为什么我的Android应用程序因NullPointerException而崩溃？

Question

META-EDIT #2: On second thought, that's what I will do, as mocking up the question I would ask if I did make a new question ended up with a far different question from this one.

META-EDIT: This question is getting quite long, does not have an answer, and has shifted in topic somewhat (to the point where I would ask a much different question if rewriting it from scratch, despite it still being the same problem ). Should I continue to update it, or should I make a new question? I'm new here, so I don't know what the standard etiquette is for this.

I am building an Android application that will allow the user to navigate a campus by inputting the number of the room they are currently in and the number of the room which they wish to get to. I think I am nearly finished, but (despite several weeks of fruitless work) I have been unable to fix one particular bug, which causes the program to crash with:

java.lang.IllegalStateException: Could not execute method of the activity
  at android.view.View$1.onClick(View.java:3633)
  at android.view.View.performClick(View.java:4240)
  at android.view.View$PerformClick.run(View.java:17721)
  at android.on.Handler.handleCallback(Handler.java:730)
  at android.on.Handler.dispatchMessage(Handler.java:92)
  at android.os.Looper.loop(Looper.java:137)
  at android.app.ActivityThread.main(ActivityThread.java:5103)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Mathod.java:525)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvokationTargetExeption
  at java.lang.reflect.Method.invokeNative(Native Method)
  at Java.lang.reflect.Method.invoke(Method.java:525)
  at android.view.View$1.onClick(View.java:3628)
  ... 11 more
Caused by: java.lang.NullPointerException
  at ghamas.navigator.WorldMap.makePath(WorldMap.java:669)
  at ghamas.navigator.MainActivity.makeRoute(MainActivity.java:81)
  at ghamas.navigator.MainActivity.callMakeRoute(MainActivity.java:61)
  ... 14 more

WorldMap.makePath():

ArrayList<Coordinates> makePath(Coordinates startNode, Coordinates endNode, ArrayList<Coordinates> pathSoFar, ArrayList<Coordinates> closedNodes, ArrayList<Coordinates> openNodes)
{   //recursively finds the path from startNode to endNode:
    //start @ starting node, make list of ways out of it
    //for each of these potential paths, find all the potential paths out of them
    //and so on until these paths reach the end
    //as the recursion collapses, the best paths are passed back up, and the others discarded
    //this ensures that the path returned by the last call of the method is the best one
    //this method is very, very inefficient, but is very simple
    //mainly, however, since the map has a very tiny number of potential paths, relatively speaking, the inefficiency is acceptable
    //if first call (just starting)
    if (openNodes.size() == 0 && !closedNodes.contains(startNode)) { openNodes.add(startNode); }
    int a = startNode.z;                //traced NullPointerException back to here
    Coordinates n = openNodes.get(0);   //get a node to test
    openNodes.remove(0);                //remove it from the open nodes, so don't repeat it later
    closedNodes.add(n);                 //record that have done this one
    ArrayList<Coordinates> adjacent = getAdjacentCoords(n);
    //get the nodes that are adjacent to this one
    for (int i = 0; i < adjacent.size(); i++)
    {
        //if this adjacent node has not yet been checked - this prevents infinite loops
        if (!openNodes.contains(adjacent.get(i)) && !closedNodes.contains(adjacent.get(i)))
        {   //add it to the list of nodes to check
            openNodes.add(adjacent.get(i));
        }
    }
    //if reached destination
    if (n == endNode)
    {   //done
        pathSoFar.add(n);
        return pathSoFar;
    }
    else
    {
        ArrayList<ArrayList<Coordinates>> pathList = new ArrayList<ArrayList<Coordinates>>(); //list of potential paths that come from this node + path
//          openNodes = coordOrder(openNodes, endNode); //don't need this (right now, at least), as dealing with a tiny number of nodes
        for (int i = 0; i < openNodes.size(); i++)
        {   //recursively add the paths - should be max. 3 - inward path + four other directions, but only ever put max 3 in the map
            pathList.add(makePath(startNode, endNode, pathSoFar, closedNodes, openNodes));
        }
        int lowVal = 1024;  //length of beth path from here to end
        int iLow = -1;      //index of the best path from here to end
        //check all paths found just before
        for (int i = 0; i < pathList.size(); i++)
        {   //if this path is smaller than the previous smallest found one, this is the new smallest found one
            if (pathList.get(i).size() < lowVal) { iLow = i; lowVal = pathList.get(i).size(); i = 0; }
        }
        //return the best path to proceed from this node to the end
        return pathList.get(iLow);
    }
}

MainActivity.makeRoute():

public ArrayList<Coordinates> makeRoute(String start, String end)
{
    destination = end;
    ArrayList<Coordinates> newCoordArr = new ArrayList<Coordinates>();
    ArrayList<Coordinates> path = world.makePath(world.findCoordsWithRoom(start), world.findCoordsWithRoom(end), newCoordArr, newCoordArr, newCoordArr);
    return path;
}

MainActivity.callMakeRoute():

public void callMakeRoute (View view)
{   //function called when button in UI tab is pressed
    String startstr = ((EditText)pagerAdapter.getItem(0).getView().findViewById(R.id.starting_room_field)).getText().toString();
    String endstr = ((EditText)pagerAdapter.getItem(0).getView().findViewById(R.id.ending_room_field)).getText().toString();
    ArrayList<String> newTextArr = instruct(makeRoute(startstr, endstr));   //get the route
    String newText = ""; //move the newTextArr to a single string
    Integer i = 0;
    //translate route to format the textview tab can handle
    //that is, a single line, with newline characters between instructions
    for (String s : newTextArr)
    {
        newText.concat(i.toString() + ") ");    //the number of the step, i.e. 1) ... 2) ... 3) ... etc.
        newText.concat(s);                      //the step text itself, e.g. "Turn left...", "Continue forwards", etc.
        newText.concat("\n\n");                 //skip a line between steps
        i++;                                    //next step
    }
    //push the new text to the text tab's TextView
    ((TextView)(pagerAdapter.getItem(1).getView().findViewById(R.id.text_view_text_spot))).setText(newText);
}

The Coordinates class holds the integers x, y, and z.

This is a component of the WorldMap class:

Node[][][] map =
{
    {   //first floor
        //00   01   02   03   04   05   06   07   08   09
        {dne, dne, dne, dne, dne, cls, dne, dne, dne, dne}, //00
        {dne, dne, dne, dne,  oc,  cl,  cf, dne, dne, dne}, //01
        {dne, dne, dne, dne, dne, dne, dne, dne, dne, dne}, //02
        {dne, dne, dne, dne, og2,  g4,  gc,  g2, gs1, dne}, //03
        {dne, dne, dne, dne, dne, dne, gs2,  g1,  g3, dne}, //04
        {dne, ot3, dne, ot1,  op, dne, og1, gal, dne, dne}, //05
        {dne, ot4, dne, dne, dne, dne,  a2,  a1, dne, dne}, //06
        {dne,  t3, dne, dne, dne, dne, dne,  a3,  as, dne}, //07
        {dne,  t1, tl1, ot2, dne, dne, dne,  a4, dne, dne}, //08
        { ts,  t2, tl2, ot5, dne, dne, dne, dne, dne, dne}, //09
        {dne,  t4, tls, dne, dne, dne, dne, dne, dne, dne}, //10
    },
    {   //second floor
        //00   01   02   03   04   05   06   07   08   09
        {dne, dne, dne, dne, dne, CLS, dne, dne, dne, dne}, //00
        {dne, dne, dne, dne, dne,  CL,  C2,  C4, dne, dne}, //01
        {dne, dne, dne, dne, dne,  C1,  C3,  C5, dne, dne}, //02
        {dne, dne, dne, dne, dne,  G4, GC1,  G3, GS1, dne}, //03
        {dne, dne, dne, dne, dne, GC2, dne,  G1,  G2, dne}, //04
        {dne, dne, dne, dne, dne, GS2, dne, GAL, dne, dne}, //05
        {dne, dne, dne, dne, dne, dne,  A5,GALS, dne, dne}, //06
        {dne, dne, dne, dne, dne, dne,  A3,  A1, dne, dne}, //07
        {dne, dne, dne, dne, dne, dne, dne,  A2,  AS, dne}, //08
        { TS,  T4,  T3, dne, dne, dne, dne, dne, dne, dne}, //09
        {dne, TLS,  TL, dne, dne, dne, dne, dne, dne, dne}, //10
    }
};

All of the components of the array are defined like this:

Node ot1 = new Node(
    new ConnectionTo[] {
        new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.north),
        new ConnectionTo(new Node(new Coordinates(0,5,4)), new Room[]{}, Direction.east),
        new ConnectionTo(new Node(new Coordinates(0,8,3)), new Room[]{}, Direction.south),
        new ConnectionTo(new Node(new Coordinates(0,5,1)), new Room[]{}, Direction.west),
        new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.up),
        new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.down)
    },  new Coordinates(0,5,3)
);

There is a considerable amount of code that I did not include here in the interest of brevity, so if I overlooked something that is needed, please tell me so I can fix it.

I am building for Android 4.3 using ADT v22.2.1-833290 as my IDE, the included emulator for my testing environment, and LogCat for debugging.

EDIT#01: The lines referenced above are: MainActivity.java:61

ArrayList<String> newTextArr = instruct(makeRoute(startstr, endstr));   //get the route

MainActivity.java:81

ArrayList<Coordinates> path = world.makePath(world.findCoordsWithRoom(start), world.findCoordsWithRoom(end), newCoordArr, newCoordArr, newCoordArr);

WorldMap.java:669

int a = startNode.z;                //traced NullPointerException back to here

Edit #02: WorldMap.findCoordswithRoom():

Coordinates findCoordsWithRoom(String roomName)
{
    //all floors; 0 -> 1
    for (int z = 0; z < map.length; z++)
    {
        //all rows; 0 -> 10
        for (int y = 0; y < map[z].length; y++)
        {
            //all cols; 0 -> 9
            for (int x = 0; x < map[z][y].length; x++)
            {
                if (map[z][y][x] == dne) { continue; }  //if this node is a "dne" node, skip it
                //all valid connections out of this node
                for (int c = 0; c < map[z][y][x].dirArr.length; c++)
                {
                    if (!map[z][y][x].dirArr[c].exists) { continue; }
                    //all rooms on this connection
                    for (int r = 0; r < map[z][y][x].dirArr[c].rooms.length; r++)
                    {
                        //if this room has the right name
                        if (map[z][y][x].dirArr[c].rooms[r].name.equals(roomName))
                        {   //found it
                            return (new Coordinates(x, y, z));
                        }
                    }
                }
            }
        }
    }
    //failed to find it
    return null;
}

EDIT #03: I've been working on this a bit more, and while I am still getting the same error, I have hit a bit of a breakthrough - the issue appears to be that the data that ends up in the Nodes declared in WorldMap is not the data included in the Nodes' declarations - rather, the Nodes end up with all fields either at their default values or with a value of null. Here is an example of a Node declaration:

Node g2 = new Node(
        new ConnectionTo[] {
            new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.north),
            new ConnectionTo(new Node(new Coordinates(0,3,8)), new Room[]{}, Direction.east),
            new ConnectionTo(new Node(new Coordinates(0,4,7)), new Room[]{}, Direction.south),
            new ConnectionTo(new Node(new Coordinates(0,3,6)), new Room[]{new Room("104",new String[]{"left","right"}),new Room("120",new String[]{"right","left"})}, Direction.west),
            new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.up),
            new ConnectionTo(new Node(new Coordinates()), new Room[]{}, Direction.down)
        },  new Coordinates(0,3,7)
    );

And here are the relevant classes and constructors:

Node:

public class Node
{
    ConnectionTo n, e, s, w, u, d;
    ConnectionTo[] dirArr;
    boolean[] hasConnection;
    Coordinates coords;
    boolean exists;
    Coordinates targetCoordsHolder;

    Node (ConnectionTo[] connections, Coordinates location)
    {
        hasConnection = new boolean[6];
        exists = true;
        n = connections[0];
        e = connections[1];
        s = connections[2];
        w = connections[3];
        u = connections[4];
        d = connections[5];
        dirArr = connections;
        coords = location;
        for (int i = 0; i < dirArr.length; i++)
        {
            hasConnection[i] = false;
            if (dirArr[i].exists) { hasConnection[i] = true; }
        }
        if (location.equals(new Coordinates()))
        {
            exists = false;
        }
    }
}

ConnectionTo:

public class ConnectionTo
{
    Direction dir;
    Room[] rooms;
    Node targetNode;
    boolean exists = true;
    double cost;
    public ConnectionTo (Node target, Room[] rms, Direction pdir, double cost)
    {
        if (target.coords.equals(new Coordinates()));
        if (!target.exists)
        {
            exists = false;
            return;
        }
        targetNode = target;
        rooms = rms;
        dir = pdir;
        this.cost = cost;
    }
    public ConnectionTo() { exists = false; }
    public ConnectionTo (Direction pdir)
    {
        this(new Node(), new Room[]{}, pdir, 256);
    }
    public ConnectionTo (Node target, Room[] rms, Direction pdir)
    {
        this (target, rms, pdir, 256);
    }
}

Room:

public class Room
{
    String name;
    int num;
    boolean nonstandardMsg;
    String[] msgs;

    Room (String roomName, int roomNum, String[] approachMsgs)
    {
        this(roomName, roomNum, approachMsgs, false);
    }
    Room (String roomName, int roomNum, String[] approachMsgs, boolean nsp)
    {
        name = roomName;
        num = roomNum;
        msgs = approachMsgs;
        nonstandardMsg = nsp;
    }
    Room (String roomName, String[] approachMsgs)
    {
        this(roomName, approachMsgs, false);
    }
    Room (String roomName, String[] approachMsgs, boolean nsp)
    {
        name = roomName;
        //if first character is a number
        if (roomName.charAt(0) == '1' || roomName.charAt(0) == '2' || roomName.charAt(0) == '3' || roomName.charAt(0) == '4' || roomName.charAt(0) == '5' || roomName.charAt(0) == '6' || roomName.charAt(0) == '7' || roomName.charAt(0) == '8' || roomName.charAt(0) == '9' || roomName.charAt(0) == '0')
        {
            //if last character is number
            if (roomName.charAt(roomName.length()-1) == '1' || roomName.charAt(roomName.length()-1) == '2' || roomName.charAt(roomName.length()-1) == '3' || roomName.charAt(roomName.length()-1) == '4' || roomName.charAt(roomName.length()-1) == '5' || roomName.charAt(roomName.length()-1) == '6' || roomName.charAt(roomName.length()-1) == '7' || roomName.charAt(roomName.length()-1) == '8' || roomName.charAt(roomName.length()-1) == '9' || roomName.charAt(roomName.length()-1) == '0')
            {
                num = Integer.parseInt(roomName);
            }
            else
            {
                num = Integer.parseInt(roomName.substring(0, roomName.length() - 2));
            }
        }
        else
        {
            num = Integer.parseInt(roomName.substring(1));
        }
        msgs = approachMsgs;
        nonstandardMsg = nsp;
    }   
}

Coordinates:

public class Coordinates
{
    int x, y, z;
    public Coordinates (int zp, int yp, int xp)
    {
        x = xp;
        y = yp;
        z = zp;
    }
    public Coordinates ()
    {
        x = -1;
        y = -1;
        z = -1;
    }
}

Answer 1

The findCoordsWithRoom is returning null by the looks of it for your start value.

map[z][y][x].dirArr[c].rooms[r].name == roomName

That code will not return true. You want to replace it with

roomName.equals(map[z][y][x].dirArr[c].rooms[r].name)

Strings should be compared with .equals and not ==. Also depending on what your dne object is you might need to make that change as well.