NSUndoManager:重做不起作用

Question

我正在创建一个使用NSSlider的简单应用程序,可以使用两个按钮将其置于最大值或最小值.撤消管理器应跟踪所有更改并允许撤消/重做使用这两个按钮所做的所有更改.
这是界面:

#import <Cocoa/Cocoa.h>

@interface AppDelegate : NSObject <NSApplicationDelegate>
{
@private
    NSUndoManager* undoManager;
}

@property (assign) IBOutlet NSWindow *window;
@property (weak) IBOutlet NSSlider *slider;


- (IBAction)putToMax:(id)sender;
- (IBAction)putToMin:(id)sender;
- (void) setSliderValue: (float) value;

@end

执行:

#import "AppDelegate.h"

@implementation AppDelegate

@synthesize window = _window;
@synthesize slider = _slider;

- (NSUndoManager*) windowWillReturnUndoManager: (NSWindow*) window
{
    return undoManager;
}

- (IBAction)putToMax:(id)sender 
{
    float value= [_slider floatValue];
    [ [undoManager prepareWithInvocationTarget: self] setSliderValue: value];
    if(![undoManager isUndoing])
        [undoManager setActionName: @"Put to Max"];
    NSLog(@"%f value added to the stack",value);
    [_slider setFloatValue: 100.0];
}

- (IBAction)putToMin:(id)sender 
{
    float value= [_slider floatValue];
    [ [undoManager prepareWithInvocationTarget: self] setSliderValue: value];
    if(![undoManager isUndoing])
        [undoManager setActionName: @"Put to Min"];
    NSLog(@"%f value added to the stack",value);
    [_slider setFloatValue: 0.0];
}

- (void) setSliderValue: (float) value
{
    [_slider setFloatValue: value];
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
}

- (id) init
{
    self=[super init];
    if(self)
    {
        undoManager=[[NSUndoManager alloc]init];
    }
    return self;
}


@end

以及该应用程序的屏幕截图:

撤消工作正常,但我有重做的问题.

例如,启动应用程序后:

• 我点击put to max按钮.
• 然后菜单编辑 - > 撤消放入最大值.

滑块返回原位.

但是如果我进入菜单编辑 - >重做放到最大,滑块不会回到它的最大位置.我不明白为什么.

Answer 1

当撤销系统执行撤消操作时,它希望您使用与撤消相同的代码注册重做操作(除了NSUndoManager知道它正在倒带 - 但您不应该在意).

因此,添加适当的NSUndoManager调用 -setSliderValue: