android第二十三步拖拽与缩放

package com.example.dragscale;

import android.os.Bundle;

import android.app.Activity;

import android.graphics.Matrix;

import android.graphics.PointF;

import android.util.FloatMath;

import android.view.Menu;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ImageView;
public class MainActivity extends Activity {
ImageView imageView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        imageView = (ImageView)this.findViewById(R.id.imageView);

        imageView.setOnTouchListener(new TouchListener());

    }

    private final class TouchListener implements OnTouchListener{
private PointF startPoint = new PointF();

        private Matrix matrix = new Matrix();

        private Matrix cuuentMatrix = new Matrix();

        private int mode= 0;

        private static final int drag=1;

        private static final int zoom=2;

        private float startDis;

        private PointF midPoint;

        @Override

        public boolean onTouch(View arg0, MotionEvent arg1) {

            switch(arg1.getAction() & MotionEvent.ACTION_MASK){

            case MotionEvent.ACTION_DOWN:

                mode=drag;

                cuuentMatrix.set(imageView.getImageMatrix());

                startPoint.set(arg1.getX(), arg1.getY());

                break;

            case MotionEvent.ACTION_MOVE:

                if(mode == drag)

                {

                    float dx=arg1.getX()-startPoint.x;

                    float dy=arg1.getY()-startPoint.y;

                    matrix.set(cuuentMatrix);

                    matrix.postTranslate(dx, dy);

                }

                else{

                    float endDis=distance(arg1);

                    if(startDis >10f){

                        float scale = endDis/startDis;

                        matrix.set(cuuentMatrix);

                        matrix.postScale(scale, scale, midPoint.x, midPoint.y);

                    }

                }

                break;

            case MotionEvent.ACTION_UP:

                mode= 0;

                break;

            case MotionEvent.ACTION_POINTER_UP:

                mode= 0;

                break;

            case MotionEvent.ACTION_POINTER_DOWN:

                mode=zoom;

                startDis=distance(arg1);

                if(startDis >10f){

                    midPoint = mid(arg1);

                    cuuentMatrix.set(imageView.getImageMatrix());

                }

                break;
}

            imageView.setImageMatrix(matrix);

            return true;

        }

        private float distance(MotionEvent arg1) {

            float dx= arg1.getX(1)-arg1.getX(0);

            float dy= arg1.getY(1)-arg1.getY(0);

            return FloatMath.sqrt(dx*dx+dy*dy);

        }

        private  PointF mid(MotionEvent arg1) {

            float midx= (arg1.getX(1)+arg1.getX(0))/2;

            float midy= (arg1.getY(1)+arg1.getY(0))/2;

            return new PointF(midx,midy);

        }
}

android第二十三步拖拽与缩放