Question

我的数据库出了问题。应用程序启动时，资产会自动加载数据库。只有在它不存在的情况下才应加载（首次启动应用程序），但它不起作用。

这是我的代码：

public static boolean copyDBFile(Context context)
{
    File dbAbsolutePathFile = new File(dbPath + dbName);
    File dbPathFile = new File(dbPath);

    //Here we make sure that the directory path for the database exists
    if(!dbPathFile.exists()) {
        dbPathFile.mkdirs();

    }



    File dbNameFile = context.getDatabasePath(dbName);

    //Here we check whether the database file exists or not. If not, we then create it
    if(!dbNameFile.exists()) {
        Log.d("database", "copy");
        //dbNameFile = new File(dbName);
        try {

            //Here we call the copyDB() method.
            copyDB(context.getAssets().open(dbName), new FileOutputStream(dbPath + dbName));

        } catch (FileNotFoundException e) {
        } catch (IOException e) {
        }

    }       
    return true;
}

private static void copyDB(InputStream inputStream, OutputStream outputStream) {


    byte[] buffer = new byte[1024];
    int length;

    //Here we copy 1K bytes at a time
    try {
        while((length=inputStream.read(buffer))>0) {
            outputStream.write(buffer, 0, length);
        }

        inputStream.close();
        outputStream.close();

    } catch (IOException e) {

    }
}

Answer 1

试试此代码

public class MyApplication extends Application
{
    @Override
    public void onCreate()
    {
        super.onCreate();
        if(! MyDBHelper.isDatabaseExist(Your_Context , YOUR_DATABASE_NAME))
        new MyDBHelper(this).ImportDatabase(this);
    }
}
public static boolean isDatabaseExist(ContextWrapper context, String dbName)
{
    File dbFile = context.getDatabasePath(dbName);
    return dbFile.exists();
}

用于导入数据库

public Boolean ImportDatabase(Context c)
    {
        InputStream myInput = null;

        try {


            myInput = c.getAssets().open("Assets/Database.db");


            // Set the output file stream up:


            SQLiteDatabase db = getReadableDatabase();  
            OutputStream myOutput = new FileOutputStream(db.getPath());
            db.close();

            // 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 and clear the streams 

            myOutput.flush(); 
            myOutput.close();
            myInput.close(); 
        } 
        catch (FileNotFoundException e) 
        {
            Log.e("Restoring Database", "file not found");
            e.printStackTrace();
            return false;
        }
        catch (IOException e) 
        {
            Log.e("Restoring Database", "IO exception");
            e.printStackTrace();
            return false;
        }
        Log.e("Restoring Database", "Restored");
        return true;
    }

检查数据库是否存在无效

1 个答案: