我有一个 BitmapView 类，它扩展了 View 类，并将位图加载到其中。有手势检测器，双击即可放大位图。 BitmapView类的代码如下
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用于启动动画的视图对象 所以我的问题是如何在双击事件上以慢动作加载位图图像和动画。
提前致谢。
看这里 在此输入链接描述