Can't spot what the error is

Question

Tried a lot searching and the solutions given were to add the activity to manifest and add the class to manifest and some more. Didn't get any solution. so pls help.

Learning sqlite database accessing by following online tutorials. Tried the following and getting a lot of errors in the logcat.

Supporting Class DbHelper

public class DbHelper extends SQLiteOpenHelper {

private static final String Name = "Record.db";
private static final int Version = 1;



public DbHelper(Context context){
    super(context,Name,null,Version);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

    db.execSQL("create table vijay(name text, id integer primary key)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
db.execSQL("drop table if exists vijay");
onCreate(db);
}

public void addRecord(String name, int id){
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put("name",name);
    values.put("id", id);

    db.insert("vijay", null, values);
    db.close();
}   
}

Main Activity class

    public class MainActivity extends Activity {

    DbHelper dbhelper = new DbHelper(getApplicationContext());

    EditText et1;
    EditText et2;
    String s;
    int ss;


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

        et1 = (EditText)findViewById(R.id.editText1);
        et2 = (EditText)findViewById(R.id.editText2);
         s = et1.getText().toString();
         ss = Integer.parseInt(et2.getText().toString());
    }

    public void add(View v){

        dbhelper.addRecord(s,ss);
        et1.setText("");
        et2.setText("");
    }


    @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;
    }
}

android manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.databaseaccess"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.databaseaccess.MainActivity"
            android:label="@string/app_name"
             >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Logcat shows many errors

 07-29 16:48:56.793: E/AndroidRuntime(870): FATAL EXCEPTION: main
07-29 16:48:56.793: E/AndroidRuntime(870): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.databaseaccess/com.example.databaseaccess.MainActivity}: java.lang.NullPointerException
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.os.Looper.loop(Looper.java:123)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-29 16:48:56.793: E/AndroidRuntime(870):  at java.lang.reflect.Method.invokeNative(Native Method)
07-29 16:48:56.793: E/AndroidRuntime(870):  at java.lang.reflect.Method.invoke(Method.java:521)
07-29 16:48:56.793: E/AndroidRuntime(870):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-29 16:48:56.793: E/AndroidRuntime(870):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-29 16:48:56.793: E/AndroidRuntime(870):  at dalvik.system.NativeStart.main(Native Method)
07-29 16:48:56.793: E/AndroidRuntime(870): Caused by: java.lang.NullPointerException
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:100)
07-29 16:48:56.793: E/AndroidRuntime(870):  at com.example.databaseaccess.MainActivity.<init>(MainActivity.java:11)
07-29 16:48:56.793: E/AndroidRuntime(870):  at java.lang.Class.newInstanceImpl(Native Method)
07-29 16:48:56.793: E/AndroidRuntime(870):  at java.lang.Class.newInstance(Class.java:1429)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-29 16:48:56.793: E/AndroidRuntime(870):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
07-29 16:48:56.793: E/AndroidRuntime(870):  ... 11 more

Answer 1

I found another mistake that lead to app crash.

1. As Shani & Abbas mentioned (Thanks to them), instantiating the class in onCreate method.

2. Values of the edittext fields were stored to a String and an int variable in the onCreate method itself before they could have some values entered. Got rid of 'em now. Put them in the button' onclick event function.

Thanks to all...

Answer 2

Just make global variable for DBHelper....

Like this:

DbHelper dbhelper ;

and then create a object for it in onCreate() method:

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

    dbhelper  = new DbHelper(MainActivity.this);


}

Answer 3

Move the following line into your OnCreate Method

DbHelper dbhelper = new DbHelper(getApplicationContext());