前言

我们平时在开发的时候，发起网络请求前，会需要显示一个Loading，一般的做法都是在xml布局上添加好Loading，然后在Activity中,setVisibility来控制Loading的显示和隐藏，这样使用起来就很不方便，因为每一个xml都得引入一个Loading布局。

而LoadingBar就更好的解决了这个问题

最近设计师在外国的一个网站上挑了一个Loading的效果图，尝试实现之后，虽然和原图有点不太一样，但是效果还是不错的。难点就是粘连效果的实现，贝塞尔曲线的点点们简直要把我折磨死了。

先上效果图：

实例代码

然后是源码，就是一个简单VIew，可以直接放在xml中使用。

package top.greendami.greendami;import 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)); }}

“精心”画了一张图，对代码做了说明。

在代码中使用

<?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>

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。