没有这样的表:从资产复制数据库时的Table1错误

Question

我的数据库存储在名为myDatabase.db的资产/数据库中，我想使用此处的代码将其复制到内部存储：

public class DatabaseOpener extends SQLiteOpenHelper {
private static String DB_PATH;
private static String DB_NAME = "table1.db";
private static int DB_VERSION = 4;
private SQLiteDatabase myDataBase;
private static Context myContext;
private static DatabaseOpener instance;
private DatabaseOpener(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
    this.myContext = context;
}
public static synchronized DatabaseOpener getInstance(Context context) {
    if (instance==null) {
        instance = new DatabaseOpener(context);
    }
    if(Build.VERSION.SDK_INT >= 4.2) {
        DB_PATH = myContext.getApplicationInfo().dataDir + "/databases/";
    } else {
        DB_PATH = "/data/data/" + myContext.getPackageName() + "/databases/";
    }
    return instance;
}
public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();
    if(dbExist) {
    } else {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
private boolean checkDataBase(){
    SQLiteDatabase checkDB = null;
    try{
        String myPath = DB_PATH + DB_NAME;
        File file = new File(myPath);
        if (file.exists() && !file.isDirectory()) {
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
        }
    }catch(SQLiteException e){
        e.printStackTrace();
    }
    if(checkDB != null){
        checkDB.close();
    }
    return checkDB != null ? true : false;
}
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
    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();
}
public void openDataBase() throws SQLException {
    String myPath = DB_PATH + DB_NAME;
    File file = new File(myPath);
    if (file.exists() && !file.isDirectory()) {
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }
}
@Override
public synchronized void close() {
    if(myDataBase != null)
        myDataBase.close();
    super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}

上面的代码成功工作，直到我卸载了我的应用程序。问题是数据库未成功复制。我拥有的文件还可以，但是当它复制到路径中时，如果我将其录制并在DB浏览器中打开，则没有表。如果我将其推入模拟器，它将再次起作用，但是我无法将其推入未根的设备中。唯一的方法是在路径上创建一个数据库文件并从资产中复制一个文件。那么，我在做什么错？另外，这就是我称为数据库opener类的方式：

    DatabaseOpener db = DatabaseOpener.getInstance(context);
    try {
        db.createDataBase();
    } catch (IOException e) {
        throw new Error ("Unable to create database");
    }
    try {
        db.openDataBase();
    }catch(SQLException sqle){
        throw sqle;
    }
    Object object = db.getObjectByName(name);
    db.close();
    return object;

编辑：我收到的错误是android.database.sqlite.SQLiteException: no such table: table1 (code 1): , while compiling。

Answer 1

卸载应用程序后，Android删除了与应用程序相关的所有本地数据存储，因此SQLDATABASE将被销毁。

，当您重新安装应用程序时，您是在创建表访问它之前的应用程序，因此会引发错误。在操纵其数据之前，请确保创建表。

您需要在onCreate(SQLiteDatabase db)

中写入

db.execSQL(CREATE_TABLE_QUERY);

Answer 2

我用以下代码解决了问题：

public DatabaseOpener(Context context) throws IOException {
    super(context, DB_NAME, null, DB_VERSION);
    this.myContext = context;
    if (Build.VERSION.SDK_INT >= 4.2) {
        DB_PATH = myContext.getApplicationInfo().dataDir + "/databases/";
    } else {
        DB_PATH = "/data/data/" + myContext.getPackageName() + "/databases/";
    }
    boolean dbexist = checkDataBase();
    if (dbexist) {
        openDataBase();
    } else {
        System.out.println("Database doesn't exist");
        createDataBase();
    }
}
public void createDataBase() throws IOException {
    boolean dbexist = checkDataBase();
    if (dbexist) {
        // System.out.println(" Database exists.");
    } 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("databases/" + DB_NAME);
    // Path to the just created empty db
    String outfilename = DB_PATH + DB_NAME;
    // Open the empty db as the output stream
    OutputStream myoutput = new FileOutputStream(DB_PATH + DB_NAME);
    // 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 openDataBase() throws SQLException {
    // Open the database
    String mypath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(mypath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close() {
    if (myDataBase != null)
        myDataBase.close();
    super.close();
}