Usterki aplikacji systemu Android podczas uruchamiania: SQLite NullPointerException w ContactsFragment

Pracuję nad integracją bazy danych, aby zapisać i zapisać podstawowe informacje kontaktowe, które będą pobierane w późniejszym czasie. Jednak moja aplikacja jest teraz upaść na starcie, więc nie mogę nawet sprawdzić, czy tabela jest tworzona itpUsterki aplikacji systemu Android podczas uruchamiania: SQLite NullPointerException w ContactsFragment

05-05 16:39:50.671 11631-11631/treehouse.greenlight E/AndroidRuntime﹕ FATAL EXCEPTION: main 
Process: treehouse.greenlight, PID: 11631 
java.lang.RuntimeException: Unable to start activity ComponentInfo{treehouse.greenlight/treehouse.greenlight.Home_screen}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2205) 
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2255) 
     at android.app.ActivityThread.access$800(ActivityThread.java:142) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:136) 
     at android.app.ActivityThread.main(ActivityThread.java:5118) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference 
     at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 
     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164) 
     at treehouse.greenlight.MyDBHandler.addContact(MyDBHandler.java:54) 
     at treehouse.greenlight.ContactsFragment.onCreateLoader(ContactsFragment.java:117) 
     at android.support.v4.app.LoaderManagerImpl.createLoader(LoaderManager.java:490) 
     at android.support.v4.app.LoaderManagerImpl.createAndInstallLoader(LoaderManager.java:499) 
     at android.support.v4.app.LoaderManagerImpl.initLoader(LoaderManager.java:553) 
     at treehouse.greenlight.ContactsFragment.onActivityCreated(ContactsFragment.java:71) 
     at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1797) 
     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:979) 
     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138) 
     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1120) 
     at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1929) 
     at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547) 
     at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171) 
     at android.app.Activity.performStart(Activity.java:5285) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)

Kod Handler Baza:

public class MyDBHandler extends SQLiteOpenHelper { 

private static final int DATABASE_VERSION = 1; 
private static final String DATABASE_NAME = "contactsDB.db"; 
public static final String TABLE_CONTACTS = "contacts"; 
private Context context; 
public static final String COLUMN_ID = "_id"; 
public static final String COLUMN_NAME = "name"; 
public static final String COLUMN_PHONE = "phone"; 
public static final String COLUMN_STATUS = "status"; 
public static final String COLUMN_BLURB = "blurb"; 

public MyDBHandler(Context context, String name, 
        CursorFactory factory, int version) { 
    super(context, DATABASE_NAME, factory, DATABASE_VERSION); 

} 
    @Override 
    public void onCreate (SQLiteDatabase db){ 

     String CREATE_CONTACTS_TABLE = "CREATE TABLE " + 
       TABLE_CONTACTS + "(" 
       + COLUMN_ID + " INTEGER PRIMARY KEY," + ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME 
       + " TEXT," + ContactsContract.CommonDataKinds.Phone.NUMBER + " INTEGER," 
       + COLUMN_STATUS + " TEXT," + COLUMN_BLURB 
       + " TEXT" + ");"; 
     db.execSQL(CREATE_CONTACTS_TABLE); 
    } 

    @Override 
    public void onUpgrade (SQLiteDatabase db,int oldVersion, int newVersion){ 
     db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS); 
     onCreate(db); 
    } 
public void addContact(ContactsDb contacts) { 

    ContentValues values = new ContentValues(); 
    values.put(COLUMN_NAME, contacts.getName()); 
    values.put(COLUMN_PHONE, contacts.getPhone()); 
    values.put(COLUMN_STATUS, contacts.getStatus()); 
    values.put(COLUMN_BLURB, contacts.getBlurb()); 

    SQLiteDatabase db = this.getWritableDatabase(); 
    db.insert(TABLE_CONTACTS, null, values); 

}

logcat mówi, że problem jest z SQLiteDatabase db = this.getWriteableDatabase();

Oto moja wykraczająca Contactsfragment także:

public class ContactsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> { 

private CursorAdapter mAdapter; 
private Context context; 
TextView idView; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    // create adapter once 
    Context context = getActivity(); 
    int layout = R.layout.activity_list_item_1; 
    Cursor c = null; // there is no cursor yet 
    int flags = 0; // no auto-requery! Loader requeries. 
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags); 

} 


public void ContactsDb(Context context) { 
    this.context=context; 


} 
Uri contentUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI; 

String[] PROJECTION = { 
     ContactsContract.Contacts.HAS_PHONE_NUMBER, 
     ContactsContract.Contacts._ID, // _ID is always required 
     ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME_PRIMARY, // that is what we want to display 
     Contacts.TIMES_CONTACTED, 
     ContactsContract.CommonDataKinds.Phone.NUMBER 

}; 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 

    // each time we are started use our listadapter 
    setListAdapter(mAdapter); 
    // and tell loader manager to start loading 
    getLoaderManager().initLoader(0, null, this); 
} 

// columns requested from the database 


// and name should be displayed in the text1 textview in item layout 

public String[] has_phone = {ContactsContract.Contacts.HAS_PHONE_NUMBER}; 

    String phone = "0"; 
    int dbPhone = 0; 
private final String[] FROM = {Contacts.DISPLAY_NAME_PRIMARY, ContactsContract.CommonDataKinds.Phone.NUMBER}; 
private final int[] TO = {android.R.id.text1, dbPhone}; 


public void newContact (View view) { 
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1); 

    String name = Contacts.DISPLAY_NAME_PRIMARY; 
    int dbPhone = 
    Integer.parseInt(phone); 

    String status =""; 
    String blurb =""; 
    ContactsDb contacts = 
      new ContactsDb(name, dbPhone, status, blurb); 
    dbHandler.addContact(contacts); 

} 


@Override 
public Loader<Cursor> onCreateLoader(int id, Bundle args) { 
    Context context = this.context; 
    // load from the "Contacts table" 
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1); 

    String name = Contacts.DISPLAY_NAME_PRIMARY; 
    int phone = Integer.parseInt(ContactsContract.CommonDataKinds.Phone.NUMBER); 

    String status ="Busy"; 
    String blurb ="N/A"; 

    ContactsDb contacts = 
      new ContactsDb(name, dbPhone, status, blurb); 
    dbHandler.addContact(contacts); 

    // no sub-selection, no sort order, simply every row 
    // projection says we want just the _id and the name column 
    return new CursorLoader(getActivity(), 
      contentUri, 
      PROJECTION, 
      ContactsContract.Contacts.HAS_PHONE_NUMBER + " =? AND " + Contacts.TIMES_CONTACTED + ">=?", // This is selection string, we're looking for records that HAS_PHONE_NUMBER is 1 
      new String[]{"1", "0"}, // 1 means that contact has a phone number & 60 is the amount of times contacted (arbitrary - needs to be fixed before release) 
      null); 
}

Wreszcie, tutaj jest klasa ContactsDB:

public ContactsDb(String name, int phone, String status, String blurb) { 

    this._name = name; 
    this._phone = phone; 
    this._status = status; 
    this._blurb = blurb;

Każda pomoc jest mile widziane - Myślę, że problem tkwi w moim Kontekst jest zerowa. Po prostu nie jestem pewien, dlaczego byłby tak, jak to zdefiniowałem w moim pliku MyDBHandler. W tej chwili nie mam możliwości sprawdzenia, czy db jest tworzony, nie mówiąc już o przechowywaniu danych.

Cheers & Dzięki za poświęcony czas i cierpliwość, Shyam

Źródło

2015-05-05 Shyam

wygląda jak przypadkowo stworzył zmiennej lokalnej context zamiast używać zmiennej instancji.

Więc context jest null kiedy przechodzą go do MyDBHandler, więc podczas rozmowy this.getWritableDatabase(), this jest null. W rezultacie można uzyskać NullPointerException, jak widać w dzienniku:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference 
     at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 
     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)

spróbuj przenieść wszystkie Context związanej kod do onActivityCreated() celu zapewnienia masz ważny Context i upewnij się, aby użyć zmiennej instancji zamiast zmiennej lokalnej:

public class ContactsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> { 

private CursorAdapter mAdapter; 
private Context context; //this is the Context you will use 
TextView idView; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    // create adapter once 
    //Context context = getActivity(); //Here was the problem 
    //int layout = R.layout.activity_list_item_1; 
    //Cursor c = null; // there is no cursor yet 
    //int flags = 0; // no auto-requery! Loader requeries. 
    //mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags); 

} 


public void ContactsDb(Context context) { 
    this.context=context; 


} 
Uri contentUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI; 

String[] PROJECTION = { 
     ContactsContract.Contacts.HAS_PHONE_NUMBER, 
     ContactsContract.Contacts._ID, // _ID is always required 
     ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME_PRIMARY, // that is what we want to display 
     Contacts.TIMES_CONTACTED, 
     ContactsContract.CommonDataKinds.Phone.NUMBER 

}; 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 

    //Add this here: 
    context = getActivity(); //use the instance variable 
    int layout = R.layout.activity_list_item_1; 
    Cursor c = null; // there is no cursor yet 
    int flags = 0; // no auto-requery! Loader requeries. 
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags); 

    // each time we are started use our listadapter 
    setListAdapter(mAdapter); 
    // and tell loader manager to start loading 
    getLoaderManager().initLoader(0, null, this); 
} 

// columns requested from the database 


// and name should be displayed in the text1 textview in item layout 

public String[] has_phone = {ContactsContract.Contacts.HAS_PHONE_NUMBER}; 

    String phone = "0"; 
    int dbPhone = 0; 
private final String[] FROM = {Contacts.DISPLAY_NAME_PRIMARY, ContactsContract.CommonDataKinds.Phone.NUMBER}; 
private final int[] TO = {android.R.id.text1, dbPhone}; 


public void newContact (View view) { 

    //context should now be valid: 
    MyDBHandler dbHandler = new MyDBHandler(context, null, null, 1); 

    String name = Contacts.DISPLAY_NAME_PRIMARY; 
    int dbPhone = 
    Integer.parseInt(phone); 

    String status =""; 
    String blurb =""; 
    ContactsDb contacts = 
      new ContactsDb(name, dbPhone, status, blurb); 
    dbHandler.addContact(contacts); 

} 
//........

Źródło

2015-05-05 22:33:05

Cześć Daniel, dzięki za szybką odpowiedź. Zrobiłem tę poprawkę, ale logcat nadal daje mi ten sam błąd. To ma dla mnie sens, jednak nigdy nie nazywam ContactsFragment (i daje mi to znać, mówiąc, że metoda o takiej nazwie może być łatwo pomylona jako konstruktor). Być może zachowuję mój ContactsDb jako taki i tworzę inny konstruktor ContactsFragment? – Shyam

Wow Daniel, świetny połów ... to był dokładnie problem. Odtąd zamknę to w mojej czaszce, że kontekst powinien być zadeklarowany w onCreate! Twoje zdrowie – Shyam

Usterki aplikacji systemu Android podczas uruchamiania: SQLite NullPointerException w ContactsFragment

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