No se pueden obtener datos de la base de datos sqlite
El problema es que cuando ejecuto mi código, la aplicación se detiene con un error (java.lang.RuntimeException: no se puede iniciar la actividad ComponentInfo {com.twixt.pranav.pos / com.twixt.pranav.pos.View.Activity.Cart }: java.lang.NullPointerException: intento de invocar el método virtual 'java.io.File android.content.Context.getDatabasePath (java.lang.String)' en una referencia de objeto nulo) en el código que puede ver que he insertado un dato manualmente
He visto preguntas similares pero no hay soluciones para ello.
Esta es mi clase
class FragmentCart : Fragment() {
private val database: SQLiteHelper = SQLiteHelper(activity)
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View {
val mView = inflater!!.inflate(R.layout.fragment_cart, container, false)
if (database != null) {
val array_list = database.cartdatas()
Toast.makeText(activity, "" , Toast.LENGTH_SHORT).show()
}
return mView
}
Clase auxiliar de SQLite
public class SQLiteHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "POS_SQLiteDatabase.db";
public SQLiteHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table CATEGORIES (ID INTEGER, NAME VARCHAR, COLOR VARCHAR)");
db.execSQL("create table CART (ITEM_ID INTEGER, ITEM_NAME VARCHAR, QUANTITY FLOAT, PRICE FLOAT, ONLINE INTEGER, DATE_ VARCHAR, FLAG INTEGER)");
db.execSQL("insert into CART values(321,'test name',1.1,50,1,'test date',0)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS CATEGORIES");
db.execSQL("DROP TABLE IF EXISTS CART");
onCreate(db);
}
public Boolean insetCartData(int item_id,String item_name,float quantity,float price,int online,String date, String flag){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("ITEM_ID",item_id);
contentValues.put("ITEM_NAME",item_name);
contentValues.put("QUANTITY",quantity);
contentValues.put("PRICE",price);
contentValues.put("ONLINE",online);
contentValues.put("DATE_",date);
contentValues.put("FLAG",flag);
database.insert("CART",null,contentValues);
return true;
}
public ArrayList<String> cartdatas(){
/* SQLiteDatabase database=this.getReadableDatabase();
Cursor cursor=database.rawQuery("SELECT * FROM CART where ITEM_ID="+id+"",null);
return cursor;*/
ArrayList<String> array_list = new ArrayList<String>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor res = db.rawQuery( "select * from CART", null );
res.moveToFirst();
while(res.isAfterLast() == false){
array_list.add(res.getString(res.getColumnIndex("ITEM_NAME")));
res.moveToNext();
}
return array_list;
}
}
Y error
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.twixt.pranav.pos, PID: 4602
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.twixt.pranav.pos/com.twixt.pranav.pos.View.Activity.Cart}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getDatabasePath(java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getDatabasePath(java.lang.String)' on a null object reference
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:292)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:262)
at com.twixt.pranav.pos.Controller.SQLiteHelper.cartdatas(SQLiteHelper.java:62)
at com.twixt.pranav.pos.View.Fragment.FragmentCart.onCreateView(FragmentCart.kt:38)
at android.app.Fragment.performCreateView(Fragment.java:2508)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1279)
at android.app.FragmentManagerImpl.addAddedFragments(FragmentManager.java:2407)
at android.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2186)
at android.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2142)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2043)
at android.app.FragmentManagerImpl.dispatchMoveToState(FragmentManager.java:3032)
at android.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:2979)
at android.app.FragmentController.dispatchActivityCreated(FragmentController.java:178)
at android.app.Activity.performCreate(Activity.java:7006)
at android.app.Activity.performCreate(Activity.java:6991)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Application terminated.