I have an SQlite database in my Assets folder my app runs but when i click the button to show data from the copied database my app crashes

Question

am new to Android programming please help look through my code i am failing to identify why it crashes when i click the button.(the button is supposed to show data from a database copied from Assets)

package com.example.atumusiime.mydatabasetrialapplication;

import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.view.View;
import android.widget.Button;


public class MainActivity extends Activity {

    DbHelper check;
    Button display;

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

        SQLiteDatabase db = null;
        DbHelper helper = new DbHelper(MainActivity.this);
        helper.onCreate(db);
        show();

    }

    public void show(){
        DbHelper helper = new DbHelper(this);
        helper.open();
        display = (Button)findViewById(R.id.btn_submit);
        display.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Cursor res = check.showdata();

                if(res.getCount() == 0) {
                    show_msg("Error","Nothing found");
                    return;
                }
                StringBuffer buffer = new StringBuffer();
                while (res.moveToNext()){
                    buffer.append("ID:"+ res.getString(0)+"\n");
                    buffer.append("Name:"+ res.getString(1)+"\n");
                    buffer.append("Date Of Birth:"+ res.getString(2)+"\n\n");
                }
                show_msg("Member Bio Data",buffer.toString());
            }
        });
    }

    public void show_msg(String Tittle, String Message){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(Tittle);
        builder.setMessage(Message);
        builder.show();


    }

    @Override
    public void onStart() {
        super.onStart();

    }

    @Override
    public void onStop() {
        super.onStop();


    }

}


package com.example.atumusiime.mydatabasetrialapplication;

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.util.Log;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;

/**
 * Created by atumusiime on 10/31/2016.
 */
public class DbHelper extends SQLiteOpenHelper {

    public static final String DB_NAME = "mydb.db";
    public static final int version = 1;
    public static final String product_table = "tblproduct";
    public static final String order_id = "_id";
    public static final String pname = "pname";
    public static final String desc = "desc";
    public static final String quantity = "quantity";
    public static final String rating = "rating";

    private SQLiteDatabase ourdb;
    public Context cont;

    public DbHelper(Context context) {
        super(context, DB_NAME, null, version);
        this.cont = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        try {
            File dbFile = cont.getDatabasePath(DB_NAME);
            if (dbFile.exists()){
                Toast.makeText(cont, "Database Already Exist..." , Toast.LENGTH_LONG).show();}
            else{ this.getReadableDatabase();
                InputStream input = cont.getAssets().open(DB_NAME);
                int size = input.available();
                input.close();
                if (size > 0){Log.d("file" , dbFile.getPath());
                    copyDataBase(dbFile);
                    //this.close();
                     } else {
                    // TODO Auto-generated method stub
                    db.execSQL("create table " + product_table +" ( "+ order_id + " INTEGER PRIMARY KEY AUTOINCREMENT , " + pname + " TEXT NOT NULL ," + desc + " TEXT ," + rating + " INTEGER ," + quantity +" INTEGER );");
                    }
                }
            } catch (IOException e) { e.printStackTrace();}
        this.ourdb = db;
    }

    private void copyDataBase(File dbFile) throws IOException {

        //Open your local db as the input stream
        InputStream myInput = cont.getAssets().open(DB_NAME);

        //Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(dbFile);

        //transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer))>0)
        {
            myOutput.write(buffer, 0, length);
            Log.d("buf", "" + length);
        }

        //Close the streams
        myOutput.flush();
        myOutput.close();`enter code here`
        myInput.close();

    }

    public DbHelp`enter code here`er open() throws SQLException
    {
        if (this.ourdb == null)
        {
            this.ourdb = this.getWritableDatabase();
        }

        return this;
    }

    public synchronized void close()
    {
        if(this.ourdb.isOpen())
            this.ourdb.close();
    }
    public long insert(String name, String des, Float ratings, int quan) throws SQLException
    {
        // TODO Auto-generated method stub
        ContentValues cv = new ContentValues();
        cv.put(pname, name);
        cv.put(desc, des);
        cv.put(rating, ratings);
        cv.put(quantity, quan);
        return this.ourdb.insertOrThrow(product_table, null, cv);

    }

    public Cursor getAllData() throws SQLException
    {
        // TODO Auto-generated method stub
        String [] colums = new String[]{order_id ,pname ,desc ,rating ,quantity};
        Cursor c = this.ourdb.query(product_table,colums, null, null, null, null, null, null);
        return c;
    }

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

    }

     Cursor showdata(){

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor result = db.rawQuery("SELECT * FROM tblproduct",null);
        return result;
    }
}

I have created a method show() in MainActivity that has the on click listener for the button in the onclick listner i call a method from my Dbhelper class i then try to display the data in an alert dialog, i have tried all i know but cat get the App to show the data i will be grateful please help

Please see my logcat 10-31 12:32:27.363 921-921/com.example.atumusiime.mydatabasetrialapplication E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPointerException at com.example.atumusiime.mydatabasetrialapplication.MainActivity$1.onClick(MainActivity.java:40) at android.view.View.performClick(View.java:4204) at android.view.View$PerformClick.run(View.java:17355) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method) 10-31 12:37:27.944 921-921/com.example.atumusiime.mydatabasetrialapplication I/Process: Sending signal. PID: 921 SIG: 9

Thanks namingFailed for your comment i have edited the question to add the logcat information, it was too long so i started at FATAL EXCEPTION — Tumus Tony, Oct 31 '16 at 13:02

score 0 · Answer 1 · answered Oct 31 '16 at 13:09

Remove helper.onCreate(db); It is not required . If you want to use standard way to read from existing database , see here :

http://blog.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

Else there is a simpler way .There is a library called SQLiteAssetHelper which exactly streamlined for this purpose . To understand how to use SqliteAssetHelper , read the official documentation here :

https://github.com/jgilfelt/android-sqlite-asset-helper/blob/master/README.markdown

Thanks Rishabh i have removed Helpe.onCreate but it still crushes when i click the button let me read the links provided thanks again. — Tumus Tony, Oct 31 '16 at 13:32

I have an SQlite database in my Assets folder my app runs but when i click the button to show data from the copied database my app crashes

1 Answers1