Android编程实现canvas绘制饼状统计图功能示例【自动适应条目数量与大小】

PieChartView pieChartView = (PieChartView) findViewById(R.id.pie_chart);PieChartView.PieItemBean[] items = new PieChartView.PieItemBean[]{    new PieChartView.PieItemBean("娱乐", 200),    new PieChartView.PieItemBean("旅行", 100),    new PieChartView.PieItemBean("学习", 120),    new PieChartView.PieItemBean("人际关系", 160),    new PieChartView.PieItemBean("交通", 100),    new PieChartView.PieItemBean("餐饮", 480)};pieChartView.setPieItems(items);

public class PieChartView extends View {  private int screenW, screenH;  /**   * The paint to draw text, pie and line.   */  private Paint textPaint, piePaint, linePaint;  /**   * The center and the radius of the pie.   */  private int pieCenterX, pieCenterY, pieRadius;  /**   * The oval to draw the oval in.   */  private RectF pieOval;  private float smallMargin;  private int[] mPieColors = new int[]{Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW, Color.MAGENTA, Color.CYAN};  private PieItemBean[] mPieItems;  private float totalValue;  public PieChartView(Context context) {    super(context);    init(context);  }  public PieChartView(Context context, AttributeSet attrs) {    super(context, attrs);    init(context);  }  public PieChartView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    init(context);  }  private void init(Context context) {    //init screen    screenW = ScreenUtils.getScreenW(context);    screenH = ScreenUtils.getScreenH(context);    pieCenterX = screenW / 2;    pieCenterY = screenH / 3;    pieRadius = screenW / 4;    smallMargin = ScreenUtils.dp2px(context, 5);    pieOval = new RectF();    pieOval.left = pieCenterX - pieRadius;    pieOval.top = pieCenterY - pieRadius;    pieOval.right = pieCenterX + pieRadius;    pieOval.bottom = pieCenterY + pieRadius;    //The paint to draw text.    textPaint = new Paint();    textPaint.setAntiAlias(true);    textPaint.setTextSize(ScreenUtils.dp2px(context, 16));    //The paint to draw circle.    piePaint = new Paint();    piePaint.setAntiAlias(true);    piePaint.setStyle(Paint.Style.FILL);    //The paint to draw line to show the concrete text    linePaint = new Paint();    linePaint.setAntiAlias(true);    linePaint.setStrokeWidth(ScreenUtils.dp2px(context, 1));  }  //The degree position of the last item arc's center.  private float lastDegree = 0;  //The count of the continues 'small' item.  private int addTimes = 0;  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    if (mPieItems != null && mPieItems.length > 0) {      float start = 0.0f;      for (int i = 0; i < mPieItems.length; i++) {        //draw pie        piePaint.setColor(mPieColors[i % mPieColors.length]);        float sweep = mPieItems[i].getItemValue() / totalValue * 360;        canvas.drawArc(pieOval, start, sweep, true, piePaint);        //draw line away from the pie        float radians = (float) ((start + sweep / 2) / 180 * Math.PI);        float lineStartX = pieCenterX + pieRadius * 0.7f * (float) (Math.cos(radians));        float lineStartY = pieCenterY + pieRadius * 0.7f * (float) (Math.sin(radians));        float lineStopX, lineStopY;        float rate;        if (getOffset(start + sweep / 2) > 60) {          rate = 1.3f;        } else if (getOffset(start + sweep / 2) > 30) {          rate = 1.2f;        } else {          rate = 1.1f;        }        //If the item is very small, make the text further away from the pie to avoid being hided by other text.        if (start + sweep / 2 - lastDegree < 30) {          addTimes++;          rate += 0.2f * addTimes;        } else {          addTimes = 0;        }        lineStopX = pieCenterX + pieRadius * rate * (float) (Math.cos(radians));        lineStopY = pieCenterY + pieRadius * rate * (float) (Math.sin(radians));        canvas.drawLine(lineStartX, lineStartY, lineStopX, lineStopY, linePaint);        //write text        String itemTypeText = mPieItems[i].getItemType();        String itemPercentText = Utility.formatFloat(mPieItems[i].getItemValue() / totalValue * 100) + "%";        float itemTypeTextLen = textPaint.measureText(itemTypeText);        float itemPercentTextLen = textPaint.measureText(itemPercentText);        float lineTextWidth = Math.max(itemTypeTextLen, itemPercentTextLen);        float textStartX = lineStopX;        float textStartY = lineStopY - smallMargin;        float percentStartX = lineStopX;        float percentStartY = lineStopY + textPaint.getTextSize();        if (lineStartX > pieCenterX) {          textStartX += (smallMargin + Math.abs(itemTypeTextLen - lineTextWidth) / 2);          percentStartX += (smallMargin + Math.abs(itemPercentTextLen - lineTextWidth) / 2);        } else {          textStartX -= (smallMargin + lineTextWidth - Math.abs(itemTypeTextLen - lineTextWidth) / 2);          percentStartX -= (smallMargin + lineTextWidth - Math.abs(itemPercentTextLen - lineTextWidth) / 2);        }        canvas.drawText(itemTypeText, textStartX, textStartY, textPaint);        //draw percent text        canvas.drawText(itemPercentText, percentStartX, percentStartY, textPaint);        //draw text underline        float textLineStopX = lineStopX;        if (lineStartX > pieCenterX) {          textLineStopX += (lineTextWidth + smallMargin * 2);        } else {          textLineStopX -= (lineTextWidth + smallMargin * 2);        }        canvas.drawLine(lineStopX, lineStopY, textLineStopX, lineStopY, linePaint);        lastDegree = start + sweep / 2;        start += sweep;      }    }  }  public PieItemBean[] getPieItems() {    return mPieItems;  }  public void setPieItems(PieItemBean[] pieItems) {    this.mPieItems = pieItems;    totalValue = 0;    for (PieItemBean item : mPieItems) {      totalValue += item.getItemValue();    }    invalidate();  }  private float getOffset(float radius) {    int a = (int) (radius % 360 / 90);    switch (a) {      case 0:        return radius;      case 1:        return 180 - radius;      case 2:        return radius - 180;      case 3:        return 360 - radius;    }    return radius;  }  static class PieItemBean {    private String itemType;    private float itemValue;    PieItemBean(String itemType, float itemValue) {      this.itemType = itemType;      this.itemValue = itemValue;    }    public String getItemType() {      return itemType;    }    public void setItemType(String itemType) {      this.itemType = itemType;    }    public float getItemValue() {      return itemValue;    }    public void setItemValue(float itemValue) {      this.itemValue = itemValue;    }  }}