3 Graphics jCanvasExt......................................................................................................32
4.3.4 GoogleMaps...................................................................................................................33
5 B4i NativeObject........................................................................................................................34
5.1 B4i NativeObject methods.................................................................................................34
5.1.1 ArrayFromEdgeInsets ....................................................................................................34
5.1.2 ArrayFromPoint .............................................................................................................34
5.1.3 ArrayFromRange............................................................................................................34
5.1.4 ArrayFromRect ..............................................................................................................34
5.1.5 ArrayFromSize...............................................................................................................35
5.1.6 ArrayToNSData .............................................................................................................35
5.1.7 AsBoolean......................................................................................................................35
5.1.8 AsNumber ......................................................................................................................35
5.1.9 AsString .........................................................................................................................35
5.1.10 ColorToUIColor.........................................................................................................35
5.1.11 CreateBlock................................................................................................................36
5.1.12 GetField......................................................................................................................36
5.1.13 Initialize( ....................................................................................................................36
5.1.14 IsInitialized.................................................................................................................36
5.1.15 MakeEdgeInsets.........................................................................................................36
5.1.16 MakePoint ..................................................................................................................37
5.1.17 MakeRange ................................................................................................................37
5.1.18 MakeRect ...................................................................................................................37
5.1.19 MakeSize....................................................................................................................37
5.1.20 NSDataToArray .........................................................................................................37
5.1.21 RunMethod.................................................................................................................38
5.1.22 RunMethodWithBlocks .............................................................................................38
5.1.23 SetField ......................................................................................................................38
5.1.24 Tag..............................................................................................................................38
5.1.25 UIColorToColor.........................................................................................................38
5.2 How to use it ......................................................................................................................39
5.3 B4i examples......................................................................................................................40
5.3.1 SetButtonTextColor .......................................................................................................40
5.3.2 Hide the StatusBar..........................................................................................................40
5.3.3 Setting the status bar to use a light theme......................................................................40
5.3.4 Check StatusBar state.....................................................................................................40
5.3.5 Get Border properties.....................................................................................................41
5.3.6 Getting current device language.....................................................................................41
5.3.7 Set the NavigationBar text color....................................................................................41

Main contributors: Klaus Christl (klaus), Erel Uziel (Erel)
To search for a given word or sentence use the Search function in the Edit menu.
All the source code and files needed (layouts, images etc.) of the example projects in this booklet
are included in the SourceCode folder.
Updated for:
B4A version 10.2
B4i version 6.80
B4J version 8.50
B4X Booklets:
B4X Getting Started
B4X Basic Language
B4X IDE Integrated Development Environment
B4X Visual Designer
B4X Help tools
B4XPages Cross-platform projects
B4X CustomViews
B4X Graphics
B4X XUI B4X User Interface
B4X SQLite Database
B4X JavaObject NativeObject
B4R Example Projects
You can consult these booklets online in this link [B4X] Documentation Booklets.
Be aware that external links don’t work in the online display.

1 B4X platforms 5 B4X JavaObject NativeObject XUI
1 B4X platforms
B4X is a suite of BASIC programming languages for different platforms.
B4X suite supports more platforms than any other tool
ANDROID | IOS | WINDOWS | MAC | LINUX | ARDUINO | RASPBERRY PI | ESP8266 | AND
MORE...
• B4A Android
B4A is a 100% free development tool for Android applications, it includes all the features
needed to quickly develop any type of Android app.
• B4i iOS
B4i is a development tool for native iOS applications.
B4i follows the same concepts as B4A, allowing you to reuse most of the code and build
apps for both Android and iOS.
• B4J Java / Windows / Mac / Linux / Raspberry PI
B4J is a 100% free development tool for desktop, server and IoT solutions.
With B4J you can easily create desktop applications (UI), console programs (non-UI) and
server solutions.
The compiled apps can run on Windows, Mac, Linux and ARM boards (such as Raspberry
Pi).
• B4R Arduino / ESP8266
B4R is a 100% free development tool for native Arduino and ESP8266 programs.
B4R follows the same concepts of the other B4X tools, providing a simple and powerful
development tool.
B4R, B4A, B4J and B4i together make the best development solution for the Internet of
Things (IoT).
• B4XPages
B4XPages is an internal library for B4A, B4i and B4J allowing to develop easily cross-
platform programs.
B4XPages is explained in detail in the B4XPages Cross-platform projects booklet.
Even, if you want to develop only in one platform it is interesting to use the B4XPages
library it makes the program flow simpler especially for B4A.

2 General 6 B4X JavaObject NativeObject
2 General
JavaObject can be used to access Android or Java objects or properties not directly exposed to B4A
or B4J.
The library is the same for B4A and B4J.
NativeObject is similar to JavaObject but for B4i.
To use JavaObject or NativeObject you should know or learn how the operating systems are
constructed and how they work.
The purpose of this booklet is to give an ‘entry point’ with examples, to better understand how to
use it.
It is not an encyclopedia of routines.

3 B4A JavaObject 7 B4X JavaObject NativeObject
3 B4A JavaObject
The purpose of JavaObject library is similar to the purpose of Reflection library. Both libraries
allow you to directly call Java APIs based on Java reflection features.
JavaObject design is different than Reflection library and, in most cases, simpler to use. However,
JavaObject doesn't replace Reflection library as it doesn't support all of its features. In many cases
you can use both libraries together (both are lightweight libraries).
JavaObject approach is more "object oriented". You declare a JavaObject object which then
"wraps" any other object and provide three methods: SetField, GetField and RunMethod.
JavaObject variable is similar to an Object variable with the addition of the reflection methods.
Notes
• JavaObject can only access public methods and fields (unlike Reflection library).
• JavaObject doesn't include the helper methods to access the context and other fields as in
Reflection library. You can use both libraries together when these fields are needed.
• There is almost no overhead for a JavaObject instance. It is better to create multiple
JavaObjects instead of reusing a single instance.

3.1 B4A JavaObject methods 8 B4X JavaObject NativeObject
3.1 B4A JavaObject methods
3.1.1 CreateEvent
CreateEvent (Interface As String, EventName As String, DefaultReturnValue As Object)
Creates an instance of the interface and binds it to the object.
Interface - The full interface name.
EventName - The prefix of the event sub.
DefaultReturnValue - This value will be returned if no value was returned from the event sub. This
can happen if the Activity is paused for example.
B4A example:
Sub Activity_Create(FirstTime As Boolean)
Dim btn As Button
btn.Initialize("")
Activity.AddView(btn, 0, 0, 200dip, 200dip)
Dim jo As JavaObject = btn
Dim e As Object = jo.CreateEvent("android.view.View.OnTouchListener", "btnTouch",
False)
jo.RunMethod("setOnTouchListener", Array As Object(e))
End Sub
And the event routine:
Sub btnTouch_Event (MethodName As String, Args() As Object) As Object
Dim MotionEvent As JavaObject = Args(1) 'args(0) is View
Dim x As Float = MotionEvent.RunMethod("getX", Null)
Dim y As Float = MotionEvent.RunMethod("getY", Null)
Log(x & ", " & y)
Dim Action As Int = MotionEvent.RunMethod("getAction", Null)
Log("Action = " & Action)
Return True
End Sub
And the Android documentation: View.OnTouchListener, MotionEvent.
If you look at the documentation, you may notice that there is a lot to learn.

3.1.2 CreateEventFromUI
CreateEventFromUI (Interface As String, EventName As String, ReturnValue As Object)
Similar to CreateEvent. The event will be sent to the message queue and then be processed (similar
to CallSubDelayed).
3.1.3 GetField
GetField (Field As String)
Gets the value of the given field.
3.1.4 GetFielJO
GetFieldJO (Field As String)
Similar to GetField. Returns a JavaObject instead of Object.
Returns a JavaObject.
3.1.5 InitializeArray
InitializeArray (ClassName As String, Values As Object())
Creates an array with the given class and values.
3.1.6 InitializeContext
B4A only method.
Initializes the object with the current context (current Activity or Service).

3.1.7 InitializeNewInstance
InitializeNewInstance (ClassName As String, Params As Object())
Creates a new instance of the given class.
ClassName - The full class name.
Params - An array of objects to pass to the constructor (or Null).
3.1.8 InitializeStatic
InitializeStatic (ClassName As String)
Initializes the object. The object will wrap the given class (for static access).
3.1.9 IsInitialized
Returns a Boolean.

3.1.10 RunMethod
RunMethod (MethodName As String, Params As Object())
Runs the given method and returns the method return value.
MethodName - The case-sensitive method name.
Params - Method parameters (or Null).
Returns an Object.
B4A example:
Get and sets the Labels padding.
Private joLabel1 As JavaObject = Label1 'wrap the Label object
Log("Label1 Left padding = " & joLabel1.RunMethod("getPaddingLeft", Null))
Log("Label1 Top padding = " & joLabel1.RunMethod("getPaddingTop", Null))
Log("Label1 Right padding = " & joLabel1.RunMethod("getPaddingRight", Null))
Log("Label1 Bottom padding = " & joLabel1.RunMethod("getPaddingBottom", Null))
joLabel1.RunMethod("setPadding", Array As Object(10dip, 10dip, 10dip, 10dip))
Android documentation: View.
Don’t be afraid! It’s a huge chapter! To see the padding methods, you need to scroll down very
deep.

3.1.11 RunMethodJO
RunMethodJO (MethodName As String, Params As Object())
Similar to RunMethod. Returns a JavaObject instead of Object.
3.1.12 SetField
SetField (FieldName As String, Value As Object)
Sets the value of the given field.
Returns Void.

3.2 B4A JavaObject How to use it 13 B4X JavaObject NativeObject
3.2 How to use it
Let’s add the Ellipsize property to a view. This property is implemented in B4A, but not the
MARQUEE mode which allows scrolling the text in the TextView.
First, we need to look at the Android Documentation.
Enter ‘ellipsize’ in the Search field in the top right corner.
The first search result:
Click on:
Below this title you find all public methods of the TextView.
It is a huge ‘chapter’!

Scroll down until you find setEllipsize.
In text we see that we need to setSingleLine
We see that we must add a parameter. Click on .
Here find the different possible parameters.

Example code for ellipsize MARQUEE:
Private lblTest As Label
Private jo = TextView As JavaObject
jo.RunMethod("setSingleLine", Array As Object(True))
jo.RunMethod("setEllipsize", Array As Object("MARQUEE"))
jo.RunMethod("setSelected", Array As Object(True)) ' needed for MARQUEE
And a generalized routine:
'Sets the Ellipsizing of a TextView (Label, EditText)
'original text 'This is a test text'
'Mode can be
'"START" ... This is a te
'"MIDDLE" This is ... text
'"END" This is a tes...
'"MARQUEE" This is a test t scrolling text
Sub setEllipsize(TextView As Label, Mode As String)
Dim jo = TextView As JavaObject
jo.RunMethod("setEllipsize", Array As Object(Mode))
End Sub
To disable the Ellipsize property use:
jo.RunMethod("setEllipsize", Null)
You can also limit the number of scrollings:
jo.RunMethod("setMarqueeRepeatLimit", Array As Object(Limit))
You need to explore and test a lot to become more experienced.

3.3 B4A examples 16 B4X JavaObject NativeObject
3.3 B4A examples
Some of these examples exist in the forum in View Utils.
3.3.1 Get B4A Context
The two routines are used in conjunction.
3.3.1.1 GetB4A
Sub GetBA As JavaObject
Dim jo As JavaObject
Dim cls As String = Me
cls = cls.SubString("class ".Length)
jo.InitializeStatic(cls)
Return jo.GetFieldJO("processBA")
End Sub
3.3.1.2 getContext
Sub GetContext As JavaObject
Return GetBA.GetField("context")
End Sub

3.3.2 ViewUtils
These methods concern Views and are in the forum.
3.3.2.1 getParent
This property has been added to B4A.
'Returns the parent view of the given view
Sub getParent(v As View) As View
Dim jo = v As JavaObject
Return jo.RunMethod("getParent", Null)
End Sub
3.3.2.2 getRootView
'Returns the root view of the given view, it's mainly the Activity
Sub getRootView(v As View) As View
Return jo.RunMethod("getRootView", Null)
End Sub
3.3.2.3 setRotation
'Sets the rotation angle of the given view
'v = view
'Angle = rotation angle in degrees
Sub setRotation(v As View, Angle As Float)
jo.RunMethod("setRotation", Array As Object(Angle))
End Sub
3.3.2.4 setRotationX
'Sets the rotation angle around the X axis of the given view
'v = view
Sub setRotationX(v As View, Angle As Float)
jo.RunMethod("setRotationX", Array As Object(Angle))
End Sub

3.3.2.5 setRotationY
'Sets the rotation angle around the Y axis of the given view
'v = view
Sub setRotationY(v As View, Angle As Float)
jo.RunMethod("setRotationY", Array As Object(Angle))
End Sub
3.3.2.6 setPivotX
'Sets the X pivot point of the given view
'v = view
'X = X coordinate of the pivot in pixels
'reference upper left corner, default pivot middle of the view
Sub setPivotX(v As View, X As Float)
jo.RunMethod("setPivotX", Array As Object(X))
End Sub
3.3.2.7 getPivotX
'Gets the X pivot point of the given view
Sub getPivotX(v As View) As Float
Return jo.RunMethod("getPivotX", Null)
End Sub
3.3.2.8 setPivotY
'Sets the Y pivot point of the given view
'v = view
'Y = Y coordinate of the pivot in pixels
'reference upper left corner, default pivot middle of the view
Sub setPivotY(v As View, Y As Float)
jo.RunMethod("setPivotY", Array As Object(Y))
End Sub
3.3.2.9 getPivotY
'Gets the Y pivot point of the given view
Sub getPivotY(v As View) As Float
Return jo.RunMethod("getPivotY", Null)
End Sub

3.3.3 EditText Utils
These methods concern EditText views and are in the forum EditText Utils.
All the methods below can be used without a sub like:
Dim jo = edt As JavaObject
jo.RunMethod("setTextIsSelectable", Array As Object(True))
jo.RunMethod("setCursorVisible", Array As Object(True))
jo.RunMethod("setSelection", Array As Object(5, 10))
3.3.3.1 setCursorVisible
'Sets the cursor visible or hides it
Sub setCursorVisible(edt As EditText, Visible As Boolean)
jo.RunMethod("setCursorVisible", Array As Object(Visible))
End Sub
3.3.3.2 setTextIsSelectable
'Sets the text selectable or not selectable
Sub setTextIsSelectable(edt As EditText, Selectable As Boolean)
jo.RunMethod("setTextIsSelectable", Array As Object(Selectable))
End Sub
3.3.3.3 setSelection
'Selects the text between the two indexes.
Sub setSelection(edt As EditText, StartIndex As Int, EndIndex As Int)
jo.RunMethod("setSelection", Array As Object(StartIndex, EndIndex))
End Sub
3.3.3.4 getSelectionStart
'Gets the selection start index
Sub getSelectionStart(edt As EditText) As Int
Return jo.RunMethod("getSelectionStart", Null)
End Sub
3.3.3.5 getSelectionEnd
'Gets the selection end index
Sub getSelectionEnd(edt As EditText) As Int
Return jo.RunMethod("getSelectionEnd", Null)
End Sub

3.3.3.6 getLineHeight
'Gets the line height
Sub getLineHeight(edt As EditText) As Int
Return jo.RunMethod("getLineHeight", Null)
End Sub
3.3.3.7 getLineCount
'Gets the line count
Sub getLineCount(edt As EditText) As Int
Return jo.RunMethod("getLineCount", Null)
End Sub
3.3.3.8 getHighLightColor / setHighLightColor
'Sets the highlight color
Sub setHighLightColor(edt As EditText, Color As Int)
Private joEdt = edt As JavaObject
joEdt.RunMethod("setHighlightColor", Array(Color))
End Sub
'Gets the highlight color
Sub getHighLightColor(edt As EditText) As Int
Private joEdt = edt As JavaObject
Return joEdt.RunMethod("getHighlightColor", Null)
End Sub

3.3.3.9 GetXYCursor
'gets the x and y coordinates, in pixels, of the cursor in an EditText view
'the Y coordinate is at the base line, on top or on bottom of the line
'retuens an array of Ints
'X = xy(0) and Y = xy(1)
'the reference is the top left corner of the EditText
'YPosition can be "BaseLine", "TopOfLine", "BottomOfLine"
Private Sub GetXYCursor(edt As EditText, YPosition As String) As Int()
Private joEditText, joLayout As JavaObject
Private PaddingLeft, PaddingTop, ScrollY, Pos, Line, LineBaseline, LineTop,
LineBottom As Int
Private xy(2) As Int
joEditText = edt
PaddingLeft = joEditText.RunMethod("getPaddingLeft", Null)
PaddingTop = joEditText.RunMethod("getPaddingTop", Null)
ScrollY = joEditText.RunMethod("getScrollY", Null)
' pos = edt.SelectionStart
Pos = joEditText.RunMethod("getSelectionStart", Null)
joLayout = joEditText.RunMethod("getLayout", Null)
Line = joLayout.RunMethod("getLineForOffset", Array As Object(Pos)) 'line numbsr
LineBaseline = joLayout.RunMethod("getLineBaseline", Array As Object(Line))
LineTop = joLayout.RunMethod("getLineTop", Array As Object(Line))
LineBottom = joLayout.RunMethod("getLineBottom", Array As Object(Line))
xy(0) = joLayout.RunMethod("getPrimaryHorizontal", Array As Object(Pos)) +
PaddingLeft ' X coordinate
Select Case YPosition
Case "BaseLine"
xy(1) = LineBaseline + PaddingTop - ScrollY 'base line Y coordinate
Case "TopOfLine"
xy(1) = LineTop + PaddingTop - ScrollY 'top of the line Y coordinate
Case "BottomOfLine"
xy(1) = LineBottom + PaddingTop - ScrollY 'text bottom line
End Select
Return xy
End Sub

3.3.4 Label Utils
Examples from the forum LabelUtils.
The methods below can also be used without a sub, like:
Private jobj As JavaObject
Private lblTest As Label
'
'
jobj = lblTest
jobj.RunMethod("setLines", Array As Object(2))
jobj.RunMethod("setEllipsize", Array As Object("END"))
3.3.4.1 setEllipsize
This property has been addid in B4A.
'Sets the Ellipsizing of a TextView (Label, EditText)
' Mode can be
' original text 'This is a test text'
'"START" ... This is a te
'"MIDDLE" This is ... text
'"END" This is a tes...
'"MARQUEE This is a test t
Sub setEllipsize(TextView As Label, Mode As String)
jo.RunMethod("setEllipsize", Array As Object(Mode))
End Sub
3.3.4.2 resetEllipsize
'Removes the Ellipsizing of a TextView (Label, EditText)
Sub resetEllipsize(TextView As Label)
jo.RunMethod("setSingleLine", Array As Object(False))
End Sub
3.3.4.3 setSingleLIne
'Sets the TextView to single line
Sub setSingleLine(TextView As Label, SingleLine As Boolean)
jo.RunMethod("setSingleLine", Array As Object(SingleLine))
End Sub

3.3.4.4 setLines
'Limits the line number to the given value
Sub setLines(TextView As Label, LineNumber As Int)
jo.RunMethod("setLines", Array As Object(LineNumber))
End Sub
3.3.4.5 setMarqueeRepeat
'Sets the Marquee repeat limit
' default is three times
' set -1 for repeat indefinitely
Sub setMarqueeRepeatLimit(TextView As Label, Limit As Int)
jo.RunMethod("setMarqueeRepeatLimit", Array As Object(Limit))
End Sub
3.3.4.6 Stop or run the horizontal scrolling
jobj.RunMethod("setHorizontallyScrolling", Array As Object(False))
'or
jobj.RunMethod("setHorizontallyScrolling", Array As Object(True))
3.3.4.7 setShadowLayer
'Adds a shadow to a text
'lbl = the view to add a shadow, can be and EditText or a Label
'Radius = parameter for blur, radius = 1 no blur, the bigger radius the more blur
'dx = horizontal offset of the shadow in pixels
'dy = vertical offset of the shadow in pixels
'Color = shadow color
Sub setShadowLayer(lbl As View, Radius As Float, dx As Float, dy As Float, Color As Int)
Dim jo = lbl As JavaObject
jo.RunMethod("setShadowLayer", Array(Radius, dx, dy , Color))
End Sub

4 B4J JavaObject 24 B4X JavaObject NativeObject
4 B4J JavaObject
4.1 B4J JavaObjec Methods
4.1.1 CreateEvent
CreateEvent (Interface As String, EventName As String, DefaultReturnValue As Object)
Creates an instance of the interface and binds it to the object.
Interface - The full interface name.
EventName - The prefix of the event sub.
DefaultReturnValue - This value will be returned if no value was returned from the event sub. This
can happen if the Activity is paused for example.
B4A example:
Sub Activity_Create(FirstTime As Boolean)
Dim btn As Button
btn.Initialize("")
Activity.AddView(btn, 0, 0, 200dip, 200dip)
Dim jo As JavaObject = btn
Dim e As Object = jo.CreateEvent("android.view.View.OnTouchListener", "btnTouch",
False)
jo.RunMethod("setOnTouchListener", Array As Object(e))
End Sub
And the event routine:
Sub btnTouch_Event (MethodName As String, Args() As Object) As Object
Dim MotionEvent As JavaObject = Args(1) 'args(0) is View
Dim x As Float = MotionEvent.RunMethod("getX", Null)
Dim y As Float = MotionEvent.RunMethod("getY", Null)
Log(x & ", " & y)
Dim Action As Int = MotionEvent.RunMethod("getAction", Null)
Log("Action = " & Action)
Return True
End Sub
And the Java documentation: View.OnTouchListener, MotionEvent.

If you look at the documentation, you may notice that there is a lot to learn.

4.1.2 CreateEventFromUI
CreateEventFromUI (Interface As String, EventName As String, ReturnValue As Object)
Similar to CreateEvent. The event will be sent to the message queue and then be processed (similar
to CallSubDelayed).
4.1.3 GetField
GetField (Field As String)
Gets the value of the given field.
4.1.4 GetFielJO
GetFieldJO (Field As String)
Similar to GetField. Returns a JavaObject instead of Object.
4.1.5 InitializeArray
InitializeArray (ClassName As String, Values As Object())
Creates an array with the given class and values.
4.1.6 InitializeContext
B4A only method.
Initializes the object with the current context (current Activity or Service).

4.1.7 InitializeNewInstance
InitializeNewInstance (ClassName As String, Params As Object())
Creates a new instance of the given class.
Params - An array of objects to pass to the constructor (or Null).
4.1.8 InitializeStatic
InitializeStatic (ClassName As String)
Initializes the object. The object will wrap the given class (for static access).
4.1.9 IsInitialized
Returns a Boolean.

4.1.10 RunMethod
RunMethod (MethodName As String, Params As Object())
Runs the given method and returns the method return value.
MethodName - The case-sensitive method name.
Params - Method parameters (or Null).
Returns an Object.
B4A example:
Get and sets the Labels padding.
Private joLabel1 As JavaObject = Label1 'wrap the Label object
Log("Label1 Left padding = " & joLabel1.RunMethod("getPaddingLeft", Null))
Log("Label1 Top padding = " & joLabel1.RunMethod("getPaddingTop", Null))
Log("Label1 Right padding = " & joLabel1.RunMethod("getPaddingRight", Null))
Log("Label1 Bottom padding = " & joLabel1.RunMethod("getPaddingBottom", Null))
joLabel1.RunMethod("setPadding", Array As Object(10dip, 10dip, 10dip, 10dip))
Android documentation: View.
Don’t be afraid! It’s a huge chapter! To see the padding methods, you need to scroll down very
deep.

4.1.11 RunMethodJO
RunMethodJO (MethodName As String, Params As Object())
Similar to RunMethod. Returns a JavaObject instead of Object.
4.1.12 SetField
SetField (FieldName As String, Value As Object)
Sets the value of the given field.
Returns Void.

4.2 B4J JavaObject How to use it 30 B4X JavaObject NativeObject
4.2 How to use it
You need to look at the Java documentation.
It looks like this:
On the top left you find all the Packages, and just below, all classes:

4.3 B4J examples 31 B4X JavaObject NativeObject
4.3 B4J examples
https://www.b4x.com/android/forum/threads/google-map-with-custom-style.84894/#content
https://www.b4x.com/android/forum/threads/jgauges.70538/#content
https://www.b4x.com/android/forum/threads/excel-charts-and-templates-with-jpoi-
library.57689/#content
https://www.b4x.com/android/forum/threads/class-textflow-similar-to-b4a-b4i-
richstring.61237/#content
https://www.b4x.com/android/forum/threads/jcanvasext-extends-canvas-methods.86407/#content
https://www.b4x.com/android/forum/threads/using-javaobject-and-javafx-linechart.34777/#content
4.3.1 setMouseTransparent
Enables mouse events being transmitted to underlying nodes.
In B4J, when a node covers other nodes, like a Pane, the mouse events are not submitted to
underlying nodes.
This is the same as in B4i, it is inverse in B4A.
In B4i, you can use the UserInteractionEnabled property.
In B4J you can use the code below to enable mouse events beeing submitted to underlying nodes.
Private jo = MyNode As JavaObject
jo.RunMethod("setMouseTransparent", Array As Object(True))
The value is False by default.
4.3.2 setTextAlignment
The standard Alignment property does not work properly with multiline labels. It aligns the content
based on the first line.
You can use this code instead:
Dim jo As JavaObject = Label1
jo.RunMethod("setTextAlignment", Array("CENTER"))

4.3.3 Graphics jCanvasExt
The jCanvasExt class can be found in the forum in this thread:
jCanvasExt Extends Canvas methods.
The Java documentation:
https://docs.oracle.com/javase/8/javafx/api/javafx/scene/canvas/GraphicsContext.html

4.3.4 GoogleMaps
The GoogleMaps library is based on this open source project: http://rterp.github.io/GMapsFX/.
Under the hood it uses JavaFX WebView with GoogleMaps JavaScript API V3.
The Library Documentation.
https://www.b4x.com/android/forum/threads/googlemapsdemo.91906/#content
https://www.b4x.com/android/forum/threads/class-googlemapsextra.56871/#content

5 B4i NativeObject 34 B4X JavaObject NativeObject
5 B4i NativeObject
5.1 B4i NativeObject methods
5.1.1 ArrayFromEdgeInsets
ArrayFromEdgeInsets (EdgeInsets As NSData*)
Converts a UIEdgeInsets to an array with the Left, Top, Right and Bottom values.
Returns: Float()
5.1.2 ArrayFromPoint
ArrayFromPoint(Point As NSData*)
Converts a CGPoint to an array with the X and Y values.
Returns: Float()
5.1.3 ArrayFromRange
ArrayFromRange (Range As NSData*)
Converts a NSRange to an array with the location and length values.
Returns: Int()
5.1.4 ArrayFromRect
ArrayFromRect (Rect As NSData*)
Converts a CGRect to an array with the X, Y, Width and Height values.
Returns: Float()

5.1.5 ArrayFromSize
ArrayFromSize (Size As NSData*)
Converts a CGSize to an array with the Width and Height values.
Returns: Float()
5.1.6 ArrayToNSData
ArrayToNSData (Arr As Byte())
Converts an array of bytes to NSData object.
Returns : NSObject
5.1.7 AsBoolean
Returns the wrapped object as a Boolean value.
Returns : BOOL
5.1.8 AsNumber
Returns the wrapped object as a numeric value.
Returns: NSObject
5.1.9 AsString
Returns the wrapped object as a String value.
Returns: NSString
5.1.10 ColorToUIColor
ColorToUIColor (Color As Int)
Converts B4i color value to UIColor.
Returns: UIColor

5.1.11 CreateBlock
CreateBlock (bi As B4I*, SubName As NSString*, NumberOfParameters As Int, Delayed As
BOOL)
Creates a block that raises the given sub.
SubName - The event prefix. The sub signature should be: SubName_Event (Args() As Object) As
Object.
NumberOfParameters - The number of parameters passed to the block. Should be between 0 to 2.
Delayed - Whether the event is raised immediately or it is sent to the message queue.
Returns: Id
5.1.12 GetField
GetField (Field As NSString*)
Gets the value of the given property or field.
Returns: B4INativeObject
5.1.13 Initialize(
Initialize (ClassName As NSString*)
Initializes a new object and sets it to reference the given class.
5.1.14 IsInitialized
Tests whether this object was initialized.
Returns: BOOL
5.1.15 MakeEdgeInsets
MakeEdgeInsets (Left As Float, Top As Float, Right As Float, Bottom As Float
Creates a UIEdgeInsets struct.
Returns: NSData

5.1.16 MakePoint
Creates a CGPoint struct.
Returns: NSData
5.1.17 MakeRange
MakeRange (StartLocation As Int, Length As Int)
Creates a NSRange struct.
Returns: NSData
5.1.18 MakeRect
MakeRect (X As Float, Y As Float, Width As Float, Height As Float)
Creates a CGRect struct.
Returns: NSData
5.1.19 MakeSize
MakeSize (Width As Float, Height As Float)
Creates a CGSize struct.
Returns: NSData
5.1.20 NSDataToArray
NSDataToArray (Data As NSObject*)
Converts an NSData object to an array of bytes.
Returns: Byte()

5.1.21 RunMethod
RunMethod (MethodName As NSString*, Params As NSObject())
Runs the given method. Params can be Null if there are no parameters.
Note that a method name is the full name with the colons.
5.1.22 RunMethodWithBlocks
RunMethodWithBlocks (MethodName As NSString*, Params As NSObject())
Similar to RunMethod. Runs a method that expects a block.
5.1.23 SetField
SetField (FieldName As NSString*, Value As NSObject*)
Sets the value of the given property or field.
Returns: Void
5.1.24 Tag
Gets or sets the Tag object. This is a placeholder for any object you like to tie to this object.
Readable As NSObject
Writeable As NSObject
5.1.25 UIColorToColor
UIColorToColor (UIColor As UIColor*)
Converts a UIColor to B4i color value.
Returns: Int

5.2 B4i NativeObject How to use it 39 B4X JavaObject NativeObject
5.2 How to use it

5.3 B4i examples 40 B4X JavaObject NativeObject
5.3 B4i examples
5.3.1 SetButtonTextColor
'state: 0 = normal, 1 = pressed, 2 = disabled
Sub SetButtonTextColor(btn As Button, clr As Int, state As Int)
Dim no As NativeObject = btn
no.RunMethod("setTitleColor:forState:", Array(no.ColorToUIColor(clr), state))
End Sub
SetButtonTextColor(Button1, Colors.Grean, 1)
5.3.2 Hide the StatusBar
1. Add this attribute:
#PlistExtra: <key>UIViewControllerBasedStatusBarAppearance</key><false/>
2. Add this code:
Dim no As NativeObject = app
no.RunMethod("setStatusBarHidden:animated:", Array(True, False))
5.3.3 Setting the status bar to use a light theme
1. Add this attribute:
#PlistExtra: <key>UIViewControllerBasedStatusBarAppearance</key><false/>
2. Add this code:
Sub SetStatusBarStyleLight
Dim no As NativeObject = app
no.RunMethod("setStatusBarStyle:", Array(1))
End Sub
5.3.4 Check StatusBar state
Sub IsStatusBarHidden As Boolean
Dim no As NativeObject = App
Return no.GetField("statusBarHidden").AsBoolean
End Sub

5.3 B4i examples 41 B4X JavaObject NativeObject
5.3.5 Get Border properties
Gets the Border properties of a Panel :
Dim no As NativeObject = Panel1
Dim BorderWidth As Float = no.GetField("layer").GetField("borderWidth").AsNumber
Dim BorderRadius As Int = no.GetField("layer").GetField("cornerRadius").AsNumber
Dim BorderUIColor As Int= no.UIColorToColor(no.GetField("layer").GetField("borderColor"
))
5.3.6 Getting current device language
Sub GetPreferredLanguage As String
Dim no As NativeObject
Return no.Initialize("NSLocale").RunMethod("preferredLanguages", Null).RunMethod("obj
ectAtIndex:", Array(0)).AsString
End Sub
Or, without the county ID.
Sub GetPreferredLanguage As String
Dim no As NativeObject
Dim s As String = no.Initialize("NSLocale").RunMethod("preferredLanguages", Null).Run
Method("objectAtIndex:", Array(0)).AsString
If s.Length > 2 Then s = s.Substring2(0, 2)
Return s
End Sub
5.3.7 Set the NavigationBar text color
Private Sub Application_Start (Nav As NavigationController)
NavControl = Nav
Page1.Initialize("Page1")
Page1.RootPanel.LoadLayout("1")
NavControl.ShowPage(Page1)
Page1.Title = "Title"
SetTitleColor(Nav, Colors.Red)
End Sub
Sub SetTitleColor(nav As NavigationController, clr As Int)
Dim attributes As NativeObject
attributes = attributes.Initialize("B4IAttributedString").RunMethod("createAttribute
s::", Array(Font.CreateNew(18), attributes.ColorToUIColor(clr)))
Dim no As NativeObject = nav
no.GetField("navigationBar").RunMethod("setTitleTextAttributes:", Array(attributes))
End Sub

B4X JavaObject and NativeObject

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