How to set color resource as a wallpaper in android?

Question

I want to set a solid color as a wallpaper in android, but when I click on the button, the app unfortunately stops.

Here is my code:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button btn = (Button) findViewById(R.id.btn);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            WallpaperManager wm = WallpaperManager.getInstance(getApplicationContext());
            try {
                wm.setResource(R.color.red);
                Toast.makeText(getApplicationContext(), "Wallpaper changed", Toast.LENGTH_LONG).show();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    });
}

Here is the code of colors.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="red">#ff4366</color>
</resources>

Logcat:

10-24 15:59:26.216  12529-12529/com.danish.testapp D/AndroidRuntime﹕ Shutting down VM
    --------- beginning of crash
10-24 15:59:26.216  12529-12529/com.danish.testapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.danish.testapp, PID: 12529
    java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String java.lang.CharSequence.toString()' on a null object reference
            at android.content.res.Resources.openRawResource(Resources.java:1271)
            at android.content.res.Resources.openRawResource(Resources.java:1241)
            at android.app.WallpaperManager.setResource(WallpaperManager.java:739)
            at com.danish.testapp.MainActivity$1.onClick(MainActivity.java:30)
            at android.view.View.performClick(View.java:5198)
            at android.view.View$PerformClick.run(View.java:21147)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

I have also set the required permissions in the manifest.

Answer 1

For WallpaperManager you must set drawable.

wm.setResource(R.drawable.your_drawable);

Edited

also you must set permission.

android.permission.SET_WALLPAPER

for set color with drawable you can using

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item>
        <shape>
            <solid android:color="@color/your_coloe" />
        </shape>
    </item>

</selector>

Edited

Finally Resolved:

I Writing a sample. it' worked. enjoy it.

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_CODE = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WallpaperManager wm = WallpaperManager.getInstance(this);

        Drawable drawable = getResources().getDrawable(R.drawable.mydrawable);
        Bitmap bitmap = drawableToBitmap(drawable);
        Log.i(getClass().getName(), "bitmap = " +bitmap);
        try {
            wm.setBitmap(bitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }
        Toast.makeText(this, "Wallpaper changed",
                Toast.LENGTH_LONG).show();



    }



    public static Bitmap drawableToBitmap (Drawable drawable) {
        Bitmap bitmap = null;

        if (drawable instanceof BitmapDrawable) {
            BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
            if(bitmapDrawable.getBitmap() != null) {
                return bitmapDrawable.getBitmap();
            }
        }

        if(drawable.getIntrinsicWidth() <= 0 || drawable.getIntrinsicHeight() <= 0) {
            bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888); // Single color bitmap will be created of 1x1 pixel
        } else {
            bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
        }

        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
        drawable.draw(canvas);
        return bitmap;
    }
}