I am currently making an application for IOS with the Monotouch framework which has a UITableView with a customized UITableViewCell (designed with XCode) containing UISwitches.
I manage the cells through the UITableViewSource but I clearly have a problem while managing the callbacks to the delegate methods assignated to the event UISwitch.ValueChanged of my cell’s switches.
Here is the UITableViewSource code I am working on, it might be more explicit :
// 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;
}
}
Actually, the result of that above code, is that I can scroll up/down in the tableView without problems and I can even get the line “SHOW BUTTONHANDLER” printed until I am not clicking on a switch that already gone out of the screen by scrolling.
But, when I click on a switch that is part of a cell which has been drawn before in the top of the list and which reappeared after I scrolled back to the top, then I get the following error :
[7864:1507] -[UIControlTargetAction BridgeSelector]: unrecognized selector sent to instance 0x14462a70
or the following stack trace :
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.
=================================================================
So, do you have an idea for a solution ? The delegate methods to the switches seem to be uncorrectly registered but I don’t know what is wrong. Because I also tried this without the
if (!this.allocatedCells.Contains(indexPath.Row))
line, in order to register delegates only once, but the result is the same. Do I need to remove that if and try to “unregister” the delegate when the cell goes out of the screen ?
I hope you have an idea, and dont hesitate to post your opinions/advices/remarks about all this.
Thanks in advance !
Ok, I found the problem with my code, it was due to the delegates binded to the switches. Actually, I forgot to unregister the delegates of the cells which were going out of the screen.
The fact of dequeing a ReuseableCell doesnt removes delegates linked to the content of the cell => this lead to call my showButtonHandler(sender, args) method with a sender whose references changed.
So, the solution for my code is to change the last part to :
In my case, it isnt even necessary to register cells in my old allocatedCells list.
The old delegates are removed (-=) from the switch once the cell is being reused, and replaced(+=) with a new fresh reference.
Thank you all, whatever.