NSUndoManager only撤消，不是重做

Question

我寫了簡單的撤消和重做根據NSUndoManager的示例代碼更改背景顏色。所有的東西都可以很好地與撤消動作配合使用。但使用重做，它不會跳轉到之前註冊的NSUndoManager的註冊方法。 跟蹤代碼：關於你加什麼

#import "ViewController.h" 
enum color {kWhite = 0, kRed, kOrange, kYellow, kGreen, kCyan, kBlue, kMagenta}; 
@interface ViewController(){ 
    enum color kColor; 
    NSArray * colorArr; 
    NSUndoManager * undoManager; 
} 
- (IBAction)changeColor:(id)sender; 
- (IBAction)undo:(id)sender; 
- (IBAction)redo:(id)sender; 


@end 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view, typically from a nib.] 
    kColor = kWhite; 
    colorArr = [NSArray arrayWithObjects:[UIColor whiteColor], [UIColor redColor], [UIColor orangeColor], [UIColor yellowColor], [UIColor greenColor], [UIColor cyanColor], [UIColor blueColor], [UIColor magentaColor], nil]; 
    undoManager = [[NSUndoManager alloc] init]; 
    undoManager.levelsOfUndo = 7; 

    NSNotificationCenter * nc = [NSNotificationCenter defaultCenter]; 
    [nc addObserver:self selector:@selector(undoManagerDidUndo:) name:NSUndoManagerDidUndoChangeNotification object:self.undoManager]; 
    [nc addObserver:self selector:@selector(undoManagerDidRedo:) name:NSUndoManagerDidRedoChangeNotification object:self.undoManager]; 
} 

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

- (IBAction)changeColor:(id)sender { 
    [[undoManager prepareWithInvocationTarget:self] 
    setcolor:kColor]; 

    kColor ++; 
    if(kColor > kMagenta) kColor = kWhite; 

    [self.view setBackgroundColor:colorArr[kColor]]; 
} 
-(void) setcolor:(enum color) color{ 
    kColor = color; 
    [self.view setBackgroundColor:colorArr[kColor]]; 
    NSLog(@"zzzz %d", color); 
}; 

- (IBAction)undo:(id)sender { 
    [undoManager undo]; 
} 

- (IBAction)redo:(id)sender { 
    [undoManager redo]; 
} 

#pragma mark - Undo support 

// ------------------------------------------------------------------------------- 
// undoManagerDidUndo: 
// Handler for the NSUndoManagerDidUndoChangeNotification. Redisplays the table 
// view to reflect the changed value. 
// See also: -setEditing:animated: 
// ------------------------------------------------------------------------------- 
- (void)undoManagerDidUndo:(NSNotification *)notification 
{ 
    //[self.view setBackgroundColor:colorArr[kColor]]; 
} 

// ------------------------------------------------------------------------------- 
// undoManagerDidRedo: 
// Handler for the NSUndoManagerDidRedoChangeNotification. Redisplays the table 
// view to reflect the changed value. 
// See also: -setEditing:animated: 
// ------------------------------------------------------------------------------- 
- (void)undoManagerDidRedo:(NSNotification *)notification 
{ 
    //[self.view setBackgroundColor:colorArr[kColor]]; 
} 
@end 

Answer 1

// 
// ViewController.m 
// UndoManager 
// 
// Created by Eugene Buleyko on 01.08.14. 
// Copyright (c) 2014 Eugene Buleyko. All rights reserved. 
// 

#import "ViewController.h" 

enum color {kWhite = 0, kRed, kOrange, kYellow, kGreen, kCyan, kBlue, kMagenta}; 

@interface ViewController() { 
    enum color kColor; 
    NSArray * colorArr; 
    NSUndoManager * undoManager; 
} 

- (IBAction)changeColor:(id)sender; 
- (IBAction)undo:(id)sender; 
- (IBAction)redo:(id)sender; 

@end 

@implementation ViewController 

@synthesize buttonRedo, buttonUndo; 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    kColor = kWhite; 
    colorArr = [NSArray arrayWithObjects:[UIColor whiteColor], [UIColor redColor], [UIColor orangeColor], [UIColor yellowColor], [UIColor greenColor], [UIColor cyanColor], [UIColor blueColor], [UIColor magentaColor], nil]; 
    undoManager = [[NSUndoManager alloc] init]; 
    undoManager.levelsOfUndo = 9; 

    NSNotificationCenter * nc = [NSNotificationCenter defaultCenter]; 
    [nc addObserver:self selector:@selector(undoManagerDidUndo:) name:NSUndoManagerDidUndoChangeNotification object:self.undoManager]; 
    [nc addObserver:self selector:@selector(undoManagerDidRedo:) name:NSUndoManagerDidRedoChangeNotification object:self.undoManager]; 

    [self setcolor:kColor]; 
} 

- (void)didReceiveMemoryWarning 
{ 
    [super didReceiveMemoryWarning]; 
} 

- (IBAction)changeColor:(id)sender { 

    kColor ++; 

    if (kColor > kMagenta) { 
     kColor = kWhite; 
    } 
    [self setcolor:kColor]; 

    [self.view setBackgroundColor:colorArr[kColor]]; 

} 
-(void) setcolor:(enum color) color{ 

// if ([self.view backgroundColor] == colorArr[color]) { 
//  NSLog(@"=="); 
//   
// } else { 
//  NSLog(@"!="); 
// } 

    kColor = color; 

    [[undoManager prepareWithInvocationTarget:self] setcolor:kColor]; 
    //[undoManager setActionname:@"Add"]; 
}; 


- (IBAction)undo:(id)sender { 
    [undoManager undo]; 
} 

- (IBAction)redo:(id)sender { 
    [undoManager redo]; 
} 

#pragma mark - Undo support 

- (void)undoManagerDidUndo:(NSNotification *)notification 
{ 
    [self.view setBackgroundColor:colorArr[kColor]]; 

    if (![undoManager canUndo]) self.buttonUndo.enabled = NO; 
    if ([undoManager canRedo]) self.buttonRedo.enabled = YES; 

} 

- (void)undoManagerDidRedo:(NSNotification *)notification 
{ 
    [self.view setBackgroundColor:colorArr[kColor]]; 

    if (![undoManager canRedo]) self.buttonRedo.enabled = NO; 
    if ([undoManager canUndo]) self.buttonUndo.enabled = YES; 
} 


@end