android 绘制自定义控件，android绘制同心圆，android绘制小三角，android画虚线

一：实现同心圆加小三角指向效果

同心圆

public class RingView extends View{
    private Paint paint;
    private Context context;
    private int radius;//半径
    private int color;//颜色值
    public RingView(Context context) {
        // TODO Auto-generated constructor stub
        this(context, null);
    }
    public RingView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        this.context = context;
        this.paint = new Paint();
        this.paint.setAntiAlias(true); //消除锯齿
    }
    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        int center = getWidth()/2;
        //绘制内圆
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.parseColor("#91d439"));
        canvas.drawCircle(center,center, 22, this.paint);
        //绘制外圆(空心)
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.parseColor("#91d439"));
        paint.setStrokeWidth(6);  
        canvas.drawCircle(center,center, 30, this.paint);
        super.onDraw(canvas);
    }
    public int getRadius() {
        return radius;
    }
    public void setRadius(int radius) {
        this.radius = radius;
    }
    public int getColor() {
        return color;
    }
    public void setColor(int color) {
        this.color = color;
    }   
}

这里的getWidth可以根据控件设置的宽度来得到

小三角

public class mytriangle extends View{
    private Paint paint;
    private Context context;
    private int radius;//半径
    private int color;//颜色值
    public mytriangle(Context context) {
        // TODO Auto-generated constructor stub
        this(context, null);
    }
    public mytriangle(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        this.context = context;
        this.paint = new Paint();
        this.paint.setAntiAlias(true); //消除锯齿
    }
    @Override
    protected void onDraw(Canvas canvas) {     
        float x= getX();//得到控件的所在位置
        float y= getX();
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.parseColor("#b9dc8c"));
       // canvas.drawText("画三角形：", 10, 200, paint);  
        // 绘制这个三角形,你可以绘制任意多边形  
        Path path = new Path();  
       // y=(float) (y+15.5);
        path.moveTo(Dp2Px(context,x+10),Dp2Px(context,y));// 此点为多边形的起点  
        path.lineTo(Dp2Px(context,x), Dp2Px(context,y+7));  
        path.lineTo(Dp2Px(context,x+10), Dp2Px(context,y+14));  
        path.close(); // 使这些点构成封闭的多边形  
        canvas.drawPath(path,paint);       
        super.onDraw(canvas);
    }
    public float Dp2Px(Context context, float dp) { 
        final float scale = context.getResources().getDisplayMetrics().density; 
        return (float) (dp * scale + 0.5f); 
    }
    public int getRadius() {
        return radius;
    }
    public void setRadius(int radius) {
        this.radius = radius;
    }
    public int getColor() {
        return color;
    }
    public void setColor(int color) {
        this.color = color;
    }   
}

布局文件中使用用全类名访问就可以了，还可以设置自动义属性,
getx(),gety得到控件的所在的坐标位置

 int[] location = new  int[2] ;
        getLocationOnScreen(location);//获取在整个屏幕内的绝对坐标包括通知栏  
        System.out.println("OnScreen x:"+location[0]+" y:"+location[1]);

注意:不要以为获取到了这个位置设置下就可以让控件在具体的位置了，而是所在布局文件类型以,0,0开始，所有
不要去设置位置默认就在那个位置,设置了反而让控件不在本身正确的位置了

<com.lc.mycontrol.RingView 
             android:layout_width="100dp"
             android:layout_height="100dp"
            />

二：画虚线

xml布局：

   <com.lc.mycontrol.DashedLine 
        android:id="@+id/dashedLine"
        android:layout_width="wrap_content" 
        android:layout_marginLeft="50dp"        
        android:layout_height="300dp"                                   
         />

view

public class DashedLine extends View{
    private final String namespace = "http://com.smartmap.driverbook";
    private float startX;
    private float startY;
    private float endX;
    private float endY;
    private Rect mRect;
    Context contextgb;
    public DashedLine(Context context, AttributeSet attrs) {
        super(context, attrs); 
        contextgb = context;
    }
    @Override
    protected void onDraw(Canvas canvas) {
        int[] location = new  int[2] ;
        //this.getLocationInWindow(location); //获取在当前窗口内的绝对坐标        
        //System.out.println("InWindow x:"+location[0]+" y:"+location[1]);  
        this.getLocationOnScreen(location);//获取在整个屏幕内的绝对坐标
        System.out.println("OnScreen x:"+location[0]+" y:"+location[1]); 
        // TODO Auto-generated method stub
        super.onDraw(canvas);        
        Paint paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.WHITE);
        Path path = new Path();        
        //location[0]获取到控件所在的x坐标,可以设置改控件位置
        path.moveTo(5, Dp2Px(contextgb,10));
        path.lineTo(5, Dp2Px(contextgb,56));      
        PathEffect effects = new DashPathEffect(new float[]{2,2,2,2},2);
        paint.setPathEffect(effects);
        paint.setStrokeWidth((float) 1.5);
        canvas.drawPath(path, paint);
    }
    public float Dp2Px(Context context, float dp) { 
        final float scale = context.getResources().getDisplayMetrics().density; 
        return (float) (dp * scale + 0.5f); 
    }
}