自定义view画圆

新建一个类

BallView 

继承view

public class BallView extends View {

    private int typedArrayInteger;
    private float cx=100;
    private float cy=100;
    private float aa;
    private float aFloat;

    public BallView(Context context) {
        this(context,null);
    }

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

    public BallView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.BallView);
        aFloat = typedArray.getDimension(R.styleable.BallView_ballsize, 70);
        Log.i("123333312",""+aFloat);
        //对自定义属性对象做回收资源逻辑的处理
        typedArray.recycle();

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
       // ）    用canvas将屏幕设为白色
        canvas.drawColor(Color.WHITE);
        Paint paint = new Paint();

        paint.setAntiAlias(true);
        //2）   设置画笔颜色为红色
        paint.setColor(Color.RED);
        paint.setStrokeWidth(5);
        paint.setStyle(Paint.Style.FILL);
//

        canvas.drawCircle(cx,cy,aFloat,paint);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                cx = event.getX();
                cy = event.getY();
                Log.i("","按下时：x坐标:"+event.getRawX()+"   "+"按下时：y坐标:"+event.getRawY());
                break;
            case MotionEvent.ACTION_MOVE:
                cx = event.getX();
                cy = event.getY();
                Log.i("","移动时：x坐标:"+event.getRawX()+"   "+"移动时：y坐标:"+event.getRawY());

                break;
            case MotionEvent.ACTION_UP:
                cx = event.getX();
                cy = event.getY();
                Log.i("","抬起时：x坐标:"+event.getRawX()+"   "+"抬起时：y坐标:"+event.getRawY());
                break;

        }
        invalidate();
        return true;
    }
}

///////////////////////////////////////////////////////////////////////////

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="BallView">
        <attr name="ballsize" format="dimension"></attr>

    </declare-styleable>


</resources>

///////////////////////////////activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
   >

    <chenshuai.bwie.com.ballviewdemo.BallView
        android:id="@+id/ballv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:ballsize="70dp"/>

</RelativeLayout>