UITextField 使用详解

先附上效果图：

效果图.gif

后期会给大家写一个转账，把输入的金额转换为大写金额。大概功能，小数点只能输入一位，小数点后面最多只能有两位，也就是精确到分，实时的把你输入的小写金额转换为大写金额。先把效果图给大家附上：

转账效果图.gif

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSLog(@"textField = %@", textField.text);
    NSLog(@"range = %@", NSStringFromRange(range));
    NSLog(@"string = %@", string);
 }
 
// UITextField 输入说明
// 输入中文检测, 连续输入中文，注意观察数据的变化!
![Simulator Screen Shot 2016年12月7日 上午11.14.05](media/14799750828330/Simulator%20Screen%20Shot%202016%E5%B9%B412%E6%9C%887%E6%97%A5%20%E4%B8%8A%E5%8D%8811.14.05.png)

2016-12-07 11:12:11.764 狮王黄金[59001:796624] textField =  , range = {0, 0}, string = a
2016-12-07 11:12:12.679 狮王黄金[59001:796624] textField = a , range = {0, 1}, string = 啊
2016-12-07 11:12:13.359 狮王黄金[59001:796624] textField = 啊 , range = {1, 0}, string = z
2016-12-07 11:12:13.530 狮王黄金[59001:796624] textField = 啊z , range = {2, 0}, string = h
2016-12-07 11:12:13.657 狮王黄金[59001:796624] textField = 啊zh , range = {3, 0}, string = a
2016-12-07 11:12:13.698 狮王黄金[59001:796624] textField = 啊zha , range = {4, 0}, string = n
2016-12-07 11:12:13.832 狮王黄金[59001:796624] textField = 啊zhan , range = {5, 0}, string = g
2016-12-07 11:12:13.939 狮王黄金[59001:796624] textField = 啊zhang , range = {6, 0}, string = q
2016-12-07 11:12:13.997 狮王黄金[59001:796624] textField = 啊zhang q , range = {8, 0}, string = i
2016-12-07 11:12:14.182 狮王黄金[59001:796624] textField = 啊zhang qi , range = {1, 8}, string = 张琦
2016-12-07 11:12:14.767 狮王黄金[59001:796624] textField = 啊张琦 , range = {3, 0}, string = z
2016-12-07 11:12:14.966 狮王黄金[59001:796624] textField = 啊张琦z , range = {4, 0}, string = h
2016-12-07 11:12:15.028 狮王黄金[59001:796624] textField = 啊张琦zh , range = {5, 0}, string = a
2016-12-07 11:12:15.180 狮王黄金[59001:796624] textField = 啊张琦zha , range = {6, 0}, string = n
2016-12-07 11:12:15.212 狮王黄金[59001:796624] textField = 啊张琦zhan , range = {7, 0}, string = g
2016-12-07 11:12:15.351 狮王黄金[59001:796624] textField = 啊张琦zhang , range = {8, 0}, string = q
2016-12-07 11:12:15.455 狮王黄金[59001:796624] textField = 啊张琦zhang q , range = {10, 0}, string = i
2016-12-07 11:12:15.586 狮王黄金[59001:796624] textField = 啊张琦zhang qi , range = {11, 0}, string = q
2016-12-07 11:12:15.708 狮王黄金[59001:796624] textField = 啊张琦zhang qi q , range = {13, 0}, string = i
2016-12-07 11:12:19.296 狮王黄金[59001:796624] textField = 啊张琦zhang qi qi , range = {3, 11}, string = 张琪琪

// 删除时间
![Simulator Screen Shot 2016年12月7日 上午11.16.30](media/14799750828330/Simulator%20Screen%20Shot%202016%E5%B9%B412%E6%9C%887%E6%97%A5%20%E4%B8%8A%E5%8D%8811.16.30.png)

2016-12-07 11:16:04.270 狮王黄金[59001:796624] textField = 啊张琦张琪琪 , range = {5, 1}, string = 
2016-12-07 11:16:05.481 狮王黄金[59001:796624] textField = 啊张琦张琪 , range = {4, 1}, string = 
2016-12-07 11:16:06.141 狮王黄金[59001:796624] textField = 啊张琦张 , range = {3, 1}, string = 
2016-12-07 11:16:06.604 狮王黄金[59001:796624] textField = 啊张琦 , range = {2, 1}, string = 
2016-12-07 11:16:07.167 狮王黄金[59001:796624] textField = 啊张 , range = {1, 1}, string = 
2016-12-07 11:16:08.239 狮王黄金[59001:796624] textField = 啊 , range = {0, 1}, string =    // 此时已经删除完了， 但是 textField 还是会打印一个 啊

//总结 ：     
if (string.length) { // 说明此时是输入
        self.btnChange.selected = YES;
    } else {  // 说明此时是删除
        if (range.location) {  // 说明还没有删除到最后一个了
            self.btnChange.selected = YES;
        } else {
            self.btnChange.selected = NO;
        }
    }
    self.btnChange.enabled = self.btnChange.selected;
    return YES;

// 清除按钮要单独处理一下， 不然文字删除了，按钮还是可用的。
- (BOOL)textFieldShouldClear:(UITextField *)textField {
    self.btnChange.selected = NO;
    self.btnChange.userInteractionEnabled = self.btnChange.selected;
    return YES;
}

注意：禁用按钮不要用 self.btnChange.enabled = NO; 因为设置这个属性会让影响你按钮的背景颜色。大家可以用这 self.btnChange.userInteractionEnabled = self.btnChange.selected;

相信通过数据大家都会知道其中的规律。
此时运行程序， 你就会惊喜的发现咱们想要的效果了。
有不懂的地方可以第一时间问我。