NullPointerException open method

Question

I'm trying to get data from a database to a list view when ı run my application it gives a java.lang.NullPointerException. I couldn't find where the problem is? Could you help me, please?

my DataBase class:

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;


public class DataBase extends SQLiteOpenHelper {

public static final int DATA_BASE_VERSION = 1;
public static final String DATA_BASE_NAME = "testView.db";

public static final String TABLE_NAME = "testView";
public static final String COL_ID = "id";
public static final String COL_TEXT = "text1";

public static final String[] ALL_COL = new String[]{COL_ID, COL_TEXT};

public static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "("
        + COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT ,"
        + COL_TEXT + " TEXT);";


public DataBase(Context context) {
    super(context, DATA_BASE_NAME, null, DATA_BASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_TABLE);

}

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

}
}

my DBController:

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import java.sql.SQLException;

public class DBController  {
private DataBase dataBase;
private Context context;
private SQLiteDatabase dbase;

public DBController(Context context){
    this.context=context;
}


public DBController open() throws SQLException{
    dataBase = new DataBase(this.context);
    dbase = dataBase.getWritableDatabase();
    return this;
}

public void close(){
    dataBase.close();
}
public void insertData(String text){

    ContentValues contentValues=new ContentValues();
    contentValues.put(DataBase.COL_TEXT,text);
    dbase.insert(DataBase.TABLE_NAME, null, contentValues);
}

public Cursor readData(){

    String[]allColumn=new String[]{DataBase.COL_ID,DataBase.COL_TEXT};
    Cursor     cursor=dbase.query(DataBase.TABLE_NAME,allColumn,null,null,null,null,null);
    if (cursor!=null){
        cursor.moveToFirst();
    }
    return cursor;
}

}

my MainActivity:

import android.database.Cursor;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

import java.sql.SQLException;

public class MainActivity extends AppCompatActivity {

    EditText et;
    Button btn;
    ListView lv;
    DBController dbController;
    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        try {
            dbController.open();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        et= (EditText) findViewById(R.id.addText);
        btn= (Button) findViewById(R.id.addButton);
        lv= (ListView) findViewById(R.id.listViewInfo);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name=et.getText().toString();
                dbController.insertData(name);
                Cursor cursor=dbController.readData();

                String[]from=new String[]{DataBase.COL_ID, DataBase.COL_TEXT};
                int[]to=new int[]{R.id.textID,R.id.displayText};

                SimpleCursorAdapter simpleCursorAdapter=new SimpleCursorAdapter(MainActivity.this,R.layout.display_layout,cursor,from,to);

                simpleCursorAdapter.notifyDataSetChanged();

                lv.setAdapter(simpleCursorAdapter);
                dbController.close();
            }
        });

    }
}

the logcat:

02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite        E/AndroidRuntime: FATAL EXCEPTION: main

02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime: Process: com.example.p4.listeviewsqlite, PID: 6467
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.p4.listeviewsqlite/com.example.p4.listeviewsqlite.MainActivity}: java.lang.NullPointerException
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.access$800(ActivityThread.java:135)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:136)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5001)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:515)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:  Caused by: java.lang.NullPointerException
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at com.example.p4.listeviewsqlite.MainActivity.onCreate(MainActivity.java:25)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5231)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.access$800(ActivityThread.java:135) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:136) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5001) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
02-21 15:37:54.009 6467-6467/com.example.p4.listeviewsqlite E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:515)

and thanks for your help :)

score 0 · Accepted Answer · answered Feb 21 '16 at 21:22

0

Your object DBController, is never constructed, there is the reason of the NPE

you are doning in the onCreate

try {
    dbController.open();

but the object dbController is never initialized...

calling the constructor will solve this problem..

answered Feb 21 '16 at 21:22

ΦXocę 웃 Пepeúpa ツ

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where is dbController defined?? – ΦXocę 웃 Пepeúpa ツ Feb 21 '16 at 21:28
thank's man but now a have :java.lang.IllegalArgumentException: column '_id' does not exist can you halp me please – bedrani sidali Feb 21 '16 at 21:31
your table doesnt have a column named id.... – ΦXocę 웃 Пepeúpa ツ Feb 21 '16 at 21:33

NullPointerException open method

1 Answers1