Learn Xamarin Absolute Beginners - Permissions, Building the App GUI & Menus

Learn Xamarin Absolute Beginners
Permissions, Building the App GUI Menus
Eng Teong Cheah
Microsoft MVP in Visual Studio &
Development Technologies

Agenda
•Permissions
•Building the App GUI
•Menus

Permissions
In Android, by default, no application has permissions to perform any
operations that would have an effect on the user or the operating
system. In order for an App to perform a task, it must declare the
permissions. The App cannot perform the task until the permission
are granted by the Android system. This mechanism of permissions
stops applications from doing as they wish without the user’s
constent.

Permissions
Permissions are to be
recorded in
AndroidManifest.xml file. To
add permissions, we double-
click on properties, then go
to Android Manifest Required
permissions will appear.
Check the appropriate
permissions you wish to add.

Permissions
Camera – It provides permission to access the device’s camera.
Internet – It provides access to network resources.
ReadContacts – It provides access to read the contacts on your
device.
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.READ_CONTACTS" />

Permissions
ReadExtrnalStorage – It provides access to read and store data on an
external storage.
Calendar – It allows an app access to the calendar on the user device
and events. This permission can be dangerous, as it grants an app
the ability to send emails to guests without the owner’s awareness.
The syntax for adding this permission is as shown below:
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission-group.CALENADAR" />

Permissions
SMS – An app with this permission has the ability to use the devices
messaging services. It includes reading, writing, and editing SMS and
MMS messages. Its syntax is as shown below.
Location – An app with this permission can access the device’s
location using the GPS network.
<uses-permission android:name="android.permission-group.SMS" />
<uses-permission android:name="android.permission-group.LOCATION" />

Permissions
Bluetooth – An app this permission can exchange data files with
other Bluetooth enabled devices wirelessly.
<uses-permission android:name="android.permission.BLUETOOTH" />

Building the App GUI
When a new Android project is
created, there are some files that are
added to the project, by default. We
call these default project files and
folders as Android Resources. Take a
look at the following screenshot.

Android Resources
The default Android resources include the following -
AndroidManifest.xml file – It contains information about your Android
applications, e.g. the application name, permissions, etc.
Resources folder - Resources can be images, layouts, strings, etc.
that can be loaded via Android’s resource system.

Android Resources
Resources / drawable folder – It stores all the images that you are
going to use in your application.
Resources / layout folder -It contains all the Android XML file (.axml)
that Android uses to build user interfaces.
The Resources / value folder - It contains XML files to declare key-
value pairs for strings (and other types) throughout an application.
This is how localization for multiple languages is normally set up on
Android.

Android Resources
Resources.designer.cs – This file is created automatically when the
Android projected is created and it conatins unique identifiers that
reference the Android resources.
MainActivity.cs file - This is the first activity of your Android
application and from where the main application actions are
launched from.

Android Resources
Resource files can be accessed programmatically through a unique ID
which is stored in the resources.designer.cs file. The ID is contained
user a class call Resource. Any resource added to the project is
automatically generated inside the resource class.

Menus
Popup Menus
A popup menu refers to a menu that is attached to a view; it is also
referred to as a shortcut menu. Let’s see how to add a popup menu
to an Android App.
Create a new project and call popUpMenu App. Open Main.axml and
create a button which will be used to display the popup menu.

Menus
Popup Menus
<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
android:orientation = "vertical"
android:background = "#d3d3d3"
android:layout_width = "fill_parent"
android:layout_height = "fill_parent">
<Button
android:id = "@+id/popupButton"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
android:text = "Show popup menu"
android:background = "@android:color/holo_green_dark"
android:textColor = "@android:color/black" />
</LinearLayout>

Menus
Popup Menus
Create a new folder under the Resources folder and call it Menu.
Inside the Menu folder, add a new xml file called popMenu.xml.
Under popMenu.xml, add the following menu items.

Menus
<?xml version = "1.0" encoding="utf-8"?>
<menu xmlns:android = "http://schemas.android.com/apk/res/android">
<item
android:id = "@+id/file_settings"
android:icon = "@drawable/img_settings"
android:title = "Settings"
android:showAsAction = "ifRoom">
<item
android:id = "@+id/new_game1"
android:icon = "@drawable/imgNew"
android:title = "New File Settings"/>
<item
android:id = "@+id/help"
android:icon = "@drawable/img_help"
android:title = "Help" />
<item
android:id = "@+id/about_app"
android:title = "About app"/>
</item>
</menu>

Menus
Popup Menus
After adding the menu items, go to mainActivity.cs to display the
popup menu on button click.
protected override void OnCreate(Bundle bundle) {
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
Button showPopupMenu = FindViewById<Button>(Resource.Id.popupButton);
showPopupMenu.Click += (s, arg) => {
PopupMenu menu = new PopupMenu(this, showPopupMenu);
menu.Inflate(Resource.Menu.popMenu);
menu.Show();
};
}

Menus
Option Menus
Options Menu is a collection of menus that are primary to an App
and are mainly used to store settings, search, etc. Here, we are going
to create a menu for settings with three items inside, i.e., New File
Settings, Help, and About App.
To create an options menu, we must create a new XML layout file in
the resources folder. First of all, we will add a new XML file. Right-click
on the Layout folder, then go to Add-> New item -> Visual C# ->
XML file.

Menus
Option Menus
Choose an appropriate name for the layout file. In our example, we
will call our file myMenu.xml.
Inside myMenu.xml, we are going to create a new menu and add
items inside. The following code shows how to do it.

Menus
<?xml version = "1.0" encoding = "utf-8"?>
<menu xmlns:android = "http://schemas.android.com/apk/res/android">
<item
android:id = "@+id/file_settings"
android:icon = "@drawable/img_settings"
android:title = "Settings"
android:showAsAction = "ifRoom">
<menu>
<item
android:id = "@+id/new_game1"
android:icon = "@drawable/imgNew"
android:title = "New File Settings" />
<item
android:id = "@+id/help"
android:title = "Help" />
<item
android:id = "@+id/about_app"
android:title = "About app"/>
</menu>
</item>
</menu>

Menus
Option Menus
Next, we navigate to MainActivity.cs and create an override class for
onOptionsMenu().
public override bool OnCreateOptionsMenu(IMenu menu) {
MenuInflater.Inflate(Resource.Menu.myMenu, menu);
return base.OnPrepareOptionsMenu(menu);
}

Menus
Option Menus
Next, we create an action to respond to the settings menu when it is
selected. To do this, we create another override class for the
OnOptionsItemSelected() menu.
public override bool OnOptionsItemSelected(IMenuItem item) {
if (item.ItemId == Resource.Id.file_settings) {
// do something here...
return true;
}
return base.OnOptionsItemSelected(item);
}

Menus
Option Menus
Our final complete code will looks as follows-
namespace optionsMenuApp {
[Activity(Label = "options Menu", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity {
public override bool OnCreateOptionsMenu(IMenu menu) {
MenuInflater.Inflate(Resource.Menu.myMenu, menu);
return base.OnPrepareOptionsMenu(menu);
}
public override bool OnOptionsItemSelected(IMenuItem item) {
if (item.ItemId == Resource.Id.file_settings) {
// do something here...
return true;
}
return base.OnOptionsItemSelected(item);
}
}
}

Related Content
•TutorialsPoint
www.tutorialspoint.com

Learn Xamarin Absolute Beginners - Permissions, Building the App GUI & Menus

More Related Content

What's hot (20)

Similar to Learn Xamarin Absolute Beginners - Permissions, Building the App GUI & Menus (20)

More from Eng Teong Cheah (20)

Recently uploaded (20)

Learn Xamarin Absolute Beginners - Permissions, Building the App GUI & Menus