Viewpager中使得ImageView放大缩小

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;

public class TouchImageView extends ImageView {

Matrix matrix;static final int NONE = 0;static final int DRAG = 1;static final int ZOOM = 2;int mode = NONE;PointF last = new PointF();PointF start = new PointF();float minScale = 1f;float maxScale = 3f;float[] m;int viewWidth, viewHeight;static final int CLICK = 3;float saveScale = 1f;protected float origWidth, origHeight;int oldMeasuredWidth, oldMeasuredHeight;ScaleGestureDetector mScaleDetector;Context context;public TouchImageView(Context context) {    super(context);    sharedConstructing(context);}public TouchImageView(Context context, AttributeSet attrs) {    super(context, attrs);    sharedConstructing(context);}private void sharedConstructing(Context context) {    super.setClickable(true);    this.context = context;    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());    matrix = new Matrix();    m = new float[9];    setImageMatrix(matrix);    setScaleType(ScaleType.MATRIX);    setOnTouchListener(new OnTouchListener() {        @Override        public boolean onTouch(View v, MotionEvent event) {            mScaleDetector.onTouchEvent(event);            PointF curr = new PointF(event.getX(), event.getY());            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    last.set(curr);                    start.set(last);                    mode = DRAG;                    break;                case MotionEvent.ACTION_MOVE:                    if (mode == DRAG) {                        float deltaX = curr.x - last.x;                        float deltaY = curr.y - last.y;                        float fixTransX = getFixDragTrans(deltaX, viewWidth, origWidth * saveScale);                        float fixTransY = getFixDragTrans(deltaY, viewHeight, origHeight * saveScale);                        matrix.postTranslate(fixTransX, fixTransY);                        fixTrans();                        last.set(curr.x, curr.y);                    }                    break;                case MotionEvent.ACTION_UP:                    mode = NONE;                    int xDiff = (int) Math.abs(curr.x - start.x);                    int yDiff = (int) Math.abs(curr.y - start.y);                    if (xDiff < CLICK && yDiff < CLICK)                        performClick();                    break;                case MotionEvent.ACTION_POINTER_UP:                    mode = NONE;                    break;            }            setImageMatrix(matrix);            invalidate();            return true;        }    });}public void setMaxZoom(float x) {    maxScale = x;}private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {    @Override    public boolean onScaleBegin(ScaleGestureDetector detector) {        mode = ZOOM;        return true;    }    @Override    public boolean onScale(ScaleGestureDetector detector) {        float mScaleFactor = detector.getScaleFactor();        float origScale = saveScale;        saveScale *= mScaleFactor;        if (saveScale > maxScale) {            saveScale = maxScale;            mScaleFactor = maxScale / origScale;        } else if (saveScale < minScale) {            saveScale = minScale;            mScaleFactor = minScale / origScale;        }        if (origWidth * saveScale <= viewWidth || origHeight * saveScale <= viewHeight)            matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2, viewHeight / 2);        else            matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY());        fixTrans();        return true;    }}void fixTrans() {    matrix.getValues(m);    float transX = m[Matrix.MTRANS_X];    float transY = m[Matrix.MTRANS_Y];    float fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale);    float fixTransY = getFixTrans(transY, viewHeight, origHeight * saveScale);    if (fixTransX != 0 || fixTransY != 0)        matrix.postTranslate(fixTransX, fixTransY);}float getFixTrans(float trans, float viewSize, float contentSize) {    float minTrans, maxTrans;    if (contentSize <= viewSize) {        minTrans = 0;        maxTrans = viewSize - contentSize;    } else {        minTrans = viewSize - contentSize;        maxTrans = 0;    }    if (trans < minTrans)        return -trans + minTrans;    if (trans > maxTrans)        return -trans + maxTrans;    return 0;}float getFixDragTrans(float delta, float viewSize, float contentSize) {    if (contentSize <= viewSize) {        return 0;    }    return delta;}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    viewWidth = MeasureSpec.getSize(widthMeasureSpec);    viewHeight = MeasureSpec.getSize(heightMeasureSpec);    if (oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight            || viewWidth == 0 || viewHeight == 0)        return;    oldMeasuredHeight = viewHeight;    oldMeasuredWidth = viewWidth;    if (saveScale == 1) {        //Fit to screen.        float scale;        Drawable drawable = getDrawable();        if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0)            return;        int bmWidth = drawable.getIntrinsicWidth();        int bmHeight = drawable.getIntrinsicHeight();        Log.d("bmSize", "bmWidth: " + bmWidth + " bmHeight : " + bmHeight);        float scaleX = (float) viewWidth / (float) bmWidth;        float scaleY = (float) viewHeight / (float) bmHeight;        scale = Math.min(scaleX, scaleY);        matrix.setScale(scale, scale);        // Center the image        float redundantYSpace = (float) viewHeight - (scale * (float) bmHeight);        float redundantXSpace = (float) viewWidth - (scale * (float) bmWidth);        redundantYSpace /= (float) 2;        redundantXSpace /= (float) 2;        matrix.postTranslate(redundantXSpace, redundantYSpace);        origWidth = viewWidth - 2 * redundantXSpace;        origHeight = viewHeight - 2 * redundantYSpace;        setImageMatrix(matrix);    }    fixTrans();}

}