CustomInfoWindowBackground.java

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.CornerPathEffect;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

public class CustomMarkerInfoWindowBackground extends Drawable {
    private Path path = new Path();
    private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

    public CustomMarkerInfoWindowBackground(int paintColor) {
        paint.setColor(paintColor);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setPathEffect(new CornerPathEffect(12));
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        canvas.drawPath(path, paint);
    }

    @Override
    public void setAlpha(int alpha) {
        paint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {
        paint.setColorFilter(colorFilter);
    }

    @Override
    public int getOpacity() {
        return paint.getAlpha();
    }

    @Override
    protected void onBoundsChange(Rect bounds) {
        super.onBoundsChange(bounds);
        computeDrawable(bounds);
        invalidateSelf();
    }

    private void computeDrawable(Rect bounds) {
        path.reset();
        path = createDrawable(bounds);
    }

    private Path createDrawable(Rect bounds) {
        Path drawablePath = new Path();
        drawablePath.moveTo(bounds.centerX(), bounds.bottom);
        drawablePath.lineTo(bounds.left, (int) (bounds.bottom * 0.8));
        drawablePath.lineTo(bounds.left, bounds.top);
        drawablePath.lineTo(bounds.right, bounds.top);
        drawablePath.lineTo(bounds.right, (int) (bounds.bottom * 0.8));
        drawablePath.lineTo(bounds.centerX(), bounds.bottom);
        drawablePath.close();
        return drawablePath;
    }
}