当设置了 scrollEnabled 为 NO 以后，当输入的文字超出可显示区域以后，第一行的左上角会出现一个很小的闪烁的光标，虽然是系统的默认实现，但是看上去就像是个 bug
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| textView.scrollEnabled = NO;
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（此处省略截图）
解决思路
监听文字输入是否超出，超出以后隐藏光标，焦点在可视范围内的时候显示光标。
光标隐藏
光标创建逻辑被封装在 UITextView 内部，无法直接访问，不过我们可以通过修改 tintColor 来实现
UITextView+CaretUtil
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| @interface UITextView (CaretUtil)
@property (nonatomic, strong) UIColor *originTextViewTintColor;
- (void)updateCaretColor;
@end
#import "UITextView+CaretUtil.h"
#import <objc/runtime.h>
static void *kOriginTextViewTintColorKey = "OriginTextViewTintColor";
@implementation UITextView (CaretUtil)
- (void)updateCaretColor {
if (self.selectedTextRange) {
NSLayoutManager *layoutManager = self.layoutManager;
NSTextContainer *textContainer = self.textContainer;
UITextPosition *beginning = self.beginningOfDocument;
UITextRange *selectedRange = self.selectedTextRange;
UITextPosition *selectionStart = selectedRange.start;
UITextPosition *selectionEnd = selectedRange.end;
const NSInteger location = [self offsetFromPosition:beginning toPosition:selectionStart];
const NSInteger length = [self offsetFromPosition:selectionStart toPosition:selectionEnd];
NSRange textRange = NSMakeRange(location, length);
NSRange glyphRange = [layoutManager glyphRangeForCharacterRange:textRange actualCharacterRange:nil];
CGRect caretRect = [layoutManager boundingRectForGlyphRange:glyphRange inTextContainer:textContainer];
if (caretRect.size.height == 0) {
self.tintColor = [UIColor clearColor];
} else {
self.tintColor = self.originTextViewTintColor;
}
}
}
- (void)setOriginTextViewTintColor:(UIColor *)originTextViewTintColor {
objc_setAssociatedObject(self, kOriginTextViewTintColorKey, originTextViewTintColor, OBJC_ASSOCIATION_RETAIN);
}
- (UIColor *)originTextViewTintColor {
return objc_getAssociatedObject(self, kOriginTextViewTintColorKey);
}
@end
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选中的时候更新光标颜色
这里直接采取继承，覆写 setSelectedTextRange: 方法，希望代码侵入性低一点的可以选择 AOP
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| - (void)setSelectedTextRange:(UITextRange *)selectedTextRange {
[super setSelectedTextRange:selectedTextRange];
[self updateCaretColor];
}
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###TextView Delegate 中更新光标颜色
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| - (void)textViewDidChange:(UITextView *)textView {
[textView updateCaretColor];
}
- (void)textViewDidBeginEditing:(UITextView *)textView {
[textView updateCaretColor];
}
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