blocks|key|1497396|text|使用UITextField，您就不能这样做。但是如果你看到标题，你有_selectedRange和其他的，如果你添加了一些类别，你可能会用到它们;)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1497397|​|1497398|iOS5及更高版本的更新：|1497399|现在，UITextField和UITextView符合UITextInput协议，因此可以:)|1497400|选择插入符号前的最后5个字符如下所示：|1497401|//+Get+current+selected+range+,+this+example+assumes+is+an+insertion+point+or+empty+selection
UITextRange+*selectedRange+=+[textField+selectedTextRange];

//+Calculate+the+new+position,+-+for+left+and+%2B+for+right
UITextPosition+*newPosition+=+[textField+positionFromPosition:selectedRange.start+offset:-5];

//+Construct+a+new+range+using+the+object+that+adopts+the+UITextInput,+our+textfield
UITextRange+*newRange+=+[textField+textRangeFromPosition:newPosition+toPosition:selectedRange.start];

//+Set+new+range
[textField+setSelectedTextRange:newRange];|code-block|syntax|javascript|1497402|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|U|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|V|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

With UITextField, you cannot. But if you see the headers, you have _selectedRange and others that might be used if you add some categories to it ;)
 
<h3>Update for iOS5 and above :</h3>
Now UITextField and UITextView conform to UITextInput protocol so it is possible :)
Selecting the last 5 characters before the caret would be like this:
<pre><code>// Get current selected range , this example assumes is an insertion point or empty selection
UITextRange *selectedRange = [textField selectedTextRange];

// Calculate the new position, - for left and + for right
UITextPosition *newPosition = [textField positionFromPosition:selectedRange.start offset:-5];

// Construct a new range using the object that adopts the UITextInput, our textfield
UITextRange *newRange = [textField textRangeFromPosition:newPosition toPosition:selectedRange.start];

// Set new range
[textField setSelectedTextRange:newRange];
</code></pre>

blocks|key|3879579|text|这两种方法都适用于我：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3879580|[UITextField+selectAll:self];|code-block|syntax|javascript|3879581|和：|3879582|UITextField.selectedRange+=+NSMakeRange(0,+5);|3879583|但前提是文本字段是第一响应者。(换句话说，只有在显示键盘的情况下。)因此，您需要在这两个select方法之前添加以下内容：|3879584|[UITextField+becomeFirstResponder];|3879585|如果希望文本显示为选中状态，请执行以下操作。|3879586|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

These both work for me:

<pre><code>[UITextField selectAll:self];
</code></pre>

and:

<pre><code>UITextField.selectedRange = NSMakeRange(0, 5);
</code></pre>

but only if the text field is the first responder. (In other words, only if the keyboard is showing.) So, you need to precede either of the select methods with this:

<pre><code>[UITextField becomeFirstResponder];
</code></pre>

if you want the text to appear selected.

blocks|key|3879629|text|要选择特定范围的字符，可以在iOS+5%2B中执行以下操作|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3879630|int+start+=+2;
int+end+=+5;
UITextPosition+*startPosition+=+[self+positionFromPosition:self.beginningOfDocument+offset:start];
UITextPosition+*endPosition+=+[self+positionFromPosition:self.beginningOfDocument+offset:end];
UITextRange+*selection+=+[self+textRangeFromPosition:startPosition+toPosition:endPosition];
self.selectedTextRange+=+selection;|code-block|syntax|javascript|3879631|因为UITextField和其他UIKit元素有自己的私有子类UITextPosition和UITextRange，所以不能直接创建新值，但可以使用文本字段从对文本开头或结尾的引用和整数偏移量创建它们。|offset|length|style|CODE|3879632|也可以进行相反操作，以获取当前选择的起点和终点的整数表示形式：|3879633|int+start+=+[self+offsetFromPosition:self.beginningOfDocument+toPosition:self.selectedTextRange.start];
int+end+=+[self+offsetFromPosition:self.beginningOfDocument+toPosition:self.selectedTextRange.end];|3879634|下面是一个类别，其中添加了使用NSRanges.+https://gist.github.com/4463233处理选择的方法。|3879635|entityMap|0|LINK|mutability|MUTABLE|url|https://gist.github.com/4463233^0|0|0|2|B|V|E|1A|B|0|0|0|F|7|P|V|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@$I|13|J|14|K|L]|$I|15|J|16|K|L]|$I|17|J|18|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|1B|8|@$I|1C|J|1D|K|L]]|9|@$I|1E|J|1F|1|1G]]|A|$]]|$1|S|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

To select a specific range of characters you can do something like this in iOS 5+

<pre><code>int start = 2;
int end = 5;
UITextPosition *startPosition = [self positionFromPosition:self.beginningOfDocument offset:start];
UITextPosition *endPosition = [self positionFromPosition:self.beginningOfDocument offset:end];
UITextRange *selection = [self textRangeFromPosition:startPosition toPosition:endPosition];
self.selectedTextRange = selection;
</code></pre>

Since <code>UITextField</code>s and other UIKit elements have their own private subclasses of <code>UITextPosition</code> and <code>UITextRange</code> you can not create new values directly, but you can use the text field to create them for you from a reference to the beginning or end of the text and an integer offset.

You can also do the reverse to get integer representations of the start and end points of the current selection:

<pre><code>int start = [self offsetFromPosition:self.beginningOfDocument toPosition:self.selectedTextRange.start];
int end = [self offsetFromPosition:self.beginningOfDocument toPosition:self.selectedTextRange.end];
</code></pre>

Here is a category which adds methods to handle selections using <code>NSRange</code>s. <a href="https://gist.github.com/4463233">https://gist.github.com/4463233</a>

blocks|key|1497475|text|只是对公认的答案的一个小小的补充。在iOS+5中，当UITextView的文本长度为0(没有文本)时，下面这行代码会使我的应用程序崩溃：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1497476|[self+textRangeFromPosition:startPosition+toPosition:endPosition];|code-block|syntax|javascript|1497477|一种小的解决方法是添加length+==+0检查，如下所示：|offset|length|style|CODE|1497478|if+(textField.text+&&+textField.text.length+>+0)+{
++++//+Get+current+selected+range+,+this+example+assumes+is+an+insertion+point+or+empty+selection
++++UITextRange+*selectedRange+=+[textField+selectedTextRange];

++++//+Calculate+the+new+position,+-+for+left+and+%2B+for+right
++++UITextPosition+*newPosition+=+[textField+positionFromPosition:selectedRange.start+offset:-5];

++++//+Construct+a+new+range+using+the+object+that+adopts+the+UITextInput,+our+textfield
++++UITextRange+*newRange+=+[textField+textRangeFromPosition:newPosition+toPosition:selectedRange.start];

++++//+Set+new+range
++++[textField+setSelectedTextRange:newRange];
}|1497479|entityMap^0|0|0|B|B|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Just a small addition to the accepted answer. In iOS 5, the following line crashes my app when UITextView's text length is 0 (has no text):

<pre><code>[self textRangeFromPosition:startPosition toPosition:endPosition];
</code></pre>

A small workaround is to add a <code>length == 0</code> check like:

<pre><code>if (textField.text &amp;&amp; textField.text.length &gt; 0) {
 // Get current selected range , this example assumes is an insertion point or empty selection
 UITextRange *selectedRange = [textField selectedTextRange];

 // Calculate the new position, - for left and + for right
 UITextPosition *newPosition = [textField positionFromPosition:selectedRange.start offset:-5];

 // Construct a new range using the object that adopts the UITextInput, our textfield
 UITextRange *newRange = [textField textRangeFromPosition:newPosition toPosition:selectedRange.start];

 // Set new range
 [textField setSelectedTextRange:newRange];
}
</code></pre>

blocks|key|2471884|text|要选择不带文件扩展名的文件名，请使用以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2471885|-(void)+tableViewCellDidBeginEditing:(UITableViewTextFieldCell*)+cell
{
++++NSInteger+fileNameLengthWithoutExt+=+[self.filename+length]+-+[[self.filename+pathExtension]+length];
++++UITextField*+textField+=+cell.textField;
++++UITextPosition*+start+=+[textField+beginningOfDocument];
++++UITextPosition*+end+=+[textField+positionFromPosition:start+offset:+fileNameLengthWithoutExt+-+1];+//+the+-1+is+for+the+dot+separting+file+name+and+extension
++++UITextRange*+range+=+[textField+textRangeFromPosition:start+toPosition:end];
++++[textField+setSelectedTextRange:range];
}|code-block|syntax|javascript|2471886|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

To select the name of a file without the file extension, use this:

<pre><code>-(void) tableViewCellDidBeginEditing:(UITableViewTextFieldCell*) cell
{
 NSInteger fileNameLengthWithoutExt = [self.filename length] - [[self.filename pathExtension] length];
 UITextField* textField = cell.textField;
 UITextPosition* start = [textField beginningOfDocument];
 UITextPosition* end = [textField positionFromPosition:start offset: fileNameLengthWithoutExt - 1]; // the -1 is for the dot separting file name and extension
 UITextRange* range = [textField textRangeFromPosition:start toPosition:end];
 [textField setSelectedTextRange:range];
}
</code></pre>

blocks|key|1500851|text|斯威夫特|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1500852|选择最后5个字符：|1500853|if+let+newPosition+=+textField.positionFromPosition(textField.endOfDocument,+inDirection:+UITextLayoutDirection.Left,+offset:+5)+{

++++textField.selectedTextRange+=+textField.textRangeFromPosition(newPosition,+toPosition:+textField.endOfDocument)
}|code-block|syntax|javascript|1500854|选择任意范围：|1500855|//+Range:+3+to+7
let+startPosition+=+textField.positionFromPosition(textField.beginningOfDocument,+inDirection:+UITextLayoutDirection.Right,+offset:+3)
let+endPosition+=+textField.positionFromPosition(textField.beginningOfDocument,+inDirection:+UITextLayoutDirection.Right,+offset:+7)

if+startPosition+!=+nil+&&+endPosition+!=+nil+{
++++textField.selectedTextRange+=+textField.textRangeFromPosition(startPosition!,+toPosition:+endPosition!)
}|1500856|我的完整答案是here。|offset|length|1500857|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/34922332/3681880^0|0|0|0|0|0|7|4|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

<h1>Swift</h1>
Select the last 5 characters:
<pre><code>if let newPosition = textField.positionFromPosition(textField.endOfDocument, inDirection: UITextLayoutDirection.Left, offset: 5) {

 textField.selectedTextRange = textField.textRangeFromPosition(newPosition, toPosition: textField.endOfDocument)
}
</code></pre>
Select an arbitrary range:
<pre><code>// Range: 3 to 7
let startPosition = textField.positionFromPosition(textField.beginningOfDocument, inDirection: UITextLayoutDirection.Right, offset: 3)
let endPosition = textField.positionFromPosition(textField.beginningOfDocument, inDirection: UITextLayoutDirection.Right, offset: 7)

if startPosition != nil &amp;&amp; endPosition != nil {
 textField.selectedTextRange = textField.textRangeFromPosition(startPosition!, toPosition: endPosition!)
}
</code></pre>
My full answer is <a href="https://stackoverflow.com/a/34922332/3681880">here</a>.

blocks|key|752239|text|Swift+5.0|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|752240|下面是我如何从Panda.txt中选择文件名Panda|CODE|752241|func+textFieldDidBeginEditing(_+textField:+UITextField)+{
++++//+if+textField.text+is+`Panda.txt`,+offset+will+be+3
++++let+offset+=+String(textField.text!.split(separator:+".").last!).length
++++let+from+=+textField.position(from:+textField.beginningOfDocument,+offset:+0)
++++let+to+=+textField.position(from:+textField.beginningOfDocument,
++++++++++++++++++++++++++++++++offset:textField.text!.length+-+(offset%2B1)+)
++++//now+`Panda`+will+be+selected
++++textField.selectedTextRange+=+textField.textRange(from:+from!,+to:+to!)
}|code-block|syntax|javascript|752242|entityMap^0|0|9|0|7|9|M|5|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|H]|$9|V|A|W|B|H]]|D|@]|E|$]]|$1|I|3|J|5|K|7|X|8|@]|D|@]|E|$L|M]]|$1|N|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|O|$]]

Swift 5.0

here is how I selecte file name <code>Panda</code> from <code>Panda.txt</code>

<pre class="lang-swift prettyprint-override"><code>func textFieldDidBeginEditing(_ textField: UITextField) {
 // if textField.text is `Panda.txt`, offset will be 3
 let offset = String(textField.text!.split(separator: ".").last!).length
 let from = textField.position(from: textField.beginningOfDocument, offset: 0)
 let to = textField.position(from: textField.beginningOfDocument,
 offset:textField.text!.length - (offset+1) )
 //now `Panda` will be selected
 textField.selectedTextRange = textField.textRange(from: from!, to: to!)
}

</code></pre>

I have a UITextField in my iPhone app. I know how to make the text field select all of its text, but how can change the selection? Say I wanted to select the last 5 characters, or a specific range of characters, is that possible? if not, can I move the lines marking the beginning and end of the selection, as if the user is dragging them?

Can I select a specific block of text in a UITextField?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我的iPhone应用程序中有一个UITextField。我知道如何让文本字段选择它的所有文本，但是如何更改选择？假设我想选择最后5个字符，或者特定的字符范围，这是可能的吗？如果没有，我是否可以移动标记选择的开始和结束的线，就像用户正在拖动它们一样？

问我可以在UITextField中选择特定的文本块吗？
EN

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问我可以在UITextField中选择特定的文本块吗？EN