android 如何利用手势放大和缩小一个图片？



   

                                                            

   

        
        
        
        

         
         
         
         
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  
         
         
         
         
        }  
         
         
         
         
}  
         
         
         
         
}