TextField输入时被Keyboard挡住的解决办法

我们在TextField输入时经常会出现被虚拟键盘挡住的现象，下面是具体的解决办法

//要用到textfield的代理
@interface ScrollerViewController ()<UITextFieldDelegate> {
    BOOL keyboardIsShown;//键盘是否出现
    CGPoint offset;//记录在键盘出现前，scrollview的contentOffset
}
@property (nonatomic, retain) UIScrollView *scrollView;
@property (nonatomic, retain) UITextField *textField;
@end

首先设置scrollview和加载textField

- (void)viewDidLoad
{
    //设置ScrollView
    scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    self.scrollView.zoomScale = 1.0;
    self.scrollView.contentSize = CGSizeMake(320, 1128);
    self.scrollView.contentOffset = CGPointMake(0, 0);
    self.scrollView.bounces = NO;
    //设置显示textField
for (int i = 0; i < 10; i++) {
        UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(20, 20 + i * 38, 70, 30)];
        label.text  = [NSString stringWithFormat:@"label%i",i + 1];
        label.textAlignment = NSTextAlignmentCenter;
        label.backgroundColor = [UIColor clearColor];
        label.textColor = [UIColor whiteColor];
        textField = [[UITextField alloc] initWithFrame:CGRectMake(100, 20 + i * 38, 200, 30)];
        self.textField.backgroundColor = [UIColor whiteColor];
        self.textField.delegate = self;
        self.textField.borderStyle = UITextBorderStyleRoundedRect;
        [self.scrollView addSubview:label];
        [self.scrollView addSubview:self.textField];
        [label release];
        [self.textField release];
    }
    [self.view addSubview:self.scrollView];
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

在View出现之前，注册两个通知。它能通知你什么时候keyboard出现或消失。

- (void)viewWillAppear:(BOOL)animated{
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardDidShow:)
name:UIKeyboardDidShowNotification
                                                           object:self.view.window];
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardDidHide:)
name:UIKeyboardDidHideNotification
                                                          object:nil];
    [super viewWillAppear:animated];
}

当任何textField被点击时textFieldDidBeginEditing:被激活，你可以保存一个正在被点击textField的拷贝。

- (void)textFieldDidBeginEditing:(UITextField *)textFieldView{
    textField = textFieldView;
}

当点击keyboard上的Return键时textFieldShouldReturn:方法会响应

- (BOOL)textFieldShouldReturn:(UITextField *)textFieldView{
    [textFieldView resignFirstResponder];
returnNO;
}

当keyboard隐藏，结束输入时textFieldDidEndEditing:方法会被textfield会被设为nil。

- (void)textFieldDidEndEditing:(UITextField *)textFieldView{
    textField = nil;
}

当键盘出现时，通过notification设置，keyboardDidShow:方法开始响应。方法中最重要的是获取键盘的高度，例如输入中文时，键盘会多出一行选字提示，高度就会发生变化，所以不能设成固定的216。然后重新设置ScrollView的frame，将textField滚动到可见位置。

如果键盘已经出现时，点击另一个textField，这个方法会自动退出。因为keyboardIsShown已经设为YES。如果点击的textField有部分隐藏，它会自动滚动到可见区域。

- (void)keyboardDidShow:(NSNotification *)notification{
    //当键盘已经出现
    if (keyboardIsShown) {
return;
    }
    NSDictionary *info = [notification userInfo];
    //获取keyboard的size
    NSValue *aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = [self.view convertRect:[aValue CGRectValue] fromView:nil];
    NSLog(@"%f", keyboardRect.size.height);
    //获取scrollView的contentOffset,当前的滚动位置
    offset = self.scrollView.contentOffset;
    //当键盘存在时,重新设置scrollView的size
    CGRect viewFrame = [self.scrollView frame];
    viewFrame.size.height -= keyboardRect.size.height;
    self.scrollView.frame = viewFrame;
    //将textField滚动到可见区域
    CGRect textFieldRect = [self.textField frame];
    [self.scrollView scrollRectToVisible:textFieldRect animated:YES];
    keyboardIsShown = YES;
}

当键盘消失时，keyboardDidHide:开始响应。还原ScrollView的frame

- (void)keyboardDidHide:(NSNotification *)notification{
    //获取键盘size
    NSDictionary* info = [notification userInfo];
    NSValue* aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = [self.view convertRect:[aValue CGRectValue] fromView:nil];
    //重新设置scrollView的size，使它还原到初始size
    CGRect viewFrame = [self.scrollView frame];
    viewFrame.size.height += keyboardRect.size.height;
    self.scrollView.frame = viewFrame;
    //还原滚动位置
    self.scrollView.contentOffset = offset;
    keyboardIsShown =   NO;
}

最后在View消失前，移除两个通知

- (void)viewWillDisappear:(BOOL)animated{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidHideNotification object:nil];
}