如何在onDraw（）方法中为Bitmap设置动画

Question

我有一个类ViewmapView，它扩展了View类，并将位图加载到其中。有一个手势检测器，其中位图是双击时的缩放。 BitmapView类的代码如下所示

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.Rect;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.ScaleGestureDetector.SimpleOnScaleGestureListener;
import android.view.SurfaceView;

public class BitmapView extends View {
private Bitmap mBitmap;
private GestureDetector mGestureDetector;
private ScaleGestureDetector mScaleDetector;
private IBitmapViewController mController;

/*
 * Scale factor to get bitmap to fit on screen
 */
private float mInitialScaleFactor = 1.0f;

/*
 * Zoom factor user has requested
 */
private float mZoomFactor = 1.0f;

/*
 * The total available area for drawing on
 */
private Rect mRawScreenDimensions;

/*
 * Scale/Translate transform to draw wanted section of bitmap on screen
 */
private Matrix mTransform = new Matrix();

/*
 * Displacement (in bitmap co-ordinates) to pixel to draw in centre of screen
 */
private PointF mScrollOffset = new PointF(0.0f, 0.0f);

public BitmapView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mGestureDetector = new GestureDetector(context, mGestureListener);
    mScaleDetector = new ScaleGestureDetector(context, mScaleListener);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mRawScreenDimensions = new Rect(0, 0, w, h);
    computeInitialMatrix();
}

@Override
protected void onDraw(Canvas canvas) {
    if (mBitmap != null) {
        computeTransform();
        canvas.drawBitmap(mBitmap, mTransform, null);



    }
}

/*
 * Transform to draw desired part of bitmap on screen
 */
private void computeTransform() {
    mTransform.reset();
    // move co-ords to centre of bitmap
    mTransform.postTranslate(-mBitmap.getWidth() / 2, -mBitmap.getHeight() / 2);

    // apply scroll offset
    mTransform.postTranslate(mScrollOffset.x, mScrollOffset.y);

    // scale to fit within screen
    mTransform.postScale(mInitialScaleFactor, mInitialScaleFactor);


    // apply zoom factor
    mTransform.postScale(mZoomFactor, mZoomFactor);

    // centre bitmap on screen
    mTransform.postTranslate(mRawScreenDimensions.width() / 2, mRawScreenDimensions.height() / 2);
}


@Override
public boolean onTouchEvent(MotionEvent event) {
    mGestureDetector.onTouchEvent(event);
    mScaleDetector.onTouchEvent(event);
    return true;
}

private SimpleOnGestureListener mGestureListener = new SimpleOnGestureListener() {
    @Override
    public boolean onDoubleTap(MotionEvent e) {
        ZoomInOnPoint(e);
        return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {
        if (mController != null) {
            mController.onLongPress();
        }
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        scrollView(distanceX, distanceY);
        return true;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        boolean val = false;
        if (mController != null) {
            val = mController.onFling(e1, e2, velocityX, velocityY);
        }
        return val;
    }
};

private SimpleOnScaleGestureListener mScaleListener = new SimpleOnScaleGestureListener() {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        scaleView(detector.getScaleFactor());
        return true;
    }
};

/*
 * Zoom in the specified location of the screen
 */
private void ZoomInOnPoint(MotionEvent e) {
    // zoom in
    float zoomFactor = 2.0f;
    scaleView(zoomFactor);

    // scroll so selected position is at centre of screen
    float deltaX = (e.getX() - (mRawScreenDimensions.width() / 2)) * zoomFactor;
    float deltaY = (e.getY() - (mRawScreenDimensions.height() / 2)) * zoomFactor;
    scrollView(deltaX, deltaY);
}

/*
 * @param controller the object that will handle fling and long press events
 */
public void setController(IBitmapViewController controller) {
    mController = controller;
}

/*
 * @param bitmap the image to display
 */
public void setBitmap(Bitmap bitmap) {
    if (bitmap != null) {
        mBitmap = bitmap;
        if (mRawScreenDimensions != null) {
            computeInitialMatrix();

            // draw new image
            invalidate();
        }
    }
}

private float calcAspectRatio(float width, float height) {
    return width / height;
}

/*
 * Initial matrix transforms to put whole bitmap on screen 
 */
private void computeInitialMatrix()
{
    if ((mBitmap != null) && (mRawScreenDimensions != null)) {
        float bitmapAspect = calcAspectRatio(mBitmap.getWidth(), mBitmap.getHeight());
        float screenAspect = calcAspectRatio(mRawScreenDimensions.width(), mRawScreenDimensions.height());
        float heightRatio = mRawScreenDimensions.height() / (float)mBitmap.getHeight();
        float widthRatio = mRawScreenDimensions.width() / (float)mBitmap.getWidth();
        if (bitmapAspect < screenAspect) {
            // screen is landscape (compared to bitmap) so height is
            // limiting factor
            mInitialScaleFactor = heightRatio;
        } else {
            // screen is portrait (compared to bitmap), so width is limiting
            // factor
            mInitialScaleFactor = widthRatio;
        }
        mZoomFactor = 1.0f;
        mScrollOffset = new PointF(0.0f, 0.0f);
    }
}

/*
 * Increase/Decrease the section taken from the bitmap to draw on the screen
 * 
 *  @param zoomFactor relative zoom factor.  (e.g. 2 = increase zoom in by 2) 
 */
private void scaleView(float zoomFactor) {
    mZoomFactor *= zoomFactor;
    // maximum zoom is 16, minimum zoom is 1
    mZoomFactor = Math.max(1.0f, Math.min(mZoomFactor, 16.0f));

    clampView();
}

/*
 * Move the bitmap pixel that will be centred on screen
 * 
 * @param screenX number of screen pixels to move horizontally
 * @param screenY number of screen pixels to move vertically
 */
private void scrollView(float screenX, float screenY) {
    float scale = mZoomFactor * mInitialScaleFactor * -1;
    float deltaX = screenX / scale;
    float deltaY = screenY / scale;
    mScrollOffset.offset(deltaX, deltaY);
    clampView();
}

/*
 * Prevent user from scrolling off the bitmap 
 */
private void clampView() {
    // figure out number of bitmap pixels the screen shows
    float scaleFactor = mZoomFactor * mInitialScaleFactor;
    float screenWidth = mRawScreenDimensions.width() / scaleFactor;  
    float screenHeight = mRawScreenDimensions.height() / scaleFactor;

    // Compute horizontal scroll limit, to keep bitmap within screen
    //... If projected bitmap doesn't span whole screen width, don't allow 
    //... horizontal scroll, just centre it horizontally. (i.e. scollOffset = 0) 
    //... When doesn't span screen, bitmap pixels < screen pixels 
    float maxX = Math.max(0.0f, (mBitmap.getWidth() - screenWidth) / 2);

    // Same logic for vertical scroll
    float maxY = Math.max(0.0f, (mBitmap.getHeight() - screenHeight) / 2);

    float minX = -maxX;
    float minY = -maxY;

    // clamp the scroll
    if (maxX < mScrollOffset.x) {
        mScrollOffset.x = maxX;
    }
    if (mScrollOffset.x < minX) {
        mScrollOffset.x = minX;
    }
    if (maxY < mScrollOffset.y) {
        mScrollOffset.y = maxY;
    }
    if (mScrollOffset.y < minY) {
        mScrollOffset.y = minY;
    }
    // redraw bitmap on screen
    invalidate();
}

}

我的问题是如何在onDraw（）方法中设置动画，因为这里我没有任何视图对象，我开始动画 所以我的问题是如何在Double Tap事件中使用动画加载慢动作的位图图像。

先谢谢。