自定义view 实现小圆点拖动

主界面：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MyView myView = new MyView(this);

    }
}

view类：

public class MyView extends View {

    private Paint paint;
    private float X = 100;
    private float Y = 100;
    Rect rect = new Rect();
    private boolean M=false;

    public MyView(Context context) {
        super(context);
    }

    public MyView(Context context, @Nullable AttributeSet att) {
        super(context, att);
        paint = new Paint();
        paint.setColor(Color.RED);
        paint.setAntiAlias(true);
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawCircle(X, Y, 100, paint);
        rect.set((int) (X - 100), (int) (Y - 100), (int) (X + 100), (int) (Y + 100));
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                float x1 = event.getX();
                float y1 = event.getY();
                if(x1 >rect.left && x1 rect.top &&y1                     Toast.makeText(getContext(),"触摸事件的X值:"+x1,Toast.LENGTH_SHORT).show();
                    M = true;
                }else {
                    M = false;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if(M){
                    X = event.getX();
                    Y = event.getY();
                    invalidate();
                }

                break;
        }
        return true;
    }
}

布局文件：

    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"
    tools:context="com.bwie.day_03.MainActivity">

    android:layout_width="match_parent"
    android:layout_height="match_parent"
    />