iOS13适配三指撤销和文案限长实例详解
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在适配iOS13的过程中，UITextField输入中文的时候三指撤销产生了 crash。
Bugly报错
NSInternalInconsistencyException setGroupIdentifier:: _NSUndoStack 0x1206532f0 is in invalid state, calling setGroupIdentifier with no begin group mark
堆栈信息
CoreFoundation ___exceptionPreprocess + 220 libobjc.A.dylib objc_exception_throw + 56 Foundation -[_NSUndoStack groupIdentifier] Foundation -[NSUndoManager undoNestedGroup] + 240 UIKitCore -[UIUndoGestureInteraction undo:] + 72 UIKitCore -[UIKBUndoInteractionHUD performDelegateUndoAndUpdateHUDIfNeeded] + 96 UIKitCore -[UIKBUndoInteractionHUD controlActionUpInside:] + 152 UIKitCore -[UIApplication sendAction:to:from:forEvent:] + 96 xxxxx -[UIApplication(MemoryLeak) swizzled_sendAction:to:from:forEvent:] + 288 UIKitCore -[UIControl sendAction:to:forEvent:] + 240 UIKitCore -[UIControl _sendActionsForEvents:withEvent:] + 408 UIKitCore -[UIControl touchesEnded:withEvent:] + 520 UIKitCore -[UIWindow _sendTouchesForEvent:] + 2324 UIKitCore -[UIWindow sendEvent:] + 3352 UIKitCore -[UIApplication sendEvent:] + 336 UIKitCore ___dispatchPreprocessedEventFromEventQueue + 5880 UIKitCore ___handleEventQueueInternal + 4924 UIKitCore ___handleHIDEventFetcherDrain + 108 CoreFoundation ___CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24 CoreFoundation ___CFRunLoopDoSource0 + 80 CoreFoundation ___CFRunLoopDoSources0 + 180 CoreFoundation ___CFRunLoopRun + 1080 CoreFoundation CFRunLoopRunSpecific + 464 GraphicsServices GSEventRunModal + 104 UIKitCore UIApplicationMain + 1936 xxxxx main + 148 libdyld.dylib _start + 4
问题定位
没有太多思路的时候，通过注释代码，最终定位到了问题所在。
[self addTarget:observer
action:@selector(textChange:)
forControlEvents:UIControlEventEditingChanged];
- (void)textChange:(UITextField *)textField {
... ...
UITextRange *selectedRange = [textField markedTextRange];
if (!selectedRange || !selectedRange.start) {
if (destText.length > maxLength) {
textField.text = [destText substringToIndex:maxLength];
}
}
}
这段代码在输入的时候会限制文案的长度。三指撤销会触发UIControlEventEditingChanged事件，执行textChange，此时获取到的markedTextRange是nil，即便是存在markedText。这就导致UITextField的text有可能会被修改。修改文案后再继续执行撤销操作，必定会产生 crash。
解决方案
将文案判长和截取异步添加到主队列，在下一个runloop执行。
- (void)textChange:(UITextField *)textField {
dispatch_async(dispatch_get_main_queue(), ^{
... ...
});
}
数字截断后 crash
数字输入限制长度后，超过长度后继续输入，这个时候撤销也会产生crash，而且上面的方法不可行。目前想到的方案是在UITextField的回调方法进行输入的拦截。
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
/// 输入数字后截取字符串仍旧可以触发撤销操作导致crash, 在这里拦截一下
if (textField.keyboardType == UIKeyboardTypeNumberPad
&& range.location >= textField.tt_maxLength) {
return NO;
}
return YES;
}加载全部内容