使用UITextView（iOS / iPHone）撤消/重做 [英] Undo/redo with a UITextView (iOS/iPHone)

问题描述

我有一个视图，其中UITextView始终具有焦点。我想要做的是扩展内置的撤消/重做行为，以便在我以编程方式设置文本时支持撤消/重做（例如，当我清除它时，通过将其设置为@）。

I have a view where a UITextView always has focus. What I want to do is extend the built-in undo/redo behavior to support undo/redo for when I programmatically set the text (e.g., for when I clear it, by setting it to @"").

由于只有firstResponder获取了undo / redo事件，我以为我只是使用UITextView的undoManager属性来创建我的调用。例如，

Since only the firstResponder gets undo/redo events, I thought I'd simply use the UITextView's undoManager property to create my invocations. e.g.,

// Before clearing the text...
[[self.myTextView.undoManager prepareWithInvocationTarget:self] undoClear:self.myTextView.text]; 
[self.myTextView.undoManager setActionName:@"Clear"];

// ...

-(void)undoClear:(NSString *)textToRestore
{
    self.myTextView.text = textToRestore;
    if ([self.myTextView.undoManager isUndoing])
    {
      // Prepare the redo.
      [[self.myTextView.undoManager prepareWithInvocationTarget:self] undoClear:@""];  
    }
}

不幸的是，这不起作用。它：

Unfortunately, this is not working. It:

1. 在撤销堆栈中引入一个空项目（撤消）


2. 撤消清除在该项目后添加（如果我点击撤消，我看到撤消清除）


3. 撤消清除和重做清除工作，然后，我看到撤消清除再次，它不起作用。

任何想法？我接近这个错误了吗？

Any ideas? Am I approaching this wrong?

更新：好像我已经找到了空的撤销项目问题：它发生在我设置时之后的UITextView 的文本我调用了prepareWithInvocationTarget。如果我之前打电话，它就不会发生。有趣的是，如果我不调用prepareWithInvocationTarget（即，通常，当我设置UITextView的文本时），空项目不会被推到撤消堆栈上。

Update: It seems like I've figured out the empty undo item issue: it happens when I set the text of the UITextView after I've called prepareWithInvocationTarget. If I call it before, it doesn't happen. Funny thing is, the empty item isn't pushed onto the undo stack if I don't call prepareWithInvocationTarget (i.e., normally, when I set the text of a UITextView).

推荐答案

好的，想通了：

＃1的问题与原始帖子的更新中所述相同。

The issue with #1 is as outlined in the update to my original post.

问题＃2和＃3只是我错误地使用NSUndoManager。我的最终unClear方法（在undos上调用如下：

Issues #2 and #3 were just me using the NSUndoManager incorrectly. My final unClear method (which gets called on undos is as follows:

-(void)undoClear:(NSString *)textToRestore
{   
    NSString *textBackup = [self.myTextView.text copy];

    self.myTextView.text = textToRestore;

    if ([self.myTextView.undoManager isUndoing])
    {
        // Prepare the redo.
        [[self.myTextView.undoManager prepareWithInvocationTarget:self] undoClear:@""];     
    }
    else if ([self.myTextView.undoManager isRedoing])
    {
        [[self.myTextView.undoManager prepareWithInvocationTarget:self] undoClear:textBackup];
    }

    [textBackup release];
}

它现在正常运作。

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