一、UIWindow的簡介

1.UIWindow是一種特殊的UIView，通常在一個app中只會有一個UIWindow

2.iOS程式啟動完畢後，建立的第一個檢視控制元件就是UIWindow，接著建立控制器的view，最後將控制器的view新增到UIWindow上，於是控制器的view就顯示在螢幕上了

3.一個iOS程式之所以能顯示到螢幕上，完全是因為它有UIWindow。也就說，沒有UIWindow，就看不見任何UI介面

二、在window上新增Button

1.建立window

-(UIWindow *)window
{
    if (!_window)
    {
        id <UIApplicationDelegate> delegate = [[UIApplication sharedApplication] delegate];
        if ([delegate respondsToSelector:@selector(window)])
        {
            _window = [delegate performSelector:@selector(window)];
        }
        else
        {
            _window = [[UIApplication sharedApplication] keyWindow];
        }
    }
    return _window;
}

2.建立Buuton

-(UIButton *)levitateButton
{
    if (!_levitateButton)
    {
        _levitateButton = [UIButton buttonWithType:UIButtonTypeCustom];
        _levitateButton.frame = CGRectMake(self.view.frame.size.width - 70, self.view.frame.size.height - 200, 60, 60);
        _levitateButton.backgroundColor = MainColor;
        [_levitateButton setBackgroundImage:[UIImage imageNamed:@"Button"] forState:UIControlStateNormal];
        _levitateButton.layer.cornerRadius = 30.0f;
        _levitateButton.layer.masksToBounds = YES;
        [self.window addSubview:_levitateButton];
        [_levitateButton addTarget:self action:@selector(edit) forControlEvents:UIControlEventTouchUpInside];
        UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(panGestureRecognizer:)];
        gesture.delegate = self;
        [_levitateButton addGestureRecognizer:gesture];
    }
    return _levitateButton;
}

3.拉動懸浮按鈕移動需要遵守手勢的協議 UIGestureRecognizerDelegate

-(void)panGestureRecognizer:(UIPanGestureRecognizer *)recognizer
{
    CGPoint point = [recognizer translationInView:recognizer.view.superview];
    CGPoint center = CGPointMake(recognizer.view.center.x + point.x,recognizer.view.center.y + point.y);
    if (center.x > self.view.frame.size.width - recognizer.view.frame.size.width/2)
    {
        center.x = self.view.frame.size.width - recognizer.view.frame.size.width/2;
    }
    else if (center.x < recognizer.view.frame.size.width/2)
    {
        center.x = recognizer.view.frame.size.width/2;
    }
    else if (center.y < 109 + recognizer.view.frame.size.width/2)
    {
        center.y = 109 + recognizer.view.frame.size.width/2;
    }
    else if (center.y > self.view.frame.size.height - recognizer.view.frame.size.width/2)
    {
        center.y = self.view.frame.size.height - recognizer.view.frame.size.width/2;
    }
    [UIView animateWithDuration:0.1 animations:^{
        recognizer.view.center = center;
        [recognizer setTranslation:CGPointZero inView:recognizer.view.superview];
    }];
}
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    return YES;
}
根據自己的需要修改拉動的範圍
三、總結

上面的程式碼還稍微繁瑣點不過可以使用的,後續我會優化封裝下使程式碼更加簡潔,歡迎大家關注奔跑的蝸牛