UIWindow使用介绍

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.window.rootViewController = [self rootViewController];
    [self.window makeKeyAndVisible];
    
    return YES;
}

@interface PasswordInputView : UIWindow

+ (PasswordInputView *)shareInstance;

- (void)show;

@end

#import "PasswordInputView.h"

@interface PasswordInputView()
@property (nonatomic,weak) UITextField *textField;
@end

@implementation PasswordInputView

#pragma mark - Singleton
+ (PasswordInputView *)shareInstance {
    static id instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] initWithFrame:[UIScreen mainScreen].bounds];
    });
    
    return instance;
}

#pragma mark - Initilize
- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        [self setup];
    }
    return self;
}

- (instancetype)initWithCoder:(NSCoder *)decoder {
    if (self = [super initWithCoder:decoder]) {
        [self setup];
    }
    return self;
}

- (void)setup {
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 50, 200, 20)];
    label.text = @"请输入密码";
    [self addSubview:label];
    
    UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 80, 200, 20)];
    textField.backgroundColor = [UIColor whiteColor];
    textField.secureTextEntry = YES;
    [self addSubview:textField];
    self.textField = textField;
    
    UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(10, 110, 200, 44)];
    [button setBackgroundColor:[UIColor blueColor]];
    [button setTitle:@"确定" forState:UIControlStateNormal];
    [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [button addTarget:self action:@selector(completeButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:button];
    
    self.backgroundColor = [UIColor yellowColor];
}

#pragma mark - Common Methods
- (void)completeButtonPressed:(UIButton *)button {
    if ([self.textField.text isEqualToString:@"123456"]) {
        [self.textField resignFirstResponder];
        [self resignKeyWindow];
        self.hidden = YES;
    } else {
        [self showErrorAlertView];
    }
}

- (void)showErrorAlertView {
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil message:@"密码错误，请重新输入" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alertView show];
}

- (void)show {
    [self makeKeyWindow];
    self.hidden = NO;
}

@end

- (void)applicationDidBecomeActive:(UIApplication *)application {
    [[PasswordInputView shareInstance] show];
}