013.matrix

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="${relativePackage}.${activityClass}" >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="matrix"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

package com.example.app13;

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

public class MainActivity extends Activity {

    ImageView imageView;
    Matrix matrix = new Matrix();
    PointF oldPoint = new PointF();
    float oldLen;
    float oldDegree;
    int flat=0;//兩手指部同時放開狀況
    PointF midPoint=new PointF();//存中心點

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        imageView = (ImageView) this.findViewById(R.id.imageView1);
        imageView.setOnTouchListener(listener);
        matrix.postTranslate(100, 100);
        imageView.setImageMatrix(matrix);
    }

    View.OnTouchListener listener = new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            // TODO Auto-generated method stub

            switch (event.getAction() & event.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                flat=1;
                Log.e("MainActivity",
                        String.format("Action=%d", event.getActionMasked()));
                // Log.e("MainActivity",
                // String.format("onTouch_ACTION_DOWN %f/%f",event.getX(),event.getY()));
                oldPoint.set(event.getX(), event.getY());
                break;
            case MotionEvent.ACTION_MOVE:
                if (flat==1 && event.getPointerCount() == 1) {
                    // Log.e("MainActivity",
                    // String.format("onTouch_ACTION_MOVE %f/%f",event.getX(),event.getY()));
                    matrix.postTranslate(event.getX() - oldPoint.x,    event.getY() - oldPoint.y);
                    imageView.setImageMatrix(matrix);
                    oldPoint.set(event.getX(), event.getY());
                } else if (flat == 2 && event.getPointerCount() == 2) {
                    float newLen = getLen(event);
                    midPoint = getMidPoint(event);//
                    matrix.postScale(newLen / oldLen, newLen / oldLen,midPoint.x,midPoint.y);
                    imageView.setImageMatrix(matrix);
                    oldLen = newLen;

                    float newDegree = getDegree(event);
                    matrix.postRotate(newDegree - oldDegree,midPoint.x,midPoint.y);
                    imageView.setImageMatrix(matrix);
                    oldDegree=newDegree;
                }
                break;

            case MotionEvent.ACTION_POINTER_DOWN:
                Log.e("MainActivity", "ACTION_POINTER_DOWN");
                // Log.e("MainActivity",String.format("Action=%d",
                // event.getAction()));
                Log.e("MainActivity",
                        String.format("Action=%d", event.getActionMasked()));
                oldLen = getLen(event);
                oldDegree=getDegree(event);
                flat=2;
                break;

            case MotionEvent.ACTION_UP:
                Log.e("MainActivity", "onTouch_ACTION_UP");
                break;
            }

            return true;// 預設false為ACTION_DOWN之後不打算處理後續的event
        }
    };

    public float getLen(MotionEvent event) {
        PointF p = new PointF();
        float diffX = event.getX(1) - event.getX(0);
        float diffY = event.getY(1) - event.getY(0);
        float tmp = FloatMath.sqrt(diffX * diffX + diffY * diffY);        
        return tmp;
    }

    public PointF getMidPoint(MotionEvent event)
    {
        PointF p = new PointF();
        float diffX = (event.getX(1) + event.getX(0))/2;
        float diffY = (event.getY(1) + event.getY(0))/2;
        p.set(diffX, diffY); //x軸距離, y軸距離 
        return p;
    }
    public float getDegree(MotionEvent event) {

        float x = event.getX(1) - event.getX(0);
        float y = event.getY(1) - event.getY(0);        
        return (float)Math.toDegrees(Math.atan2(y,x));
    }
}