Objective-c:NSButton setAction 不工作

Question

我正在以编程方式制作几个按钮并尝试为每个按钮设置一个 Action ，但我似乎无法让它工作。

在我的 AppController.h 中我有这段代码:

...
IBOutlet NSButton* btnZoomIn;
IBOutlet NSButton* btnZoomOut;
...

和

- (IBAction) zoomIn : (id) sender; 

- (IBAction) zoomOut : (id) sender;

在 AppController.m 中的 awakeFromNib 方法中:

/*zoom in and out buttons*/

//get the path to the image files
NSString* zoomInImgPath = [[NSBundle mainBundle] pathForResource:@"zoomIn" ofType:@"png"];
NSString* zoomOutImgPath = [[NSBundle mainBundle] pathForResource:@"zoomOut" ofType:@"png"];

//declare the NSImages
zoomInImg = [[NSImage alloc] initWithContentsOfFile:zoomInImgPath];
zoomOutImg = [[NSImage alloc] initWithContentsOfFile: zoomOutImgPath];

//button making!
//zoomIn
btnZoomIn = [[NSButton alloc] initWithFrame:NSMakeRect(1426.0, 920.0, 25.0, 25.0)];
[btnZoomIn setButtonType:NSMomentaryPushInButton];
[btnZoomIn setTitle:@""];
[btnZoomIn setToolTip:@"Zoom In"];
[btnZoomIn setImage:zoomInImg];
[btnZoomIn setAction:@selector(zoomIn:)];
[[mainWin contentView] addSubview:btnZoomIn];

//zoomOut
btnZoomOut = [[NSButton alloc] initWithFrame:NSMakeRect(1456.0, 920.0, 25.0, 25.0)];
[btnZoomOut setButtonType:NSMomentaryPushInButton];
[btnZoomOut setTitle:@""];
[btnZoomOut setToolTip:@"Zoom Out"];
[btnZoomOut setImage:zoomOutImg];
[btnZoomOut setAction:@selector(zoomOut:)];
[[mainWin contentView] addSubview:btnZoomOut];

和

- (IBAction) zoomIn : (id) sender  { 
    NSLog(@"zoom in!");
 }

 - (IBAction) zoomOut : (id) sender { 
    NSLog(@"zoom out!");
 }

但是 zoomOut 和 zoomIn 不会被击中...

Answer 1

最可能的原因是 responder chain for action messages 中没有对象回应这些行动。当您指定一个 Action 但未指定目标时，Cocoa 会尝试通过遍历响应者链来找到响应这些 Action 消息的对象。

要么确保您在响应者链中有合适的对象，要么如果您有对该对象的引用，请将其指定为这些操作的目标:

[btnZoomIn setAction:@selector(zoomIn:)];
[btnZoomIn setTarget:objectThatRespondsToZoomIn];

[btnZoomOut setAction:@selector(zoomOut:)];
[btnZoomOut setTarget:objectThatRespondsToZoomOut];