UITextView用法

• 简介

  UITextView控件用来显示多行并且可滚动的文字内容；它可以显示超出控件大小的内容；Iphone中的Note应用就是一个UITextView；

• 创建

  在视图控制器中创建一个UITextView属性，然后在ViewDidLoad方法中实例化该控件，并设置文本内容、文字大小等属性；

  #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 : 16.0f];      self.contentInset =  UIEdgeInsetMake(10.0f, 0.0f, 0.0f, 0.0f);      [self.view addSubView: self.myTextView];  }

• 常见问题
  在点击该控件编辑区域时，键盘会遮挡主底部一部分区域，使得用户无法看到这一部分的内容。可以通过监听以下事件来解决这个问题。
  UIKeyboardWillShowNotification: 输入键盘即将从textField或者textView中出现时触发；
  UIKeyboardDidShowNotification: 输入键盘处于显示状态时触发；
  UIKeyboardWillHideNotification: 输入键盘即将消失时触发；
  UIKeyboardDidHideNotification: 输入键盘完全消失时触发；
  当键盘即将出现时，调整textView的位置。因此可以使用ContentInset属性来予以解决。

-(void) handleKeyboardIDidShow:(Notification *) notification{    NSValue *keyboardRectAsObject = [[notification userInfo] objectForKey: UIKeyboardFrameEndUserInfoKey];    CGRect keyboardRect = CGRectZero;    [keyboardRectAsObject getVlaue: &keyboardRect];    //设置文本的下间距等于键盘高度    self.myTextView.contentInset = UIEdgeInsetMake(10.0f, 0.0f, keyboardRect.size.height, 0.0f);}-(void) handleKeyBoardWillHide:(Notification *) notification{    self.myTextView.contentInset =UIEdgeInsetMake(10.0f, 0.0f, 0.0f, 0.0f);}//在该方法中开始监听键盘事件-(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 : 16.0f];    [self.view addSubView: self.myTextView];}//在该方法中停止监听键盘事件，防止视图控制器在后台监听键盘事件-(void) viewWillDisappear: (BOOL) paramAnimated{    [super viewWillDisappear];    [[NSNotificationCenter defaultCenter] removeObserver: self];}