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我是使用约束的新手，所以我对我做错了什么并不感到惊讶，但我不知道我做了什么和/或如何解决它。

这是我使用该frame属性的方法；它工作正常，文本视图显示：

-(void)displayFeedbackText {
    feedback = [[UITextView alloc] init];
    feedback.backgroundColor = [UIColor clearColor];
    feedback.font = [UIFont fontWithName:@"Helvetica Neue" size:14];
    NSString *t = @"If you have any problems with the" + 16; //Longest line of text view + padding.
    float textWidth = [t sizeWithFont:[UIFont fontWithName:@"Helvetica Neue" size:14]].width;
    float textHeight = [t sizeWithFont:[UIFont fontWithName:@"Helvetica Neue" size:14]].height;
    feedback.text=@"Thank you for buying My Haiku! \nIf you have any problems with the \napp, or if you want to share any \nthoughts or suggestions, please \nemail me at joel@xxxxx.com.";
    feedback.editable=NO;
    feedback.frame = CGRectMake(screenWidth/2-textWidth/2, (screenHeight/2-tabBarHeight) - (textHeight*6)/2, textWidth, textHeight*6);
    feedback.dataDetectorTypes=UIDataDetectorTypeAll;
    [self.view addSubview:feedback];
}

这是使用约束的方法（我已设置self.view.translatesAutoresizingMaskIntoConstraints为NOin viewDidLoad）。什么都没有显示：

-(void)displayFeedbackText {
    feedback = [[UITextView alloc] init];
    feedback.backgroundColor = [UIColor clearColor];
    feedback.font = [UIFont fontWithName:@"Helvetica Neue" size:14];
    feedback.text=@"Thank you for buying My Haiku! \nIf you have any problems with the \napp, or if you want to share any \nthoughts or suggestions, please \nemail me at joel@xxxxx.com.";
    feedback.editable=NO;
    feedback.dataDetectorTypes=UIDataDetectorTypeAll;
    NSLayoutConstraint *constraintX = [NSLayoutConstraint constraintWithItem:feedback attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];
    NSLayoutConstraint *constraintY = [NSLayoutConstraint constraintWithItem:feedback attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
    [self.view addConstraint:constraintX];
    [self.view addConstraint:constraintY];
    [self.view addSubview:feedback];
}

我做错了什么，我该如何解决？

非常感谢你的帮助。

4

1 回答 1

1

我认为它没有出现，因为你没有大小限制，所以它的大小可能为零。尝试设置显式大小约束或相对于超级视图的约束。如果它们是显式约束，你可以这样做（同样使用高度约束）：

NSLayoutConstraint *widthCon = [NSLayoutConstraint constraintWithItem:feedback attribute:NSLayoutAttributeWidth relatedBy:0 toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1  constant:320];
[feedback addConstraint:widthCon];
于 2013-01-16T18:21:34.887 回答