Android图片的缩放和拖动

  
import android.app.Activity;  
import android.content.Context;  
import android.content.Intent;  
import android.graphics.Bitmap;  
import android.graphics.BitmapFactory;  
import android.graphics.Matrix;  
import android.graphics.PointF;  
import android.graphics.RectF;  
import android.os.Bundle;  
import android.util.DisplayMetrics;  
import android.util.FloatMath;  
import android.view.MotionEvent;  
import android.view.View;  
import android.view.View.OnTouchListener;  
import android.widget.ImageView;  
import android.widget.Toast;  
  
public class PhotoViewer extends Activity implements OnTouchListener {  
  
    private static final String TAG = "PhotoViewer";  
    public static final int RESULT_CODE_NOFOUND = 200;  
  
    Matrix matrix = new Matrix();  
    Matrix savedMatrix = new Matrix();  
    DisplayMetrics dm;  
    ImageView imgView;  
    Bitmap bitmap;  
  
    /** 最小缩放比例 */  
    float minScaleR = 0.5f;// 1.0f;  
    /** 最大缩放比例 */  
    static final float MAX_SCALE = 100f;// 10f;  
  
    /** 初始状态 */  
    static final int NONE = 0;  
    /** 拖动 */  
    static final int DRAG = 1;  
    /** 缩放 */  
    static final int ZOOM = 2;  
  
    /** 当前模式 */  
    int mode = NONE;  
  
    PointF prev = new PointF();  
    PointF mid = new PointF();  
    float dist = 1f;  
  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        // 获取图片资源  
        bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.tchip);  
  
        setContentView(R.layout.activity_main);  
  
        imgView = (ImageView) findViewById(R.id.imageView1);// 获取控件  
        imgView.setImageBitmap(bitmap);// 填充控件  
        imgView.setOnTouchListener(this);// 设置触屏监听  
        dm = new DisplayMetrics();  
        getWindowManager().getDefaultDisplay().getMetrics(dm);// 获取分辨率  
        // minZoom();  
        center();  
        imgView.setImageMatrix(matrix);  
  
    }  
  
    // public void SureOnClick(View v)  
    // {  
    //  
    // }  
  
    /** 
     * 触屏监听 
     */  
    public boolean onTouch(View v,MotionEvent event) {  
  
        switch (event.getAction() & MotionEvent.ACTION_MASK) {  
        // 主点按下  
        case MotionEvent.ACTION_DOWN:  
            savedMatrix.set(matrix);  
            prev.set(event.getX(),event.getY());  
            mode = DRAG;  
            break;  
        // 副点按下  
        case MotionEvent.ACTION_POINTER_DOWN:  
            dist = spacing(event);  
            // 如果连续两点距离大于10，则判定为多点模式  
            if (spacing(event) > 10f) {  
                savedMatrix.set(matrix);  
                midPoint(mid,event);  
                mode = ZOOM;  
            }  
            break;  
        case MotionEvent.ACTION_UP:  
        case MotionEvent.ACTION_POINTER_UP:  
            mode = NONE;  
            // savedMatrix.set(matrix);  
            break;  
        case MotionEvent.ACTION_MOVE:  
            if (mode == DRAG) {  
                matrix.set(savedMatrix);  
                matrix.postTranslate(event.getX() - prev.x,event.getY()  
                        - prev.y);  
            } else if (mode == ZOOM) {  
                float newDist = spacing(event);  
                if (newDist > 10f) {  
                    matrix.set(savedMatrix);  
                    float tScale = newDist / dist;  
                    matrix.postScale(tScale,tScale,mid.x,mid.y);  
                }  
            }  
            break;  
        }  
        imgView.setImageMatrix(matrix);  
        CheckView();  
        return true;  
    }  
  
    /** 
     * 限制最大最小缩放比例，自动居中 
     */  
    private void CheckView() {  
        float p[] = new float[9];  
        matrix.getValues(p);  
        setTitle("缩放级别：" + p[0] + "%");  
        if (mode == ZOOM) {  
            if (p[0] < minScaleR) {  
                // Log.d("","当前缩放级别:"+p[0]+",最小缩放级别:"+minScaleR);  
                setTitle("缩放级别：" + p[0] + "%");  
                matrix.setScale(minScaleR,minScaleR);  
            }  
            if (p[0] > MAX_SCALE) {  
                // Log.d("",最大缩放级别:"+MAX_SCALE);  
                matrix.set(savedMatrix);  
            }  
        }  
        center();  
    }  
  
    /** 
     * 最小缩放比例，最大为100% 
     */  
    private void minZoom() {  
        minScaleR = Math.min(  
                (float) dm.widthPixels / (float) bitmap.getWidth(),(float) dm.heightPixels / (float) bitmap.getHeight());  
        if (minScaleR < 1.0) {  
            matrix.postScale(minScaleR,minScaleR);  
        }  
    }  
  
    private void center() {  
        center(true,true);  
    }  
  
    /** 
     * 横向、纵向居中 
     */  
    protected void center(boolean horizontal,boolean vertical) {  
  
        Matrix m = new Matrix();  
        m.set(matrix);  
        RectF rect = new RectF(0,bitmap.getWidth(),bitmap.getHeight());  
        m.mapRect(rect);  
  
        float height = rect.height();  
        float width = rect.width();  
  
        float deltaX = 0,deltaY = 0;  
  
        if (vertical) {  
            // 图片小于屏幕大小，则居中显示。大于屏幕，上方留空则往上移，下方留空则往下移  
            int screenHeight = dm.heightPixels;  
  
            if (height < screenHeight) {  
                //deltaY = (screenHeight - height) / 2 - rect.top;  
            } else  
  
            if (rect.top > 0) {  
                deltaY = -rect.top;  
            } else if (rect.bottom < screenHeight) {  
                deltaY = imgView.getHeight() - rect.bottom;  
            }  
        }  
  
        if (horizontal) {  
            int screenWidth = dm.widthPixels;  
            if (width < screenWidth) {  
                deltaX = (screenWidth - width) / 2 - rect.left;  
            } else if (rect.left > 0) {  
                deltaX = -rect.left;  
            } else if (rect.right < screenWidth) {  
                deltaX = screenWidth - rect.right;  
            }  
        }  
        matrix.postTranslate(deltaX,deltaY);  
    }  
  
    /** 
     * 两点的距离 
     */  
    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);  
    }  
  
    /** 
     * 两点的中点 
     */  
    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);  
    }  
  
    public static class ImageViewOnClickListener implements  
            View.OnClickListener {  
        private Context context;  
        private String img_path;  
  
        public ImageViewOnClickListener(Context context,String img_path) {  
            this.img_path = img_path;  
            this.context = context;  
        }  
  
        @Override  
        public void onClick(View v) {  
            if (img_path != null) {  
                // Toast.makeText(context,"TChip",Toast.LENGTH_SHORT).show();  
                // Intent intent = new Intent(context,PhotoViewer.class);  
                // intent.putExtra("PhotoPath",img_path);  
                // context.startActivity(intent);  
            }  
  
        }  
    }  
}