Unit 2 LayoutTutorial.pptx

User Interfaces
A Layouts-Linear layout, Relative layout, Constraint layout
B Input Controls – Text input, Checkboxes, Radio buttons,
Spinner, Toggle buttons and switches
C Menus- Popup, Dialog, Context, date picker, style
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5. Android – UI – Basic XML Layouts
Basic XML Layouts - Containers
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Designing Complex Uis
• Arguably, LinearLayout is the most common modeling tool. It
offers a "box" model similar to the Java-Swing Box-Layout.
• Generally, complex UI designs result from the combination of
simpler nested boxes that show their inner pieces using a
horizontal or vertical orientation.

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Summary of Commonly-used Android containers
1. LinearLayout (the box model),
2. AbsoluteLayout (deprecated)
3. RelativeLayout (a rule-based model), and
4. TableLayout (the grid model), along with
5. ScrollView, a container designed to assist with implementing scrolling
containers.
6. ConstraintLayout
7. Other (ListView, GridView, WebView, MapView,…) discussed later

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1. Linear Layout
LinearLayout is a box model – widgets or child containers are lined
up in a column or row, one after the next.
To configure a LinearLayout, you have five main areas of control
besides the container's contents:
• orientation,
• fill model,
• weight,
• gravity,
• padding ,
• margin

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1. Linear Layout
Orientation
indicates whether the LinearLayout represents a row or a column.
Add the android:orientation property to your LinearLayout
element in your XML layout, setting the value to be horizontal for a
row or vertical for a column.
The orientation can be modified at runtime by invoking
setOrientation()

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1.1 Linear Layout: Orientation
indicates whether the LinearLayout represents a row (HORIZONTAL)
or a column (VERTICAL).
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="@+id/myLinearLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ff0033cc"
android:padding="4dip"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" >
<TextView
android:id="@+id/labelUserName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#ffff0066"
android:text="User Name"
android:textSize="16sp"
android:textStyle="bold"
android:textColor="#ff000000"
>
</TextView>
<EditText
android:id="@+id/ediName"
>
</EditText>
<Button
android:id="@+id/btnGo"
android:text="Go"
>
</Button>
</LinearLayout>
horizontal
v
e
r
t
i
c
a
l

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1.2 Linear Layout: Fill Model
• Widgets have a "natural" size based on their accompanying text.
• When their combined sizes does not exactly match the width of the Android
device's screen, we may have the issue of what to do with the remaining
space.
empty screen space
natural sizes

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All widgets inside a LinearLayout must supply dimensional attributes
android:layout_width and android:layout_height
to help address the issue of empty space.
Values used in defining height and width are:
1. Specific a particular dimension, such as 125dip (device independent pixels)
2. Provide wrap_content, which means the widget should fill up its natural
space, unless that is too big, in which case Android can use word-wrap as
needed to make it fit.
3. Provide fill_parent, which means the widget should fill up all available space
in its enclosing container, after all other widgets are taken care of.

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<LinearLayout
android:orientation="vertical"
>
<TextView
android:id="@+id/labelUserName"
>
</TextView>
<EditText
>
</EditText>
<Button
android:layout_width="125dip"
android:text="Go"
>
</Button>
</LinearLayout>
125 dip
entire row (320 dip on G1)
G1 phone resolution is: 320 x 480 dip (3.2 in).

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1.2 Linear Layout: Weight
It is used to proportionally assign space to widgets in a view.
You set android:layout_weight to a value (1, 2, 3, …) to indicates what proportion
of the free space should go to that widget.
Example
Both the TextView and the Button widgets
have been set as in the previous example.
Both have the additional property
android:layout_weight="1"
whereas the EditText control has
android:layout_weight="2"
Default value is 0
Takes: 2 /(1+1+2)
of the screen space

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1.3 Linear Layout: Gravity
• It is used to indicate how a control will align on the screen.
• By default, widgets are left- and top-aligned.
• You may use the XML property
android:layout_gravity=“…”
to set other possible arrangements:
left, center, right, top, bottom, etc.
Button has
right gravity

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1.3 CAUTION: gravity vs. layout_gravity
The difference between:
android:gravity
specifies how to place the content of an object, both on the x- and
y-axis, within the object itself.
android:layout_gravity
positions the view with respect to its parent (i.e. what the view is
contained in).
android:gravity="center"
android:layout_gravity="center"

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1.4 Linear Layout: Padding
• The padding specifies how much space there is between the boundaries of
the widget's "cell" and the actual widget contents.
• If you want to increase the internal whitespace between the edges and its
contents, you will want to use the:
• android:padding property
• or by calling setPadding() at runtime on the widget's Java object.
Note: Padding is analogous to the margins on a word processing document.

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1.3 Linear Layout: Padding and Marging

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1.3 Linear Layout: Internal Margins Using Padding
Example:
The EditText box has been changed to display 30dip of padding all around
<EditText
android:padding="30dip“
>
</EditText>
...

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1.4 Linear Layout: (External) Marging
• By default, widgets are tightly packed next to each other.
• To increase space between them use the android:layout_margin attribute
<EditText
android:layout_margin=“6dip“
>
</EditText>
...
Increased inter-widget space

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2. Relative Layout
RelativeLayout places widgets based on their relationship to other widgets in
the container and the parent container.
A
C
B
Example:
A is by the parent’s top
C is below A, to its right
B is below A, to the left of C

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2. Relative Layout - Referring to the container
Some positioning XML (boolean) properties mapping a widget according to its
location respect to the parent’s place are:
• android:layout_alignParentTop says the widget's top should align with the top of the
container
• android:layout_alignParentBottom the widget's bottom should align with the bottom of the
container
• android:layout_alignParentLeft the widget's left side should align with the left side of the
container
• android:layout_alignParentRight the widget's right side should align with the right side of
the container
• android:layout_centerInParent the widget should be positioned both horizontally and
vertically at the center of the container
• android:layout_centerHorizontal the widget should be positioned horizontally at the center
of the container
• android:layout_centerVertical the widget should be positioned vertically at the center of the
container

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2. Relative Layout – Referring to other widgets
The following properties manage positioning of a widget respect to other
widgets:
• android:layout_above indicates that the widget should be placed above the
widget referenced in the property
• android:layout_below indicates that the widget should be placed below the
widget referenced in the property
• android:layout_toLeftOf indicates that the widget should be placed to the left
of the widget referenced in the property
• android:layout_toRightOf indicates that the widget should be placed to the
right of the widget referenced in the property

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2. Relative Layout – Referring to other widgets – cont.
• android:layout_alignTop indicates that the widget's top should be aligned with the
top of the widget referenced in the property
• android:layout_alignBottom indicates that the widget's bottom should be aligned
with the bottom of the widget referenced in the property
• android:layout_alignLeft indicates that the widget's left should be aligned with the
left of the widget referenced in the property
• android:layout_alignRight indicates that the widget's right should be aligned with
the right of the widget referenced in the property
• android:layout_alignBaseline indicates that the baselines of the two widgets
should be aligned

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2. Relative Layout – Referring to other widgets
In order to use Relative Notation in Properties you need to consistently:
1. Put identifiers (android:id attributes) on all elements that you will
need to address.
2. Syntax is: @+id/... (for instance an EditText box could be XML called:
android:id="@+id/ediUserName")
3. Reference other widgets using the same identifier value (@+id/...) already
given to a widget. For instance a control below the EditText box could say:
android:layout_below="@+id/ediUserName"

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2. Relative Layout – Example
<RelativeLayout
android:id="@+id/myRelativeLayout"
android:background="#ff000099"
xmlns:android="http://schemas.android.com/apk/res/andr
oid">
<TextView
android:id="@+id/lblUserName"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true">
</TextView>
<EditText
android:id="@+id/ediUserName"
android:layout_below="@+id/lblUserName"
android:layout_alignParentLeft="true"
android:layout_alignLeft="@+id/myRelativeLayout"
android:padding="20dip">
</EditText>
<Button
android:layout_alignRight="@+id/ediUserName"
android:text="Go"
android:textStyle="bold">
</Button>
<Button
android:id="@+id/btnCancel"
android:layout_toLeftOf="@+id/btnGo"
android:text="Cancel"
android:textStyle="bold">
</Button>
</RelativeLayout>
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2. Relative Layout – Comment (as of Aug. 2009)
Use the Eclipse ADT Layout Editor for laying out RelativeLayouts.
DroidDraw is of very little help in this respect.
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3. Table Layout
1. Android's TableLayout allows you to position your widgets in a
grid made of identifiable rows and columns.
2. Columns might shrink or stretch to accommodate their contents.
3. TableLayout works in conjunction with TableRow.
4. TableLayout controls the overall behavior of the container, with
the widgets themselves positioned into one or more TableRow
containers, one per row in the grid.
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3. Table Layout
Rows are declared by you by putting widgets as children of a
TableRow inside the overall TableLayout.
The number of columns is determined by Android ( you control the
number of columns in an indirect way).
So if you have three rows, one with two widgets, one with three
widgets, and one with four widgets, there will be at least four
columns.
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0 1
0 1 2
0 1 2 3

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3. Table Layout
However, a single widget can take up more than one column by
including the android:layout_span property, indicating the number
of columns the widget spans (this is similar to the colspan attribute
one finds in table cells in HTML)
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<TableRow>
<TextView android:text="URL:" />
<EditText
android:id="@+id/entry"
android:layout_span="3" />
</TableRow>

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3. Table Layout
Ordinarily, widgets are put into the first available column of each row.
In the example below, the label (“URL”) would go in the first column
(column 0, as columns are counted starting from 0), and the TextField would go
into a spanned set of three columns (columns 1 through 3).
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Label
(URL)
EditText EditText-span EditText-span
Column 0 Column 1 Column 2
Button
Cancel
Column 3
Button
OK
android:layout_span="3"
android:layout_columns="2"

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3. Table Layout –
Example
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<TableLayout
android:id="@+id/myTableLayout"
>
<TableRow>
<TextView
android:text="URL:" />
<EditText android:id="@+id/ediUrl"
android:layout_span=“2"/>
</TableRow>
<View
android:layout_height="3dip"
android:background="#0000FF" />
<TableRow>
<Button android:id="@+id/cancel"
android:layout_column="2"
android:text="Cancel" />
<Button android:id="@+id/ok"
android:text="OK" />
</TableRow>
<View
android:background="#0000FF" />
</TableLayout>
Skip columns: 0, 1
Strech up to column 2
Note to the reader:
Experiment changing
layout_span to 1, 2, 3

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3. Table Layout
By default, each column will be sized according to the "natural" size
of the widest widget in that column.
If your content is narrower than the available space, you can use
the TableLayout property:
android:stretchColumns =“…”
Its value should be a single column number (0-based) or a comma-
delimited list of column numbers. Those columns will be stretched
to take up any available space yet on the row.
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3. Table Layout
In our running example we stretch columns 2, 3, and 4 to fill the
rest of the row.
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...
<TableLayout
android:id="@+id/myTableLayout"
android:stretchColumns ="2,3,4"
>
...
TODO: try to stretch one column at the time 1, then 2, and so on.

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4. ScrollView Layout
When we have more data than what can be shown on a single
screen you may use the ScrollView control.
It provides a sliding or scrolling access to the data. This way the user
can only see part of your layout at one time, but the rest is available
via scrolling.
This is similar to browsing a large web page that forces the user to
scroll up the page to see the bottom part of the form.
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4. Example ScrollView Layout
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<ScrollView
android:id="@+id/myScrollView1"
android:background="#ff009999"
>
<LinearLayout
android:id="@+id/myLinearLayoutVertical"
>
<LinearLayout
android:id="@+id/myLinearLayoutHorizontal1"
android:orientation="horizontal"
>
<ImageView
android:id="@+id/myPicture"
android:src="@drawable/icon" />
<TextView
android:id="@+id/textView1"
android:text="Line1"
android:textSize="70dip" />
</LinearLayout>
<View
android:background="#ffccffcc" />
<TextView
<View
<TextView
<View
<TextView
<View
<TextView
</LinearLayout>
</ScrollView>

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4. Example ScrollView Layout
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Scroller
Combining an
ImageView & TextView
in a horizontal Linear Layout
Simple
TextView

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5. Miscellaneous.
Absolute Layout
• A layout that lets you
specify exact locations (x/y
coordinates) of its children.
• Absolute layouts are less
flexible and harder to
maintain than other types
of layouts without absolute
positioning.
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5. Miscellaneous Absolute Layout (cont.)
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<AbsoluteLayout
xmlns:android="http://schemas.android.com
/apk/res/android"
>
<TextView
android:id="@+id/tvUserName"
android:layout_x="0dip"
android:layout_y="10dip"
>
</TextView>
<EditText
android:id="@+id/etName"
android:layout_y="38dip"
>
</EditText>
<Button
android:layout_width="120dip"
android:text="Go"
android:layout_y="170dip" />
</AbsoluteLayout>

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Questions?
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Unit 2 LayoutTutorial.pptx

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