UIScreen mirroredScreen屬性總是返回零

如果設備（原始iPad）不支持鏡像，但想要在iPad 2上使用屏幕鏡像，我想在外部連接的顯示器上顯示唯一的內容。現在，當我嘗試對此進行編碼時如下：UIScreen mirroredScreen屬性總是返回零

if ([UIScreen instancesRespondToSelector:@selector(mirroredScreen)] && [[UIScreen mainScreen] mirroredScreen] == nil) { 
    // Mirroring not supported. Present unique content on external display 
}

[[UIScreen mainScreen] mirroredScreen]總是返回nil。

我做錯了什麼？

來源

2011-04-04 Anupam Godbole

據我瞭解的文檔，mirroredScreen將參考主屏幕，如果您訪問實際上是鏡像屏幕的輔助屏幕上的屬性。如：

if ([[UIScreen screens] count] > 1) { 
    UIScreen *secondaryScreen = [[UIScreen screens] objectAtIndex:1]; 
    NSLog(@"%@", secondaryScreen.mirroredScreen); // will reference the mainScreen 
}

[[UIScreen mainScreen] mirroredScreen]隨後將始終返回nil因爲mainScreen不鏡像本身。

來源

2011-04-04 18:17:55

蘋果有一個關於推薦的方式，如果屏幕鏡像或不在這裏檢測：http://developer.apple.com/library/ios/#qa/qa1738/_index.html

UIScreen *aScreen; 

NSArray *screens = [UIScreen screens]; 
for (aScreen in screens) 
{ 
    if ([aScreen respondsToSelector:@selector(mirroredScreen)] 
       && [aScreen mirroredScreen] == [UIScreen mainScreen]) 
    { 
     // The main screen is being mirrored. 
    } 
    else 
    { 
     // The main screen is not being mirrored, or 
     // you are not running on a compatible device. 
    } 
}

來源

2011-04-20 12:30:10 Sylverb

UIScreen mirroredScreen屬性總是返回零

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