iOS屏幕根据键盘自动变化高度

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
<UITextFieldDelegate>

@end

#import "ViewController.h"

#define W [UIScreen mainScreen].bounds.size.width
#define H [UIScreen mainScreen].bounds.size.height

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  
  
  UITextField *field=[[UITextField alloc]initWithFrame:CGRectMake(100, 300, 50, 50)];
  field.backgroundColor=[UIColor redColor];
  field.delegate=self;
  [self.view addSubview:field];
}

#pragma -mark -UITextFieldDelegate
-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
  [textField resignFirstResponder];
  
  //self.view 恢复原位
  NSTimeInterval animationDuration=0.10f;
  [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
  [UIView setAnimationDuration:animationDuration];
  float width = W;
  float height = H;
  float Y = 0.0f;
  CGRect rect=CGRectMake(0.0f,Y,width,height);
  self.view.frame=rect;
  [UIView commitAnimations];

  
  return YES;
}

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
  NSTimeInterval animationDuration=0.30f;
  [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
  [UIView setAnimationDuration:animationDuration];
  float width = W;
  float height = H;
  //上移100个单位，按实际情况设置
  CGRect rect=CGRectMake(0.0f,-100,width,height);
  self.view.frame=rect;
  [UIView commitAnimations];
  
  return YES;
}


- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

@end