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】

本文实例讲述了Android编程实现canvas绘制饼状统计图功能。分享给大家供大家参考，具体如下：

本例的目的是实现一个简单的饼状统计图，效果如下：

特点：

1.使用非常方便，可放在xml布局文件中，然后在代码中设置内容，即：

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);

2.条目数量，大小及折线位置，长度均自适应。左侧条目往左侧划线，右侧条目往右侧划线，文字描述与百分比居中对齐，并且文字“下划线”与文字长度自适应。对于很小的条目，将自动将折线延长以尽可能避免文字遮盖

核心代码：PieChartView.Java:

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;
   }
 }
}

完整实例代码点击此处本站下载。

希望本文所述对大家Android程序设计有所帮助。