How to scale Canvas in Android

In this android programming source code example, we are going to scale Canvas in Android.

You can copy and adopt this source code example to your android project without reinventing the wheel.

Below is a step by step source code to scale Canvas in Android.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:id="@+id/canvas"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/scale"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorAccent"
        android:textColor="#ffffff"
        android:layout_alignParentBottom="true"
        android:text="Scale Canvas"/>

</RelativeLayout>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.View;
import android.widget.Button;
import android.widget.RelativeLayout;


public class CanvasActivity16 extends AppCompatActivity {
    private RelativeLayout view;
    private Button scale;
    private canvas16 customcanvas;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_canvas16);
        view = (RelativeLayout) findViewById(R.id.canvas);
        scale = (Button) findViewById(R.id.scale);
        customcanvas = new canvas16(CanvasActivity16.this, null);
        view.addView(customcanvas);
        scale.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                customcanvas.scaleCanvas();
            }
        });
    }
    public static class canvas16 extends View {
        private Paint paint;
        private boolean cc = false;
        private Canvas mcanvas;
        public canvas16(Context context, AttributeSet attributeSet){
            super(context, attributeSet);
            paint = new Paint();
            paint.setColor(getResources().getColor(R.color.colorAccent));
            paint.setStrokeWidth(10);
            paint.setStyle(Paint.Style.STROKE);
        }

        @Override
        protected void onDraw(Canvas canvas){
            super.onDraw(canvas);
            mcanvas = canvas;
            if(cc){
                mcanvas.save();
                mcanvas.scale(0.5f,0.5f);
                mcanvas.drawRect(50, 50, 200, 200, paint);
                mcanvas.restore();
            }else{
                mcanvas.drawRect(50, 50, 200, 200, paint);
                cc = false;
            }
        }

        public void scaleCanvas(){
            cc = true;
            invalidate();
        }
    }
}

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