Android RadarView雷达图（蜘蛛网图）的实现代码

公司产品需要一个雷达图来展示各维度的比重，网上找了一波，学到不少，直接自己上手来撸一记

无图言虚空

简单分析一波，确定雷达图正几边形的--正五边形 int count=5，分为几个层数--4 层 int layerCount=4

@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 drawPolygon(canvas);//画边
 drawLines(canvas);//画线
 drawText(canvas);//描绘文字
 drawRegion(canvas);//覆盖区域
}

主要这几步，开撸！

自定义RadarView继承View

确定需要使用的变量，初始化paint，计算圆心角

private int count = 5; //几边形
private int layerCount = 4; //层数
private float angle; //每条边对应的圆心角
private int centerX; //圆心x
private int centerY; //圆心y
private float radius; //半径
private Paint polygonPaint; //边框paint
private Paint linePaint; //连线paint
private Paint txtPaint; //文字paint
private Paint circlePaint; //圆点paint
private Paint regionColorPaint; //覆盖区域paint
private Double[] percents = {0.91, 0.35, 0.12, 0.8, 0.5}; //覆盖区域百分比
private String[] titles = {"dota", "斗地主", "大吉大利，晚上吃鸡", "炉石传说", "跳一跳"};//文字

public RadarView(Context context) {
 this(context, null, 0);
}

public RadarView(Context context, @Nullable AttributeSet attrs) {
 this(context, attrs, 0);
}

public RadarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 //计算圆心角
 angle = (float) (Math.PI * 2 / count);

polygonPaint = new Paint();
 polygonPaint.setColor(ContextCompat.getColor(context, R.color.radarPolygonColor));
 polygonPaint.setAntiAlias(true);
 polygonPaint.setStyle(Paint.Style.STROKE);
 polygonPaint.setStrokeWidth(4f);

linePaint = new Paint();
 linePaint.setColor(ContextCompat.getColor(context, R.color.radarLineColor));
 linePaint.setAntiAlias(true);
 linePaint.setStyle(Paint.Style.STROKE);
 linePaint.setStrokeWidth(2f);

txtPaint = new Paint();
 txtPaint.setColor(ContextCompat.getColor(context, R.color.radarTxtColor));
 txtPaint.setAntiAlias(true);
 txtPaint.setStyle(Paint.Style.STROKE);
 txtPaint.setTextSize(DensityUtil.dpToPx(context, 12));

circlePaint = new Paint();
 circlePaint.setColor(ContextCompat.getColor(context, R.color.radarCircleColor));
 circlePaint.setAntiAlias(true);

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

}

确定中心点

需要正五边形得有一个圆，圆内接正五边形，在onSizeChanged方法里获取圆心，确定半径

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
 super.onSizeChanged(w, h, oldw, oldh);
 radius = Math.min(h, w) / 2 * 0.7f;
 centerX = w / 2;
 centerY = h / 2;
}

绘制正五边形

绘制正五边形同时描绘最外围的点，确定分为4层，半径 / 层数 =每层之间的间距，从最里层开始画正五边形，每层第一个点位于中心点正上方

private void drawPolygon(Canvas canvas) {
 Path path = new Path();
 float r = radius / layerCount;
 for (int i = 1; i <= layerCount; i++) {
  float curR = r * i; //当前所在层的半径
  for (int j = 0; j < count; j++) {
   if (j == 0) {
    //每一层第一个点坐标
    path.moveTo(centerX, centerY - curR);
   } else {
    //顺时针记录其余顶角的点坐标
    float x = (float) (centerX + Math.sin(angle * j) * curR);
    float y = (float) (centerY - Math.cos(angle * j) * curR);
    path.lineTo(x, y);
   }
  }
  //最外层的顶角外面的五个小圆点(图中红色部分)
  if (i == layerCount) {
   for (int j = 0; j < count; j++) {
    float x = (float) (centerX + Math.sin(angle * j) * (curR + 12));
    float y = (float) (centerY - Math.cos(angle * j) * (curR + 12));
    canvas.drawCircle(x, y, 4, circlePaint);
   }
  }
  path.close();
  canvas.drawPath(path, polygonPaint);
 }
}

绘制连线

绘制最内层顶角到最外层顶角的连线

private void drawLines(Canvas canvas) {
 float r = radius / layerCount;
 for (int i = 0; i < count; i++) {
  //起始坐标 从中心开始的话 startx=centerX , startY=centerY
  float startX = (float) (centerX + Math.sin(angle * i) * r);
  float startY = (float) (centerY - Math.cos(angle * i) * r);
  //末端坐标
  float endX = (float) (centerX + Math.sin(angle * i) * radius);
  float endY = (float) (centerY - Math.cos(angle * i) * radius);
  canvas.drawLine(startX, startY, endX, endY, linePaint);
 }
}

至此简易雷达图成型，可以修改正几边形，多少层数（后续继续添加文字）

//设置几边形，**注意：设置几边形需要重新计算圆心角**
public void setCount(int count){
 this.count = count;
 angle = (float) (Math.PI * 2 / count);
 invalidate();
}

//设置层数
public void setLayerCount(int layerCount){
 this.layerCount = layerCount;
 invalidate();
}

设置正六边形、六层

radarView.setCount(6);
radarView.setLayerCount(6);

对于以下图形的，可以设置第一个点坐标位于中心点正右侧 (centerX+curR,centerY) ，顺时针计算其余顶点坐标 x = (float) (centerX+curR*Math.cos(angle*j)), y = (float) (centerY+curR*Math.sin(angle*j)) ，同理连线等其余坐标相应改变...

描绘文字

由于各产品维度内容不同，所需雷达图样式不一，这里只是描绘下不同位置的文字处理情况，具体需求还得按产品来，因产品而异

private void drawText(Canvas canvas) {
 for (int i = 0; i < count; i++) {
  //获取到雷达图最外边的坐标
  float x = (float) (centerX + Math.sin(angle * i) * (radius + 12));
  float y = (float) (centerY - Math.cos(angle * i) * (radius + 12));
  if (angle * i == 0) {
   //第一个文字位于顶角正上方
   txtPaint.setTextAlign(Paint.Align.CENTER);
   canvas.drawText(titles[i], x, y - 18, txtPaint);
   txtPaint.setTextAlign(Paint.Align.LEFT);
  } else if (angle * i > 0 && angle * i < Math.PI / 2) {
   //微调
   canvas.drawText(titles[i], x + 18, y + 10, txtPaint);
  } else if (angle * i >= Math.PI / 2 && angle * i < Math.PI) {
   //最右下的文字获取到文字的长、宽，按文字长度百分比向左移
   String txt = titles[i];
   Rect bounds = new Rect();
   txtPaint.getTextBounds(txt, 0, txt.length(), bounds);
   float height = bounds.bottom - bounds.top;
   float width = txtPaint.measureText(txt);
   canvas.drawText(txt, x - width * 0.4f, y + height + 18, txtPaint);
  } else if (angle * i >= Math.PI && angle * i < 3 * Math.PI / 2) {
   //同理最左下的文字获取到文字的长、宽，按文字长度百分比向左移
   String txt = titles[i];
   Rect bounds = new Rect();
   txtPaint.getTextBounds(txt, 0, txt.length(), bounds);
   float width = txtPaint.measureText(txt);
   float height = bounds.bottom - bounds.top;
   canvas.drawText(txt, x - width * 0.6f, y + height + 18, txtPaint);
  } else if (angle * i >= 3 * Math.PI / 2 && angle * i < 2 * Math.PI) {
   //文字向左移动
   String txt = titles[i];
   float width = txtPaint.measureText(txt);
   canvas.drawText(txt, x - width - 18, y + 10, txtPaint);
  }

}
}

绘制覆盖区域

绘制覆盖区域，百分比取连线长度的百分比(如果从中心点开始的连线，则是半径的百分比)，此处用半径radius减去间隔r即连线长度

private void drawRegion(Canvas canvas) {
 Path path = new Path();
 float r = radius / layerCount;//每层的间距
 for (int i = 0; i < count; i++) {
  if (i == 0) {
   path.moveTo(centerX, (float) (centerY - r - (radius - r) * percents[i]));
  } else {
   float x = (float) (centerX + Math.sin(angle * i) * (percents[i] * (radius - r) + r));
   float y = (float) (centerY - Math.cos(angle * i) * (percents[i] * (radius - r) + r));
   path.lineTo(x, y);
  }
 }
 path.close();
 canvas.drawPath(path, regionColorPaint);
}

至此，一个简单的雷达图完毕。以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

来源：https://juejin.im/post/5ab4ae945188255587237d9a