如何在预加载的数据库中填充ListView

Question

I'm trying to create a listview using a preloaded database, the app is running but the data is not showing. Pls help me. Im using Database Browser for Sqlite. Or can someone give me an example of this?

This is my DataListView.java

package com.example.thetrial;
import java.util.ArrayList;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;  
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CursorAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class DataListView extends Activity {
private DBHelper dbDBHelper = null;
private Cursor ourCursor = null;
private DBAdapter adapter = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    try{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    ListView myListView = (ListView)findViewById(R.id.myListView);
dbDBHelper = new DBHelper(this);
dbDBHelper.createDataBase();
dbDBHelper.openDataBase();
ourCursor = dbDBHelper.getCursor();
startManagingCursor(ourCursor);
adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
}catch (Exception e){

    Log.e("Error", "Error in code: " + e.toString());
    e.printStackTrace();
}
}
class DBAdapter extends CursorAdapter{
    DBAdapter(Cursor c){
        super(DataListView.this,c,0);
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        // TODO Auto-generated method stub
        DBHolder holder = (DBHolder)view.getTag();
        holder.populateFrom(cursor, dbDBHelper);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        // TODO Auto-generated method stub
        LayoutInflater inflater = getLayoutInflater();
        View view=inflater.inflate(R.layout.row, parent, false);
        DBHolder holder = new DBHolder(view);
        view.setTag(holder);
        return(view);
    }

}
static class DBHolder {
    private TextView name = null;
    DBHolder (View view){
        name = (TextView)view.findViewById(R.id.text);

    }
    void populateFrom(Cursor c, DBHelper r){
    name.setText(r.getName(c)); 
    }
    }
}

DBHelper.java

package com.example.thetrial;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Locale;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;

public class DBHelper extends SQLiteOpenHelper{

public SQLiteDatabase DB;
private static String DB_Path = "/data/data/com.example.thetrial/databases/";
private static String DB_Name = "trialakoagain.db";
public  static final String TABLE_Name = "linux_comm";
public static final String Column_Id = "_id";
public static final String Column_Comm = "comm";
public static final String Column_Desc = "desc";
private final Context myContext;


public DBHelper(Context context) {
    super(context, DB_Name, null, 1);
    this.myContext = context;
}   

 public void createDataBase(){

        boolean dbExist = checkDataBase();
        if(!dbExist){
            this.getReadableDatabase();
            copyDataBase();
        } 
 }
        /*
        if(dbExist){
            //do nothing - database already exist
        }else{

            //By calling this method and empty database will be created into the default system path
               //of your application so we are gonna be able to overwrite that database with our database.
            this.getReadableDatabase();

            try {

                copyDataBase();

            } catch (IOException e) {

                throw new Error("Error copying database");

            }
        }

    }*/
 private boolean checkDataBase() {
        // TODO Auto-generated method stub
     SQLiteDatabase checkDB = null;

        try{
            String myPath = DB_Path + DB_Name;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
            checkDB.setLocale(Locale.getDefault());
            //checkDB.setLockingEnabled(true);
            checkDB.setVersion(1);

        }catch(SQLiteException e){

            //database does't exist yet.

        }

        if(checkDB != null){

            checkDB.close();

        }

        return checkDB != null ? true : false;
    } 

private void copyDataBase()  {
InputStream inputStream = null;
OutputStream outStream = null;
String outFileName = DB_Path + DB_Name;
try{
    inputStream = myContext.getAssets().open(DB_Name);
    outStream = new FileOutputStream(outFileName);
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) > 0){
        outStream.write(buffer,0,length);
    }
    outStream.flush();
    outStream.close();
    inputStream.close();
}catch (IOException e){
    throw new Error("Problem copying db to resource!");
}

}
public void openDataBase() throws SQLException{

        //Open the database
        String myPath = DB_Path + DB_Name;
        DB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

    }

    @Override
    public synchronized void close() {

            if(DB != null)
                DB.close();

            super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

        // Add your public helper methods to access and get content from the database.
       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
       // to you to create adapters for your views.

    public Cursor getCursor(){
        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
        queryBuilder.setTables (TABLE_Name);
        String [] asColumnToReturn = new String [] {Column_Id,Column_Comm,Column_Desc};

        Cursor mCursor = queryBuilder.query(DB, asColumnToReturn, null, null, null, null, null);
        return mCursor;

    }
    public String getName(Cursor c){
        return(c.getString(2));
    }

}

Manifest.xml

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

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="21" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".DataListView"
        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>

I'm not sure if these are correct I just watched a tutorial and it never said what are the needs of main.xml and row.xml

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ListView
android:id="@+id/myListView"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>

row.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
    android:id="@+id/text"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

Answer 1

I think the problem occurred because you forgot to add the items from database to your adapter :

adapter = new DBAdapter(ourCursor);
myListView.setAdapter(adapter);
//add your adapter data here
adapter.notifyDataSetChanged(); //dont forget to refresh your list