Question

I’m trying to draw a line over an ImageView but whenever I try it using Canvas, I have to reload the Bitmap, which is not my intention.
Is there a way to simply draw a line on an uploaded ImageView using Canvas without having to refresh the Image? Or another way to draw lines over Android ImageView?

Answer 1

Or, if you want to be able to draw any lines (rects, ovals, etc), subclass ImageView into your own ImageView and do the drawing yourself.

public class MyImageView extends ImageView {
    Paint linePaint = new Paint();


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw();

        // And draw your line.
        // (Be sure to have set the values/fields in linePaint earlier so that you draw the correct line/type/size/etc).
        canvas.drawLine(0, getHeight()/2, getWidth(), getHeight()/2, linePaint);

    }
}

And in your layout xml, don’t specify <ImageView …/>, but specify <com.mycompany.project.widget.MyImageView … /> instead.