Some guidelines how to achieve this with custom TextView
:
- Extend
TextView
component - Create
Bitmap
andCanvas
where you draw background and text - Draw wanted background color into allocated
Canvas
(e.g.Color.argb(80, 255, 255, 255)
) - Draw the text with
Paint
having modePorterDuffXfermode(Mode.CLEAR)
(Remember: Only allocateBitmap
andCanvas
once) since you draw it intoBitmap
- Draw the
Bitmap
intoTextViews
canvas
Here is some sample code to get started with:
public class TransparentTextView extends TextView {
private Paint mTextPaint;
private Bitmap mBitmapToDraw;
public TransparentTextView(Context context) {
super(context);
setup();
}
public TransparentTextView(Context context, AttributeSet attrs) {
super(context, attrs);
setup();
}
public TransparentTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setup();
}
private void setup() {
mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mTextPaint.setTextSize(getTextSize());
mTextPaint.setStyle(Paint.Style.FILL);
mTextPaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
}
@Override
protected void onDraw(Canvas canvas) {
if (mBitmapToDraw == null) {
mBitmapToDraw = Bitmap.createBitmap(getWidth(), getHeight(),
Bitmap.Config.ARGB_8888);
if (mBitmapToDraw != null) {
Canvas c = new Canvas(mBitmapToDraw);
c.drawColor(Color.argb(80, 255, 255, 255));
c.drawText(getText().toString(), getPaddingLeft(),
getPaddingTop(), mTextPaint);
}
}
if (mBitmapToDraw != null) {
canvas.drawBitmap(mBitmapToDraw, 0, 0, null);
} else {
super.onDraw(canvas);
}
}
}
If you are setting text dynamically, you will need to reset mBitmapToDraw
in order to get it refreshed.