android 图片叠加效果——两种方法的简介与内容 ，带解决Immutable bitmap passed to Canvas constructor错误

第一种是通过canvas画出来的效果:

public void first(View v) {

        // 防止出现Immutable bitmap passed to Canvas constructor错误
        Bitmap bitmap1 = BitmapFactory.decodeResource(getResources(),
                R.drawable.apple).copy(Bitmap.Config.ARGB_8888, true);
        Bitmap bitmap2 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.go)).getBitmap();

        Bitmap newBitmap = null;

        newBitmap = Bitmap.createBitmap(bitmap1);
        Canvas canvas = new Canvas(newBitmap);
        Paint paint = new Paint();

        int w = bitmap1.getWidth();
        int h = bitmap1.getHeight();

        int w_2 = bitmap2.getWidth();
        int h_2 = bitmap2.getHeight();

        paint.setColor(Color.GRAY);
        paint.setAlpha(125);
        canvas.drawRect(0, 0, bitmap1.getWidth(), bitmap1.getHeight(), paint);

        paint = new Paint();
        canvas.drawBitmap(bitmap2, Math.abs(w - w_2) / 2,
                Math.abs(h - h_2) / 2, paint);
        canvas.save(Canvas.ALL_SAVE_FLAG);
        // 存储新合成的图片
        canvas.restore();

        image.setImageBitmap(newBitmap);
    }

public void first(View v) {

        // 防止出现Immutable bitmap passed to Canvas constructor错误
        Bitmap bitmap1 = BitmapFactory.decodeResource(getResources(),
                R.drawable.apple).copy(Bitmap.Config.ARGB_8888, true);
        Bitmap bitmap2 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.go)).getBitmap();

        Bitmap newBitmap = null;

        newBitmap = Bitmap.createBitmap(bitmap1);
        Canvas canvas = new Canvas(newBitmap);
        Paint paint = new Paint();

        int w = bitmap1.getWidth();
        int h = bitmap1.getHeight();

        int w_2 = bitmap2.getWidth();
        int h_2 = bitmap2.getHeight();

        paint.setColor(Color.GRAY);
        paint.setAlpha(125);
        canvas.drawRect(0, 0, bitmap1.getWidth(), bitmap1.getHeight(), paint);

        paint = new Paint();
        canvas.drawBitmap(bitmap2, Math.abs(w - w_2) / 2,
                Math.abs(h - h_2) / 2, paint);
        canvas.save(Canvas.ALL_SAVE_FLAG);
        // 存储新合成的图片
        canvas.restore();

        image.setImageBitmap(newBitmap);
    }

 

Canvas canvas = new Canvas(newBitmap); 当以newBitmap创建Canvas时，所以操作都已经在该图上实现了。

该例子可以想做是播放器开始播放的效果，计算好中间位置，先覆盖一层透明灰色的正方形，然后在中间画上自己播放的按钮。

第二种是使用系统的LayerDrawable类，该类主要用来控制多个图片的结合：

public void second(View v) {

        Bitmap bitmap1 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.apple)).getBitmap();
        Bitmap bitmap2 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.go)).getBitmap();

        Drawable[] array = new Drawable[2];
        array[0] = new BitmapDrawable(bitmap1);
        array[1] = new BitmapDrawable(bitmap2);
        LayerDrawable la = new LayerDrawable(array);
        // 其中第一个参数为层的索引号，后面的四个参数分别为left、top、right和bottom
        la.setLayerInset(0, 0, 0, 0, 0);
        la.setLayerInset(1, 20, 20, 20, 20);
        image.setImageDrawable(la);
    }

public void second(View v) {

        Bitmap bitmap1 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.apple)).getBitmap();
        Bitmap bitmap2 = ((BitmapDrawable) getResources().getDrawable(
                R.drawable.go)).getBitmap();

        Drawable[] array = new Drawable[2];
        array[0] = new BitmapDrawable(bitmap1);
        array[1] = new BitmapDrawable(bitmap2);
        LayerDrawable la = new LayerDrawable(array);
        // 其中第一个参数为层的索引号，后面的四个参数分别为left、top、right和bottom
        la.setLayerInset(0, 0, 0, 0, 0);
        la.setLayerInset(1, 20, 20, 20, 20);
        image.setImageDrawable(la);
    }

关联数组array，控制每一层的位置

 装载自：http://blog.csdn.net/gh102/article/details/6719624

注意：上面防止出现Immutable bitmap passed to Canvas constructor错误

原因是如果不用copy的方法，直接引用会对资源文件进行修改，而android是不允许在代码里修改res文件里的图片