Invalid Cast Exception

[Naelo]

Hey,

I recently ran into a problem with 'Invalid Cast Exception - Cannot cast from source to destination type'.

I cannot locate where the error is, cause my log full of things looking like this:

InvalidCastException: Cannot cast from source type to destination type.
 at MusicPlayer.WindowGUI (Int32 windowID) [0x00000] in <filename unknown>:0 

 at UnityEngine.GUILayout+LayoutedWindow.DoWindow (Int32 windowID) [0x00000] in <filename unknown>:0 

 at UnityEngine.GUI+_Window.Do () [0x00000] in <filename unknown>:0 

 at UnityEngine.GUI.EndWindows (UnityEngine.IDList idlist) [0x00000] in <filename unknown>:0 

 at UnityEngine.GUIUtility.EndGUI (Int32 doLayout, Int32 doWindows, UnityEngine.IDList idlist) [0x00000] in <filename unknown>:0 

(Filename: Line: -1)

Is it something with my plugin\'s GUI?

I add my GUI via

RenderingManager.AddToPostDrawQueue(3, new Callback(drawGUI));

First, I removed all namespaces, still no avail.

The weird thing is, when adding some print() commands to drawGUI() it shows me

that the error is happening after drawGUI has finished?

drawGUI looks like this:

  private void drawGUI()
  {
    GUI.skin = HighLogic.Skin;
    if (guiMode == 'exp')
    {
      windowPos = GUILayout.Window(1, windowPos, WindowGUI, 'Music Player', GUILayout.MinWidth(200));
    }
    else if (guiMode == 'mini')
    {
      windowPos = GUILayout.Window(1, windowPos, WindowGUI, 'Music Player', GUILayout.MinWidth(200), GUILayout.MaxHeight(100));
    }
  }

And WindowGUI:

  private void WindowGUI(int windowID)
  {
    GUIStyle mySty = new GUIStyle(GUI.skin.button);
    mySty.normal.textColor = mySty.focused.textColor = Color.white;
    mySty.hover.textColor = mySty.active.textColor = Color.yellow;
    mySty.onNormal.textColor = mySty.onFocused.textColor = mySty.onHover.textColor = mySty.onActive.textColor = Color.green;
    mySty.padding = new RectOffset(8, 8, 8, 8);
    mySty.fixedWidth = 200;

    GUIStyle scrollSty = new GUIStyle(GUI.skin.scrollView);


    GUILayout.BeginVertical();

    if (guiMode == 'exp')
    {
      if (GUILayout.Button('Minimize', GUILayout.ExpandWidth(true)))
      {
        guiMode = 'mini';
      }
    }
    else if (guiMode == 'mini')
    {
      if (GUILayout.Button('Expand', GUILayout.ExpandWidth(true)))
      {
        guiMode = 'exp';
      }
    }

    GUILayout.Label((string)musiclib[curSongPos], GUILayout.ExpandWidth(true));

    GUILayout.BeginHorizontal();
    if (GUILayout.Button('Play',GUILayout.Width(mySty.fixedWidth / 3)))
    {
      player.Play();
    }
    if (GUILayout.Button('Pause',GUILayout.Width(mySty.fixedWidth / 3)))
    {
      player.Pause();
    }
    if (GUILayout.Button('Stop',GUILayout.Width(mySty.fixedWidth / 3)))
    {
      player.Stop();
    }
    GUILayout.EndHorizontal();

    GUILayout.BeginHorizontal();
    if(GUILayout.Button('Prev', GUILayout.Width(mySty.fixedWidth / 2))){
      prevSong();
    }
    if (GUILayout.Button('Next', GUILayout.Width(mySty.fixedWidth / 2)))
    {
      nextSong();
    }
    GUILayout.EndHorizontal();

    player.volume = GUILayout.HorizontalSlider(player.volume, 0.01f, 1.0f, GUILayout.ExpandWidth(true));

    if (guiMode == 'exp')
    {
      GUILayout.BeginScrollView(new Vector2(0, 0), GUILayout.ExpandWidth(true), GUILayout.Height(200));
      int ti = 0;
      foreach (MusicPath actpath in musiclib)
      {
        if (GUILayout.Button(actpath.showname, GUILayout.ExpandWidth(true)))
        {
          selectSong(ti);
        }
        ti+=1;
      }
      GUILayout.EndScrollView();
    }

    GUILayout.EndVertical();
    GUI.DragWindow(new Rect(0, 0, 10000, 20));

  }

These are pretty much the only functions that are called all the time.

Any Ideas? I\'m pretty much stuck :/

Thanks,

Naelo

[Romfarer]

I think the exception is being thrown here:

GUILayout.Label((string)musiclib[curSongPos], GUILayout.ExpandWidth(true)); 

musiclib[curSongPos] seems to return as int32 and you are trying to cast it into a string.

Edit: so to explain a little further. Invalid Cast Exception can only happen when you cast something i.e.

Part p = (Part)Object.Initialize(something);

The section you have provided from your output log is also the place it is being reported, albeit poorly at that. It is just a trace of the error, where the top line tells you exactly where the exception occurred, in your case at MusicPlayer.WindowGUI (Int32 windowID) [0x00000] in <filename unknown>:0 . So you know it happened in your WindowGUI method and it has something to do with Int32. Unfortunately the filename references are useless here.

[kellven]

I agree with Romfarer, only 2 things to add:

1. If

musiclib[curSongPos]

does resolve to an int, and you want to display it, might want to try removing the (string) cast, and making it

musiclib[curSongPos].tostring()

2. If you\'re still getting problems, try adding a few

Debug.Log('Made it this far: 0');

lines inside whatever block is causing the problems, that\'s helped me figure out exactly where the problem occurs many times debugging my own code. The last log to show up before you hit the exception in the place to start looking.

[Naelo]

Yes - that was the problem!

I used to only store strings in that ArrayList but then... I changed it to a custom class which has two attributes.

Trying to convert the class to a string obviously doesnt work.

Thanks for the help, I would never have spotted that.

[kellven]

Actually, you CAN convert a class to a string, that\'s why I mentioned .tostring().

If you\'re using VS, just type override then space, and select object.tostring(). Or write the override yourself. Useful if you want a data-container object to be 'string-able' for debug printing/etc.