CODEWITHSUNDEEP
androiddatabasesqlite
schocka94
schocka94

Reputation: 41

NullpointerException SQLite Data in ListView

My next Problem.

I wanna display the data in a listview and i get a Nullpointerexception. My Datasource is a SQLite Database. In the following Text is the Activity and the LogCat.

Please help me!

public class ListHaltestelleActivity extends Activity {
private SimpleAdapter simpleAdapter;
private SQLiteDatabase db;
protected static final String TAG = "DataAdapter";

private SQLiteDatabase mDb;
DatabaseHelper myDbHelper = new DatabaseHelper(this);
    //put the table name and column in constants
    public static final String COLUMN_NAME = "scotty_haltestelle";
    Intent intent;

.
.
.
.

public void setListView()
{
    try
    {
        myDbHelper.getReadableDatabase();
        // Alle Daten der Datenbank abrufen mithilfe eines Cursors
        Cursor cursor = db.rawQuery("Select name from scotty_haltestelle",null);

        cursor.moveToFirst();
        ListView listview = (ListView)findViewById(R.id.listView);
        List<Map<String, String>> haltestellenList = new ArrayList<Map<String, String>>();

        while (cursor.moveToNext()){
            //in this string we get the record for each row from the column "name"
            String name = cursor.getString(0);

            String outPut = name;
            haltestellenList.add(createHaltestelle("haltestelle", outPut));
        }

        simpleAdapter = new SimpleAdapter(ListHaltestelleActivity.this, haltestellenList,
                android.R.layout.simple_list_item_1,
                new String[] { "haltestelle" }, new int[] { android.R.id.text1 });
        listview.setAdapter(simpleAdapter);

        //here we close the cursor because we do not longer need it
        //}
        cursor.close();
    }
    catch (SQLException mSQLException)
    {
        Log.e(TAG, "getTestData >>"+ mSQLException.toString());
        throw mSQLException;
    }
}

 // Hash - Map in der die Haltestelle mit Name und dann Number gespeichert wird
    private HashMap<String, String> createHaltestelle(String name, String number) {
        HashMap<String, String> haltestelleNameNo = new HashMap<String, String>();
        haltestelleNameNo.put(name, number);

        return haltestelleNameNo;

Here is the logcat:

java.lang.RuntimeException: Unable to start activity ComponentInfo{at.atn.android/at.atn.android.ListHaltestelleActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
            at android.app.ActivityThread.access$700(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4998)
            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:777)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at at.atn.android.ListHaltestelleActivity.setListView(ListHaltestelleActivity.java:76)
            at at.atn.android.ListHaltestelleActivity.onCreate(ListHaltestelleActivity.java:61)
            at android.app.Activity.performCreate(Activity.java:5243)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
            

Thanks for your Help

Upvotes: 0

Views: 70

Answers (2)

koljaTM
koljaTM

Reputation: 10262

Instead of

myDbHelper.getReadableDatabase();

do 

db=myDbHelper.getReadableDatabase();

Upvotes: 1

laalto
laalto

Reputation: 152827

You forgot to assign a value to the db member variable, throwing out the result of myDbHelper.getReadableDatabase(). This causes the NPE as db is not initialized.

Later in the code you will skip the first row as moveToFirst() is followed by moveToNext().

Upvotes: 1

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