NSPanel 导致后续使用 NSOpenPanel 产生异常

Question

我有一个使用 NSOpenPanel 的应用程序，这样用户就可以 select 导入多个文件，并且还有一个典型的首选项面板。首选项面板存储在 .xib 文件中。

用户调用首选项面板后出现问题。在此之前，NSOpenPanel 工作得非常好，所有逻辑都在完成块中执行，并且可以一次又一次地重新调用。但是，一旦用户选择了首选项选项并取消了 sheet，那么随后对 -(IBAction)addFiles: 的每次调用都会导致异常：

它们是这样声明的：

@interface BQSAppDelegate
{
    NSOpenPanel *addFilesPanel;
}
@property(assign)IBOutlet NSPanel*prefs_panel; //connected to a NSPanel in the .xib

并使用：

@implementation BQSAppDelegate

-(void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// other initialisations not to do with addFilesPanel….
    addFilesPanel = [NSOpenPanel openPanel];
    addFilesPanel.canChooseDirectories = YES;
    addFilesPanel.allowsMultipleSelection = YES;
}

-(IBAction)addFiles:(id)sender //button on main window pressed
{
    [addFilesPanel beginSheetModalForWindow:self.window completionHandler:^(NSInteger result) {
        if (addFilesPanel.URLs.count < 1 || result != NSFileHandlingPanelOKButton) {
            NSLog(@“User cancelled”);
            [addFilesPanel orderOut:self]; //I’ve tried it without this line with exactly the same results
        }
        else {
            //do things…
        }
    }];
}

-(IBAction)preferences:(id)sender //bound to the usual Apple+’,” shortcut and app menu item
{
    if (self.prefs_panel.isVisible) {
        return;
    }
    [self.window beginSheet:self.prefs_panel completionHandler:^(NSModalResponse returnCode) {
        NSLog(@"completed"); //is never executed...
    }];
}

-(IBAction)ok_prefs:(id)sender //called when the user presses a button on the Preference panel
{    
    [self.prefs_panel orderOut:self];
}

例外情况是：

2015-03-18 20:35:29.913 QS[3634:241869] *** Assertion failure in void associateSheetWithHost(NSWindow *, NSWindow *)(), /SourceCache/ViewBridge/ViewBridge-103/ViewBridgeUtilities.m:83
2015-03-18 20:35:29.914 QS[3634:241869] sheet <NSVBOpenPanel: 0x1003504f0> already has a host <NSWindow: 0x6000001e5e00>
2015-03-18 20:35:29.917 QS[3634:241869] (
    0   CoreFoundation                      0x00007fff95e7366c __exceptionPreprocess + 172
    1   libobjc.A.dylib                     0x00007fff8db6776e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff95e7344a +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x00007fff9399e471 -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] + 169
    4   ViewBridge                          0x00007fff8c931333 -[NSWindow(ViewBridgeNeedsSPI) _setSheetHost:] + 305
    5   AppKit                              0x00007fff8b367a2f -[NSVBSavePanel beginSheetModalForWindow:completionHandler:] + 69
    6   QS                          0x0000000100017684 -[BQSAppDelegate addFolders:] + 212
    7   libsystem_trace.dylib               0x00007fff8be72cd7 _os_activity_initiate + 75
    8   AppKit                              0x00007fff8acd8b71 -[NSApplication sendAction:to:from:] + 452
    9   AppKit                              0x00007fff8acd8970 -[NSControl sendAction:to:] + 86
    10  AppKit                              0x00007fff8aeae86c __26-[NSCell _sendActionFrom:]_block_invoke + 131
    11  libsystem_trace.dylib               0x00007fff8be72cd7 _os_activity_initiate + 75
    12  AppKit                              0x00007fff8ad21509 -[NSCell _sendActionFrom:] + 144
    13  libsystem_trace.dylib               0x00007fff8be72cd7 _os_activity_initiate + 75
    14  AppKit                              0x00007fff8ad3c085 -[NSCell trackMouse:inRect:ofView:untilMouseUp:] + 2775
    15  AppKit                              0x00007fff8ad3b2b9 -[NSButtonCell trackMouse:inRect:ofView:untilMouseUp:] + 491
    16  AppKit                              0x00007fff8ad3a899 -[NSControl mouseDown:] + 714
    17  AppKit                              0x00007fff8b238a18 -[NSWindow _reallySendEvent:] + 12721
    18  AppKit                              0x00007fff8acbf16e -[NSWindow sendEvent:] + 446
    19  AppKit                              0x00007fff8ac71451 -[NSApplication sendEvent:] + 4183
    20  AppKit                              0x00007fff8aafd608 -[NSApplication run] + 711
    21  AppKit                              0x00007fff8aae8a14 NSApplicationMain + 1832
    22  QS                          0x0000000100001fe2 main + 34
    23  libdyld.dylib                       0x00007fff90d485c9 start + 1

这一定与我调用 and/or 关闭 NSPanel 的方式有关，但我不知道是什么。非常感谢您的帮助。

Answer 1

这是一条神秘的错误消息，尽管评论解决了问题，但我不确定我是否理解它的措辞。我认为它与 sheet 相关联的模态运行循环有关，并且可能与此有关——也许所有除非您调用 endSheet.

，否则模态会话的开销仍然在某处活跃着

提示来自 this related question about the completion handler not being invoked. 第二个未被接受的答案似乎表明您必须终止模态会话，而不仅仅是终止 sheet。

NSPanel 导致后续使用 NSOpenPanel 产生异常

NSPanel causes subsequent use of NSOpenPanel to generate an exception

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