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我有一个SVG，我想要在Android中使用手势进行缩放和平移。它有效，但对我的口味来说不够顺利。那么，我该如何改进这个课程，以便能够在所有缩放级别下工作的平滑平移，并保持在您的手指之下，使用捏手势缩放从手势区域（AKA焦点）进行缩放，并且作为奖励双击应该会导致抓取图像回到1.0？我正在使用这个SVG library。一个可以接受的答案应该满足这些功能要求，而不是突然跳出来，坚持到GestureDetectors，除非可以做出一个他们不会工作的情况。Android画布 - 缩放和翻译
public class MapView extends ViewGroup {
private static final float MINIMUM_SCALE_FACTOR = 1.0f;
private static final float MAXIMUM_SCALE_FACTOR = 10.0f;
private Picture mPicture;
private Paint mPaint;
private ScaleGestureDetector mScaleDetector;
private GestureDetector mMoveDetector;
private float mScaleFactor;
private float mScaleFocusX;
private float mScaleFocusY;
private float mFocusX = 0.0f;
private float mFocusY = 0.0f;
private float mImageHeight;
private float mImageWidth;
private int mViewHeight;
private int mViewWidth;
private RectF mDrawingRect;
public MapView(Context context) {
super(context);
init(context);
}
public MapView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public MapView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
public void init(Context context) {
Log.d(getClass().getCanonicalName(), "Initialized.");
this.setBackgroundColor(Color.WHITE);
this.mPaint = new Paint();
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(Color.BLUE);
mPaint.setStrokeWidth(2);
mPaint.setAntiAlias(true);
this.mScaleFactor = MINIMUM_SCALE_FACTOR;
// Setup Gesture Detectors
this.mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
this.mMoveDetector = new GestureDetector(context, new MoveListener());
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
Log.d(getClass().getCanonicalName(), "onLayout");
this.mDrawingRect = getDrawingSquare();
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
this.mViewWidth = w;
this.mViewHeight = h;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Log.d(getClass().getCanonicalName(), "onDraw()");
canvas.save();
canvas.scale(mScaleFactor, mScaleFactor, mScaleFocusX, mScaleFocusY);
canvas.translate(mFocusX, mFocusY);
canvas.drawRect((int) mDrawingRect.left, (int) mDrawingRect.top, (int) mDrawingRect.right, (int) mDrawingRect.bottom, mPaint);
canvas.drawPicture(mPicture, mDrawingRect);
canvas.restore();
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
mScaleDetector.onTouchEvent(ev);
mMoveDetector.onTouchEvent(ev);
return true;
}
public RectF getDrawingSquare() {
float width = getWidth();
float height = getHeight();
Log.d(getClass().getCanonicalName(), "Picture width " + width + " - height " + height);
float side = Math.min(width, height);
return new RectF(0, 0, side, side);
}
public void setSVG(SVG svg) {
Log.d(getClass().getCanonicalName(), "SVG to Picture.");
this.mPicture = svg.getPicture();
this.mImageHeight = mPicture.getHeight();
this.mImageWidth = mPicture.getWidth();
invalidate();
}
private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor(); // scale change since previous event
mScaleFocusX = detector.getFocusX();
mScaleFocusY = detector.getFocusY();
// Don't let the object get too small or too large.
mScaleFactor = Math.max(MINIMUM_SCALE_FACTOR, Math.min(mScaleFactor, MAXIMUM_SCALE_FACTOR));
invalidate();
return true;
}
}
private class MoveListener extends GestureDetector.SimpleOnGestureListener {
// @Override
// public boolean onDown(MotionEvent e) {
// return true;
// }
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
scrollBy((int)distanceX, (int)distanceY);
// mFocusX += distanceX;
// mFocusY += distanceY;
// return true;
return true;
}
}
}