在Mac上区分Cocoa中的单击和双击 [英] Distinguishing a single click from a double click in Cocoa on the Mac

问题描述

我有一个自定义 NSView （它是许多人之一，他们都住在一个 NSCollectionView 认为这是相关的，但谁知道）。当我点击视图，我想让它改变其选择状态（并重新绘制自己相应）;当我双击视图时，我想让它为刚刚双击的对象弹出一个更大的预览窗口。

I have a custom NSView (it's one of many and they all live inside an NSCollectionView — I don't think that's relevant, but who knows). When I click the view, I want it to change its selection state (and redraw itself accordingly); when I double-click the view, I want it to pop up a larger preview window for the object that was just double-clicked.

我的第一个看起来像这样： / p>

My first looked like this:

- (void)mouseUp: (NSEvent *)theEvent {
    if ([theEvent clickCount] == 1) [model setIsSelected: ![model isSelected]];
    else if ([theEvent clickCount] == 2) if ([model hasBeenDownloaded]) [mainWindowController showPreviewWindowForPicture:model];
}

除非，当我双击视图时，选择状态改变和，窗口弹出。这不是我想要的。

which mostly worked fine. Except, when I double-click the view, the selection state changes and the window pops up. This is not exactly what I want.

似乎我有两个选择。我可以恢复选择状态响应双击（撤消错误的单击）或者我可以finagle某种 NSTimer 解决方案构建在延迟之前响应单击。换句话说，我可以确保在更改选择状态之前不会第二次点击。

It seems like I have two options. I can either revert the selection state when responding to a double-click (undoing the errant single-click) or I can finagle some sort of NSTimer solution to build in a delay before responding to the single click. In other words, I can make sure that a second click is not forthcoming before changing the selection state.

这看起来更加优雅，所以这是我第一次采取的方法。我从Google发现的唯一真正的指导是在一个未命名的网站，其名称有连字符。

This seemed more elegant, so it was the approach I took at first. The only real guidance I found from Google was on an unnamed site with a hyphen in its name. This approach mostly works with one big caveat.

未解决的问题是我的 NSTimer 等待多长时间？ 。未命名的站点建议使用Carbon函数 GetDblTime（）。除了在64位应用程序不可用，我可以找到它唯一的文档说，它返回时钟滴答。我不知道如何将这些转换为秒 NSTimer 。

The outstanding question is "How long should my NSTimer wait?". The unnamed site suggests using the Carbon function GetDblTime(). Aside from being unusable in 64-bit apps, the only documentation I can find for it says that it's returning clock-ticks. And I don't know how to convert those into seconds for NSTimer.

那么这里的正确答案是什么？使用 GetDblTime（）？ 撤消双击的选择？我不知道可可惯用的方法。

So what's the "correct" answer here? Fumble around with GetDblTime()? "Undo" the selection on a double-click? I can't figure out the Cocoa-idiomatic approach.

推荐答案

延迟选择状态的改变是（从什么I'

Delaying the changing of the selection state is (from what I've seen) the recommended way of doing this.

实现起来非常简单：

- (void)mouseUp:(NSEvent *)theEvent
{
    if([theEvent clickCount] == 1) {
        [model performSelector:@selector(toggleSelectedState) afterDelay:[NSEvent doubleClickInterval]];
    }
    else if([theEvent clickCount] == 2)
    {
        if([model hasBeenDownloaded])
        {
                [NSRunLoop cancelPreviousPerformRequestsWithTarget: model]; 
                [mainWindowController showPreviewWindowForPicture:model];
        }
    }
}

双击间隔可以作为 NSEvent ）上的类方法访问

(Notice that in 10.6, the double click interval is accessible as a class method on NSEvent)

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