在iOS8委托方法中的零对象 - 自定义键盘 [英] nil object in iOS8 delegate methods - custom keyboards

问题描述

我正在构建一个自定义键盘
，我正在我的 InputViewController 中实现以下委托方法。

但我总是获取 _textInput = nil _

I'm building a custom keyboard and I'm implementing the following delegate methods in my InputViewController.
But I always get _textInput = nil_

- (void)textWillChange:(id<UITextInput>)textInput
- (void)textDidChange:(id<UITextInput>)textInput
- (void) selectionWillChange:(id<UITextInput>)textInput
- (void) selectionDidChange:(id<UITextInput>)textInput

有人知道如何解决它吗？

是 nil 为什么？

我需要自己实现吗？

Does anybody know how to fix it?
Is it nil for a reason?
Do I need to implement something by myself?

推荐答案

好问题。但是似乎 UITextInputDelegate 不是您实现的协议。

Good question. But it seems that UITextInputDelegate is not a protocol that you implement.

从苹果标题为较低级文本处理的文档技术：

由于外部原因，文本视图中发生更改 - 即
他们不是' t由文本输入系统的调用引起的 - UITextInput
对象应发送 textWillChange：， textDidChange：，
selectionWillChange：和 selectionDidChange：消息到输入
委托（它持有引用）。例如，当用户点击
a文本视图，并设置所选文本的范围以将
插入点放在手指下方时，您将发送 selectionWillChange：
更改所选范围之前，您更改范围后发送 selectionDidChange：
。

When changes occur in the text view due to external reasons—that is, they aren't caused by calls from the text input system—the UITextInput object should send textWillChange:, textDidChange:, selectionWillChange:, and selectionDidChange: messages to the input delegate (which it holds a reference to). For example, when users tap a text view and you set the range of selected text to place the insertion point under the finger, you would send selectionWillChange: before you change the selected range, and you send selectionDidChange: after you change the range.

从 docs ：

And from the docs on UITextInputDelegate:

UIKit提供了一个私有文本输入代理，它以
运行时分配给其类采用
的UITextInput协议的对象的inputDelegate属性。

The UIKit provides a private text input delegate, which it assigns at runtime to the inputDelegate property of the object whose class adopts the UITextInput protocol.

上面的含义是我们不实现这些委托方法;我们使用它们通知 inputDelegate ，您已经通过除键盘输入之外的方式更改了您的文本或选择。

The implication of the above is that we don't implement these delegate methods; we use them to inform the inputDelegate that you have changed your text or selection via means other than keyboard input.

以下是示例方法，说明了这一点：

Here is an example method that illustrates this:

- (void)delete:(id)sender;
{
    if (selection && ![selection isEmpty]) {
        [inputDelegate textWillChange:self];
        [inputDelegate selectionWillChange:self];
        [self replaceRange:selection withText:@""];
        [inputDelegate selectionDidChange:self];
        [inputDelegate textDidChange:self];
    }
}

具有更多示例的示例代码 here 。

Sample code with more examples here.

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