draw object/image on canvas

Question

Is there another way to draw an object on a canvas in android?

This code inside draw() doesn't work:

Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pushpin);

         canvas.drawBitmap(bmp, screenPts.x, screenPts.y-50, null);

Well actually, it's working on my 1st code but when I've transfered this to another class called MarkOverlay, it's not working anymore.

  markerOverlay = new MarkerOverlay(getApplicationContext(), p);
                      listOfOverlays.add(markerOverlay);

What parameter should I pass to MarkerOverlay to make this code work? The error is somewhere in getResources().

FYI, canvas.drawOval is perfectly working but I really want to draw an Image not an Oval. :)

score 41 · Answer 1 · edited Aug 12 '15 at 15:27

41

I prefer to do this as it only generates the image once:

public class CustomView extends View {

    private Drawable mCustomImage;

    public CustomView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mCustomImage = context.getResources().getDrawable(R.drawable.my_image);
    }

    ...

    protected void onDraw(Canvas canvas) {
        Rect imageBounds = canvas.getClipBounds();  // Adjust this for where you want it

        mCustomImage.setBounds(imageBounds);
        mCustomImage.draw(canvas);
    }
}

edited Aug 12 '15 at 15:27

Roger C S Wernersson

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answered Sep 18 '12 at 22:52

Emlyn

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10

+1 for not making allocations or unpacking an image in onDraw – user1532390 Feb 15 '13 at 15:22
1

gives me this eclipse warning: Avoid object allocations during draw operations: Use Canvas.getClipBounds(Rect) instead of Canvas.getClipBounds() which allocates a temporary Rect – bhaskarc Dec 14 '13 at 06:40
1

This can be made even better if you follow the simple optimizer hits given by Eclipse. Ie. canvas.getClipBounds(imageBounds); mCustomImage.setBounds(imageBounds); Having a super fast onDraw is very important. – slott May 07 '15 at 07:30
`getResources().getDrawable()` is deprecated as of API 22. Use `ResourcesCompat.getDrawable(getResources(), R.drawable.name, null);` instead. – Izaak Cornelis Jun 12 '20 at 18:17

score 26 · Answer 2 · edited Feb 11 '13 at 16:44

26

package com.canvas;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;

public class Keypaint extends View {
    Paint p;

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        p=new Paint();
        Bitmap b=BitmapFactory.decodeResource(getResources(), R.drawable.icon);
        p.setColor(Color.RED);
        canvas.drawBitmap(b, 0, 0, p);
    }

    public Keypaint(Context context) {
        super(context);
    }
}

edited Feb 11 '13 at 16:44

rodrigo-silveira

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answered Apr 28 '12 at 10:54

Nivish Mittal

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8

You have to free up Bitmap data with Bitmap.recycle() or else you get a nasty memory leak: creating a new bitmap in every drawing cycle. – Andras Balázs Lajtha Mar 31 '13 at 07:16
20

Dont decode image in onDraw - do as much of the heavy lifting outside the render loop. – slott May 07 '15 at 07:24
is it possible to set video view on canvas? – Vivek Thummar Mar 03 '20 at 10:06

draw object/image on canvas

2 Answers2

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