mCirclePaint = new Paint();
mCirclePaint.setAntiAlias(true);
mCirclePaint.setStrokeWidth(CIRCLE_LINE_WIDTH);
mCirclePaint.setStyle(Paint.Style.STROKE);
mCirclePaint.setColor(ContextCompat.getColor(context, R.color.circle_color));

mCircleInnerPaint = new Paint();
mCircleInnerPaint.setAntiAlias(true);
mCircleInnerPaint.setStyle(Paint.Style.FILL);
mCircleInnerPaint.setColor(ContextCompat.getColor(context, R.color.circle_inner_color));

mTextPaint = new TextPaint();
mTextPaint.setAntiAlias(true);
mTextPaint.setStyle(Paint.Style.FILL);
mTextPaint.setTypeface(Typeface.DEFAULT_BOLD);
mTextPaint.setColor(ContextCompat.getColor(context, R.color.circle_text_color));
mTextPaint.setTextSize(TEXT_SIZE);

然后讓我們分別繪制出這三個部分獲取自定義View的寬和高

float halfWidth = getMeasuredWidth() / 2;
float halfHeight = getMeasuredHeight() / 2;

繪制外圓

canvas.drawCircle(halfWidth, halfHeight, CIRCLE_RADIUS,mCirclePaint);

繪制內(nèi)圓

canvas.drawCircle(halfWidth, halfHeight,CIRCLE_RADIUS - CIRCLE_LINE_WIDTH / 2，mCircleInnerPaint);

繪制文字

canvas.drawText(mProgressText,halfWidth - mTextPaint.measureText(mProgressText) / 2,halfHeight - (mTextPaint.ascent() + mTextPaint.descent()) / 2,mTextPaint);

最后的效果如下圖

繪制完了基本的圖案，下一步就是實現(xiàn)進度條的動畫效果

進度條是實時變化的，所以需要不斷的去更新進度，進度可以用圓弧開繪制

設(shè)置進度的方法

public void setProgress(float progress) {
 if (progress > 100) {
  progress = 100;
 }
 if (progress < 0) {
  progress = 0;
 }
 mProgress = progress;
 mProgressText = "Pause";
 mStartProgress = true;
 postInvalidate();
}

在Activity中開一個線程模擬網(wǎng)絡(luò)請求后更新進度條的操作

沒30毫秒更新一次數(shù)據(jù)，當進度超過100，停止刷新界面

private void startProgress() {
 new Thread() {
 @Override
 public void run() {
  super.run();
  float currentProgress = mCustomView.getCurrentProgress();
  ++currentProgress;
  mCustomView.setProgress(currentProgress);
  try {
   sleep(30);
   if (currentProgress <= 100) {
    startProgress();
   } else {
    mCustomView.progressFinished();
   }
  } catch (InterruptedException e) {
    e.printStackTrace();
  }
 }
 }.start();
}

最核心的部分，進度更新后更新繪制圓形進度條

float halfWidth = getMeasuredWidth() / 2;
float halfHeight = getMeasuredHeight() / 2;
if (null == mCircleRectF) {
  mCircleRectF = new RectF(halfWidth - CIRCLE_RADIUS, halfHeight - CIRCLE_RADIUS,      halfWidth + CIRCLE_RADIUS, halfHeight + CIRCLE_RADIUS);
}
if (mStartProgress) {
  float swipeProgress = mProgress / 100f * 360;
  LogUtils.e("swipeProgress = " + swipeProgress);
  canvas.drawArc(mCircleRectF, -90, swipeProgress, true, mCirclePaint);
} else {
  canvas.drawCircle(halfWidth, halfHeight, CIRCLE_RADIUS,mCirclePaint);
}

繪制的思路就是把progress進度轉(zhuǎn)換為圓弧的弧度，然后不斷繪制出來，這里要注意，從-90開始，也就是時鐘的0點時刻開始繪制。如果進度已經(jīng)繪制完成，或者還沒有開始，則直接繪制一個圓形。

大概思路就是這樣，最后上兩張效果圖