UITextField 的初始键盘动画的超慢滞后/延迟

问题描述

好吧，这个问题让我发疯了.

Alright, this problem has been driving me nuts.

触摸 UITextField 后，键盘弹出大约需要 3-4 秒.这仅在应用启动后第一次弹出键盘时发生，之后动画立即开始.

It takes roughly 3-4 seconds for the keyboard to pop up after I touch my UITextField. This only occurs on the first time the keyboard pops up since the app launched, afterwards the animation starts instantly.

一开始我以为是加载太多图片的问题，或者我的UITableView，但我刚刚创建了一个只有一个UITextField的全新项目，我仍然遇到这个问题.我正在使用 iOS 5、Xcode 4.2 版，并在 iPhone 4S 上运行.

At first I thought it was problem of loading too many images, or my UITableView, but I just created a brand new project with only a UITextField, and I still experience this problem. I'm using iOS 5, Xcode ver 4.2, and running on an iPhone 4S.

这是我的代码:

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(20, 20, 280, 30)];
    textField.borderStyle = UITextBorderStyleRoundedRect;
    textField.delegate = self;
    [self.view addSubview:textField];
}

@end

这是所有应用程序的共同问题吗?

Is this a common problem for all apps?

现在，我可以让它变得更好的唯一方法是让 textField 在 viewDidAppear 中成为/退出第一响应者，但这并不能完全解决问题- 它只是将延迟加载到视图加载时.如果我在视图加载时立即单击 textField，我仍然会遇到问题；如果我在视图加载后等待 3-4 秒再触摸 textField，我不会得到延迟.

Right now, the only way I can make it somewhat better is by having textField become/resign first responder in viewDidAppear, but that doesn't solve the problem entirely - it just loads the delay onto when the view loads instead. If I click on textField immediately when the view loads, I still get the problem; if I wait 3-4 seconds after the view loads before touching the textField, I don't get the delay.

推荐答案

所以问题不只是像我之前想象的那样仅限于第一次安装，而是每次启动应用程序时都会发生.这是我完全解决问题的解决方案.

So the problem is NOT just limited to the first install as I had previously thought, but happens every time the app is launched. Here's my solution that solves the issue completely.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  // Preloads keyboard so there's no lag on initial keyboard appearance.
  UITextField *lagFreeField = [[UITextField alloc] init];
  [self.window addSubview:lagFreeField];
  [lagFreeField becomeFirstResponder];
  [lagFreeField resignFirstResponder];
  [lagFreeField removeFromSuperview];
}

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