Android 可缩放无尽环

Question

我正在尝试创建一个无尽的可缩放环，像这样 -

每当用户进行缩放时，就会在中心创建新的小圆圈，并且外圈会变大。我正在使用pinch zoom in relative layout创建以下效果，但无法正确实现。我为此创建了一个存储库，如果您能提供帮助，请告诉我 https://github.com/rohankandwal/zoomable-growing-circles

更新:- 更改了提到的 stackoverflow 答案上的 dispatchDraw 方法 -

protected void dispatchDraw(Canvas canvas) {
    Paint myPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    myPaint.setStyle(Paint.Style.STROKE);
    int strokeWidth = 4;  // or whatever
    myPaint.setStrokeWidth(strokeWidth);
    myPaint.setColor(0xffff0000);   //color.RED
    float radius = (float) (0.5 * (width + height) * 2.5);
    for (int i = 1; i <= 51; i=i+10) {
      canvas.drawCircle(canvas.getWidth() / 2, canvas.getWidth() / 2, (radius) + mScaleFactor + i,
        myPaint);
    }
    canvas.save();
    super.dispatchDraw(canvas);
    canvas.restore();
  }

此代码允许圆圈增长 -

没有捏缩放的原始图像

捏合缩放时的图像

如您所见，缩放正在工作，但不知道缩放到一定级别时如何创建新圆圈。

Answer 1

如果我正确理解你想要什么，你的代码就没有太多需要改变的

在OnPinchListener中:

public boolean onScale(ScaleGestureDetector detector) {
    // 1 : no zoom
    final float zoomLevel = detector.getCurrentSpan() / startingSpan;
    zoomableRadarLayout.scale(zoomLevel, startFocusX, startFocusY);
    return true;
}

和在ZoomableRadarLayout中:

// current pinch
private float mScaleFactor = 1;
// previous pinches
private float mAccumulatedScaleFactor = 1;


protected void dispatchDraw(Canvas canvas) {
    ...

    float radius = (float) (0.5 * (width + height) * 2.5);

    // space between circles
    int step = 10;
    // radius of the outer circle
    int outerRadius = (int) (radius * mScaleFactor * mAccumulatedScaleFactor);
    // radius of the inner circle
    int innerRadius = 0;

    for (int i = outerRadius; i >= innerRadius; i = i - step) {
        canvas.drawCircle(canvas.getWidth() / 2, canvas.getWidth() / 2, i, myPaint);
    }

    ...

}

public void restore() {
    // add the ending pinch to the previous ones
    mAccumulatedScaleFactor = mAccumulatedScaleFactor * mScaleFactor;
    mScaleFactor = 1;
    this.invalidate();
}

顺便说一句，如果可能的话，建议在绘图时避免创建诸如 Paint 之类的绘图对象。例如将创建放入某个 init 方法中。