将光标移动到位置Objective-C

Question

我有一个UITextView,我想要两个按钮.当用户点击后退按钮时,我希望光标向后移动1个字符.当他们点击前进按钮时,光标应向前移动1个字符.我怎么能这样做？

Answer 1

我是为你写的,参考下面的答案.你可以将我写的代码放到一个基本项目中并试一试.

解决方案的想法:

您可以通过指定要选择的文本范围以编程方式选择文本块(请参阅参考).你问什么是范围？它基本上是一个起始位置和长度.由于您只关心光标位置,因此可以忽略长度(即将其保持为零)并将"选择"的起始位置调整为+1或-1.

参考:

我可以在UITextField中选择特定的文本块吗？

代码说明:

在下面的代码中,有两个按钮(前进和后退)和每个按钮的目标方法,用于更改UITextView中的光标位置.请注意,这tv是UITextView的类变量/属性(需要声明为此类).

代码:

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *forward = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    forward.frame = CGRectMake(20, 20, 100, 50);
    [forward setTitle:@"Forward" forState:UIControlStateNormal];
    [forward addTarget:self action:@selector(moveForward:) forControlEvents:UIControlEventTouchUpInside];

    UIButton *back = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    back.frame = CGRectMake(130, 20, 100, 50);
    [back setTitle:@"Back" forState:UIControlStateNormal];    
    [back addTarget:self action:@selector(moveBack:) forControlEvents:UIControlEventTouchUpInside];

    tv = [[UITextView alloc] initWithFrame:CGRectMake(20, 120, 280, 100)];
    [self.view addSubview:forward];
    [self.view addSubview:back];
    [self.view addSubview:tv];    
}


-(void)moveForward:(id)sender {
    UITextRange *selectedRange = [tv selectedTextRange];
    // Calculate the new position, - for left and + for right

    if (tv.selectedRange.location < tv.text.length) {
        UITextPosition *newPosition = [tv positionFromPosition:selectedRange.start offset:1];

        UITextRange *newRange = [tv textRangeFromPosition:newPosition toPosition:newPosition];

        // Set new range
        [tv setSelectedTextRange:newRange];
    }
}

-(void)moveBack:(id)sender {
    UITextRange *selectedRange = [tv selectedTextRange];
    // Calculate the new position, - for left and + for right

    if (tv.selectedRange.location > 0) {
        UITextPosition *newPosition = [tv positionFromPosition:selectedRange.start offset:-1];

        UITextRange *newRange = [tv textRangeFromPosition:newPosition toPosition:newPosition];

        // Set new range
        [tv setSelectedTextRange:newRange];
    }
}