如何在UITextView中添加双击手势

Question

目前我想让UITextView有一个双击的手势。似乎UITableView有它自己的双击手势，当我们双击时，一些文本将被选中。所以我想在我自己的手势识别器中删除这个默认的双击手势。我尝试了很多方法，都失败了。似乎没有办法删除UITextView的默认识别器。我也想在这个UITextView上添加一个透明的视图来做双击事件，但这个子视图将阻止UITextView上的其他手势。有什么方法可以在UITextView中添加双击手势识别器吗？我真的希望能有一个解决办法。

我仍然期待着iOS5的解决方案:)

Answer 1

我在iOS6上有一个解决方案，我们可以使用UIGestureRecognizerDelegate，然后重写gestureRecognizerShouldBegin:和gestureRecognizer:shouldReceiveTouch：。在这两个方法中，我们可以检查手势是否为doubleTapGestureForZooming，如果不是，则返回NO，或者返回YES。这在iOS6中很好用，但是在iOS5中这两个委托方法还没有被调用，所以iOS5可能需要另一个变通方法。最后，我得到了解决办法，我们可以覆盖UITextView的addGestureRecognizer方法来删除默认手势，希望这能对其他人有所帮助。

PS:我们真的不能移除UITextView的系统手势，我们甚至不能改变它们的属性。似乎当事件发生时，UItextview的所有手势都会被再次添加。

Answer 2

还有许多其他手势识别器附加到文本视图。因为你似乎并不需要它们。您可以删除它们。

myTextView.gestureRecognizers = nil;

在添加双击识别器之前。它起作用了。

然后，您可以添加

UITapGestureRecognizer *tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(mySelector)];
tapRecognizer.numberOfTapsRequired = 2;
tapRecognizer.numberOfTouchesRequired = 1;
[myTextView addGestureRecognizer:tapRecognizer];

Answer 3

我知道这个问题有点老了，但为了让未来的搜索者能及时了解这个问题，我想我应该添加另一个从iOS 7到10都适用的解决方案。它基本上汇集了here和here讨论过的解决方案，但对它们进行了微调，使UITextView能够识别自定义双击。

它通过将UITextView子类化并覆盖addGestureRecognizer:方法来实现这一点，以便将我们的自定义回调注入到双击手势中，并将单击手势配置为遵守新的双击钩子。

我之所以在addGestureRecognizer:中这样做，是因为UITextView会根据其当前状态不断地删除和添加手势，因此您必须不断地将其重置回来。

这段代码应该足以让人入门：

@interface MyCustomTextView ()

/**
 *  we want to keep track of the current single-tap gesture so we can make sure
 *  it waits for a double-tap gesture to fail before firing
 */
@property (weak, nonatomic) UITapGestureRecognizer *singleTap;

/**
 *  we want to keep track of the current double-tap gesture so we can tell a single
 *  tap gesture to ignore this double-tap when the single tap gesture changes
 */
@property (weak, nonatomic) UITapGestureRecognizer *doubleTap;

@end


@implementation MyCustomTextView

/**
 *  this will fire when the text view is double-tapped
 *
 *  @param tgr
 */
- (void)_handleTwoTaps:(UITapGestureRecognizer *)tgr
{
    // ADD CODE HERE
}

/**
 *  the reason why I've overridden this methods is these gestures change quite a bit
 *  depending on the state of the UITextView, (eg, when in focus and out of focus)
 *  and so this provides a reliable way to make sure any new gestures get updated
 *  with custom overrides.
 *
 *  @param gestureRecognizer
 */
- (void)addGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
{
    [super addGestureRecognizer:gestureRecognizer];
    if ([gestureRecognizer isKindOfClass:[UITapGestureRecognizer class]]) {
        UITapGestureRecognizer *tgr = (UITapGestureRecognizer *)gestureRecognizer;
        if ([tgr numberOfTapsRequired] == 1 && [tgr numberOfTouchesRequired] == 1) {
            self.singleTap = tgr;
            if (self.doubleTap) {
                [tgr requireGestureRecognizerToFail:self.doubleTap];
            }

        } else if ([tgr numberOfTapsRequired] == 2 && [tgr numberOfTouchesRequired] == 1) {
            [tgr addTarget:self action:@selector(_handleTwoTaps:)];
            self.doubleTap = tgr;
            if (self.singleTap) {
                [self.singleTap requireGestureRecognizerToFail:tgr];
            }
        }
    }
}

// NOTE: I'm not sure if this is needed but it's been there for years
// and so I thought I would include it just in case
- (void)removeGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
{
    if ([gestureRecognizer isKindOfClass:[UITapGestureRecognizer class]]) {
        UITapGestureRecognizer *tgr = (UITapGestureRecognizer *)gestureRecognizer;
        if ([tgr numberOfTapsRequired] == 2 && [tgr numberOfTouchesRequired] == 1) {
            [tgr removeTarget:self action:@selector(_handleTwoTaps:)];
        }
    }
    [super removeGestureRecognizer:gestureRecognizer];
}

@end