Question

我在assert /文件夹中有一个数据库文件，我用代码复制数据库。但在将其复制到设备后，表格丢失了。只有当我在Android P（8.1）中运行应用程序并且它与其他Android版本一起正常工作时我才检查Nougat并且它工作正常。

如果Android P有任何新的更新，请帮忙。??

复制数据库代码：

public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();

    if (dbExist) {
        //do nothing - database already exist            
    } else {

             this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");
        }
    }
}

private boolean checkDataBase() {

    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    } catch (SQLiteException e) {
        //database does't exist yet.
        e.printStackTrace();
    }

    if (checkDB != null) {

        checkDB.close();

    }

    return checkDB != null ? true : false;
}

private void copyDataBase() throws IOException {

    InputStream myInput = myContext.getAssets().open(DB_NAME);
    String outFileName = DB_PATH + DB_NAME;

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

    //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);
    }

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

}

Answer 1

我通过在this.getReadableDatabase（）之后添加this.close（）解决了android P中的问题

this.getReadableDatabase();
this.close();

我希望此解决方案对您有用。

Answer 2

要解决此问题，请尝试 SQLiteHelper onUpgrade()中的以下代码：

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if(newVersion>oldVersion)
  copyDatabase();
}

Answer 3

private final static String DB_PATH = "/data/data/packageName/databases/";

DbHelper.java

//Database HelperClass Constuctor
public DBHelper(Context context)
{
        super(context, "db.sqlite", null, 1);
        Log.e(TAG, "DBHelper: construction");
        this.context = context;
        dbFile = new File(DB_PATH + dbName);
        if (!dbFile.exists()) 
        {
            SQLiteDatabase db = super.getReadableDatabase();
            db.close();
            copyDataBase(db.getPath());
        }    
 }

在调用this.close();之后通过调用getReadableDatabase();关闭数据库

仅在Android P（8.1）模拟器中出错：android.database.sqlite.SQLiteException：没有这样的表:(代码1 SQLITE_ERROR）：

3 个答案: