iphone - UITextView 中模拟按键的性能问题

Question

我使用以下代码来模拟 UITextView 中的按键(并将滚动设置到插入位置):

NSRange selectedRange = textview.selectedRange;

NSString *currentText = textview.text;

NSString *yourString = @"x";

NSString *firstPart = [currentText substringToIndex: selectedRange.location];
NSString *lastPart = [currentText substringFromIndex: selectedRange.location];

NSString *modifiedText = [firstPart stringByAppendingFormat:@"%@%@", yourString, lastPart];

textview.text = modifiedText;

NSInteger loc = selectedRange.location + 1;
NSInteger len = textview.selectedRange.length;

NSRange newRange = NSMakeRange(loc, len);
textview.selectedRange = newRange;

如您所见，我划分了textview.text，在光标位置插入@“x”并修改了整个文本。事实上，除非文本文件的长度很大，否则这非常有效。这听起来很合乎逻辑，因为我将整个事情分成几部分，每个模拟键也是如此。

因此，对于一个小文本文件，我没有任何问题，但对于一个大文本文件，我可以看到相当大的滞后。

有什么办法可以实现更好的性能吗？

Answer 1

您应该使用
，而不是在每次击键时重写整个文本-(void)insertText:(NSString*)text 方法

示例代码来自here :

@interface UIResponder(UIResponderInsertTextAdditions)
- (void) insertText: (NSString*) text;
@end

@implementation UIResponder(UIResponderInsertTextAdditions)

- (void) insertText: (NSString*) text
{
    // Get a refererence to the system pasteboard because that's
    // the only one @selector(paste:) will use.
    UIPasteboard* generalPasteboard = [UIPasteboard generalPasteboard];

    // Save a copy of the system pasteboard's items
    // so we can restore them later.
    NSArray* items = [generalPasteboard.items copy];

    // Set the contents of the system pasteboard
    // to the text we wish to insert.
    generalPasteboard.string = text;

    // Tell this responder to paste the contents of the
    // system pasteboard at the current cursor location.
    [self paste: self];

    // Restore the system pasteboard to its original items.
    generalPasteboard.items = items;

    // Free the items array we copied earlier.
    [items release];
}

@end