Android自定义圆形进度条

绘制自定义的圆形进度条，分为三个步骤，内圆、外圆、文字。
其中内圆和文字比较好绘制，进度条的变化是由外圆来控制的，所以核心就是绘制外圆。

首先定义分别定义这三个画笔，两个Paint和一个TextPaint

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);

然后让我们分别绘制出这三个部分

获取自定义View的宽和高

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

绘制外圆

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

绘制内圆

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

绘制文字

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

最后的效果如下图

device-2016-10-11-180030.png

绘制完了基本的图案，下一步就是实现进度条的动画效果

进度条是实时变化的，所以需要不断的去更新进度，进度可以用圆弧开绘制

设置进度的方法

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

在Activity中开一个线程模拟网络请求后更新进度条的操作

没30毫秒更新一次数据，当进度超过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，进度更新后更新绘制圆形进度条

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);
}

绘制的思路就是把progress进度转换为圆弧的弧度，然后不断绘制出来，这里要注意，从-90开始，也就是时钟的0点时刻开始绘制。如果进度已经绘制完成，或者还没有开始，则直接绘制一个圆形。

大概思路就是这样，最后上两张效果图

device-2016-10-11-175952.png device-2016-10-11-180110.png

如果有什么更好的实现思路，可以一起讨论学习。