iOS.UIKit.05.UIScrollView

1、案例介绍：利用UIScrollView, 避免键盘遮挡控件；图0一、图02实际上是存在第三个UIButton的，滑动屏幕能够看到，如图06。效果如图01，图02。

图01图02图03图06

2、案例步骤：

一、选择Single View Application新建项目，取名cq.30.ScrollView，如图03。

二、Main.storyboard如图04，图05。

图04图05

三、CQ30ViewController.h

#import <UIKit/UIKit.h>

@interface CQ30ViewController : UIViewController<UITextFieldDelegate>
{
    BOOL keyboardVisible;   //键盘出现标识
}
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property (weak, nonatomic) IBOutlet UITextField *textField;
@end

四、CQ30ViewController.m

》经过UITextFieldDelegate实现对UITextField放弃第一响应者身份，关闭键盘

#pragma mark -- UITextFieldDelegate method
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];
    return YES;
}

》注册监听键盘打开与关闭通知

-(void) viewWillAppear:(BOOL)animated {
    
    //注册键盘出现通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector (keyboardDidShow:)
                                                 name: UIKeyboardDidShowNotification object:nil];
    //注册键盘隐藏通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector (keyboardDidHide:)
                                                 name: UIKeyboardDidHideNotification object:nil];
    [super viewWillAppear:animated];
}


-(void) viewWillDisappear:(BOOL)animated {
    //解除键盘出现通知
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name: UIKeyboardDidShowNotification object:nil];
    //解除键盘隐藏通知
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name: UIKeyboardDidHideNotification object:nil];
    
    [super viewWillDisappear:animated];
}

》经过监听键盘的打开与关闭动态改变UIScrollView的frame，聚焦当前UITextField。

-(void) keyboardDidShow: (NSNotification *)notif {
    
    if (keyboardVisible) {//键盘已经出现要忽略通知
        return;
    }
    // 得到键盘尺寸
    NSDictionary* info = [notif userInfo];
    NSValue* aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGSize keyboardSize = [aValue CGRectValue].size;
    
    //从新定义ScrollView的尺寸
    CGRect viewFrame = self.scrollView.frame;
    viewFrame.size.height -= (keyboardSize.height);
    self.scrollView.frame = viewFrame;
    
    //滚动到当前文本框
    CGRect textFieldRect = [self.textField frame];
    [self.scrollView scrollRectToVisible:textFieldRect animated:YES];
    
    keyboardVisible = YES;
}

-(void) keyboardDidHide: (NSNotification *)notif {
    
    NSDictionary* info = [notif userInfo];
    NSValue* aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGSize keyboardSize = [aValue CGRectValue].size;
    
    CGRect viewFrame = self.scrollView.frame;
    viewFrame.size.height += keyboardSize.height;
    self.scrollView.frame = viewFrame;
    
    if (!keyboardVisible) {
        return;
    }
    
    keyboardVisible = NO;
    
}