Android实现一个带粘连效果的LoadingBar

package top.greendami.greendami;import android/209837.html">android/243960.html">android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Path;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.view.View;/** * Created by GreendaMi on 2017/3/17. */public class PPView extends View { String TAG = "PPView"; //动画开关 boolean isLoading = true; Context mContext; private int mWidth = 100; private int mheight = 100; public int mColor; public Paint mPaint = new Paint(); float time = 0; //小球与中间打球的最远距离 float distance = 100; public PPView(Context context) {  super(context);  mContext = context; } public PPView(Context context, @Nullable AttributeSet attrs) {  super(context, attrs);  mContext = context;  mColor = context.getResources().getColor(R.color.colorPrimary);  init(); } private void init() {  mPaint.setAntiAlias(true);  mPaint.setColor(mColor); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  super.onMeasure(widthMeasureSpec, heightMeasureSpec);  int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);  int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);  //宽度至少是高度的4倍  if (widthSpecSize < 4 * heightSpecSize) {   widthSpecSize = 4 * heightSpecSize;  }  mWidth = widthSpecSize;  mheight = heightSpecSize;  distance = 1.2f * mheight;  setMeasuredDimension(widthSpecSize, heightSpecSize); } @Override protected void onDraw(Canvas canvas) {  super.onDraw(canvas);  if (isLoading) {   //大圆半径   float bigR = mheight * 0.32f + mheight * 0.03f * Math.abs((float) Math.sin(Math.toRadians(time)));   float smallR = mheight * 0.22f + mheight * 0.03f * Math.abs((float) Math.cos(Math.toRadians(time)));   float bigx = (getWidth()) / 2;   //画中间大圆   canvas.drawCircle(bigx, mheight / 2, bigR, mPaint);   float smalx = getSmallCenterX();   //画小圆   canvas.drawCircle(smalx, mheight / 2, smallR, mPaint);   //画链接   //小球在右侧   if (smalx > bigx) {    Path path = new Path();    //上面的贝塞尔曲线的第一个点，在大圆身上    float x1 = bigx + bigR * (float) Math.cos(Math.toRadians(time));    float y1 = mheight / 2 - bigR * (float) Math.sin(Math.toRadians(time));    if (y1 > mheight / 2 - smallR) {     y1 = mheight / 2 - smallR;     x1 = bigx + (float) (Math.sqrt(bigR * bigR - smallR * smallR));    }    //上面的贝塞尔曲线的第三个点，在小圆身上    float x2 = smalx - smallR * (float) Math.cos(Math.toRadians(time));    float y2 = mheight / 2 - smallR * (float) Math.sin(Math.toRadians(time));    if (y2 > mheight / 2 - smallR * 0.8) {     y2 = mheight / 2 - smallR * 0.8f;     x2 = smalx - smallR * (float) (Math.sqrt(1-0.64f));    }    //下面的贝塞尔曲线的第三个点，在小圆身上    float x3 = smalx - smallR * (float) Math.cos(Math.toRadians(time));    float y3 = mheight / 2 + smallR * (float) Math.sin(Math.toRadians(time));    if (y3 < mheight / 2 + smallR * 0.8) {     y3 = mheight / 2 + smallR * 0.8f;     x3 = smalx - smallR * (float) (Math.sqrt(1-0.64f));    }    //下面的贝塞尔曲线的第一个点，在大圆身上    float x4 = bigx + bigR * (float) Math.cos(Math.toRadians(time));    float y4 = mheight / 2 + bigR * (float) Math.sin(Math.toRadians(time));    if (y4 < mheight / 2 + smallR) {     y4 = mheight / 2 + smallR;     x4 = bigx + (float) (Math.sqrt(bigR * bigR - smallR * smallR));    }    path.moveTo(x1, y1);    path.quadTo((bigx + smalx) / 2, mheight / 2, x2, y2);    // 绘制贝赛尔曲线（Path）    path.lineTo(x3, y3);    path.quadTo((bigx + smalx) / 2, mheight / 2, x4, y4);    canvas.drawPath(path, mPaint);   }   //小球在左侧   if (smalx < bigx) {    Path path = new Path();    float x1 = bigx + bigR * (float) Math.cos(Math.toRadians(time));    float y1 = mheight / 2 - bigR * (float) Math.sin(Math.toRadians(time));    if (y1 > mheight / 2 - smallR) {     y1 = mheight / 2 - smallR;     x1 = bigx - (float) (Math.sqrt(bigR * bigR - smallR * smallR));    }    float x2 = smalx - smallR * (float) Math.cos(Math.toRadians(time));    float y2 = mheight / 2 - smallR * (float) Math.sin(Math.toRadians(time));    if (y2 > mheight / 2 - smallR * 0.8) {     y2 = mheight / 2 - smallR * 0.8f;     x2 = smalx + smallR * (float) (Math.sqrt(1-0.64f));    }    float x3 = smalx - smallR * (float) Math.cos(Math.toRadians(time));    float y3 = mheight / 2 + smallR * (float) Math.sin(Math.toRadians(time));    if (y3 < mheight / 2 + smallR * 0.8) {     y3 = mheight / 2 + smallR * 0.8f;     x3 = smalx + smallR * (float) (Math.sqrt(1-0.64f));    }    float x4 = bigx + bigR * (float) Math.cos(Math.toRadians(time));    float y4 = mheight / 2 + bigR * (float) Math.sin(Math.toRadians(time));    if (y4 < mheight / 2 + smallR) {     y4 = mheight / 2 + smallR;     x4 = bigx - (float) (Math.sqrt(bigR * bigR - smallR * smallR));    }    path.moveTo(x1, y1);    path.quadTo((bigx + smalx) / 2, mheight / 2, x2, y2);    // 绘制贝赛尔曲线（Path）    path.lineTo(x3, y3);    path.quadTo((bigx + smalx) / 2, mheight / 2, x4, y4);    canvas.drawPath(path, mPaint);   }   postInvalidate();  } } //计算小球的X坐标 private float getSmallCenterX() {  //此处控制速度  time = time + 2.5f;  return mWidth / 2 + distance * (float) Math.cos(Math.toRadians(time)); }}

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/white" tools:context="top.greendami.greendami.MainActivity"> <top.greendami.greendami.PPView  android:layout_centerInParent="true"  android:layout_width="400dp"  android:layout_height="80dp" /></RelativeLayout>