获取桌面壁纸作为App背景

    最近做app领导要求所有app都要用桌面壁纸来作为app的背景图。于是写了以下代码来实现：

private void setBackground() {
try {

LinearLayout rl = (LinearLayout) findViewById(R.id.fm_main);
WallpaperManager wm = WallpaperManager.getInstance(this);
Drawable d = wm.getDrawable();

if (d != null) {

rl.setBackground(d);
} else {
rl.setBackgroundResource(R.drawable.wallpaper);
}

}

这样做当然是可以，但是发现背景图会被严重压缩，跟桌面上的壁纸效果相差太大。

用各种压缩，拉伸，裁剪都不起作用，简直要抓狂啊。后来想，launcher里面既然可以做到，为何不模仿launcher的做法呢？

于是查看launcher设置壁纸的源码，发现自定义了一个Drawable：

static class WallpaperDrawable extends Drawable {

        Bitmap mBitmap;

        int mIntrinsicWidth;

        int mIntrinsicHeight;

public void setBitmap(Bitmap bitmap) {

            mBitmap = bitmap;

            if (mBitmap == null)

                return;

            mIntrinsicWidth = mBitmap.getWidth();

            mIntrinsicHeight = mBitmap.getHeight();

        }

@Override

        public void draw(Canvas canvas) {

            if (mBitmap == null) return;

            int width = canvas.getWidth();

            int height = canvas.getHeight() ;

      int x = (width - mIntrinsicWidth) / 2;

            int y = (height - mIntrinsicHeight) / 2;

            canvas.drawBitmap(mBitmap, x, y, null);

        }

@Override

        public int getOpacity() {

            return android.graphics.PixelFormat.OPAQUE;

        }

 @Override

        public void setAlpha(int alpha) {

            // Ignore

        }

        @Override

        public void setColorFilter(ColorFilter cf) {

            // Ignore

        }

结合自己的一些代码，最终解决了背景倍压扁的问题：

// drawable转bitmap
private static Bitmap drawableToBitmap(Drawable drawable) {
int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();

Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
Bitmap bitmap = Bitmap.createBitmap(width, height, config);
Canvas canvas = new Canvas(bitmap);

drawable.setBounds(0, 0, width, height);
drawable.draw(canvas);
return bitmap;
}

最后，修改setBackground方法：

private void setBackground() {
try {

LinearLayout rl = (LinearLayout) findViewById(R.id.fm_main);
WallpaperManager wm = WallpaperManager.getInstance(this);
Drawable d = wm.getDrawable();

if (d != null) {

Bitmap bitmap = drawableToBitmap(d);
WallpaperDrawable wd = new WallpaperDrawable();
wd.setBitmap(bitmap);

rl.setBackground(d);

} else {
rl.setBackgroundResource(R.drawable.wallpaper);
}

}