UITextView用法

• 簡介

  UITextView控件用來顯示多行并且可滾動的文字内容；它可以顯示超出控件大小的内容；Iphone中的Note應用就是一個UITextView；

• 建立

  在視圖控制器中建立一個UITextView屬性，然後在ViewDidLoad方法中執行個體化該控件，并設定文本内容、文字大小等屬性；

#import "MyViewController.h"

  @interface MyViewController()
  @property(nonatomic, strong) UITextView *myTextView;
  @end  

  @implementation
  -(void) viewDidLoad{
      [super viewDidLoad];

      self.myTextView = [[UITextView alloc] initWithFrame: self.view.bounds];
      self.myTextView.text = @"please write some words here...";
      self.myTextView.font = [UIFont systemFontOfSize : f];
      self.contentInset =  UIEdgeInsetMake(f, f, f, f);

      [self.view addSubView: self.myTextView];
  }
           

• 常見問題

  在點選該控件編輯區域時，鍵盤會遮擋主底部一部分區域，使得使用者無法看到這一部分的内容。可以通過監聽以下事件來解決這個問題。

  UIKeyboardWillShowNotification: 輸入鍵盤即将從textField或者textView中出現時觸發；

  UIKeyboardDidShowNotification: 輸入鍵盤處于顯示狀态時觸發；

  UIKeyboardWillHideNotification: 輸入鍵盤即将消失時觸發；

  UIKeyboardDidHideNotification: 輸入鍵盤完全消失時觸發；

  當鍵盤即将出現時，調整textView的位置。是以可以使用ContentInset屬性來予以解決。

-(void) handleKeyboardIDidShow:(Notification *) notification{
    NSValue *keyboardRectAsObject = [[notification userInfo] objectForKey: UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = CGRectZero;
    [keyboardRectAsObject getVlaue: &keyboardRect];
    //設定文本的下間距等于鍵盤高度
    self.myTextView.contentInset = UIEdgeInsetMake(f, f, keyboardRect.size.height, f);
}

-(void) handleKeyBoardWillHide:(Notification *) notification{
    self.myTextView.contentInset =UIEdgeInsetMake(f, f, f, f);
}

//在該方法中開始監聽鍵盤事件
-(void) viewWillAppear:(BOOL) paramAnimated{
    [super viewWillAppear: paramAnimated];

    [[NSNotificationCenter defaultCenter] 
        addObserver: self
        selector: @selector:(handleKeyboardDidShow:)]
        name: UIKeyboardDidShowNotification
        object: nil];

    [[NSNotificationCenter defaultCenter]
        addObserver: self
        selector: @selector(handleKeyboardWillHide:)
        name: UIKeyboardWillHideNotification
        object: nil];

    self.myTextView = [[UITextView alloc] initWithFrame: self.view.bounds];
    self.myTextView.text = @"please write some words here... ";
    self.myTextView.font = [UIFont systemFontOfSize : f];
    [self.view addSubView: self.myTextView];
}

//在該方法中停止監聽鍵盤事件，防止視圖控制器在背景監聽鍵盤事件
-(void) viewWillDisappear: (BOOL) paramAnimated{
    [super viewWillDisappear];

    [[NSNotificationCenter defaultCenter] removeObserver: self];
}