图形错误，同时以编程方式创建UILabel，UITextField等
我以编程方式创建了一个登录视图和一个表视图。
在某些我无法复制的情况下，会出现一些奇怪的视觉错误：
下面，我添加了两个屏幕截图，其中大部分应用程序都已停用，仅显示错误：
http://uppix.net/b/c/4/dd1e41acb94b7d0ad8eb173772e97.png http://uppix.net/b/f/2/a5993440c07753b851701068330be.png
在这里你可以看到文本混合了不同的字体大小。
这种错误不会定期发生或可以重现。
我添加了以下登录屏幕的代码：
// Implement loadView to create a view hierarchy programmatically, without
// using a nib.
- (void)loadView {
UIView *myView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
UIFont* font = [UIFont systemFontOfSize:14];
float midLine = 100.0;
float height = 30.0;
float borderY = 70.0;
float borderX = 10.0;
float width = 320.0 - borderX * 2.0;
float paddingX = 10.0;
float paddingY = 5.0;
CGRect usernameLabelRect = CGRectMake(borderX, borderY, midLine, height);
CGRect usernameFieldRect = CGRectMake(borderX + midLine + paddingX, borderY,
width - midLine - paddingX - 40 , height);
CGRect passwordLabelRect = CGRectMake(borderX, borderY + height + paddingY,
midLine, height);
CGRect passwordFieldRect = CGRectMake(borderX + midLine + paddingX,
borderY + height + paddingY,
width - midLine - paddingX - 40, height);
CGRect loginButtonRect = CGRectMake(borderX + 40,
borderY + height*2 + paddingY*2, width - 80,
height);
//CGRect warningRect = CGRectMake(borderX,
// borderY * height * 3.0 + paddingY *3.0,
// width, height);
CGRect warningRect = CGRectMake(borderX, 175, width, 40);
UILabel* usernameLabel = [[UILabel alloc] initWithFrame:usernameLabelRect];
usernameLabel.textAlignment = UITextAlignmentRight;
usernameLabel.font = font;
usernameLabel.text = @"Username:";
UILabel* passwordLabel = [[UILabel alloc] initWithFrame:passwordLabelRect];
passwordLabel.textAlignment = UITextAlignmentRight;
passwordLabel.font = font;
passwordLabel.text = @"Password:";
usernameField = [[UITextField alloc] initWithFrame:usernameFieldRect];
[usernameField setBorderStyle:UITextBorderStyleRoundedRect];
//[usernameField setPlaceholder:@"<Username>"];
usernameField.font = font;
usernameField.autocapitalizationType = UITextAutocapitalizationTypeNone;
usernameField.autocorrectionType = UITextAutocorrectionTypeNo;
passwordField = [[UITextField alloc] initWithFrame:passwordFieldRect];
passwordField.font = font;
[passwordField setBorderStyle:UITextBorderStyleRoundedRect];
//[passwordField setPlaceholder:@"<Password>"];
passwordField.autocapitalizationType = UITextAutocapitalizationTypeNone;
passwordField.autocorrectionType = UITextAutocorrectionTypeNo;
passwordField.secureTextEntry = YES;
loginButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
loginButton.frame = loginButtonRect;
[loginButton setTitle: @"Einloggen" forState:UIControlStateNormal];
[loginButton setTitleColor:[UIColor blackColor]
forState:UIControlEventTouchDown];
loginButton.contentVerticalAlignment =
UIControlContentVerticalAlignmentCenter;
loginButton.contentHorizontalAlignment =
UIControlContentHorizontalAlignmentCenter;
[loginButton addTarget:self action:@selector(OnLoginClicked:)
forControlEvents:UIControlEventTouchUpInside];
[loginButton setBackgroundColor:[UIColor clearColor]];
warningLabel = [[UILabel alloc] initWithFrame:warningRect];
warningLabel.font = font;
warningLabel.numberOfLines = 3;
warningLabel.text =
@"Wenn Sie die Applikation jetzt schließen, so werden Ihre Logindaten verworfen.";
[myView addSubview:usernameLabel];
[myView addSubview:passwordLabel];
[myView addSubview:usernameField];
[myView addSubview:passwordField];
[myView addSubview:loginButton];
[myView addSubview:warningLabel];
/*
[usernameLabel release];
[passwordLabel release];
[usernameField release];
[passwordField release];
[loginButton release];
[warningLabel release];
*/
self.view = myView;
[myView release];
}
我无法将所有屏幕定位在我的脑海中，但它在我看来像许多场地重叠：这是故意的吗？ 也许这是原因？ 我通常在代码中创建视图，但这可能是IB的一种情况！
您没有为表格视图显示任何代码，但是在将子视图添加到单元格之前，我看起来类似的问题，然后下一次使用DequeueReusableCell对单元格进行清除时，您再次添加子视图而不检查它们是否存在或清除它们。 这会导致各种重叠，就像第一个截图一样。
问题是我从Not-The-Main-Thread调用UIKit消息，这会导致各种图形问题。 解决它通过使用performSelectorOnMainThread：在我的代码中的几个地方=）
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