Question Comment utiliser une base de données existante avec une application Android [dupliquer]


Cette question a déjà une réponse ici:

J'ai déjà créé une base de données SQLite. Je veux utiliser ce fichier de base de données avec mon projet Android. Je souhaite regrouper cette base de données avec mon application.

Au lieu de créer une nouvelle base de données, comment l’application peut-elle accéder à cette base de données et l’utiliser comme base de données?


292
2018-02-02 08:54


origine


Réponses:


REMARQUE: Avant d'essayer ce code, veuillez trouver cette ligne dans le code ci-dessous:

private static String DB_NAME ="YourDbName"; // Database name

DB_NAME est le nom de votre base de données. On suppose que vous avez une copie de la base de données dans le dossier assets, par exemple si votre nom de base de données est ordersDB, la valeur de DB_NAME sera ordersDB,

private static String DB_NAME ="ordersDB";

Gardez la base de données dans dossier d'actifs puis suivez les instructions ci-dessous:

Classe DataHelper:

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

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DataBaseHelper extends SQLiteOpenHelper
{
    private static String TAG = "DataBaseHelper"; // Tag just for the LogCat window
    //destination path (location) of our database on device
    private static String DB_PATH = "";
    private static String DB_NAME ="YourDbName";// Database name
    private SQLiteDatabase mDataBase;
    private final Context mContext;

    public DataBaseHelper(Context context)
    {
        super(context, DB_NAME, null, 1);// 1? Its database Version
        if(android.os.Build.VERSION.SDK_INT >= 17){
           DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
        }
        else
        {
           DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
        }
        this.mContext = context;
    }

    public void createDataBase() throws IOException
    {
        //If the database does not exist, copy it from the assets.

        boolean mDataBaseExist = checkDataBase();
        if(!mDataBaseExist)
        {
            this.getReadableDatabase();
            this.close();
            try
            {
                //Copy the database from assests
                copyDataBase();
                Log.e(TAG, "createDatabase database created");
            }
            catch (IOException mIOException)
            {
                throw new Error("ErrorCopyingDataBase");
            }
        }
    }

    //Check that the database exists here: /data/data/your package/databases/Da Name
    private boolean checkDataBase()
    {
        File dbFile = new File(DB_PATH + DB_NAME);
        //Log.v("dbFile", dbFile + "   "+ dbFile.exists());
        return dbFile.exists();
    }

    //Copy the database from assets
    private void copyDataBase() throws IOException
    {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer))>0)
        {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    //Open the database, so we can query it
    public boolean openDataBase() throws SQLException
    {
        String mPath = DB_PATH + DB_NAME;
        //Log.v("mPath", mPath);
        mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
        //mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
        return mDataBase != null;
    }

    @Override
    public synchronized void close()
    {
        if(mDataBase != null)
            mDataBase.close();
        super.close();
    }
}

Ecrivez une classe DataAdapter comme:

import java.io.IOException;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

public class TestAdapter
{
    protected static final String TAG = "DataAdapter";

    private final Context mContext;
    private SQLiteDatabase mDb;
    private DataBaseHelper mDbHelper;

    public TestAdapter(Context context)
    {
        this.mContext = context;
        mDbHelper = new DataBaseHelper(mContext);
    }

    public TestAdapter createDatabase() throws SQLException
    {
        try
        {
            mDbHelper.createDataBase();
        }
        catch (IOException mIOException)
        {
            Log.e(TAG, mIOException.toString() + "  UnableToCreateDatabase");
            throw new Error("UnableToCreateDatabase");
        }
        return this;
    }

    public TestAdapter open() throws SQLException
    {
        try
        {
            mDbHelper.openDataBase();
            mDbHelper.close();
            mDb = mDbHelper.getReadableDatabase();
        }
        catch (SQLException mSQLException)
        {
            Log.e(TAG, "open >>"+ mSQLException.toString());
            throw mSQLException;
        }
        return this;
    }

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

     public Cursor getTestData()
     {
         try
         {
             String sql ="SELECT * FROM myTable";

              Cursor mCur = mDb.rawQuery(sql, null);
             if (mCur!=null)
             {
                mCur.moveToNext();
             }
             return mCur;
         }
         catch (SQLException mSQLException)
         {
             Log.e(TAG, "getTestData >>"+ mSQLException.toString());
             throw mSQLException;
         }
     }
}

Maintenant, vous pouvez l'utiliser comme:

TestAdapter mDbHelper = new TestAdapter(urContext);
mDbHelper.createDatabase();
mDbHelper.open();

Cursor testdata = mDbHelper.getTestData();

mDbHelper.close();

EDIT: Merci à JDx

Pour Android 4.1 (Jelly Bean), changez:

DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";

à:

DB_PATH = context.getApplicationInfo().dataDir + "/databases/";

dans la classe DataHelper, ce code fonctionnera sur plusieurs utilisateurs de JB 4.2.


320
2018-02-02 09:16



Si vous possédez une base de données pré-construite, copiez-la dans un dossier d'actifs et créez une nouvelle classe comme DataBaseHelper qui implémente SQLiteOpenHelper  Que d'utiliser le code suivant:

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

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseHelperClass extends SQLiteOpenHelper{
 //The Android's default system path of your application database.
private static String DB_PATH = "/data/data/package_name/databases/";
// Data Base Name.
private static final String DATABASE_NAME = "DBName.sqlite";
// Data Base Version.
private static final int DATABASE_VERSION = 1;
// Table Names of Data Base.
static final String TABLE_Name = "tableName";

public Context context;
static SQLiteDatabase sqliteDataBase;

/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 * Parameters of super() are    1. Context
 *                              2. Data Base Name.
 *                              3. Cursor Factory.
 *                              4. Data Base Version.
 */
public DataBaseHelperClass(Context context) {       
    super(context, DATABASE_NAME, null ,DATABASE_VERSION);
    this.context = context;
}

/**
 * Creates a empty database on the system and rewrites it with your own database.
 * 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.
 * */
public void createDataBase() throws IOException{
    //check if the database exists
    boolean databaseExist = checkDataBase();

    if(databaseExist){
        // Do Nothing.
    }else{
        this.getWritableDatabase();         
        copyDataBase(); 
    }// end if else dbExist
} // end createDataBase().

/**
 * Check if the database already exist to avoid re-copying the file each time you open the application.
 * @return true if it exists, false if it doesn't
 */
public boolean checkDataBase(){
    File databaseFile = new File(DB_PATH + DATABASE_NAME);
    return databaseFile.exists();        
}

/**
 * Copies your database from your local assets-folder to the just created empty database in the
 * system folder, from where it can be accessed and handled.
 * This is done by transferring byte stream.
 * */
private void copyDataBase() throws IOException{ 
    //Open your local db as the input stream
    InputStream myInput = context.getAssets().open(DATABASE_NAME); 
    // Path to the just created empty db
    String outFileName = DB_PATH + DATABASE_NAME; 
    //Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName); 
    //transfer bytes from the input file to the output file
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer))>0){
        myOutput.write(buffer, 0, length);
    }

    //Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close(); 
}

/**
 * This method opens the data base connection.
 * First it create the path up till data base of the device.
 * Then create connection with data base.
 */
public void openDataBase() throws SQLException{      
    //Open the database
    String myPath = DB_PATH + DATABASE_NAME;
    sqliteDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);  
}

/**
 * This Method is used to close the data base connection.
 */
@Override
public synchronized void close() { 
    if(sqliteDataBase != null)
        sqliteDataBase.close(); 
    super.close(); 
}

/**
* Apply your methods and class to fetch data using raw or queries on data base using 
* following demo example code as:
*/
public String getUserNameFromDB(){
    String query = "select User_First_Name From "+TABLE_USER_DETAILS;
    Cursor cursor = sqliteDataBase.rawQuery(query, null);
    String userName = null;
    if(cursor.getCount()>0){
        if(cursor.moveToFirst()){
    do{
                userName = cursor.getString(0);
            }while (cursor.moveToNext());
        }
    }
    return userName;
}


@Override
public void onCreate(SQLiteDatabase db) {
    // No need to write the create table query.
    // As we are using Pre built data base.
    // Which is ReadOnly.
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // No need to write the update table query.
    // As we are using Pre built data base.
    // Which is ReadOnly.
    // We should not update it as requirements of application.
}   
}

J'espère que ceci vous aidera...


13
2017-12-28 12:35



J'ai eu des problèmes avec les autres DatabaseHelpers concernant ce problème, je ne sais pas pourquoi.
C'est ce qui a fonctionné pour moi:

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

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper {

  private static final String TAG = DatabaseHelper.class.getSimpleName();

  private final Context context;
  private final String assetPath;
  private final String dbPath;

  public DatabaseHelper(Context context, String dbName, String assetPath)
      throws IOException {
    super(context, dbName, null, 1);
    this.context = context;
    this.assetPath = assetPath;
    this.dbPath = "/data/data/"
        + context.getApplicationContext().getPackageName() + "/databases/"
        + dbName;
    checkExists();
  }

  /**
   * Checks if the database asset needs to be copied and if so copies it to the
   * default location.
   * 
   * @throws IOException
   */
  private void checkExists() throws IOException {
    Log.i(TAG, "checkExists()");

    File dbFile = new File(dbPath);

    if (!dbFile.exists()) {

      Log.i(TAG, "creating database..");

      dbFile.getParentFile().mkdirs();
      copyStream(context.getAssets().open(assetPath), new FileOutputStream(
          dbFile));

      Log.i(TAG, assetPath + " has been copied to " + dbFile.getAbsolutePath());
    }

  }

  private void copyStream(InputStream is, OutputStream os) throws IOException {
    byte buf[] = new byte[1024];
    int c = 0;
    while (true) {
      c = is.read(buf);
      if (c == -1)
        break;
      os.write(buf, 0, c);
    }
    is.close();
    os.close();
  }

  @Override
  public void onCreate(SQLiteDatabase db) {
  }

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

11
2017-12-12 17:15



Si vous avez déjà une base de données, conservez-la dans votre dossier d'actifs et copiez-la dans votre application. Pour plus de détails, voir Bases de bases de données Android.


6
2018-02-02 09:10



Vous pouvez le faire en utilisant un fournisseur de contenu. Chaque élément de données utilisé dans l'application reste privé à l'application. Si une application souhaite partager des données entre applications, il existe uniquement une technique pour y parvenir, en utilisant un fournisseur de contenu, qui fournit une interface pour accéder à ces données privées.


4
2018-02-02 09:03