android 多点触摸放大缩小图片

package org.example.touch;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;

import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;

public class Touch extends Activity implements OnTouchListener, OnClickListener {
private static final String TAG = "Touch" ;

// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
PointF start = new PointF();
PointF mid = new PointF();
float oldDist;
private ImageView view;
private Button zoomIn, zoomOut;

//button zoom
private float scaleWidth = 1;
private float scaleHeight = 1;
private Bitmap bmp, zoomedBMP;
private int zoom_level = 0;
private static final double ZOOM_IN_SCALE = 1.25;//放大系数
private static final double ZOOM_OUT_SCALE = 0.8;//缩小系数

// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//放大按钮
zoomIn = (Button) findViewById(R.id.zoom_in);
//缩小按钮
zoomOut = (Button) findViewById(R.id.zoom_out);
zoomIn.setOnClickListener(this);
zoomOut.setOnClickListener(this);
view = (ImageView) findViewById(R.id.imageView);
view.setOnTouchListener(this);
//取得drawable中图片，放大，缩小，多点触摸的作用对象
bmp = BitmapFactory.decodeResource(Touch.this.getResources(), R.drawable.butterfly);

}

public boolean onTouch(View v, MotionEvent event) {
// Handle touch events here...
ImageView view = (ImageView) v;

// Handle touch events here...
switch (event.getAction() & MotionEvent.ACTION_MASK) {
//设置拖拉模式
case MotionEvent.ACTION_DOWN:
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
Log.d(TAG, "mode=DRAG" );
mode = DRAG;
break;

case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
Log.d(TAG, "mode=NONE" );
break;
//设置多点触摸模式
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
Log.d(TAG, "oldDist=" + oldDist);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
Log.d(TAG, "mode=ZOOM" );
}
break;
//若为DRAG模式，则点击移动图片
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
matrix.set(savedMatrix);
// 设置位移
matrix.postTranslate(event.getX() - start.x,
event.getX() - start.x);
}
//若为ZOOM模式，则多点触摸缩放
else if (mode == ZOOM) {
float newDist = spacing(event);
Log.d(TAG, "newDist=" + newDist);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
//设置缩放比例和图片中点位置
matrix.postScale(scale, scale, mid.x, mid.y);
}
}
break;
}

// Perform the transformation
view.setImageMatrix(matrix);

return true; // indicate event was handled
}
//计算移动距离
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);
}
//计算中点位置
private void midPoint(PointF point, MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}

//放大，缩小按钮点击事件
@Override
public void onClick(View v) {
if(v == zoomIn){
enlarge();
}else if (v == zoomOut) {
small();
}

}

//按钮点击缩小函数
private void small() {

int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();

scaleWidth = (float) (scaleWidth * ZOOM_OUT_SCALE);
scaleHeight = (float) (scaleHeight * ZOOM_OUT_SCALE);

Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
zoomedBMP = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix,
true);
view.setImageBitmap(zoomedBMP);
}

//按钮点击放大函数
private void enlarge() {
try {
int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();

scaleWidth = (float) (scaleWidth * ZOOM_IN_SCALE);
scaleHeight = (float) (scaleHeight * ZOOM_IN_SCALE);

Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
zoomedBMP = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix,
true);
view.setImageBitmap(zoomedBMP);
} catch (Exception e) {
//can't zoom because of memory issue, just ignore, no big deal
}

}
}

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/fhy_2008/archive/2011/02/23/6202476.aspx

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