android:tileMode="repeat" 失灵

android:tileMode="repeat" 失效
症状描述：
有些时候android:tileMode="repeat"这种样式的背景会莫名其妙的不起作用，背景图依然被拉伸而不是平铺。

解决方法：
调用函数，参数为要设置repeat背景的view
public static void fixBackgroundRepeat(View view) {
      Drawable bg = view.getBackground();
      if(bg != null) {
           if(bg instanceof BitmapDrawable) {
                BitmapDrawable bmp = (BitmapDrawable) bg;
                bmp.mutate(); // make sure that we aren't sharing state anymore
                bmp.setTileModeXY(TileMode.REPEAT, TileMode.REPEAT);
           }
      }
}

参考：http://stackoverflow.com/questions/4077487/background-image-not-repeating-in-android-layout