ios - 弹出 Objective -C 时如何保留 ViewController

Question

当 View Controller 从堆栈中弹出时，如何保留它？

基本上我有一个 Mp3 播放器 View Controller 。当我在那个 View Controller 中时，我可以播放音乐。当音乐正在播放并且我导航到另一个 Controller 时，音乐停止播放，当我导航回该 Controller 时，它会启动它的另一个实例。所以我想解决办法可能是保留 View Controller ？

这就是我启动音乐播放器 View Controller 的方式:

NSString *songLargeArtworkURL = [self.songArtworkURL stringByReplacingOccurrencesOfString:@"large" withString:@"crop"];
MusicPlayerViewController *musicPlayer = [[MusicPlayerViewController alloc] init];
musicPlayer.songName = self.testString;
musicPlayer.songArtWork = songLargeArtworkURL;
musicPlayer.songStream = self.songStreamURL;
[self.navigationController pushViewController:musicPlayer animated:YES];

Answer 1

不要使用 MusicPlayerViewController 的局部变量，而是使用实例变量。仅在第一次时分配 musicPlayer 实例。如下图所示:

NSString *songLargeArtworkURL = [self.songArtworkURL stringByReplacingOccurrencesOfString:@"large" withString:@"crop"];
if(! musicPlayer) {
    musicPlayer = [[MusicPlayerViewController alloc] init];
}
musicPlayer.songName = self.testString;
musicPlayer.songArtWork = songLargeArtworkURL;
musicPlayer.songStream = self.songStreamURL;
[self.navigationController pushViewController:musicPlayer animated:YES];

上面的代码确保，仅在第一次实例化音乐播放器。随后，它会推送音乐播放器的同一实例