Android Null pointer exception

Question

Im getting a 'NullPointerException' when I try and load my intent to a class that handles my listview of the data from my database. I'm a total newbie when it comes to listviews so hopefully someone can tell me where Ive gone wrong!

I was thinking that the null pointer was due to the fact no data was being found at the first row posistion that the cursor is at, but I think looking at the logcat, its an issue with my XML layout 'entries'?

Heres my class for the ListView:

package com.example.sqliteexample;



import android.app.Activity;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter;
import android.widget.ListView;

public class SQLView extends Activity {

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    HotOrNot H = new HotOrNot(this, null, null);

    setContentView(R.layout.layout);
     ListView listContent = (ListView)findViewById(R.id.contentList);

     HotOrNot Content = new HotOrNot(this, null, null);

    Cursor cursor = Content.getData();

    startManagingCursor(cursor);

    @SuppressWarnings("static-access")
    String [] from = new String [] {H.KEY_NAME, H.KEY_HOTNESS};
    int [] to = new int [] {R.id.txtName, R.id.txtAge};

    @SuppressWarnings("deprecation")
    SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(this, R.layout.entries, cursor, from, to);

    listContent.setAdapter(cursorAdapter);

The 'getData' method from my DB handler class:

public Cursor getData() {

        String [] columns = new String[]{KEY_ROWID, KEY_NAME, KEY_HOTNESS};
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);


        return c;

HotOrNot DB handler class:

package com.example.sqliteexample;

import android.app.ListActivity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.ListView;

public class HotOrNot {

public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "persons_name";
public static final String KEY_HOTNESS = "persons_hotness";

private static String DATABASE_NAME = "HotOrNotdb";
private static String DATABASE_TABLE = "peopleTable";
private static int DATABASE_VERSION = 30;

private static DBHelper ourHelper;
private static Context ourContext;
private static SQLiteDatabase ourDatabase;

ListView listview;


public void DB_NAME(String DBName)
{
    DATABASE_NAME = DBName;

}

public String returnDB_NAME()
{
    return DATABASE_NAME;
}


public void DB_tableNAME(String DBtName)
{
    DATABASE_TABLE = DBtName;

}

public String returnDB_tNAME()
{
    return DATABASE_TABLE;
}


public void DB_NAME(int DBVersion)
{
    DATABASE_VERSION = DBVersion;

}

public int returnDB_VERSION()
{
    return DATABASE_VERSION;
}



// class constructor for context. when the object is constructed in the main programme
// the context of that class i.e 'this' is sent to this constructor to set the object context.
// null values set on SQLiteDatabase and DBhelper as there is nothing to pass from the called
// objects.
public HotOrNot (Context c, SQLiteDatabase newSQL, DBHelper BD)
{
    ourContext = c;
    ourDatabase = newSQL;
    ourHelper = BD;

}







private static class DBHelper extends SQLiteOpenHelper
{
    public DBHelper(Context context) {
        super(context, KEY_NAME, null, DATABASE_VERSION);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {


        db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
                KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                KEY_NAME + " TEXT NOT NULL, " +
                KEY_HOTNESS + " TEXT NOT NULL);"

                );


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
        onCreate(db);
    }
}



    public HotOrNot open() throws SQLException
    {

        ourHelper = new DBHelper(ourContext);
        ourDatabase = ourHelper.getWritableDatabase();
        return this;

    }

    public void close()
    {
        ourHelper.close();

    }

    public long createEntry(String name, String hotness) {


        ContentValues cv = new ContentValues();
        cv.put(KEY_NAME, name);
        cv.put(KEY_HOTNESS, hotness);
        return ourDatabase.insert(DATABASE_TABLE, null, cv);

    }

    public Cursor getData() {

        String [] columns = new String[]{KEY_ROWID, KEY_NAME, KEY_HOTNESS};
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
        //String result = "";

        //int iRow = c.getColumnIndex(KEY_ROWID);
        //int iName = c.getColumnIndex(KEY_NAME);
        //int ihotness = c.getColumnIndex(KEY_HOTNESS);

        //for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext())
        //{
            //result = result + c.getString(iRow) + "" + c.getString(iName) + "" + c.getString(ihotness);

        //}

        //c.close();

        return c;
    }

    public String getName(long l) {

        String [] columns = new String[]{KEY_ROWID, KEY_NAME, KEY_HOTNESS};
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + l, null, null, null, null);
        if(c != null)
        {
            // move to the selected row
        c.moveToFirst();
        String name = c.getString(1);
        return name;
        }
        return null;

    }


    public String getHotness(long l) {

        String [] columns = new String[]{KEY_ROWID, KEY_NAME, KEY_HOTNESS};
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "=" + l, null, null, null, null);
        if(c != null)
        {
            // move to the selected row
        c.moveToFirst();
        String hotness = c.getString(2);
        return hotness;

    }
        return null;


    }

    public void updateEntry(long newl, String nameEdit, String hotnessEdit) {
    ContentValues cvUpdate = new ContentValues();

    cvUpdate.put(KEY_NAME, nameEdit);
    cvUpdate.put(KEY_HOTNESS, hotnessEdit);

    ourDatabase.update(DATABASE_TABLE, cvUpdate, KEY_ROWID + "=" + newl, null);


    }

    public void delID(long l) {
        ourDatabase.delete(DATABASE_TABLE, KEY_ROWID + "=" + l, null);

    }

}

My XML layout for the listview:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
    android:id="@+id/txtName"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Name:" />

<TextView
    android:id="@+id/txtAge"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Age:" />

</LinearLayout>

The listview XML layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ListView
    android:id="@+id/contentList"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
</ListView>

</LinearLayout>

Logcat:

01-11 00:23:26.655: D/AndroidRuntime(272): Shutting down VM
01-11 00:23:26.655: W/dalvikvm(272): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
01-11 00:23:26.675: E/AndroidRuntime(272): FATAL EXCEPTION: main
01-11 00:23:26.675: E/AndroidRuntime(272): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sqliteexample/com.example.sqliteexample.SQLView}: java.lang.NullPointerException
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.os.Looper.loop(Looper.java:123)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread.main(ActivityThread.java:4627)
01-11 00:23:26.675: E/AndroidRuntime(272):  at java.lang.reflect.Method.invokeNative(Native Method)
01-11 00:23:26.675: E/AndroidRuntime(272):  at java.lang.reflect.Method.invoke(Method.java:521)
01-11 00:23:26.675: E/AndroidRuntime(272):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
01-11 00:23:26.675: E/AndroidRuntime(272):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
01-11 00:23:26.675: E/AndroidRuntime(272):  at dalvik.system.NativeStart.main(Native Method)
01-11 00:23:26.675: E/AndroidRuntime(272): Caused by: java.lang.NullPointerException
01-11 00:23:26.675: E/AndroidRuntime(272):  at com.example.sqliteexample.HotOrNot.getData(HotOrNot.java:143)
01-11 00:23:26.675: E/AndroidRuntime(272):  at com.example.sqliteexample.SQLView.onCreate(SQLView.java:24)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-11 00:23:26.675: E/AndroidRuntime(272):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)

seems like ourDatabase is null. where do you initialize it? — Zhedar
– Zhedar, Commented Jan 11, 2013 at 0:31
Added the DBhandler class guys. You can see where the object instance of 'ourDatabase' is created.....should i be refeecing this in the listview instead of 'hotornot'? — user1352057
– user1352057, Commented Jan 11, 2013 at 0:33

Sam · Accepted Answer · 2013-01-11 00:33:11Z

3

You simply forgot to call open().

HotOrNot Content = new HotOrNot(this, null, null);
Content.open();
Cursor cursor = Content.getData();

(But please read about Java naming conventions, which state variables should start with a lowercase letter.)

answered Jan 11, 2013 at 0:33

Sam

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1 Comment

Sam Over a year ago

I'm glad I could help, I wish the short-sighted individual that downvoted me would realize their mistake...

DGomez · Accepted Answer · 2013-01-11 00:34:27Z

0

public HotOrNot (Context c, SQLiteDatabase newSQL, DBHelper BD)
{
    ourContext = c;
    ourDatabase = newSQL;
    ourHelper = BD;

}

Here, you're passing null in the onCreate to the SQLiteDatabase

HotOrNot H = new HotOrNot(this, null, null);

answered Jan 11, 2013 at 0:34

DGomez

1,4909 silver badges27 bronze badges

2 Comments

A--C Over a year ago

@user1352057 I'd say if you would've called open(), you would have avoided the NPE. Also, please put your inner classes at the end of your file, not in the middle, it's confusing to read.

user1352057 Over a year ago

The construcor is fine DGomez. But ty for yr answer. @Sam, you were 100% correct!

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