UIWindow介绍
阅读原文时间:2023年07月09日阅读:2

  1、作为容器,包含app所要显示的所有视图

  3、与UIViewController协同工作,方便完成设备方向旋转的支持

  1、addSubview

  2、rootViewController

三、WindowLevel

    const UIWindowLevel UIWindowLevelNormal;
    const UIWindowLevel UIWindowLevelAlert;
    const UIWindowLevel UIWindowLevelStatusBar;
    typedef CGFloat UIWindowLevel;

CGFloat _windowSublevel;),不过系统并没有把则个属性开出来。UIWindow的默认级别是UIWindowLevelNormal,我们打印输出这三个level的值分别如下:

46:08.752 UIViewSample[395:f803] Normal window level: 0.000000

  • 2012-03-27 22:46:08.754 UIViewSample[395:f803] Normal window level: 2000.000000

  • 2012-03-27 22:46:08.755 UIViewSample[395:f803] Normal window level: 1000.000000

      这样印证了他们级别的高低顺序从小到大为Normal < StatusBar < Alert,下面请看小的测试代码:

TestWindowLevel

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
self.window.backgroundColor = [UIColor yellowColor];
[self.window makeKeyAndVisible];

UIWindow \*normalWindow = \[\[UIWindow alloc\] initWithFrame:\[\[UIScreen mainScreen\] bounds\]\];  
normalWindow.backgroundColor = \[UIColor blueColor\];  
normalWindow.windowLevel = UIWindowLevelNormal;  
\[normalWindow makeKeyAndVisible\];  

CGRect windowRect = CGRectMake(50,   
                               50,   
                               \[\[UIScreen mainScreen\] bounds\].size.width - 100,   
                               \[\[UIScreen mainScreen\] bounds\].size.height - 100);  
UIWindow \*alertLevelWindow = \[\[UIWindow alloc\] initWithFrame:windowRect\];  
alertLevelWindow.windowLevel = UIWindowLevelAlert;  
alertLevelWindow.backgroundColor = \[UIColor redColor\];  
\[alertLevelWindow makeKeyAndVisible\];  

UIWindow \*statusLevelWindow = \[\[UIWindow alloc\] initWithFrame:CGRectMake(0, 50, 320, 20)\];  
statusLevelWindow.windowLevel = UIWindowLevelStatusBar;  
statusLevelWindow.backgroundColor = \[UIColor blackColor\];  
\[statusLevelWindow makeKeyAndVisible\];  

NSLog(@"Normal window level: %f", UIWindowLevelNormal);  
NSLog(@"Normal window level: %f", UIWindowLevelAlert);  
NSLog(@"Normal window level: %f", UIWindowLevelStatusBar);  

return YES;  

}

  1)我们生成的normalWindow虽然是在第一个默认的window之后调用makeKeyAndVisible,但是仍然没有显示出来。这说明当Level层级相同的时候,只有第一个设置为KeyWindow的显示出来,后面同级的再设置KeyWindow也不会显示。

  2)statusLevelWindow在alertLevelWindow之后调用makeKeyAndVisible,淡仍然只是显示在alertLevelWindow的下方。这说明UIWindow在显示的时候是不管KeyWindow是谁,都是Level优先的,即Level最高的始终显示在最前面。

有时候,我们也希望在应用开发中,将某些界面覆盖在所有界面最上层。这个时候,我们就可以手工创建一个新的UIWindow。例如,想做一个密码保护功能,在用户从应用的任何界面按Home键退出,过段时间再从后台切换回来时,显示一个密码输入界面。

Demo界面很简单,每次启动应用或者从后台进入应用,都会显示输入密码界面,只有密码输入正确,才能使用应用。

大致代码如下:

PasswordInputWindow.h 文件。   定义一个继承自UIWindow的子类 PasswordInputWindow,  shareInstance 是单例, show方法就是用来显示输入密码界面。

@interface PasswordInputView : UIWindow

  • (PasswordInputView *)shareInstance;

  • (void)show;

@end

PasswordInputWindow.m 文件。

#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

1.代码中我实现了initWithFrame和initWithCoder两个方法,这样可以保证,不管用户是纯代码还是xib实现的初始化,都没有问题。

2.如果我们创建的UIWindow需
要处理键盘事件,那就要合理的将其设置为keyWindow。keyWindow是被系统设计用来接受键盘和其他非触摸事件的UIWindow。我们可以
通过makeKeyWindow 和 resignKeyWindow 方法来将自己创建的UIWindow实例设置成keyWindow。

3. 加入以下代码,就可以保证,程序每次从后台进入的时候,先显示输入密码界面了。

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