怎么在Android应用中添加一个圆形进度条效果

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<resources>

 <declare-styleable name="CustomProgressBar">
  <!-- 圆形进度条进度显示的颜色 -->
  <attr name="roundProgressColor" format="color"></attr>
  <!-- 外圈圆的颜色 -->
  <attr name="roundColor" format="color"></attr>
  <!-- 圆的总宽度 -->
  <attr name="roundWidth" format="dimension"></attr>
  <!-- 字体显示的大小 -->
  <attr name="textSize" format="dimension"></attr>
  <!-- 字体显示的颜色　-->
  <attr name="textColor" format="color"></attr>
  <!-- 进度的最大值 -->
  <attr name="max" format="integer"></attr>
  <!-- 是否显示文字 -->
  <attr name="textShow" format="boolean"></attr>
 </declare-styleable>

</resources>

package xxx.xxx.xxx;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Typeface;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

import test.dn.com.dn_test.R;

/**
 * Created by Administrator on 2017/5/16 0016.
 */

public class CircleProgressBar extends View {

 private int max; //最大值
 private int roundColor; //圆形进度条的颜色
 private int roundProgressColor;//圆形进度条进度的颜色
 private int textColor;  //字体的颜色
 private float textSize;  //字体的大小
 private float roundWidth; //圆的宽度
 private boolean textShow; //是否显示圆
 private int progress; //当前进度
 private Paint mPaint; //画笔
 public static final int STROKE = 0;
 public static final int FILL = 1;

 public CircleProgressBar(Context context, @Nullable AttributeSet attrs) {
  super(context, attrs);
  //初始化一只笔
  mPaint = new Paint();
  //获取xml当中设置的属性，如果没有设置，则设置一个默认值
  TypedArray typedArray = context.obtainStyledAttributes(attrs , R.styleable.CustomProgressBar);
  max = typedArray.getInteger(R.styleable.CustomProgressBar_max , 100);
  roundColor = typedArray.getColor(R.styleable.CustomProgressBar_roundColor, Color.RED);
  roundProgressColor = typedArray.getColor(R.styleable.CustomProgressBar_roundProgressColor , Color.BLUE);
  textColor = typedArray.getColor(R.styleable.CustomProgressBar_textColor , Color.GREEN);
  textSize = typedArray.getDimension(R.styleable.CustomProgressBar_textSize , 55);
  roundWidth = typedArray.getDimension(R.styleable.CustomProgressBar_roundWidth , 10);
  textShow = typedArray.getBoolean(R.styleable.CustomProgressBar_textShow , true);

 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //画背景圆环
  int center = getWidth() / 2;
  //设置半径
  float radius = center - roundWidth / 2;
  //设置圆圈的颜色
  mPaint.setColor(roundColor);
  mPaint.setStyle(Paint.Style.STROKE);
  mPaint.setStrokeWidth(roundWidth);//圆环的宽度
  mPaint.setAntiAlias(true);//设置抗锯齿

  //画外圈
  canvas.drawCircle(center , center ,radius , mPaint);

  //画进度百分比
  mPaint.setColor(textColor);
  mPaint.setStrokeWidth(0);
  //设置字体大小
  mPaint.setTextSize(textSize);
  mPaint.setTypeface(Typeface.DEFAULT);
  //设置笔帽
  mPaint.setStrokeCap(Paint.Cap.ROUND);
  //设置文字的摆放方式为居中
  mPaint.setTextAlign(Paint.Align.CENTER);
  //获取当前进度的值
  int percent = (int) (progress / (float)max * 100);
  String strPercent = percent + "%";
  //获取画笔的文字属性，总共有bottom , top , leading , ascent , descent 这个以后会详细讲解
  Paint.FontMetricsInt fm = mPaint.getFontMetricsInt();
  if(percent != 0){
   canvas.drawText(strPercent , getWidth() / 2 ,
     getWidth() / 2 + (fm.bottom - fm.top) / 2 - fm.bottom, mPaint);
  }
  //画圆弧
  RectF oval = new RectF(center - radius , center - radius ,center + radius , center + radius);
  mPaint.setColor(roundProgressColor);
  mPaint.setStrokeWidth(roundWidth);
  mPaint.setStyle(Paint.Style.STROKE);
  //设置笔帽
  mPaint.setStrokeCap(Paint.Cap.ROUND);
  //话进度
  canvas.drawArc(oval , 0 , 360 * progress / max , false , mPaint);
 }

 public void setProgress(int progress){
  if(progress < 0){
   throw new IllegalArgumentException("进度progress不能小于0");
  }
  if(progress > max){
   progress = max;
  }
  if(progress <= max){
   this.progress = progress;
   postInvalidate();
  }

 }
}

 <xxx.xxx.CircleProgressBar
  android:id="@+id/progressbar"
  android:layout_width="100dp"
  android:layout_height="100dp"
  app:roundProgressColor="#ff00ff"
  app:textColor="#666666"
  app:textSize="20dp"
  app:roundWidth="15dp"
  />

mProgressBar = (CircleProgressBar) findViewById(R.id.progressbar);
  mProgressBar.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v) {
    //模拟http请求
    new Thread(new Runnable() {
     @Override
     public void run() {
      while (progress <= 100){
       progress += 2;
       mProgressBar.setProgress(progress);
       //模拟网络请求，每隔100毫秒增加一个进度
       SystemClock.sleep(100);
      }
     }
    }).start();
   }
  });