Android: Drawing tiled bitmaps with bottom or some other alignments similar to css background-position

Question

I want to set a background of a View with a tiled bitmap, but the tiling needs to be anchored to the bottom-left, instead of the top-left corner (the default). For example, if t

Answer 1

Just a thought, and it's pretty roundabout, but could you flip your image vertically, and then apply a transform to your background to flip that vertically as well?

Answer 2

Another way would be to extend BitmapDrawable and override the paint() method:

In this method we avoid creating a new bitmap having the size of the view.

class MyBitmapDrawable extends BitmapDrawable {
    private Paint mPaint = new Paint(Paint.FILTER_BITMAP_FLAG | Paint.DITHER_FLAG);
    private boolean mRebuildShader = true;
    private Matrix mMatrix = new Matrix();

    @Override
    public void draw(Canvas canvas) {
        Bitmap bitmap = getBitmap();
        if (bitmap == null) {
            return;
        }

        if (mRebuildShader) {
            mPaint.setShader(new BitmapShader(bitmap, TileMode.REPEAT, TileMode.REPEAT));
            mRebuildShader = false;
        }

        // Translate down by the remainder
        mMatrix.setTranslate(0, getBounds().bottom % getIntrinsicHeight());
        canvas.save();
        canvas.setMatrix(mMatrix);
        canvas.drawRect(getBounds(), mPaint);
        canvas.restore();
    }
}

It can be set to the view like this:

view.setBackgroundDrawable(new MyBitmapDrawable(getResources().getDrawable(R.drawable.smiley).getBitmap()));

Answer 3

Using a custom view might involve handling all the drawing yourself, not just the background image.

Instead, I propose to set the view's background programmatically as shown:

// This drawable refers to an image directly and NOT an XML
BitmapDrawable smiley = (BitmapDrawable) getResources().getDrawable(R.drawable.smiley);

// Create a new bitmap with the size of the view
Bitmap bgBitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bgBitmap);

// Translate down by the remainder
Matrix matrix = new Matrix();
matrix.setTranslate(0, view.getHeight() % smiley.getIntrinsicHeight());
canvas.setMatrix(matrix);

// Tile the smileys
Paint paint = new Paint();
paint.setShader(new BitmapShader(smiley.getBitmap(), TileMode.REPEAT, TileMode.REPEAT));
canvas.drawPaint(paint);

view.setBackgroundDrawable(new BitmapDrawable(bgBitmap));

Points to consider:

• I'm not sure if view.getWidth() & view.getHeight() are the correct methods to get the dimensions.
• What if smiley size is bigger than the view?