Question

我有一个观点，里面有一个UIImage。图像不是静态的，如果我拖动手指（使用拖动事件），我可以移动它。问题是有时图像会移动到UIView帧之外。什么是将它保持在父框架范围内的适当方法？

- UIViewA

-------- UIViewB

-------------- UIImage的

--------------的UIButton

我想在UIViewB中保留UIImage

- (IBAction)myButtonSingleTap:(UIButton *)sender {
    imDragging = YES;
    [_myButton addTarget:self action:@selector(dragBegan:withEvent:) forControlEvents: UIControlEventTouchDown];

}

- (IBAction)myButtonDragInside:(UIButton *)sender
{
    [_myButton addTarget:self action:@selector(draging:withEvent:) forControlEvents: UIControlEventTouchDragInside];

}
- (void)dragBegan:(UIControl *)c withEvent:ev {

    UITouch *touch = [[ev allTouches] anyObject];
    startingTouchPoint = [touch locationInView:self.view];

}
- (void)draging:(UIControl *)c withEvent:ev {
    UITouch *touch = [[ev allTouches] anyObject];
    currentTouchPoint = [touch locationInView:self.view];
    _movingPic.frame = CGRectMake(currentTouchPoint.x, currentTouchPoint.y, 28, 23);
}

Answer 1

您需要在拖动过程中检查视图的位置。

在某些时候，您将根据用户的拖动方向等设置图像的帧...

在此过程中，您应该进行逻辑检查，如...

If new location x value is less than 0 then set new location x = 0.
If new location x value plus image width is greater than view width then set new location x = view width - image width.

等...

然后使用新位置作为将图像移动到的点。

Answer 2

尝试将触控识别器添加到父视图而不是整个视图

Answer 3

在设置新帧之前，请确保它包含在移动视图的超视图边界内。

- (void)draging:(UIControl *)c withEvent:ev
{
    UITouch *touch = [[ev allTouches] anyObject];
    currentTouchPoint = [touch locationInView:self.view];
    CGRect newFrame = CGRectMake(currentTouchPoint.x, currentTouchPoint.y, 28, 23);
    newFrame.x = MAX(newFrame.x, 0);
    newFrame.y = MAX(newFrame.y, 0);
    newFrame.x = MIN(newFrame.x, _movingPic.superview.bounds.size.width - 28);
    newFrame.y = MIN(newFrame.y, _movingPic.superview.bounds.size.height - 23);
    _movingPic.frame = newFrame;
}

为什么子视图不会保留在父框架中？

3 个答案: