Android自定view画圆效果

package sjx.com.custonview;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.Window;/** * dell 孙劲雄 * 2017/9/1 * 19:57 */public class Custonm extends View {  private float currentX = 40;  private float currentY = 50;  public Custonm(Context context) {    super(context);  }  public Custonm(Context context, AttributeSet attrs) {    super(context, attrs);  }  public Custonm(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);  }//测量  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);  }//摆放  @Override  protected void onLayout(boolean changed, int left, int top, int right, int bottom) {    super.onLayout(changed, left, top, right, bottom);  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    Paint paint=new Paint();    paint.setColor(Color.RED);    paint.setStyle(Paint.Style.FILL);    paint.setAntiAlias(true);    canvas.drawCircle(currentX,currentY,30,paint);  }  @Override  public boolean dispatchTouchEvent(MotionEvent event) {    return super.dispatchTouchEvent(event);  }  @Override  public boolean onTouchEvent(MotionEvent event) {    currentX=event.getX();    currentY=event.getY();    invalidate();    switch (event.getAction()){      case MotionEvent.ACTION_DOWN:        Log.i("sss", "按下");        break;      case MotionEvent.ACTION_MOVE:        Log.i("sss", "移动");        break;      case MotionEvent.ACTION_UP:        Log.i("sss", "弹起");        break;    }    return true;  }}