向TableLayout添加行时，ContextWrapper.getResources空指针

Question

I've edited the question to reflect the answer. I was instantiating a new Artists() every time the getArtists() DatabaseHelper method was called. So I deleted artists = new Artists(); in getArtists() in the DatabaseHelper class. Instead of immediately instantiating it over and over again, I learned how to just use the context of it in the constructor. So I get the reference of Artists() in the DatabaseHelper constructor, like this.

public DatabaseController(Context c){
        myContext = c;
        artists = (Artists) myContext;
    }

// ORIGINAL QUESTION/CODE

I'm getting a NPE at android.content.ContextWrapper.getResources(ContextWrapper.java:89) and I can't figure out what is going on. Many searches have pointed out that the problem is that getResources is being called somewhere that isn't onCreate, but I don't call getResources anywhere.

I'm trying to fetch data from the database and programatically populate a TableLayout from it.

Here is the Artist Activity.

public class Artists extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private DatabaseController dbcon;
    public TableLayout table;
    public static int artistPopulateCatcher = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_artists);
        table = (TableLayout)findViewById(R.id.table_artists);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_artists);


        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        if(artistPopulateCatcher == 0) {
            dbcon = new DatabaseController(this);
            dbcon.open();
            dbcon.getArtists();
            dbcon.close();
        }
    }

    public void AddNewArtistDialog(View view) {


        final AlertDialog.Builder builder = new AlertDialog.Builder(this);
        final View layout = LayoutInflater.from(this).inflate(R.layout.addartistdialog, null);
        builder.setView(layout)
                .setPositiveButton("Submit", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                        final EditText name = (EditText) layout.findViewById(R.id.edittext_artist_name);
                        final EditText email = (EditText) layout.findViewById(R.id.edittext_artist_email);
                        final CheckBox is21 = (CheckBox) layout.findViewById(R.id.checkBox_is21);

                        String artistIs21;
                        String artistName;
                        String artistEmail;

                        if (is21.isChecked()){
                            artistIs21 = "Yes";
                            artistName = name.getText().toString();
                            artistEmail = email.getText().toString();
                            dbcon.open();
                            dbcon.AddArtist(artistName, artistIs21, artistEmail);
                            dbcon.close();

                        } else{
                            artistIs21 = "No";
                            artistName = name.getText().toString();
                            artistEmail = email.getText().toString();
                            dbcon.open();
                            dbcon.AddArtist(artistName, artistIs21, artistEmail);
                            dbcon.close();
                        }
                        dialog.cancel();

                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        builder.show();
    }

    public void PopulateArtist(String artist, int draw, String is21, String email){
        Log.d("TAG", artist+", "+draw+", "+is21);


        TableRow tr = new TableRow(this);
        tr.setLayoutParams(new TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT, TableLayout.LayoutParams.WRAP_CONTENT));

        TextView artistName = new TextView(this);
        TextView artistDraw = new TextView(this);
        TextView artistIs21 = new TextView(this);
        TextView artistEmail = new TextView(this);

        artistName.setText(artist);
        artistDraw.setText(String.valueOf(draw));
        artistIs21.setText(is21);
        artistEmail.setText(email);

        tr.addView(artistName);
        tr.addView(artistDraw);
        tr.addView(artistIs21);
        tr.addView(artistEmail);

        table.addView(tr, new TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT, TableLayout.LayoutParams.MATCH_PARENT));
    }

My Database Controller:

public class DatabaseController{

    private DatabaseHelper dbHelper;
    public Context myContext;
    private SQLiteDatabase db;
    public Artists artists;

    public DatabaseController(Context c){
        myContext = c;
    }

    public DatabaseController open() throws SQLException{
        dbHelper = new DatabaseHelper(myContext);
        db = dbHelper.getWritableDatabase();
        return this;
    }

    public void close(){
        dbHelper.close();
    }

    public void AddArtist(String name, String is21, String email){
        ContentValues values = new ContentValues();
        values.put(DatabaseHelper.KEY_NAME, name);
        values.put(DatabaseHelper.KEY_IS21, is21);
        values.put(DatabaseHelper.KEY_EMAIL, email);
        values.put(DatabaseHelper.KEY_DRAW, 0);
        db.insert(DatabaseHelper.TABLE_ARTISTS, null, values);
    }

    public Cursor getArtists() {
        artists.artistPopulateCatcher = 1;
        artists = new Artists();
        Cursor cursor = db.rawQuery("SELECT * FROM Artists", null);
        cursor.moveToFirst();
        while (cursor.isAfterLast() == false){
            String name = cursor.getString(cursor.getColumnIndex("Name"));
            int draw = cursor.getInt(cursor.getColumnIndex("Draw"));
            String is21 = cursor.getString(cursor.getColumnIndex("Is21"));
            String email = cursor.getString(cursor.getColumnIndex("Email"));

            artists.PopulateArtist(name, draw, is21, email);

            cursor.moveToNext();
        }
        return cursor;
    }

    public int updateArtist(int _id, String artistName, int draw, String is21, String email){
        ContentValues cv = new ContentValues();
        cv.put(dbHelper.KEY_ID, _id);
        cv.put(dbHelper.KEY_NAME, artistName);
        cv.put(dbHelper.KEY_DRAW, draw);
        cv.put(dbHelper.KEY_IS21, is21);
        cv.put(dbHelper.KEY_EMAIL, email);
        int i = db.update(dbHelper.TABLE_ARTISTS, cv, dbHelper.KEY_ID + " = "+_id, null);
        return i;
    }
}

And here's the stacktrace:

java.lang.RuntimeException: Unable to start activity ComponentInfo{scarycat.promotertools/scarycat.promotertools.Artists}: java.lang.NullPointerException
                                                                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2237)
                                                                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286)
                                                                          at android.app.ActivityThread.access$800(ActivityThread.java:144)
                                                                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1246)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                          at android.os.Looper.loop(Looper.java:212)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5137)
                                                                          at java.lang.reflect.Method.invokeNative(Native Method)
                                                                          at java.lang.reflect.Method.invoke(Method.java:515)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:902)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:718)
                                                                          at dalvik.system.NativeStart.main(Native Method)
                                                                       Caused by: java.lang.NullPointerException
                                                                          at android.content.ContextWrapper.getResources(ContextWrapper.java:89)
                                                                          at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:78)
                                                                          at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:542)
                                                                          at android.view.View.<init>(View.java:3569)
                                                                          at android.view.ViewGroup.<init>(ViewGroup.java:459)
                                                                          at android.widget.LinearLayout.<init>(LinearLayout.java:168)
                                                                          at android.widget.TableRow.<init>(TableRow.java:61)
                                                                          at scarycat.promotertools.Artists.PopulateArtist(Artists.java:112)
                                                                          at scarycat.promotertools.DatabaseController.getArtists(DatabaseController.java:53)
                                                                          at scarycat.promotertools.Artists.onCreate(Artists.java:55)
                                                                          at android.app.Activity.performCreate(Activity.java:5231)
                                                                          at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
                                                                          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2201)
                                                                          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286) 
                                                                          at android.app.ActivityThread.access$800(ActivityThread.java:144) 
                                                                          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1246) 
                                                                          at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                          at android.os.Looper.loop(Looper.java:212) 
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5137) 
                                                                          at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                          at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:902) 
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:718) 
                                                                          at dalvik.system.NativeStart.main(Native Method) 

Answer 1

I was instantiating a new Artists() in the getArtists() method in DatabaseHelper. I deleted that line and up in the constructor I put artists = (Artists) myContext;