Introduction to Android Canvas – Simple Example

The Canvas can be used to draw graphics in android. It provides methods to draw oval, rectangle, picture, text, line etc.

The Paint class is used with canvas to draw objects. It holds the information of color and style.

In this example, we will draw some 2D Shapes.

We will create class that extends View and use Canvas to draw a Circle, Rectangle and Text.

Here is the complete example.

package demo1.coderzheaven.com.demo1;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    int initX = 200, initY = 200, radius = 100, rectWidth = 500, rectHeight = 400;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        CanvasView demoview = new CanvasView(this);
        setContentView(demoview);
    }

    private class CanvasView extends View {
        public CanvasView(Context context) {
            super(context);
        }

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

            // custom drawing code here
            Paint paint = new Paint();
            paint.setStyle(Paint.Style.FILL);

            // make the entire canvas white
            paint.setColor(Color.WHITE);
            canvas.drawPaint(paint);

            // draw blue circle with anti aliasing turned on
            paint.setAntiAlias(true);
            paint.setColor(Color.BLUE);
            canvas.drawCircle(initX, initY, radius, paint);

            // draw red rectangle with anti aliasing turned off
            paint.setAntiAlias(true);
            paint.setColor(Color.RED);
            canvas.drawRect(initX, initY + 300, rectWidth + radius, initY + rectHeight , paint);

            paint.setStyle(Paint.Style.FILL);
            paint.setColor(Color.GREEN);
            paint.setTextSize(40);
            canvas.drawText("CoderzHeaven, Heaven of all working codes", initX, initY + 600, paint);

            if (Build.VERSION.SDK_INT != Build.VERSION_CODES.M)
                canvas.restore();
        }
    }
}