Android Multi Touch Zoom example

안드로이드에서 Multi Touch이벤트를 이용하여 이미지를 확대하는 예

안드로이드 2.2 부터 지원되는 ScaleGestureDetector클래스를 이용하여 이미지를 확대하는 예

layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <com.example.androidapp.TouchExampleView
	    android:id="@+id/zoomView"
	    android:layout_width="match_parent"
	    android:layout_height="match_parent"/>
</LinearLayout>

TestActivity.java

package com.example.androidapp;

import android.app.Activity;
import android.os.Bundle;

public class TestActivity extends Activity {
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}

}

TouchExampleView.java

package com.example.androidapp;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class TouchExampleView extends View {
	
    private Drawable mIcon;
    private float mPosX;
    private float mPosY;
    
    // Android 2.2 부터 지원되는 유용한 클래스
    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.0f;
    
    public TouchExampleView(Context context) {
        this(context, null, 0);
    }
    
    public TouchExampleView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }
    
    public TouchExampleView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mIcon = context.getResources().getDrawable(R.drawable.ic_launcher);
        mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(), mIcon.getIntrinsicHeight());
        
        // Create our ScaleGestureDetector
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // Let the ScaleGestureDetector inspect all events.
        mScaleDetector.onTouchEvent(ev);
        return true;
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        mIcon.draw(canvas);
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            //mScaleFactor *= detector.getScaleFactor(); // 아래와 동일한 의미
            mScaleFactor *= mScaleDetector.getScaleFactor();
            invalidate();
            return true;
        }
    }
}