Will的部落格

此範例為用一個NavigationBar，並新增一個Undo與Done按鈕，

控制已編輯的UITextView。

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UITextViewDelegate>
{
    NSString *prevText;
}
@end
 

ViewController.m

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIBarButtonItem *undoBtn;
@property (weak, nonatomic) IBOutlet UIBarButtonItem *doneBtn;
- (IBAction)undoClick:(id)sender;
- (IBAction)doneClick:(id)sender;
@property (weak, nonatomic) IBOutlet UITextView *bigTextView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    _undoBtn.enabled = NO;
    _doneBtn.enabled = NO;
}

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


- (IBAction)undoClick:(id)sender
{
    _bigTextView.text = prevText;
}


- (IBAction)doneClick:(id)sender
{
    [_bigTextView resignFirstResponder];
}

- (void)textViewDidBeginEditing:(UITextView *)textView
{
    prevText = textView.text;
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    _undoBtn.enabled = YES;
    _doneBtn.enabled = YES;
    
    return YES;
}

- (void)textViewDidEndEditing:(UITextView *)textView
{
    _undoBtn.enabled = NO;
    _doneBtn.enabled = NO;
}
@end