Android自定义View――扇形统计图的实现代码

  private int mHeight, mWidth;//宽高
  private Paint mPaint;//扇形的画笔
  private Paint mTextPaint;//画文字的画笔

  private int centerX, centerY;//中心坐标

  //"其他"的value
  //扇形图分成太多快 所以要合并一部分为其他 即图中灰色部分
  private double rest;

  private int maxNum = 5;//扇形图的最大块数 超过的item就合并到其他

  String others = "其他";//“其他”块要显示的文字
  double total;//数据的总和 
  double[] datas;//数据集
  String[] texts;//每个数据对应的文字集

  //颜色 默认的颜色
  private int[] mColors = {
      Color.parseColor("#FF4081"), Color.parseColor("#ffc0cb"),
      Color.parseColor("#00ff00"), Color.parseColor("#0066ff"), Color.parseColor("#ffee00")
  };

  private int mTextSize;//文字大小 单位：像素

  private int radius = 1000;//半径 在画图时初始化

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    //获取宽高 不要设置wrap_content
    mHeight = MeasureSpec.getSize(heightMeasureSpec);
    mWidth = MeasureSpec.getSize(widthMeasureSpec);

  }

@Override
protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //无数据 直接返回
  if (datas == null || datas.length == 0) return;

  centerX = (getRight() - getLeft()) / 2;
  centerY = (getBottom() - getTop()) / 2;
  int min = mHeight > mWidth ? mWidth : mHeight;
  if (radius > min / 2) {
    radius = (int) ((min - getPaddingTop() - getPaddingBottom()) / 3.5);
  }

  //画各个扇形
  drawCircle(canvas);

  //画线与文字
  drawLineAndText(canvas);

}

  //画扇形
  private void drawCircle(Canvas canvas) {
    int centerX =( getRight() - getLeft() )/2;//中点
    int centerY = ( getBottom() - getTop()) /2;
    RectF rect = new RectF((float) (centerX - radius), centerY-radius,
        centerX+radius,centerY+radius);//圆形区域

    int start = 0;//扇形开始的角度
    for (int i = 0; i < (maxNum<datas.length?maxNum:datas.length); i++) {
      float angles = (float) ((datas[i] * 1.0f /total) * 360);//计算扇形的角度
      mPaint.setColor(mColors[i%mColors.length]);//颜色
      canvas.drawArc(rect,start,angles,true,mPaint);//画扇形
      start += angles;//下一个扇形开始的角度
    }

    //画"其他"部分 即图中灰色的部分
    rest =0;//保存其他部分的value
    for(int i=maxNum;i<datas.length;i++){
      rest+=datas[i];
    }
    float angles = (float) 360 - start;//角度
    mPaint.setColor(Color.GRAY);
    canvas.drawArc(rect,start,angles,true,mPaint);

  }

//画线与文字
  private void drawLineAndText(Canvas canvas) {
    int start = 0;
    //平移画布到中心 所以下面的坐标是从中点开始算起的
    canvas.translate(centerX, centerY);
    mPaint.setStrokeWidth(4);//线条宽度

    //如果数据集过大 那么要合并到其他
    for (int i = 0; i < (maxNum < datas.length ? maxNum : datas.length); i++) {
      float angles = (float) ((datas[i] * 1.0f / total) * 360);
      //画线条和文字
      drawLine(canvas, start, angles, texts[i], mColors[i % mColors.length]);
      start += angles;
    }
    //画其他部分的线条和文字
    if (start < 360)//如果start小于360 说明有其他部分
      drawLine(canvas, start, 360 - start, others, Color.GRAY);

  }

  private void drawLine(Canvas canvas, int start, float angles, String text, int color) {
    mPaint.setColor(color);
    float stopX, stopY;
    stopX = (float) ((radius + 40) * Math.cos((2 * start + angles) / 2 * Math.PI / 180));
    stopY = (float) ((radius + 40) * Math.sin((2 * start + angles) / 2 * Math.PI / 180));

    canvas.drawLine((float) ((radius - 20) * Math.cos((2 * start + angles) / 2 * Math.PI / 180)),
        (float) ((radius - 20) * Math.sin((2 * start + angles) / 2 * Math.PI / 180)),
        stopX, stopY, mPaint
    );
    //画横线
    int dx;//判断横线是画在左边还是右边
    int endX;
    if (stopX > 0) {
      endX = (centerX - getPaddingRight() - 20);
    } else {
      endX = (-centerX + getPaddingLeft() + 20);
    }
    //画横线
    canvas.drawLine(stopX, stopY,
        endX, stopY, mPaint
    );
    dx = (int) (endX - stopX);

    //测量文字大小
    Rect rect = new Rect();
    mTextPaint.getTextBounds(text, 0, text.length(), rect);
    int w = rect.width();
    int h = rect.height();
    int offset = 20;//文字在横线的偏移量
    //画文字 文字的Y坐标值的是文字底部的Y坐标
    canvas.drawText(text, 0, text.length(), dx > 0 ? stopX + offset : stopX - w - offset, stopY + h, mTextPaint);

    //测量百分比大小
    String percentage = angles / 3.60 + "";
    percentage = percentage.substring(0, percentage.length() > 4 ? 4 : percentage.length()) + "%";
    mTextPaint.getTextBounds(percentage, 0, percentage.length(), rect);
    w = rect.width() - 10;
    //画百分比
    canvas.drawText(percentage, 0, percentage.length(), dx > 0 ? stopX + offset : stopX - w - offset, stopY - 5, mTextPaint);

  }

  public abstract class ArcViewAdapter<T> {

    public void setData(List<T> list) {
      datas = new double[list.size()];
      texts = new String[list.size()];
      for (int i = 0; i < list.size(); i++) {
        total += getValue(list.get(i));
        datas[i] = getValue(list.get(i));
        texts[i] = getText(list.get(i));
      }
      invalidate();//请求重绘
    }

    //通过传来的数据集的某个元素 得到具体的数字
    public abstract double getValue(T t);

    //通过传来的数据集的某个元素 得到具体的描述
    public abstract String getText(T t);
  }

ArcView arcView = (ArcView) findViewById(R.id.arc);
    List<Times> times = new ArrayList<>();
    for (int i = 6; i > 0; i--) {
      Times t = new Times();//这个类就只有两个变量
      t.hour = i;
      t.text = "Number"+i;
      times.add(t);
    }

    //初始化适配器
    ArcView.ArcViewAdapter myAdapter = arcView.new ArcViewAdapter<Times>(){
      @Override
      public double getValue(Times times) {
        return times.hour;
      }

      @Override
      public String getText(Times times) {
        return times.text;
      }
    };
    myAdapter.setData(times);//绑定数据