Android沿路径移动对象

Question

我创建了一个圆形路径,并在屏幕上显示它们如下:

public void onDraw(Canvas canvas){

        Path sPath = new Path();
        sPath.moveTo(100, 100);
        sPath.lineTo(300, 100);
        sPath.lineTo(300, 300);
        sPath.lineTo(100,300);
        sPath.lineTo(100,100);
        sPath.close();

        Paint ballPaint = new Paint();
        ballPaint.setColor(Color.GREEN);
        Paint pathPaint = new Paint();
        pathPaint.setColor(Color.BLUE);

        canvas.drawPath(sPath, ballPaint);
        canvas.drawCircle(100,100,20,pathPaint);
    }

我想让圆圈沿着路径移动,我该怎么做？

Answer 1

是的,可以沿路径移动图像.我将提供简单的解决方案来展示原理.以下代码将沿路径设置圆圈的动画.

int iCurStep = 0;// current animation step

@Override
protected void onDraw(Canvas canvas) {
    PathMeasure pm = new PathMeasure(sPath, false);
    float fSegmentLen = pm.getLength() / 20;//we'll get 20 points from path to animate the circle
    float afP[] = {0f, 0f};

    if (iCurStep <= 20) {
        pm.getPosTan(fSegmentLen * iCurStep, afP, null);
        canvas.drawCircle(afP[0],afP[1],20,pathPaint);
        iCurStep++;
        invalidate();
    } else {
        iCurStep = 0;
    };
};

Answer 2

以下是我使用的动画师:

目的:沿路径"路径"移动视图"视图"

V21 +:

ValueAnimator pathAnimator = ObjectAnimator.ofFloat(view, "x", "y", path)

V11 +:

ValueAnimator pathAnimator = ValueAnimator.ofFloat(0.0f, 1.0f);

pathAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
float[] point = new float[2];

@Override
    public void onAnimationUpdate(ValueAnimator animation) {
        float val = animation.getAnimatedFraction();
        PathMeasure pathMeasure = new PathMeasure(path, true);
        pathMeasure.getPosTan(pathMeasure.getLength() * val, point, null);
        view.setX(point[0]);
        view.setY(point[1]);
    }
});

Answer 3

v21 +:这会在路径上创建一个二次贝塞尔曲线,并沿着它动画myView.

final Path path = new Path();
path.quadTo(controlX, controlY, finalX, finalY);
ObjectAnimator.ofFloat(myView, View.X, View.Y, path).start();

Answer 4

您需要将圆圈每帧朝下一个路点移动一点，并在到达那里后进行检测，然后开始朝下一个路点移动。据我所知，没有内置系统。