[置顶] iOS捕捉键盘移动（根据键盘移动view跟随上下）

#pragma mark- vc
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"与xxx聊天中";

//从IOS7开始，导航条和状态栏合为一体，而且呈半透明状，viewController.view的坐标0，0点在屏幕左上方，如果子视图位置在view的顶部，就会被导航条遮盖，所以，viewController会对自身的第一个子视图(scrollView)顶部添加64像素的contentInset，避免scrollView内容被查盖。
self.automaticallyAdjustsScrollViewInsets = NO;

_table.contentInset = UIEdgeInsetsMake(64, 0, 0, 0);
_table.delegate = self;
_table.dataSource = self;

//设置分割线的样式。
_table.separatorStyle = UITableViewCellSeparatorStyleNone;

//scrollView滑动时键盘消失；
//_table.keyboardDismissMode = UIScrollViewKeyboardDismissModeOnDrag;

[self loadSubView];

//监听键盘frame变化的通知，键盘位置发生变化时，让输入框位置也随之变化。
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveKeyboardFrameChangeNotification:) name:UIKeyboardWillChangeFrameNotification object:nil];

_array = [[NSMutableArray alloc] initWithCapacity:0];

[_table registerNib:[UINib nibWithNibName:@"SelfCell" bundle:nil] forCellReuseIdentifier:@"self"];

[_table registerNib:[UINib nibWithNibName:@"OtherCell" bundle:nil] forCellReuseIdentifier:@"other"];
}

- (void)loadSubView{
_inputView = [[UIView alloc] initWithFrame:CGRectMake(0, 627, 375, 40)];
[self.view addSubview:_inputView];

UIImageView *imgView = [[UIImageView alloc] initWithFrame:_inputView.bounds];
imgView.image = [UIImage imageNamed:@"chatinputbg.png"];
[_inputView addSubview:imgView];
[imgView release];

_textField = [[UITextField alloc] initWithFrame:CGRectMake(3, 3, 369, 34)];
_textField.borderStyle = UITextBorderStyleRoundedRect;
//设置return键的样式
_textField.returnKeyType = UIReturnKeySend;
//自动可用return键。
_textField.enablesReturnKeyAutomatically = YES;
//英文首字母是否大写。
_textField.autocapitalizationType = UITextAutocapitalizationTypeNone;
//清除键的显示方式。
_textField.clearButtonMode = UITextFieldViewModeWhileEditing;
[_inputView addSubview:_textField];

_textField.delegate = self;
}

#pragma mark- notificationMethod
- (void)receiveKeyboardFrameChangeNotification:(NSNotification *)noti{
//NSLog(@"%@",noti.userInfo);

//NSValue值类,基本类型和结构体不能直接放入数组和字典中，如果需要把结构体放入数组或字典，那么必须把结构体转换为NSValue，然后把NSValue放入字典或数组。
NSValue *value = [noti.userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];

//CGRect rect = [value CGRectValue];
CGRect rect;
[value getValue:&rect];

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:[[noti.userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue]];
//7是键盘动画专用速率
[UIView setAnimationCurve:[[noti.userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue]];
_inputView.frame = CGRectMake(0, rect.origin.y-40, 375, 40);
_table.frame = CGRectMake(0, 0, 375, _inputView.frame.origin.y);
if (_array.count>1) {
[_table scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:_array.count-1 inSection:0] atScrollPosition:UITableViewScrollPositionNone animated:NO];
}
[UIView commitAnimations];
}

#pragma mark- scrollViewDelegate
//scrollView将要开始拖拽时的回调方法。
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
[self.view endEditing:YES];
}

#pragma mark- textField
//return键点击时调用。
- (BOOL)textFieldShouldReturn:(UITextField *)textField{

[_array addObject:textField.text];
textField.text = @"";
[_table reloadData];

//scrollToRowAtIndexPath让tableView滚动到某一行，atScrollPosition参数是让这一行滚动出来之后显示在tableView上的位置（如果有可能）
[_table scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:_array.count-1 inSection:0] atScrollPosition:UITableViewScrollPositionNone animated:YES];
return YES;
}

#pragma mark- table
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return _array.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{

NSString *text = [_array objectAtIndex:indexPath.row];
//boundingRectWithSize计算出文本显示的边框大小。第一个参数是限定的宽度和高度。第二个参数是计算选项，第三个参数是计算的文本的具体属性。
NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
style.lineBreakMode = NSLineBreakByCharWrapping;
CGRect rect = [text boundingRectWithSize:CGSizeMake(220, 0) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:17],NSParagraphStyleAttributeName:style} context:nil];
[style release];

if (indexPath.row%2 == 0) {
SelfCell *cell = [tableView dequeueReusableCellWithIdentifier:@"self"];
cell.messageLabel.frame = CGRectMake(30, 10, rect.size.width, rect.size.height);
cell.bubbleImageView.frame = CGRectMake(20, 5, rect.size.width+20, rect.size.height+10);
cell.messageLabel.text = text;
return cell;
}else{
OtherCell *cell = [tableView dequeueReusableCellWithIdentifier:@"other"];
cell.messageLabel.frame = CGRectMake(375-rect.size.width-30, 10, rect.size.width, rect.size.height);
cell.bubbleImageView.frame = CGRectMake(375-rect.size.width-40, 5, rect.size.width+20, rect.size.height+10);
cell.messageLabel.text = text;
return cell;
}
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
NSString *text = [_array objectAtIndex:indexPath.row];
CGRect rect = [text boundingRectWithSize:CGSizeMake(220, 0) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:17]} context:nil];
return rect.size.height+20;
}

- (void)awakeFromNib {
// Initialization code
UIImage *img = [UIImage imageNamed:@"bubble.png"];
//stretchableImageWithLeftCapWidth设置边帽，能够使图片在拉伸或压缩时只按照某个像素点的颜色进行填充。（保证图片拉伸时不变形）
self.bubbleImageView.image = [img stretchableImageWithLeftCapWidth:25 topCapHeight:20];

self.messageLabel.numberOfLines = 0;
//折行方式
self.messageLabel.lineBreakMode = NSLineBreakByCharWrapping;
}