手动撸个Android雷达图（蜘蛛网图）RadarView

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 privatefloatangle; //每条边对应的圆心角 private int centerX; //圆心x private int centerY; //圆心y privatefloatradius; //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。同时欢迎关注微信公众号

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