安卓沿Path运动轨迹

当然是先看效果拉～中间那个圆圈，顺着圆圈的轨迹运动。

实现一个跟随Path路径运动的效果

思路

1.绘制一个路径
2.得到路径的每个点的坐标
3.用属性动画沿着路径点的坐标运动

实现

1.用

mPathMeasure = new PathMeasure(mPath,false);
mPathMeasure.getPosTan(0, mCurrentPosition, null);

得到每个点的坐标（我是根据  http://blog.csdn.net/tianjian4592/article/details/47067161 这篇博客学习的）

PathMeasure 就是把 Path “拉直”，然后给了我们一个接口(getLength)告诉我们path的总长度，我们再根据具体的长度取得相应坐标

2.属性动画，用的是ValueAniamtor

代码

package com.example.myapp.view;

import android.animation.Animator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;

/**
* Created by zyr
* DATE: 16-3-7
* Time: 上午11:52
* Email: yanru.zhang@renren-inc.com
*/
public class HeartView extends View {
private Paint mPaint;
private Path mPath;
private Path mPath2;
private Paint mPaint2;

private ValueAnimator valueAnimator;
private PathMeasure mPathMeasure;
private float[] mCurrentPosition = new float[2];
public HeartView(Context context) {
this(context, null);
}

public HeartView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public HeartView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}

private void init() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setColor(Color.RED);
mPaint.setTextSize(40);
mPaint.setStyle(Paint.Style.STROKE);

mPaint2 = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint2.setColor(Color.BLUE);
mPaint2.setTextSize(40);
mPaint2.setStyle(Paint.Style.FILL);

mPath = new Path();
mPath.addCircle(200, 200, 200, Path.Direction.CW);

mPath2 = new Path();
mPathMeasure = new PathMeasure(mPath,false);
mPathMeasure.getPosTan(0, mCurrentPosition, null);
mPath2.moveTo(mCurrentPosition[0], mCurrentPosition[1]);
setLayerType(View.LAYER_TYPE_SOFTWARE, null);//关闭硬件加速

valueAnimator = ValueAnimator.ofFloat(0,mPathMeasure.getLength());
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
float value = (Float)animation.getAnimatedValue();
mPathMeasure.getPosTan(value, mCurrentPosition, null);
mPath2.lineTo(mCurrentPosition[0],mCurrentPosition[1]);
postInvalidate();
}
});
valueAnimator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {

}

@Override
public void onAnimationEnd(Animator animation) {

}

@Override
public void onAnimationCancel(Animator animation) {

}

@Override
public void onAnimationRepeat(Animator animation) {
mPath2 = new Path();
mPathMeasure = new PathMeasure(mPath,false);
mPathMeasure.getPosTan(0, mCurrentPosition, null);
mPath2.moveTo(mCurrentPosition[0], mCurrentPosition[1]);
if(mPaint2.getColor() ==  Color.BLUE){
mPaint2.setColor(Color.YELLOW);
}else{
mPaint2.setColor(Color.BLUE);
}
}
});
valueAnimator.setDuration(5000);
valueAnimator.setRepeatCount(-1);
valueAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
valueAnimator.start();

}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(500,500);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.BLACK);

canvas.save();
canvas.translate(50, 50);
canvas.drawPath(mPath, mPaint);
canvas.drawCircle(mCurrentPosition[0], mCurrentPosition[1], 20, mPaint);
canvas.drawPath(mPath2, mPaint2);
canvas.restore();

}
}