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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