iOS.UIKit.05.UIScrollView

一、案例介绍：利用UIScrollView,
避免键盘遮挡控件；图01、图02其实是存在第三个UIButton的，滑动屏幕可以看到，如图06。效果如图01，图02。

图01图02图03图06

二、案例步骤：

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

2、Main.storyboard如图04，图05。

图04图05

3、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

4、CQ30ViewController.m

》通过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];

}

》通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;

    }

    // 获得键盘尺寸

    NSDictionary* info = [notif userInfo];

    NSValue* aValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];

    CGSize keyboardSize = [aValue CGRectValue].size;
//重新定义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;
}

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