模仿 UITextView 的默认双击行为

Question

有谁知道当用户用两根手指在UITextView 中点击时会调用什么方法？

当用户用两根手指点击时，段落中的整个文本都会被选中。我想以编程方式实现相同的选择，以使此段落选择在我的自定义单击手势方法中可用。

Answer 1

从UITextView双击手势识别器的默认行为来看，我认为selectAll:是被调用来处理文本选择的方法。同样，您可以通过在现有的tapTextViewGesture: 方法中使用selectAll: 来强制您的文本视图在识别您的单击手势识别器时选择文本（如您的评论中所述）。

如果您希望文本选项自动显示以响应默认的双击手势识别器（即剪切、复制、粘贴等），请将selectAll: 设置为self：

- (IBAction)tapTextViewGesture:(id)sender {
    [self.textView selectAll:self]; 
}

否则，要简单地选择文本而不显示菜单，请将其设置为nil：

- (IBAction)tapTextViewGesture:(id)sender {
    [self.textView selectAll:nil]; 
}

更新

正如 cmets 中的 OP 所指出的，UITextView 双击手势识别器最初只会导致选择单个段落。

首先，从当前光标位置显示编辑菜单：

// Access the application's shared menu
UIMenuController *menu = [UIMenuController sharedMenuController];

// Calculate the cursor's position within the superview
// and convert it to a CGRect
CGPoint cursorPosition = [self.textView caretRectForPosition:self.textView.selectedTextRange.start].origin;
CGPoint cursorPositionInView = [self.textView convertPoint:cursorPosition toView:self.view];
CGRect menuRect = CGRectMake(cursorPositionInView.x, cursorPositionInView.y, 0, 0);

// Show the menu from the cursor's position
[menu setTargetRect:menuRect inView:self.view];
[menu setMenuVisible:YES animated:YES];

然后选择当前段落，这是我的建议：

// Break the text into components separated by the newline character
NSArray *paragraphs = [self.textView.text componentsSeparatedByString:@"\n"];

// Keep a tally of the paragraph character count
int characterCount = 0;

// Go through each paragraph
for (NSString *paragraph in paragraphs) {

    // If the total number of characters up to the end
    // of the current paragraph is greater than or
    // equal to the start of the textView's selected
    // range, select the most recent paragraph and break
    // from the loop
    if (characterCount + paragraph.length >= self.textView.selectedRange.location) {
        [self.textView setSelectedRange:NSMakeRange(characterCount, paragraph.length)];
        break;
    }

    // Increment the character count by adding the current
    // paragraph length + 1 to account for the newline character
    characterCount += paragraph.length + 1;
}

Answer 2

参见UITextInputTokenizer 协议参考：

采用 UITextInputTokenizer 协议的类的实例是分词器；分词器允许文本输入系统评估不同粒度的文本单元。文本单元的粒度总是根据存储或参考方向进行评估。

根据协议，使用 - (UITextRange *)rangeEnclosingPosition:(UITextPosition *)position withGranularity:(UITextGranularity)granularity inDirection:(UITextDirection)direction 并将 UITextGranularity 设置为 UITextGranularityParagraph 以检测您设置的粒度的 textRange。

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{

  if (touches.count == 2) {
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLocation = [touch locationInView:self.textView];

    //calculate the distance from touch
    UITextPosition *position = [self.textView closestPositionToPoint:touchLocation];
    NSUInteger distanceFromTouch = [self.textView offsetFromPosition:self.textView.beginningOfDocument
                                                          toPosition:position];
    //calculate the position by offset 
    UITextPosition *positionOffset = [self.textView positionFromPosition:self.textView.beginningOfDocument
                                                  offset:distanceFromTouch];

    //set up the granularity
    UITextGranularity granularity = UITextGranularityParagraph;

    //implement the protocol
    id<UITextInputTokenizer> tokenizer = self.textView.tokenizer;
    UITextRange *textRange = [tokenizer rangeEnclosingPosition:positionOffset
                                               withGranularity:granularity
                                                   inDirection:UITextWritingDirectionLeftToRight];

    //select the textRange
    [self.textView setSelectedTextRange:textRange];

    self.textView.keyboardType = UIKeyboardTypeNamePhonePad;

  }
}

不要忘记分配协议。 @interface ViewController ()<UITextInputTokenizer>