Android app is getting crashed when I try to get my db from SQLite connected to it. My first hands on android

Question

This is my database helper code. My app is getting crashed when I connect it to database.This is my first time with android. I badly want to get rid of this.Please help me with this. Thanks in advance. dbhelper.java

package com.example.krishchandran.searchez;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.jar.Attributes;
import static android.os.Build.ID;
import static java.sql.Types.VARCHAR;
/*** Created by Krish Chandran on 5/12/2017.
*/

public class DBhelper extends SQLiteOpenHelper {
private static final int VERSION = 1;
private static final String DATABASE_NAME = "SearchEZ.db";
private static final String TABLE_NAME = "searchez";
private static final String col1 = "uid";
private static final String col2 = "pwd";

private static final String create=" create table searchez( uid varchar 
not null ," + "pwd varchar not null;";
SQLiteDatabase db;
/*for constructor, there is no return type */
public DBhelper(Context context) {
    super(context, DATABASE_NAME, null, VERSION); //four parameters
    SQLiteDatabase db = this.getWritableDatabase();// This will create 
your DB and TABLE
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(create);
    this.db=db;
}
public void insertdata(credential c){
    db=this.getWritableDatabase();
    ContentValues values=new ContentValues();

    values.put(col1, c.getUid());
    values.put(col2, c.getPwd());

    db.insert(TABLE_NAME, null, values);
    db.close();
}
public String searchpwd(String uname){
    String a,b;
    b="not found";
    db=this.getReadableDatabase();
    String q="SELECT uid,pwd FROM"+ TABLE_NAME;
    Cursor C= db.rawQuery(q, null);
    if(C.moveToFirst())
    {
        do{
            a=C.getString(0);
            if(a.equals(uname)){
              b=C.getString(1);
                break;
            }
        }while(C.moveToNext());
    }
    return b;

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
 {
 String q="DROP TABLE IF EXISTS"+TABLE_NAME;
    db.execSQL(q);
    this.onCreate(db);

}

}

this is my signup class :

package com.example.krishchandran.searchez;
import android.content.Intent;
import android.net.Credentials;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class Guest extends AppCompatActivity {
DBhelper helper= new DBhelper(this);
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.content_guest);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) 
    findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", 
            Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
          }
      });
   }
   public void guestclick(View view) {
    EditText uname= (EditText)findViewById(R.id.editText);
    EditText pwd= (EditText)findViewById(R.id.editText2);

    String unames= uname.getText().toString();
    String pwds= pwd.getText().toString();
    credential C= new credential();
    C.setUid(unames);
    C.setPwd(pwds);

    helper.insertdata(C);


  }

   }

and this is my login class:

  package com.example.krishchandran.searchez;
  import android.content.Intent;
  import android.os.Bundle;
   import android.support.design.widget.FloatingActionButton;
   import android.support.design.widget.Snackbar;
  import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
   import android.view.View;
   import android.widget.EditText;
  import android.widget.Toast;

   public class userlogin extends AppCompatActivity {

DBhelper helper = new DBhelper(this);

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


}

public void loginclick(View view) {
    EditText uname = (EditText) findViewById(R.id.editText);
    EditText pwd = (EditText) findViewById(R.id.editText2);

    String unames = uname.getText().toString();
    String pwds = pwd.getText().toString();
    credential C = new credential();
    C.setUid(unames);
    C.setPwd(pwds);

    String pd = helper.searchpwd(unames);

    if (pwds.equals(pd)) {
        Intent i = new Intent(userlogin.this, second.class);
        i.putExtra("Username",unames);
        startActivity(i);
    }
    else{
        Toast T=Toast.makeText(userlogin.this,"Invalid UID and PWD", 
     Toast.LENGTH_SHORT);
        T.show();
     }
    }
    }

MY LOGCAT:

      05-18 04:00:52.941 12593-12593/? I/art: Late-enabling -Xcheck:jni

05-18 04:00:53.042 12593-12593/com.example.krishchandran.searchez W/System: ClassLoader referenced unknown path: /data/app/com.example.krishchandran.searchez-1/lib/arm64 05-18 04:00:53.051 12593-12593/com.example.krishchandran.searchez I/InstantRun: starting instant run server: is main process 05-18 04:00:53.098 12593-12593/com.example.krishchandran.searchez W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable 05-18 04:00:53.162 12593-12621/com.example.krishchandran.searchez D/AppTracker: App Event: start 05-18 04:00:53.187 12593-12622/com.example.krishchandran.searchez I/Adreno: QUALCOMM build : 853a1ff, I9c435c2712 Build Date : 01/10/17 OpenGL ES Shader Compiler Version: XE031.09.00.04 Local Branch : Remote Branch : Remote Branch : Reconstruct Branch : 05-18 04:00:53.191 12593-12622/com.example.krishchandran.searchez I/OpenGLRenderer: Initialized EGL, version 1.4 05-18 04:00:53.191 12593-12622/com.example.krishchandran.searchez D/OpenGLRenderer: Swap behavior 1 05-18 04:00:55.252 12593-12658/com.example.krishchandran.searchez D/AppTracker: App Event: stop 05-18 04:00:55.280 12593-12593/com.example.krishchandran.searchez D/AndroidRuntime: Shutting down VM 05-18 04:00:55.281 12593-12593/com.example.krishchandran.searchez E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.krishchandran.searchez, PID: 12593 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.krishchandran.searchez/com.example.krishchandran.searchez.Guest}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2630) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2814) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1527) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6290) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:290) at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223) at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163) at com.example.krishchandran.searchez.DBhelper.(DBhelper.java:31) at com.example.krishchandran.searchez.Guest.(Guest.java:15) at java.lang.Class.newInstance(Native Method) at android.app.Instrumentation.newActivity(Instrumentation.java:1094) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2620) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2814) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1527) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6290) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 05-18 04:00:55.281 12593-12593/? D/AppTracker: App Event: crash 05-18 04:00:55.294 12593-12593/? I/Process: Sending signal. PID: 12593 SIG: 9

one thing I see is, that your create string is not correct. You forget the claim at the end. Must be `String create=" create table searchez( uid varchar not null ," + "pwd varchar not null);";` — Opiatefuchs, May 18 '17 at 11:49
Be aware: If your database is already created at some test and you make some changes in the structure (new or less column), uninstall your app and install again because the database exists. — Opiatefuchs, May 18 '17 at 11:51
`private static final String create=" create table searchez( uid varchar not null ," + "pwd varchar not null;";` should definitely be `private static final String create="create table searchez(uid varchar not null, pwd varchar not null);";` the bracket is missing, also..why do you need to break the String with a "+", that is normally used because constants are used for those values. — Pararth, May 18 '17 at 11:57

score 0 · Answer 1 · answered May 18 '17 at 11:58

Without the error stack, I don´t know if this are the only reasons, buit i see two issues here:

The first, your create String is wrong, you forget the claim at the end. It must be:

String create=" create table searchez( uid varchar not null ," + "pwd varchar not null);";

Second, you missed some spaces:

searchpwd()):

String q="SELECT uid,pwd FROM "+ TABLE_NAME;//space needed after FROM

and in onUpgrade():

String q="DROP TABLE IF EXISTS "+TABLE_NAME; //space needed after EXISTS

Be awar: If you created the database at one point of testing and you make some future changes in the structure (adding or deleting a column), you have to uninstall your app before try it again.

If these are not the issues, you need to show the error stacktrace. Without this, everything is an assumption.

Android app is getting crashed when I try to get my db from SQLite connected to it. My first hands on android

1 Answers1