蛛网雷达图

蛛网雷达图

知识点：

1 数学：角度和弧度的关系。

角度和弧度的区别：
        角度：两条射线从圆心向圆周射出，形成一个夹角和夹角正对的一段弧。当这段弧长正好等于圆周长的360分之一时，两条射线的夹角的大小为1度。
        弧度：两条射线从圆心向圆周射出，形成一个夹角和夹角正对的一段弧。当这段弧长正好等于圆的半径时，两条射线的夹角大小为1弧度。   
  由定义可知：圆所对应的弧长是半径的几倍，那么角的大小就是几弧度。
         周角(360度)= 2π弧度
         平角(180度)= π弧度
      在Java中Math类的三角函数接收的参数是弧度，不是角度。
      所以2 * Math.PI即表示360°

2 正弦、余弦定理

三角形

x = cos(∠AOB) * OA
y = sin(∠AOB) * OA

3 Path的基本用法

moveTo(x,y):移动到坐标点
lineTo(x,y)：目前坐标与坐标连线，绘制出一条直线

实现步骤如下：

1 绘制单个多边形
      使用canvas.drawPath()绘制多边形
2 绘制多个多边形
3 连线中心到末端
4 绘制分值区域
    色值加透明度

1 绘制单个多边形

绘制单个多边形

2 绘制多个多边形

绘制多边形

3 连线中心到末端

连线中心到末端

4 绘制分值区域

绘制分值区域

整理代码如下：

public class SpiderWebView extends View {
//多边形变数
private int BORDER_COUNT = 8;

//角度：在java中Math类的三角函数接收的参数并不角度，而是弧度，所以需要用2 * Math.PI表示360°
private float mAngel = (float) (2 * Math.PI / BORDER_COUNT);
private int width, height;
//三种Paint：多边形Paint、直线Paint、分值区Paint
private Paint mPaintShape, mPaintLine, mPaintRegion;
//三种Path：图形Path、直线Path,分值区域Path
private Path pathShape, pathLine, pathRegion;
//多边形起始半径
private int radiu = 0;
//中心点坐标
private int centerX, centerY;

public SpiderWebView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}

public SpiderWebView(Context context) {
    super(context);
    init(context);
}

public void init(Context context) {
    //多边形绘制初始化
    mPaintShape = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaintShape.setColor(getResources().getColor(R.color.black));
    mPaintShape.setStyle(Paint.Style.STROKE);
    mPaintShape.setStrokeWidth(3);

    pathShape = new Path();

    //绘制直线初始化
    mPaintLine = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaintLine.setColor(getResources().getColor(R.color.red));
    mPaintLine.setStyle(Paint.Style.STROKE);
    mPaintLine.setStrokeWidth(3);

    pathLine = new Path();

    //绘制域值初始化
    mPaintRegion = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaintRegion.setColor(Color.parseColor("#7f33b5e5"));//透明度
    mPaintRegion.setStyle(Paint.Style.FILL_AND_STROKE);
    mPaintRegion.setStrokeWidth(3);

    pathRegion = new Path();

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    Log.d("lincoln", "onSizeChanged");
    width = w;
    height = h;
    centerX = width / 2;
    centerY = height / 2;
    radiu = Math.min(width, height) / 2;
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawColor(getResources().getColor(R.color.azure));

    //TODO OnDraw()被调用2次，问题待查找


    drawMutilShape(canvas);

    drawLine(canvas);

    drawRegion(canvas);
}

//1 绘制单个多边形
private void drawSingleShape(Canvas canvas) {
    pathShape.moveTo(centerX + radiu, centerX);
    for (int index = 0; index < BORDER_COUNT; index++) {
        float x = (float) (centerX + Math.cos(index * mAngel) * radiu);
        float y = (float) (centerY + Math.sin(index * mAngel) * radiu);
        Log.d("lincoln", "drawSingleShape:" + " x:" + x + " y:" + y);
        pathShape.lineTo(x, y);
    }
    pathShape.close();
    canvas.drawPath(pathShape, mPaintShape);
}

//2 绘制多个多边形
public void drawMutilShape(Canvas canvas){
    //每一份的值
    int each = radiu / 5;
    //2 绘制多个多边形
    for (int index = 0; index < 5; index++) {
        Log.d("lincoln", "radiu:" + radiu + " each:" + each);
        radiu = radiu - each;
        drawSingleShape(canvas);
    }

}


//3 多边形对角线相连
private void drawLine(Canvas canvas) {

    radiu = Math.min(width, height) / 2;
    int each = radiu / 5;
    radiu = radiu - each;

    for (int index = 0; index < BORDER_COUNT; index++) {
        pathLine.moveTo(centerX, centerX);
        float x = (float) (centerX + Math.cos(index * mAngel) * radiu);
        float y = (float) (centerY + Math.sin(index * mAngel) * radiu);
        Log.d("lincoln", "drawLine:" + " x:" + x + " y:" + y);
        pathLine.lineTo(x, y);
        canvas.drawPath(pathLine, mPaintLine);
    }
    //TODO 解决2次绘制的bug
    radiu = Math.min(width, height) / 2;
}

//4 绘制分值区域
float[] percents = new float[]{
        0.2F,
        0.6F,
        0.8F,
        0.5F,
        0.6F,
        0.9F,
        0.2F,
        0.8F,
        0.3F,
        0.7F,
};
public void drawRegion(Canvas canvas) {
    radiu = Math.min(width, height) / 2;
    int each = radiu / 5;
    radiu = radiu - each;
    for (int index = 0; index < BORDER_COUNT; index++) {
        float x = (float) ( Math.cos(index * mAngel) * radiu * percents[index]);
        float y = (float) ( Math.sin(index * mAngel) * radiu * percents[index]);
        Log.d("lincoln", "drawRegion:" + " x:" + x + " y:" + y);
        if (index == 0) {
            pathRegion.moveTo( centerX+x, centerY);
        } else {
            pathRegion.lineTo(centerX+x, centerY+y);
        }
    }
    pathRegion.close();
    canvas.drawPath(pathRegion, mPaintRegion);
    radiu = Math.min(width, height) / 2;

}
}

Demo源码：

Github源码

参考文章

简书当前Markdown语法与效果
安卓自定义View教程目录

简单造轮子系列 - 自定义支持手势旋转的Android Radar Chart(蛛网雷达图)

自定义View——画一个雷达图