canvas 画一个圆上有 旋转角度 的直线

####1、功能展示

2、xml 文件

activity_main.xml

 xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.menglux.mycanvasline.MainActivity">

    

        

        

    

####3、代码文件

LineView.java文件

public class LineView extends View {
    private String TAG = "LineView: ";
    private Paint paintCircle;  //圆的画笔
    private Paint paintShortLine;   //  短线的画笔
    private Paint paintLongLine;  //长线的画笔
    private int radius = 200;  //圆的半径
    private int width = 400 ;   //x 中心位置
    private int height = 400 ;   //y 中心位置

    @SuppressLint("ResourceAsColor")
    public LineView(Context context) {
        super(context);

    }

    public LineView(Context context, AttributeSet attrs) {
        super(context, attrs, 0);
    }


    //在构造函数里初始化 数据
    public LineView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        //新建 圆的画笔
        paintCircle = new Paint();
        paintCircle.setAlpha(300);     //透明度设置
        paintCircle.setColor(getResources().getColor(R.color.colorPrimary));  //画笔颜色设置
        paintCircle.setAntiAlias(true);  //抗齿距设置
        paintCircle.setStyle(Paint.Style.STROKE);  //设置画笔样式 空心
        paintCircle.setStrokeWidth(10); //设置画笔宽度

        //新建 短线的画笔
        paintShortLine = new Paint();
        paintShortLine.setAlpha(300);     //透明度设置
        paintShortLine.setColor(getResources().getColor(R.color.colorAccent));  //画笔颜色设置
        paintShortLine.setAntiAlias(true);  //抗齿距设置
        paintShortLine.setStyle(Paint.Style.STROKE);  //设置画笔样式 空心
        paintShortLine.setStrokeWidth(10); //设置画笔宽度

        //新建 长线的画笔
        paintLongLine = new Paint();
        paintLongLine.setAlpha(300);     //透明度设置
        paintLongLine.setColor(getResources().getColor(R.color.color));  //画笔颜色设置
        paintLongLine.setAntiAlias(true);  //抗齿距设置
        paintLongLine.setStyle(Paint.Style.STROKE);  //设置画笔样式 空心
        paintLongLine.setStrokeWidth(10); //设置画笔宽度


    }

        @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);


        drawCircle(canvas);  //画圆
        drawShortLine(canvas);    //画短线
        drawLongLine(canvas);   //画长线

    }

    private void drawLongLine(Canvas canvas) {

        //先保存画布现在的状态
        canvas.save();

        int startX = width;
        int startY = height - radius + 100;//y坐标即园中心点的y坐标-半径

        int stopX = startX;
        int stopY1 = startY  - 300;//整点处的线长度为 300

        canvas.rotate(30, width, height);//以圆中心进行旋转
        canvas.drawLine(startX, startY, stopX, stopY1, paintLongLine);//绘制长的线

        //绘制完后，记得把画布状态复原
        canvas.restore();
    }

    private void drawShortLine(Canvas canvas) {

        //先保存画布现在的状态
        canvas.save();

        int startX = width;
        int startY = height - radius + 50;//y坐标即园中心点的y坐标-半径

        int stopX = startX;
        int stopY1 = startY  - 100;//整点处的线长度为  100

        canvas.rotate(222, width, height);//以圆中心进行旋转 222度
        canvas.drawLine(startX, startY, stopX, stopY1, paintShortLine);//绘制短线

      //绘制完后，记得把画布状态复原
        canvas.restore();
    }


    /**
     * 绘圆形部分
     * @param canvas
     */
    private void drawCircle(Canvas canvas) {
        //获得圆的圆点坐标
        int x = width;
        int y = height;
        canvas.drawCircle(x, y, radius, paintCircle);
    }
}

demo下载

文件参考：
Android 2D绘图(Canvas+paint)详解
https://www.2cto.com/kf/201610/557341.html

Android之canvas详解
https://blog.csdn.net/whuhan2013/article/details/51404737

Android 自定义绘制圆形进度条
https://blog.csdn.net/baidu_23478311/article/details/46238973