這里說明一下，Apple沒有開放的狀態(tài)欄的API，在ios 的官方文檔沒有提到修改Window Level的方式;

先看一下Window Level的可用的值包括：

1: typedef CGFloat UIWindowLevel;

2: const UIWindowLevel UIWindowLevelNormal; // 0.0

3: const UIWindowLevel UIWindowLevelAlert; // 2000.0

4: const UIWindowLevel UIWindowLevelStatusBar; // 1000.0

默認(rèn)我們的UIView layer都是在UIWindowLevelNormal上，這也就是為什么系統(tǒng)彈出來的對話框在我們的視圖之上，因為它的Window Level級別更高。

根據(jù)WindowLevel的原理我們也就知道，如果想在系統(tǒng)的狀態(tài)欄上，添加自定義的狀態(tài)欄，就需要比UIWindowLevelStatusBar的級別更高，接下來，用代碼說明一下：

首先，先建一個Single View Application，名字自定義就可以了，

然后，新建一個類命名為： StatusBarOverlay 繼承自UIWindow類，代碼：

StatusBarOverlay.h文件

1: #import

2:

3: @interface StatusBarOverlay : UIWindow{

4: UIView *contentView;

5: UILabel *textLabel;

6: }

7:

8: @property (nonatomic, retain) UIView *contentView;

9:

10: @property (nonatomic, retain) UILabel *textLabel;

11:

12: @end

StatusBarOverlay.m文件

1: //

2: // StatusBarOverlay.m

3: // StatusBarDemo

4: //

5: // Created by jordy wang on 12-8-7.

6: // Copyright (c) 2012年 __MyCompanyName__. All rights reserved.

7: //

8:

9: #import "StatusBarOverlay.h"

10:

11: #define STATUS_BAR_ORIENTATION [UIApplication sharedApplication].statusBarOrientation

12: #define ROTATION_ANIMATION_DURATION [UIApplication sharedApplication].statusBarOrientationAnimationDuration

13:

14:

15: @interface StatusBarOverlay()

16:

17: - (void)initializeToDefaultState;

18: - (void)rotateStatusBarWithFrame:(NSValue *)frameValue;

19: - (void)setSubViewHFrame;

20: - (void)setSubViewVFrame;

21: @end

22:

23:

24: @implementation StatusBarOverlay

25: @synthesize contentView;

26: @synthesize textLabel;

27:

28: //重寫init方法

29: - (id)init

30: {

31: self = [super initWithFrame:CGRectZero];

32: if (self) {

33: self.windowLevel = UIWindowLevelStatusBar + 1;

34: self.frame = [UIApplication sharedApplication].statusBarFrame;

35: [self setBackgroundColor:[UIColor orangeColor]];

36: [self setHidden:NO];

37:

38: //內(nèi)容視圖

39: UIView *_contentView = [[UIView alloc] initWithFrame:self.bounds];

40: self.contentView = _contentView;

41: [self.contentView setAutoresizingMask:UIViewAutoresizingFlexibleWidth];

42: [self.contentView setBackgroundColor:[UIColor cyanColor]];

43: [self addSubview:self.contentView];

44: [_contentView release];

45:

46:

47: //添加textLabel

48: UILabel *_textLabel = [[UILabel alloc] initWithFrame:CGRectMake(30, 0, CGRectGetWidth(self.frame)-60, CGRectGetHeight(self.frame))];

49: self.textLabel = _textLabel;

50: [self.textLabel setBackgroundColor:[UIColor blueColor]];

51: [self.textLabel setFont:[UIFont systemFontOfSize:12]];

52: [self.textLabel setTextAlignment:UITextAlignmentCenter];

53: [self.textLabel setTextColor:[UIColor blackColor]];

54: [self.textLabel setText:@"自定義的狀態(tài)欄 author by jordy"];

55: [self.contentView addSubview:self.textLabel];

56: [_textLabel release];

57:

58: //注冊監(jiān)聽---當(dāng)屏幕將要轉(zhuǎn)動時，所出發(fā)的事件(用于操作本視圖改變其frame)

59: [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(willRotateScreenEvent:) name:UIApplicationWillChangeStatusBarFrameNotification object:nil];

60: //初始化

61: [self initializeToDefaultState];

62: }

63:

64: return self;

65: }

66:

67:

68:

69:

70: //初始化為默認(rèn)狀態(tài)

71: - (void)initializeToDefaultState

72: {

73: //獲取當(dāng)前的狀態(tài)欄位置

74: CGRect statusBarFrame = [UIApplication sharedApplication].statusBarFrame;

75: //設(shè)置當(dāng)前視圖的旋轉(zhuǎn), 根據(jù)當(dāng)前設(shè)備的朝向

76: [self rotateStatusBarWithFrame:[NSValue valueWithCGRect:statusBarFrame]];

77:

78:

79:

80: }

81:

82:

83: //旋轉(zhuǎn)屏幕

84: - (void)rotateStatusBarWithFrame:(NSValue *)frameValue

85: {

86: CGRect frame = [frameValue CGRectValue];

87: UIInterfaceOrientation orientation = STATUS_BAR_ORIENTATION;

88:

89: if (orientation == UIDeviceOrientationPortrait) {

90: self.transform = CGAffineTransformIdentity; //屏幕不旋轉(zhuǎn)

91: [self setSubViewVFrame];

92: }else if (orientation == UIDeviceOrientationPortraitUpsideDown) {

93: self.transform = CGAffineTransformMakeRotation(M_PI); //屏幕旋轉(zhuǎn)180度

94: [self setSubViewVFrame];

95: }else if (orientation == UIDeviceOrientationLandscapeRight) {

96: self.transform = CGAffineTransformMakeRotation((M_PI * (-90.0f) / 180.0f)); //屏幕旋轉(zhuǎn)-90度

97: [self setSubViewHFrame];

98: }else if (orientation == UIDeviceOrientationLandscapeLeft){

99: self.transform = CGAffineTransformMakeRotation(M_PI * 90.0f / 180.0f); //屏幕旋轉(zhuǎn)90度

100: [self setSubViewHFrame];

101: }

102:

103: self.frame = frame;

104: [self.contentView setFrame:self.bounds];

105: }

106:

107: //設(shè)置橫屏的子視圖的frame

108: - (void)setSubViewHFrame

109: {

110: self.textLabel.frame = CGRectMake(30, 0, 1024-60, 20);

111: }

112: //設(shè)置豎屏的子視圖的frame

113: - (void)setSubViewVFrame

114: {

115: self.textLabel.frame = CGRectMake(30, 0, 748-60, 20);

116: }

117:

118: #pragma mark -

119: #pragma mark 響應(yīng)屏幕即將旋轉(zhuǎn)時的事件響應(yīng)

120: - (void)willRotateScreenEvent:(NSNotification *)notification

121: {

122: NSValue *frameValue = [notification.userInfo valueForKey:UIApplicationStatusBarFrameUserInfoKey];

123: [self rotateStatusBarAnimatedWithFrame:frameValue];

124: }

125:

126: - (void)rotateStatusBarAnimatedWithFrame:(NSValue *)frameValue {

127: [UIView animateWithDuration:ROTATION_ANIMATION_DURATION animations:^{

128: self.alpha = 0;

129: } completion:^(BOOL finished) {

130: [self rotateStatusBarWithFrame:frameValue];

131: [UIView animateWithDuration:ROTATION_ANIMATION_DURATION animations:^{

132: self.alpha = 1;

133: }];

134: }];

135: }

136:

137: - (void)dealloc

138: {

139: [[NSNotificationCenter defaultCenter] removeObserver:self];

140: [textLabel release];

141: textLabel = nil;

142:

143: [contentView release];

144: contentView = nil;

145:

146: [super dealloc];

147: }

148:

149: @end

由于代碼比較簡單，并且我在上述代碼里有相應(yīng)的注釋，這里需要說明一點的是，默認(rèn)我們繼承自UIWindow的StatusBarOverlay類是hidden狀態(tài)，需要在初始化的時候設(shè)置它的hidden屬性為NO，

在屏幕旋轉(zhuǎn)過程中，自定義的狀態(tài)欄與UIViewController之間的旋轉(zhuǎn)是分離的，所以我們需要做一個隱藏的動畫，在旋轉(zhuǎn)過程前先隱藏自定義的狀態(tài)欄，旋轉(zhuǎn)結(jié)果后設(shè)置顯示狀態(tài)。

如果需要做一種動畫，比方從底部下移顯示一條信息，隔N秒后又自動收回的動畫，直接設(shè)置自定義的視圖的y坐標(biāo)就可以了，默認(rèn)y坐標(biāo)設(shè)置是0。

最后， 使用它的方式也比較簡單，只需要初始化，代碼：

StatusBarOverlay *statusBarOverlay = [[StatusBarOverlay alloc] init];

由于我公司的需求是開機自動下載的功能，所以我在初始化的時候，是放在了AppDelegate中。

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