Android Live Wallpaper. This tutorial describes the creation of live wallpapers for Android. It is based on Eclipse 4.2, Java 1.6 and Android 4.1 (Ice Cream Sandwich).
1. Pre-requisitions
The following tutorial assumes that you have already basic knowledge in Android development. Please check the https://www.vogella.com/tutorials/Android/article.html - Android development tutorial to learn the basics.
2. Overview
2.1. Live Wallpapers
Live Wallpapers are animated, interactive backgrounds for the Android home screen. A live wallpaper is similar to other Android applications and can use most of the same functionality.
2.2. How to create a live wallpaper
To create a live wallpaper, you need to create an XML file which describes your wallpaper. This file should contain a description of the application and can contain a preview and a link to a preference activity Activity which allow to customize the live wallpaper.
You also create a
service
which
must extend the
WallpaperService
class. This class is the base class for all live
wallpapers in
the
system. You must implement the
onCreateEngine()
method
and return
an
object of type
android.service.wallpaper.WallpaperService.Engine. This
objects
handles the
lifecycle
events,
animations and drawings
of
the
wallpaper. The
Engine
class defines the life
cycle methods, as for example
onCreate(),
onSurfaceCreated(),
onVisibilityChanged(),
onOffsetsChanged(),
onTouchEvent()
and
onCommand().
The
service
requires
the permission
android.permission.BIND_WALLPAPER
and
must be
registered via an
intent-filter for the
android.service.wallpaper.WallpaperService
action.
You should also enter in the
AndroidManifest.xml
file of the application
that your
application uses the
android.software.live_wallpaper
feature. This
will prevent
that your wallpaper can be
installed on
devices
which do
not support
live wallpapers.
2.3. Intent to set the wallpaper
You can use an Intent to set the Wallpaper.
// Button to set the Wallpaper
public void onClick(View view) {
Intent intent = new Intent(
WallpaperManager.ACTION_CHANGE_LIVE_WALLPAPER);
intent.putExtra(WallpaperManager.EXTRA_LIVE_WALLPAPER_COMPONENT,
new ComponentName(this, MyWallpaperService.class));
startActivity(intent);
}3. Android Wallpaper Example
Create a new project called de.vogella.android.wallpaper. Do not create an activity.
Create the /res/xml folder and create the mywallpaper.xml file.
<?xml version="1.0" encoding="UTF-8"?>
<wallpaper
xmlns:android="http://schemas.android.com/apk/res/android"
android:thumbnail="@drawable/icon"
android:description="@string/wallpaper_description"
android:settingsActivity="de.vogella.android.wallpaper.MyPreferencesActivity"/>This file contains a description of your wallpaper and a preview graphic. You can also enter a link to an activity which allow to configure the wallpaper. This resource file will be linked to from the AndroidManifest.xml. You could also include the "android:thumbnail attribute" which would point to a drawable which gives a smaller image of the running wallpaper.
Change your
AndroidManifest.xml
to the following to define
your
MyWallpaperService
service. Also define the uses-feature.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="de.vogella.android.wallpaper"
android:versionCode="1"
android:versionName="1.0" >
<application
android:icon="@drawable/icon"
android:label="@string/app_name" >
<service
android:name="MyWallpaperService"
android:enabled="true"
android:label="Wallpaper Example "
android:permission="android.permission.BIND_WALLPAPER" >
<intent-filter>
<action android:name="android.service.wallpaper.WallpaperService" >
</action>
</intent-filter>
<meta-data
android:name="android.service.wallpaper"
android:resource="@xml/mywallpaper" >
</meta-data>
</service>
<activity
android:name=".MyPreferencesActivity"
android:exported="true"
android:label="@string/app_name"
android:theme="@android:style/Theme.Light.WallpaperSettings" >
</activity>
<activity
android:name=".SetWallpaperActivity"
android:label="@string/app_name"
android:theme="@android:style/Theme.Light.WallpaperSettings" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="10" />
<uses-feature
android:name="android.software.live_wallpaper"
android:required="true" >
</uses-feature>
</manifest>We create the
MyPoint
class to save the elements we have drawn.
package de.vogella.android.wallpaper;
public class MyPoint {
String text;
private int x;
private int y;
public MyPoint(String text, int x, int y) {
this.text = text;
this.x = x;
this.y = y;
}
}Create a new activity. Create the prefs.xml preference file in the res/xml folder.
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<CheckBoxPreference android:key="touch"
android:title="Enable Touch"></CheckBoxPreference>
<EditTextPreference android:key="numberOfCircles"
android:title="Number of Circles"></EditTextPreference>
</PreferenceScreen>Create a new activity called MyPreferencesActivity and the following class.
package de.vogella.android.wallpaper;
import android.os.Bundle;
import android.preference.Preference;
import android.preference.Preference.OnPreferenceChangeListener;
import android.preference.PreferenceActivity;
import android.widget.Toast;
public class MyPreferencesActivity extends PreferenceActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.prefs);
// add a validator to the "numberofCircles" preference so that it only
// accepts numbers
Preference circlePreference = getPreferenceScreen().findPreference(
"numberOfCircles");
// add the validator
circlePreference.setOnPreferenceChangeListener(numberCheckListener);
}
/**
* Checks that a preference is a valid numerical value
*/
Preference.OnPreferenceChangeListener numberCheckListener = new OnPreferenceChangeListener() {
@Override
public boolean onPreferenceChange(Preference preference, Object newValue) {
// check that the string is an integer
if (newValue != null && newValue.toString().length() > 0
&& newValue.toString().matches("\\d*")) {
return true;
}
// If now create a message to the user
Toast.makeText(MyPreferencesActivity.this, "Invalid Input",
Toast.LENGTH_SHORT).show();
return false;
}
};
}Create the following coding for the Wallpaper service.
package de.vogella.android.wallpaper;
import java.util.ArrayList;
import java.util.List;
import android.content.SharedPreferences;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.preference.PreferenceManager;
import android.service.wallpaper.WallpaperService;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
public class MyWallpaperService extends WallpaperService {
@Override
public Engine onCreateEngine() {
return new MyWallpaperEngine();
}
private class MyWallpaperEngine extends Engine {
private final Handler handler = new Handler();
private final Runnable drawRunner = new Runnable() {
@Override
public void run() {
draw();
}
};
private List<MyPoint> circles;
private Paint paint = new Paint();
private int width;
int height;
private boolean visible = true;
private int maxNumber;
private boolean touchEnabled;
public MyWallpaperEngine() {
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(MyWallpaperService.this);
maxNumber = Integer
.valueOf(prefs.getString("numberOfCircles", "4"));
touchEnabled = prefs.getBoolean("touch", false);
circles = new ArrayList<MyPoint>();
paint.setAntiAlias(true);
paint.setColor(Color.WHITE);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(10f);
handler.post(drawRunner);
}
@Override
public void onVisibilityChanged(boolean visible) {
this.visible = visible;
if (visible) {
handler.post(drawRunner);
} else {
handler.removeCallbacks(drawRunner);
}
}
}@Override
public void onSurfaceDestroyed(SurfaceHolder holder) {
super.onSurfaceDestroyed(holder);
this.visible = false;
handler.removeCallbacks(drawRunner);
}
@Override
public void onSurfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
this.width = width;
this.height = height;
super.onSurfaceChanged(holder, format, width, height);
}
@Override
public void onTouchEvent(MotionEvent event) {
if (touchEnabled) {
float x = event.getX();
float y = event.getY();
SurfaceHolder holder = getSurfaceHolder();
Canvas canvas = null;
try {
canvas = holder.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.BLACK);
circles.clear();
circles.add(new MyPoint(
String.valueOf(circles.size() + 1), x, y));
drawCircles(canvas, circles);
}
} finally {
if (canvas != null)
holder.unlockCanvasAndPost(canvas);
}
super.onTouchEvent(event);
}
}
private void draw() {
SurfaceHolder holder = getSurfaceHolder();
Canvas canvas = null;
try {
canvas = holder.lockCanvas();
if (canvas != null) {
if (circles.size() >= maxNumber) {
circles.clear();
}
int x = (int) (width * Math.random());
int y = (int) (height * Math.random());
circles.add(new MyPoint(String.valueOf(circles.size() + 1),
x, y));
drawCircles(canvas, circles);
}
} finally {
if (canvas != null)
holder.unlockCanvasAndPost(canvas);
}
handler.removeCallbacks(drawRunner);
if (visible) {
handler.postDelayed(drawRunner, 5000);
}
}
// Surface view requires that all elements are drawn completely
private void drawCircles(Canvas canvas, List<MyPoint> circles) {
canvas.drawColor(Color.BLACK);
for (MyPoint point : circles) {
canvas.drawCircle(point.x, point.y, 20.0f, paint);
}
}
}Create the following Activity which should use a layout with one
Button
included. This Button should use the
onClick
property to point to the
onClick
method.
package de.vogella.android.wallpaper;
import android.app.Activity;
import android.app.WallpaperManager;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class SetWallpaperActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void onClick(View view) {
Intent intent = new Intent(
WallpaperManager.ACTION_CHANGE_LIVE_WALLPAPER);
intent.putExtra(WallpaperManager.EXTRA_LIVE_WALLPAPER_COMPONENT,
new ComponentName(this, MyWallpaperService.class));
startActivity(intent);
}
}If you start your application your application should allow to set the wallpaper. Your background should look similar to the following screenshot. If you have Touch enabled via the preferences you can click on the screen to remove the existing circles, also via the settings you can define the number of circles which should be displayed.
4. Links and Literature
4.2. vogella Java example code
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