android放大手势监听,使用Android的构建手势监听器和缩放侦听器来实现缩小和拖动...

我正在尝试使用Android手势侦听器和缩放侦听器来实现捏缩放和拖动。问题是当我执行缩小缩放时&＃xff0c;我想要放大的图像弹跳到特定的位置。变焦位置也不居中。

以下代码演示了我要实现的内容。任何想法为什么图像跳跃(和如何纠正它)&＃xff1f;

public class CustomView extends View {

Bitmap image;

int screenHeight;

int screenWidth;

Paint paint;

GestureDetector gestures;

ScaleGestureDetector scaleGesture;

float scale &＃61; 1.0f;

float horizontalOffset, verticalOffset;

int NORMAL &＃61; 0;

int ZOOM &＃61; 1;

int DRAG &＃61; 2;

boolean isScaling &＃61; false;

float touchX, touchY;

int mode &＃61; NORMAL;

public CustomView(Context context) {

super(context);

//initializing variables

image &＃61; BitmapFactory.decodeResource(getResources(),

R.drawable.image_name);

//This is a full screen view

screenWidth &＃61; getResources().getDisplayMetrics().widthPixels;

screenHeight &＃61; getResources().getDisplayMetrics().heightPixels;

paint &＃61; new Paint();

paint.setAntiAlias(true);

paint.setFilterBitmap(true);

paint.setDither(true);

paint.setColor(Color.WHITE);

scaleGesture &＃61; new ScaleGestureDetector(getContext(),

new ScaleListener());

gestures &＃61; new GestureDetector(getContext(), new GestureListener());

mode &＃61; NORMAL;

initialize();

}

//Best fit image display on canvas

private void initialize() {

float imgPartRatio &＃61; image.getWidth() / (float) image.getHeight();

float screenRatio &＃61; (float) screenWidth / (float) screenHeight;

if (screenRatio > imgPartRatio) {

scale &＃61; ((float) screenHeight) / (float) (image.getHeight()); // fit height

horizontalOffset &＃61; ((float) screenWidth - scale

* (float) (image.getWidth())) / 2.0f;

verticalOffset &＃61; 0;

} else {

scale &＃61; ((float) screenWidth) / (float) (image.getWidth()); // fit width

horizontalOffset &＃61; 0;

verticalOffset &＃61; ((float) screenHeight - scale

* (float) (image.getHeight())) / 2.0f;

}

invalidate();

}

&＃64;Override

protected void onDraw(Canvas canvas) {

canvas.save();

canvas.drawColor(0, Mode.CLEAR);

canvas.drawColor(Color.WHITE);

if(mode &＃61;&＃61; DRAG || mode &＃61;&＃61; NORMAL) {

//This works perfectly as expected

canvas.translate(horizontalOffset, verticalOffset);

canvas.scale(scale, scale);

canvas.drawBitmap(image, getMatrix(), paint);

}

else if (mode &＃61;&＃61; ZOOM) {

//PROBLEM AREA - when applying pinch zoom,

//the image jumps to a position abruptly

canvas.scale(scale, scale, touchX, touchY);

canvas.drawBitmap(image, getMatrix(), paint);

}

canvas.restore();

}

public class ScaleListener implements OnScaleGestureListener {

&＃64;Override

public boolean onScale(ScaleGestureDetector detector) {

float scaleFactorNew &＃61; detector.getScaleFactor();

if (detector.isInProgress()) {

touchX &＃61; detector.getFocusX();

touchY &＃61; detector.getFocusY();

scale *&＃61; scaleFactorNew;

invalidate(0, 0, screenWidth, screenHeight);

}

return true;

}

&＃64;Override

public boolean onScaleBegin(ScaleGestureDetector detector) {

isScaling &＃61; true;

mode&＃61;ZOOM;

return true;

}

&＃64;Override

public void onScaleEnd(ScaleGestureDetector detector) {

mode &＃61; NORMAL;

isScaling &＃61; false;

}

}

public class GestureListener implements GestureDetector.OnGestureListener,

GestureDetector.OnDoubleTapListener {

&＃64;Override

public boolean onDown(MotionEvent e) {

isScaling &＃61; false;

return true;

}

&＃64;Override

public boolean onScroll(MotionEvent e1, MotionEvent e2,

float distanceX, float distanceY) {

if (!isScaling) {

mode &＃61; DRAG;

isScaling &＃61; false;

horizontalOffset -&＃61; distanceX;

verticalOffset -&＃61; distanceY;

invalidate(0, 0, screenWidth, screenHeight);

} else {

mode &＃61; ZOOM;

isScaling &＃61; true;

}

return true;

}

}

&＃64;Override

public boolean onTouchEvent(MotionEvent event) {

scaleGesture.onTouchEvent(event);

gestures.onTouchEvent(event);

return true;

}

}

提前致谢。