如何在用戶輸入新行時將自動縮進添加到UITextView？

Question

當用戶輸入新行時，如何將自動縮進添加到UITextView？例如：

line1 
    line2 <user has typed "Enter"> 
    <cursor position> 
    line3 <user has typed "Enter"> 
    <cursor position> 

Answer 1

雖然看上去好像OP其實也不是尋找在這種情況下標準的壓痕，我要離開這件事對未來的答案者。

下面介紹如何在每次換行符後自動添加縮進。我已經從我近期的answer about automatically adding bullet points at every newline調整了這個答案。

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text { 

    // If the replacement text is "\n" thus indicating a newline... 
    if ([text isEqualToString:@"\n"]) { 

     // If the replacement text is being added to the end of the 
     // text view's text, i.e. the new index is the length of the 
     // old text view's text... 
     if (range.location == textView.text.length) { 
      // Simply add the newline and tab to the end 
      NSString *updatedText = [textView.text stringByAppendingString:@"\n\t"]; 
      [textView setText:updatedText]; 
     } 

     // Else if the replacement text is being added in the middle of 
     // the text view's text... 
     else { 

      // Get the replacement range of the UITextView 
      UITextPosition *beginning = textView.beginningOfDocument; 
      UITextPosition *start = [textView positionFromPosition:beginning offset:range.location]; 
      UITextPosition *end = [textView positionFromPosition:start offset:range.length]; 
      UITextRange *textRange = [textView textRangeFromPosition:start toPosition:end]; 

      // Insert that newline character *and* a tab 
      // at the point at which the user inputted just the 
      // newline character 
      [textView replaceRange:textRange withText:@"\n\t"]; 

      // Update the cursor position accordingly 
      NSRange cursor = NSMakeRange(range.location + @"\n\t".length, 0); 
      textView.selectedRange = cursor; 

     } 

     // Then return "NO, don't change the characters in range" since 
     // you've just done the work already 
     return NO; 
    } 

    // Else return yes 
    return YES; 
} 

Answer 2

對於第一行，你會寫這樣的代碼：

- (void)textViewDidBeginEditing(UITextView *)textView 
{ 
    if ([textView.text isEqualToString:@""]) 
    { 
     [textView setText:@"\t"]; 
    } 
}