Application Crashes When Trying To Display ListView via Data From SQLite Database

Question

So I made an application where there is 3 edit texts, and user will have to first enter values into them and then click on "View Records" to display a list view of the records added into the SQLite database. The adding of records is working , I am able to store data in to the database but however I am not able to Display them as it keeps crashing whenever I press "View Records" . Attached is my codes for the ViewRecords page as well as databasehelper. Please Advise. Thanks.

ViewRecords.java

package mdad.project;
import java.util.ArrayList;
import com.example.manandhowproject.R;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class ViewRecords extends Activity {
    DatabaseHelper dbhelper;
    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.viewrecords);

        dbhelper = new DatabaseHelper(this);

        populateListView();
    }

    private void populateListView()
    {
        Cursor records = dbhelper.getRecords();
        ArrayList<String> listRec = new ArrayList<String>();
        while(records.moveToNext()){
            listRec.add(records.getString(1));
        }
    ListAdapter adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,listRec);
    listView.setAdapter(adapter);

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
             String BTemp = adapterView.getItemAtPosition(i).toString();
             String HRate = adapterView.getItemAtPosition(i).toString();
             String Bmi = adapterView.getItemAtPosition(i).toString();

             Cursor data = dbhelper.getRecID(BTemp, HRate, Bmi);
             int recID = -1;
             while(data.moveToNext()){
                 recID = data.getInt(0);
             }
             if(recID > -1){

                 Intent editScreenIntent = new Intent(ViewRecords.this, EditDel.class);
                 editScreenIntent.putExtra("id",recID);
                 editScreenIntent.putExtra("Body Temperature",BTemp);
                 editScreenIntent.putExtra("Heart Rate",HRate);
                 editScreenIntent.putExtra("BMI",Bmi);
                 startActivity(editScreenIntent);
             }
             else{
                 Toast.makeText(getApplicationContext(), "No ID Associated", Toast.LENGTH_LONG).show();
             }
         }
     });
 }}

DatabaseHelper.java

package mdad.project;

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

public class DatabaseHelper extends SQLiteOpenHelper {

        public static final String DATABASE_NAME = "medrec.db";
        public static final String TABLE_NAME = "myrec_data";
        public static final String COL1 = "ID";
        public static final String COL2 = "BodyTemp";
        public static final String COL3 = "HeartRate";
        public static final String COL4 = "BMI";



     public DatabaseHelper(Context context) {
            super(context, TABLE_NAME, null, 1);
        }

    @Override
    public void onCreate(SQLiteDatabase db) {

    String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " + COL2 + " TEXT, " + COL3 + " TEXT, " + COL4 + " TEXT);";
    db.execSQL(createTable);

    }

    @Override
    public void onUpgrade (SQLiteDatabase db,int i, int i1)
    {
         db.execSQL("DROP IF TABLE EXISTS " + TABLE_NAME);
         onCreate(db);
    }

     public boolean addRecord(String BodyTemp, String HeartRate, String BMI) {
            SQLiteDatabase db = this.getWritableDatabase();
            ContentValues contentValues = new ContentValues();
            contentValues.put(COL2, BodyTemp);
            contentValues.put(COL3, HeartRate);
            contentValues.put(COL4, BMI);

            long result = db.insert(TABLE_NAME, null, contentValues);


            if (result == -1) {
                return false;
            } else {
                return true;
            }
        }


     public Cursor getRecords()
     {
         SQLiteDatabase db = this.getWritableDatabase();
         String query = "SELECT * FROM " + TABLE_NAME;
         Cursor records = db.rawQuery(query, null);
         return records;
     }

     public Cursor getRecID(String BTemp, String Hrate, String Bmi){
            SQLiteDatabase db = this.getWritableDatabase();
            String query = "SELECT " + COL1 + " FROM " + TABLE_NAME +
                    " WHERE " + COL2 + " = '" + BTemp + "AND" + COL3 + " = '" + Hrate + "AND" + COL4 + " = '" + Bmi +"'";
            Cursor data = db.rawQuery(query, null);
            return data;
        }

    public void updateBtemp(String bodytemp, int selectedID,
            String selectedBtemp) {
          SQLiteDatabase db = this.getWritableDatabase();
          String query = "UPDATE " + TABLE_NAME + " SET " + COL2 +
                    " = '" + bodytemp + "' WHERE " + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL2 + " = '" + selectedBtemp + "'";
            db.execSQL(query);

    }

    public void updateHrate(String heartrate, int selectedID,
            String selectedHrate) {
        SQLiteDatabase db = this.getWritableDatabase();
          String query = "UPDATE " + TABLE_NAME + " SET " + COL3 +
                    " = '" + heartrate + "' WHERE " + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL3 + " = '" + selectedHrate + "'";
            db.execSQL(query);

    }

    public void updateBMI(String bmi, int selectedID, String selectedBMI) {
        SQLiteDatabase db = this.getWritableDatabase();
          String query = "UPDATE " + TABLE_NAME + " SET " + COL4 +
                    " = '" + bmi + "' WHERE " + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL4 + " = '" + selectedBMI + "'";
            db.execSQL(query);

    }

    public void deleteBtemp(int selectedID, String selectedBtemp) {
           SQLiteDatabase db = this.getWritableDatabase();
            String query = "DELETE FROM " + TABLE_NAME + " WHERE "
                    + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL2 + " = '" + selectedBtemp + "'";

            db.execSQL(query);

    }

    public void deleteHrate(int selectedID, String selectedHrate) {
           SQLiteDatabase db = this.getWritableDatabase();
            String query = "DELETE FROM " + TABLE_NAME + " WHERE "
                    + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL3 + " = '" + selectedHrate + "'";

            db.execSQL(query);

    }

    public void deleteBMI(int selectedID, String selectedBMI) {
           SQLiteDatabase db = this.getWritableDatabase();
            String query = "DELETE FROM " + TABLE_NAME + " WHERE "
                    + COL1 + " = '" + selectedID + "'" +
                    " AND " + COL4 + " = '" + selectedBMI + "'";

            db.execSQL(query);

    }

}

Crash Log

02-07 00:33:27.041: E/AndroidRuntime(884): FATAL EXCEPTION: main
02-07 00:33:27.041: E/AndroidRuntime(884): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.manandhowproject/mdad.project.ViewRecords}: java.lang.NullPointerException
02-07 00:33:27.041: E/AndroidRuntime(884):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
02-07 00:55:30.310: E/AndroidRuntime(10059): FATAL EXCEPTION: main
02-07 00:55:30.310: E/AndroidRuntime(10059): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.manandhowproject/mdad.project.ViewRecords}: java.lang.NullPointerException
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.os.Looper.loop(Looper.java:137)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread.main(ActivityThread.java:5103)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at java.lang.reflect.Method.invoke(Method.java:525)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at dalvik.system.NativeStart.main(Native Method)
02-07 00:55:30.310: E/AndroidRuntime(10059): Caused by: java.lang.NullPointerException
02-07 00:55:30.310: E/AndroidRuntime(10059):    at mdad.project.ViewRecords.populateListView(ViewRecords.java:37)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at mdad.project.ViewRecords.onCreate(ViewRecords.java:26)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.Activity.performCreate(Activity.java:5133)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-07 00:55:30.310: E/AndroidRuntime(10059):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
02-07 00:55:30.310: E/AndroidRuntime(10059):    ... 11 more

public DatabaseHelper(Context context) { super(context, TABLE_NAME, null, 1); } Instead of TABLE_NAME use DATABASE_NAME — Ritesh Kumar Dubey, Feb 07 '18 at 07:14

score 2 · Answer 1 · answered Feb 07 '18 at 05:48

Remove declaration of ListView from local method in Create it will initialize it for local use.

  @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.viewrecords);

          //  ListView listView = (ListView) findViewById(R.id.listView);
            listView = (ListView) findViewById(R.id.listView);
            dbhelper = new DatabaseHelper(this);

            populateListView();
        }

score 1 · Accepted Answer · answered Feb 07 '18 at 05:55

1

You have two listView variables one defined as a class variable the other is local to and only has scope in the onCreate method.

When the populateListView method is invoked it uses the class variable listView which is null.

The fix is to ensure that you use the class listView throughout.

Therefore change :-

    ListView listView = (ListView) findViewById(R.id.listView);

to

    listView = (ListView) findViewById(R.id.listView);

answered Feb 07 '18 at 05:55

MikeT

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Thanks so much !!! Now I will work on the edit and deleting. Thanks Alot !!! – KZJing Kaixa Feb 07 '18 at 06:00

Application Crashes When Trying To Display ListView via Data From SQLite Database

2 Answers2