Android 多点触摸 multi-touch

多点触摸multi-touch

最近研究多点触摸，做了个demo。Demo中实现多点触摸缩放和使用按钮点击放大和缩小。注意2.0以上才支持多点触摸。

程序代码如下：

 

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 
        } 
       
} 
}