Question

可能重复：
How to access an existing sqlite database in Android?

我一直在寻找很长一段时间，但我找不到答案。我想在我的应用程序中复制我现有的Sqlite数据库test.db及其中的数据。因此，当用户从应用程序下载我的应用程序时，数据库随之随附。

现在我看到很多对教程this和this的引用。但它们都不适合我。

    public class DatabaseAdapter extends SQLiteOpenHelper {
         private static String dbPath= "data/data/test.test.test/databases/"; 
         private static String dbName = "test"; 
         private SQLiteDatabase applicationDatabase;  
         private final Context applicationContext;


         public DatabaseAdapter(Context context) {    
                 super(context,  dbName , null, 3);
                 this. applicationContext  = context;
         }


         public boolean checkDataBase(){  
                 File dbFile = new File( dbPath +  dbName);  
   return dbFile.exists();
   }


          public void copyDataBase() throws IOException{  
   try {

                    InputStream input =  applicationContext .getAssets().open(dbName);
                           String outPutFileName=  dbPath  +  dbName ;
                      OutputStream output = new FileOutputStream( outPutFileName); 
                       byte[] buffer = new byte[1024];
                    int length;
                    while ((length = input.read(buffer))>0){
                    output.write(buffer, 0, length);
                    }
                    output.flush();
                    output.close();
                    input.close();
         }
                       catch (IOException e) {
                     Log.v("error",e.toString());
                    }
     }


             public void openDataBase() throws SQLException{
                 String fullDbPath= dbPath + dbName;
               applicationDatabase = SQLiteDatabase.openDatabase( fullDbPath,     null,SQLiteDatabase.OPEN_READONLY);
     }

                @Override
  public synchronized void close() {
          if( applicationDatabase != null)
            applicationDatabase .close();
               super.close();
  }
@Override
public void onCreate(SQLiteDatabase arg0) {
    // TODO Auto-generated method stub

}


@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
    // TODO Auto-generated method stub

}

public void getit(){
    this.getReadableDatabase().rawQuery("SELECT * FROM test", null);
}






}

我得到错误代码= 1没有这样的表。如果我检查数据库是否已创建，但只能使用表android_metadata。

有人是一个有效的例子吗？

Answer 1

编辑 - 这是我的代码有效。我添加了您发布的信息，但可能还有其他变量没有，所以您可能需要对其进行一些修改。

public class DatabaseAdapter extends SQLiteOpenHelper {

    private Context mycontext;

    private String DB_PATH = "data/data/test.test.test/databases/";
    private static String DB_NAME = "test";
    // the extension may be .sqlite
    // or .db
    public SQLiteDatabase myDataBase;

    public DatabaseAdapter(Context context) {
        super(context, DB_NAME, null, 1);
        this.mycontext = context;
        boolean dbexist = checkdatabase();
        if (dbexist) {
        } else {
            System.out.println("Database doesn't exist");
            try {
                createdatabase();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

    public void createdatabase() throws IOException {
        boolean dbexist = checkdatabase();
        if (dbexist) {
        } else {
            this.getReadableDatabase();
            try {
                copydatabase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private boolean checkdatabase() {
        boolean checkdb = false;
        try {
            String myPath = DB_PATH + DB_NAME;
            File dbfile = new File(myPath);
            checkdb = dbfile.exists();
        } catch (SQLiteException e) {
            System.out.println("Database doesn't exist");
        }

        return checkdb;
    }

    private void copydatabase() throws IOException {

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

        // Path to the just created empty db
        @SuppressWarnings("unused")
        String outfilename = DB_PATH + DB_NAME;

        // Open the empty db as the output stream
        OutputStream myoutput = new FileOutputStream(
                "data/data/test.test.test/databases/test");

        // transfer byte to inputfile to outputfile
        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();

    }

    public void open() {
        // Open the database
        String mypath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(mypath, null,
                SQLiteDatabase.OPEN_READWRITE);

    }

    public synchronized void close() {
        myDataBase.close();
        super.close();
    }

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

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }
}

Answer 2

每张表中都有“_id”列吗？

使用现有数据库 - Android Development

2 个答案: