ios - Monotouch UISwitch.valueChanged 委托(delegate)目标错误

Question

我目前正在使用 Monotouch 框架为 IOS 制作一个应用程序，该框架有一个 UITableView 和一个包含 UISwitches 的自定义 UITableViewCell(使用 XCode 设计)。

我通过 UITableViewSource 管理单元格，但在管理分配给单元格开关事件 UISwitch.ValueChanged 的委托(delegate)方法的回调时，我显然遇到了问题。

这是我正在处理的 UITableViewSource 代码，它可能更明确:

        // This class manages the TableView content and its rows
    class MyTableViewDelegate : UITableViewSource
    {
        SatellitesViewController        satController;

        List<long>                      allocatedCells;

        public MyTableViewDelegate (SatellitesViewController controller)
        {
            satController = controller;
            allocatedCells = new List<long>();
        }

        public override int     RowsInSection (UITableView tableview, int section)
        {
            return satController.sats.Count;
        }

        // Called when the switch to show the satellite's display state is touched
        public void             showButtonHandler(object sender, EventArgs e)
        {
            System.Console.WriteLine("SHOW BUTTONHANDLER");
            if (sender != null)
            {
                CustomSwitch    switchButton = (CustomSwitch) sender;
                TLEForRedis     satToShow = this.satController.getSatTLEs(switchButton.idSat, false);

                if (satToShow != null)
                {
                    if (switchButton.On == true)
                        this.satController.glView.showSatellite(satToShow);
                    else
                        this.satController.glView.hideSatellite(satToShow.Id);
                }
            }
        }

        // Called when the switch to show the satellite's display state is touched
        public void             orbitButtonHandler(object sender, EventArgs e)
        {
            System.Console.WriteLine("ORBIT BUTTONHANDLER");
            if (sender != null)
            {
                CustomSwitch    orbitButton = (CustomSwitch) sender;
                TLEForRedis     satToShow = this.satController.getSatTLEs(orbitButton.idSat, false);

                if (satToShow != null)
                    this.satController.glView.setSatelliteOrbitDisplayState(satToShow.Id, orbitButton.On);
            }
        }

        //  Create the cell at indexPath
        public override UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath)
        {
            string          cellName;
            string          nibName;
                cellName = "PROTO_CELL";
                nibName = "CellView";   
            // Get the table cell which is described in the CellView.xib interface
            var cell = tableView.DequeueReusableCell(cellName) as CellView;

            if (cell == null)
            {
                cell = new CellView();
                var views = NSBundle.MainBundle.LoadNib(nibName, cell, null);
                cell = Runtime.GetNSObject( views.ValueAt(0) ) as CellView;
            }

            // Modify the cell with its own data
            SatsList sat = (SatsList) satController.sats [indexPath.Row];

            CustomSwitch    showButton = (CustomSwitch)cell.ViewWithTag(1);
            UILabel         satName = (UILabel)cell.ViewWithTag(2);
            UILabel         catalogNumber = (UILabel)cell.ViewWithTag(3);
            CustomSwitch    favoriteButton = (CustomSwitch)cell.ViewWithTag(4);
            CustomSwitch    orbitButton = (CustomSwitch)cell.ViewWithTag(5);

            UIColor         lightgrey = new UIColor(0.85f, 0.85f, 0.85f, 1.0f);
            tableView.BackgroundColor = lightgrey;

            if (sat != null)
            {
                satName.Text = sat.satName;
                catalogNumber.Text = string.Format("{0}", sat.catalogNumber);
            }
            else
                System.Console.WriteLine("[ERROR] Satellite was not found for row " + indexPath.Row);

            // Set switch state to on when the satellite is already being displayed
            if (this.satController.glView.checkForSatelliteExistency(sat.Id))
            {
                System.Console.WriteLine(sat.satName + "found");
                showButton.SetState(true, false);
                Satellite   sat3D = this.satController.glView.checkForSatelliteOrbit(sat.Id);
                if (sat3D.displayOrbit())
                    orbitButton.SetState(true, false);
            }
            else // force switch state to off when satellite is not displayed yet
            {   
                showButton.SetState(false, false);
                orbitButton.SetState(false, false);
            }
            favoriteButton.SetState(false, false);

            // Bind changing state switches' events in order to display or hide the corresponding satellite
            showButton.setData(sat.Id);
            favoriteButton.setData(sat.Id);
            orbitButton.setData(sat.Id);
            if (!this.allocatedCells.Contains(indexPath.Row))
            {
                showButton.ValueChanged += this.showButtonHandler;
                orbitButton.ValueChanged += this.orbitButtonHandler;
            }
            this.allocatedCells.Add(indexPath.Row);
            return cell;
        }

实际上，上面代码的结果是，我可以在 tableView 中向上/向下滚动而不会出现问题，我什至可以打印“SHOW BUTTONHANDLER”行，直到我不点击一个已经通过滚动离开屏幕的开关。但是，当我点击一个开关，该开关是之前在列表顶部绘制并在我滚动回顶部后重新出现的单元格的一部分时，我收到以下错误:

[7864:1507] -[UIControlTargetAction BridgeSelector]: unrecognized selector sent to instance 0x14462a70

或以下堆栈跟踪:

Stacktrace:

  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <IL 0x0009f, 0xffffffff>
  at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00042] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:29
  at App.Application.Main (string[]) [0x0001b] in App/Main.cs:24
  at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <IL 0x00050, 0xffffffff>

Native stacktrace:

0   App                      0x0009094c mono_handle_native_sigsegv + 284
1   App                      0x00005cd8 mono_sigsegv_signal_handler + 248
2   libSystem.B.dylib                   0x90d9c05b _sigtramp + 43
3   ???                                 0xffffffff 0x0 + 4294967295
4   UIKit                               0x0222e55a -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
5   UIKit                               0x022d3b76 -[UIControl sendAction:to:forEvent:] + 66
6   UIKit                               0x022d403f -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 503
7   UIKit                               0x02425a6c -[_UISwitchInternalView _sendActions] + 121
8   Foundation                          0x0173786d __NSFireDelayedPerform + 389
9   CoreFoundation                      0x01195966 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 22
10  CoreFoundation                      0x01195407 __CFRunLoopDoTimer + 551
11  CoreFoundation                      0x010f87c0 __CFRunLoopRun + 1888
12  CoreFoundation                      0x010f7db4 CFRunLoopRunSpecific + 212
13  CoreFoundation                      0x010f7ccb CFRunLoopRunInMode + 123
14  GraphicsServices                    0x04789879 GSEventRunModal + 207
15  GraphicsServices                    0x0478993e GSEventRun + 114
16  UIKit                               0x0222ba9b UIApplicationMain + 1175
17  ???                                 0x0ebdde65 0x0 + 247324261
18  ???                                 0x0ebdc550 0x0 + 247317840
19  ???                                 0x0b7f7bac 0x0 + 192904108
20  ???                                 0x0b7f7d86 0x0 + 192904582
21  App                      0x0000a042 mono_jit_runtime_invoke + 722
22  App                      0x00169f4e mono_runtime_invoke + 126
23  App                      0x0016e034 mono_runtime_exec_main + 420
24  App                      0x00173455 mono_runtime_run_main + 725
25  App                      0x00067245 mono_jit_exec + 149
26  App                      0x002116a5 main + 2837
27  App                      0x00003095 start + 53
28  ???                                 0x00000004 0x0 + 4

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.
=================================================================

那么，您有解决方案的想法吗？开关的委托(delegate)方法似乎未正确注册，但我不知道出了什么问题。因为我也试过没有

if (!this.allocatedCells.Contains(indexPath.Row))

行，为了只注册一次委托(delegate)，但是结果是一样的。当单元格离开屏幕时，我是否需要删除它并尝试“注销”委托(delegate)？

我希望你有一个想法，并且不要犹豫发表你对这一切的意见/建议/评论。

提前致谢!

Answer 1

好的，我发现我的代码有问题，这是由于委托(delegate)绑定(bind)到开关。实际上，我忘记注销正在离开屏幕的单元格的代表。使 ReuseableCell 出列的事实不会删除链接到单元格内容的委托(delegate) => 这导致使用引用更改的发件人调用我的 showButtonHandler(sender, args) 方法。

因此，我的代码的解决方案是将最后一部分更改为:

// Bind changing state switches' events in order to display or hide the corresponding satellite
            showButton.setData(sat.Id);
            favoriteButton.setData(sat.Id);
            orbitButton.setData(sat.Id);

            showButton.ValueChanged -= this.showButtonHandler;
            orbitButton.ValueChanged -= this.orbitButtonHandler;
            showButton.ValueChanged += this.showButtonHandler;
            orbitButton.ValueChanged += this.orbitButtonHandler;
            return cell;
        }

在我的例子中，甚至没有必要在我的旧 allocatedCells 列表中注册单元格。一旦单元格被重新使用，旧的委托(delegate)将从开关中删除 (-=)，并用新的引用替换 (+=)。

谢谢大家。