Starting to work with SQLite and Android; errors on starting the program

Question

Recently, I have been trying to use SQL together with Android. However, my code has come into errors.

The program is simple; it's supposed to take a name and an e-mail address, save it when a button is pressed, and then load the data afterwards when the Load button is pressed.

So far, I've been able to narrow it down, the setOnClickListener area, and the problems are most likely in the two cases. I don't know why they are always returning errors, though. I've written programs where setOnClickListener was working, so I'm assuming the actual errors are inside the two cases I've put in.

Here's the code: one MainActivity.java, one class, and one XML file. MainActivity.java:

package com.example.sqlpractice;

import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity implements OnClickListener{

    Button bSave, bLoad;
    EditText etName, etEmail;
    DataHandler handler;

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

        bSave = (Button) findViewById(R.id.bSave);
        bLoad = (Button) findViewById(R.id.bLoad);
        etName = (EditText) findViewById(R.id.etName);
        etEmail = (EditText) findViewById(R.id.etEmail);

        bSave.setOnClickListener(this);
        bLoad.setOnClickListener(this);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);
            return rootView;
        }
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId()){
            case R.id.bSave:
                String getName = etName.getText().toString();
                String getEmail = etEmail.getText().toString();
                handler = new DataHandler(getBaseContext());
                handler.open();
                long id = handler.insertData(getName, getEmail);
                Toast.makeText(getBaseContext(), "Data inserted", Toast.LENGTH_LONG).show();
                handler.close();
                break;

            case R.id.bLoad:
                String getName1 = "";
                String getEmail1 = "";

                handler = new DataHandler(getBaseContext());
                handler.open();
                Cursor crsLoad = handler.returnData();
                if(crsLoad.moveToFirst()) {
                    do {
                        getName1 = crsLoad.getString(0);
                        getEmail1 = crsLoad.getString(1);
                    } while(crsLoad.moveToNext());
                }
                handler.close();
                Toast.makeText(getBaseContext(), "Data loaded. Name: "+getName1 +" Email: "+getEmail1, Toast.LENGTH_LONG).show();
                break;
        }
    }
}

The errors I received:

05-27 11:08:12.503: E/AndroidRuntime(908): FATAL EXCEPTION: main
05-27 11:08:12.503: E/AndroidRuntime(908): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sqlpractice/com.example.sqlpractice.MainActivity}: java.lang.NullPointerException
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.os.Looper.loop(Looper.java:137)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread.main(ActivityThread.java:5103)
05-27 11:08:12.503: E/AndroidRuntime(908):  at java.lang.reflect.Method.invokeNative(Native Method)
05-27 11:08:12.503: E/AndroidRuntime(908):  at java.lang.reflect.Method.invoke(Method.java:525)
05-27 11:08:12.503: E/AndroidRuntime(908):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
05-27 11:08:12.503: E/AndroidRuntime(908):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-27 11:08:12.503: E/AndroidRuntime(908):  at dalvik.system.NativeStart.main(Native Method)
05-27 11:08:12.503: E/AndroidRuntime(908): Caused by: java.lang.NullPointerException
05-27 11:08:12.503: E/AndroidRuntime(908):  at com.example.sqlpractice.MainActivity.onCreate(MainActivity.java:34)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.Activity.performCreate(Activity.java:5133)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-27 11:08:12.503: E/AndroidRuntime(908):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
05-27 11:08:12.503: E/AndroidRuntime(908):  ... 11 more

DataHandler.java:

package com.example.sqlpractice;

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;

public class DataHandler {
public static final String NAME = "name";
public static final String EMAIL = "email";
public static final String TABLE_NAME = "myTable";
public static final String DATABASE_NAME = "myDatabase";
public static final int DATABASE_VERSION = 1;
public static final String TABLE_CREATE = "create table myTable (name text not     null, email text not null)";

DatabaseHelper dbHelper;
Context ctx;
SQLiteDatabase db;

public DataHandler(Context ctx) {
    this.ctx = ctx;
    dbHelper = new DatabaseHelper(ctx);
}

private static class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseHelper(Context ctx) {
        super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        try {
            db.execSQL(TABLE_CREATE);
            } catch(SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

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

}
public DataHandler open() {
    db = dbHelper.getWritableDatabase();
    return this;
}

public void close() {
    dbHelper.close();
}

public long insertData(String name, String email) {
    ContentValues content = new ContentValues();
    content.put(NAME, name);
    content.put(EMAIL, email);
    return db.insertOrThrow(TABLE_NAME, null, content);
}

public Cursor returnData() {

return db.query(TABLE_NAME, new String[] {NAME, EMAIL}, null, null, null, null, null);

}

}

fragment_main.xml:

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.sqlpractice.MainActivity$PlaceholderFragment" >

        <EditText
        android:id="@+id/etEmail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/bSave"
        android:layout_centerHorizontal="true"
        android:ems="10"
        android:hint="Enter e-mail here." >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/etName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/etEmail"
        android:layout_alignLeft="@+id/etEmail"
        android:ems="10"
        android:hint="Enter name here." />

    <Button
        android:id="@+id/bLoad"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="16dp"
        android:text="Load Data" />

    <Button
        android:id="@+id/bSave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/bLoad"
        android:layout_alignLeft="@+id/bLoad"
        android:text="Save Data" />



</RelativeLayout>

Thank you for helping.

Your views belong to the fragment layout while you initialize it in Activity — Raghunandan, May 27 '14 at 15:42
Follow http://stackoverflow.com/questions/23653778/nullpointerexception-accessing-views-in-oncreate — Raghunandan, May 27 '14 at 15:43
I tried that; doesn't work because of syntax errors. Should I ask a new question or edit this one? I'm new to this. — more whirlpools, May 28 '14 at 09:54
Never mind, I fixed it. The solution was to remove the static in the "public static class PlaceholderFragment extends Fragment {" so that it's just "public class PlaceholderFragment extends Fragment {". — more whirlpools, May 28 '14 at 10:46

Starting to work with SQLite and Android; errors on starting the program

0 Answers0