UITextField的文本框部分文本以*的方式来显示

 1 #import "AppDelegate.h"
 2 
 3 @interface AppDelegate ()<UITextFieldDelegate>// 添加代理协议
 4 
 5 @end
 6 
 7 @implementation AppDelegate
 8 
 9 
10 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
11     self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
12     // Override point for customization after application launch.
13     self.window.backgroundColor = [UIColor whiteColor];
14     
15 
16     UITextField *tf = [[UITextField alloc] initWithFrame:CGRectMake(60, 100, 180, 30)];
17     //确认代理
18     tf.delegate = self;
19     tf.keyboardType = UIKeyboardAppearanceDefault;
20 
21     tf.backgroundColor = [UIColor greenColor];
22     [self.window addSubview:tf];
23     
24     [self.window makeKeyAndVisible];
25     return YES;
26 }
27 
28 - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
29 {
30     int length = [textField.text length];
31     // 2代表*号的起始位置,9代表*号的结束位置
32     if (length > 2 && length < 9) {
33         NSMutableString *text = [textField.text mutableCopy];
34         [text replaceCharactersInRange:NSMakeRange(length - 1 , 1) withString:@"*"];
35         textField.text = text;
36     }
37     return YES;
38 }
39 
40 @end