无法打开数据库 Sqlite 文件

Question

我发现了很多关于这个问题的问题，但我无法解决它。我在资产文件夹中有一个 sqlite 数据库：

assets/data/data/{package_name}/databases/dbtest.sqlite

我尝试过：

1. 卸载项目
2. 清理项目
3. 刷新并重新启动了 ecilipse
4. 我检查了我的包名
5. 我检查了我的数据库文件名

但我无法解决它。我不知道我哪里错了。

提前致谢

DBHelper.java

public class DBHelper extends SQLiteOpenHelper {

    private static String DB_PATH = "/data/data/com.exasmple.dbexam/databases/";
    private static String DB_NAME = "dbtest.sqlite";
    public static final String APP_TABLE = "land";

    private static final int DATABASE_VER5ION = 1;
    private static final String TYPE = "type";
    private static final String ID = "id";

    private SQLiteDatabase myDataBase;
    private final Context myContext;
    public static String state;

    public DBHelper(Context context) {
        super(context, DB_NAME, null, DATABASE_VER5ION);
        this.myContext = context;
    }

    public void createDataBase() throws IOException {
        // System.out.println("Creating database");
        boolean dbExist = checkDataBase();
        if (!dbExist) {
            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) {

        }
        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;

        OutputStream myOutput = new FileOutputStream(outFileName);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }


        myOutput.flush();
        myOutput.close();
        myInput.close();
        System.out.println("Database copied into system data");

    }

    public void openDataBase() throws SQLException {

        System.out.println("Open database");
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READWRITE);// SQLiteDatabase.NO_LOCALIZED_COLLATORS);

    }

    @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) {

        db.execSQL("DROP TABLE IF EXISTS report");
        db.execSQL("DROP TABLE IF EXISTS appstatus");
        onCreate(db);
    }

    public ArrayList<String> GetGroupName() {
        String sql = "";
        // System.out.println("Inside Database");
        sql = "select chapterid from content";

        ArrayList<String> list = new ArrayList<String>();

        Cursor cursor = myDataBase.rawQuery(sql, null);

        try {
            if (cursor != null) {
                if (cursor.moveToFirst()) {
                    do {
                        list.add(cursor.getString(0));
                        System.out.println("dblist value==" + list);
                    } while (cursor.moveToNext());
                }
                if (cursor != null && !cursor.isClosed()) {
                    cursor.close();
                }
            } else
                Toast.makeText(myContext, "No values in DB", Toast.LENGTH_SHORT)
                        .show();
        } catch (Exception e) {
            System.out.println("GetGradeNames(): " + e);
        }
        return list;
    }

}

Logcat：

07-09 14:57:27.834: E/AndroidRuntime(987): FATAL EXCEPTION: main
07-09 14:57:27.834: E/AndroidRuntime(987): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.exasmple.dbexam/com.exasmple.dbexam.MainActivity}: android.database.sqlite.SQLiteException: unable to open database file
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.os.Looper.loop(Looper.java:130)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread.main(ActivityThread.java:3683)
07-09 14:57:27.834: E/AndroidRuntime(987):  at java.lang.reflect.Method.invokeNative(Native Method)
07-09 14:57:27.834: E/AndroidRuntime(987):  at java.lang.reflect.Method.invoke(Method.java:507)
07-09 14:57:27.834: E/AndroidRuntime(987):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-09 14:57:27.834: E/AndroidRuntime(987):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-09 14:57:27.834: E/AndroidRuntime(987):  at dalvik.system.NativeStart.main(Native Method)
07-09 14:57:27.834: E/AndroidRuntime(987): Caused by: android.database.sqlite.SQLiteException: unable to open database file
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.database.sqlite.SQLiteDatabase.dbopen(Native Method)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1849)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:820)
07-09 14:57:27.834: E/AndroidRuntime(987):  at com.exasmple.dbexam.DBHelper.openDataBase(DBHelper.java:138)
07-09 14:57:27.834: E/AndroidRuntime(987):  at com.exasmple.dbexam.MainActivity.onCreate(MainActivity.java:21)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-09 14:57:27.834: E/AndroidRuntime(987):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
07-09 14:57:27.834: E/AndroidRuntime(987):  ... 11 more

Answer 1

我终于从chat room 找到了答案。这可能对某人有所帮助..

我更新的 DBHelper

public class DBHelper extends SQLiteOpenHelper {
    public int GetCursor;
    // ****************** Declare all the global variable
    // ****************************//
    private Context myContext;
    public String DB_PATH = "data/data/com.exasmple.dbexam/databases/"; // path
    // of
    // your
    // datbase
    public static String DB_NAME = "Test.sqlite";// your database name
    static String ASSETS_DB_FOLDER = "db";
    private SQLiteDatabase db;

    public DBHelper(Context context) {
        super(context, DB_NAME, null, 2);
        if (db != null && db.isOpen())
            close();

        this.myContext = context;
        //DB_NAME = db_name;

        try {
            createDataBase();
            openDataBase();
        } catch (IOException e) {
            // System.out.println("Exception in creation of database : "+
            // e.getMessage());
            e.printStackTrace();
        }

    }

    

    public void createDataBase() throws IOException {
        boolean dbExist = checkDataBase();

        if (dbExist) {
            // System.out.println("Database Exist");
        } else {
            this.getReadableDatabase();

            try {
                copyDatabase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private void copyDatabase() throws IOException {
        InputStream input = myContext.getAssets().open(DB_NAME);
        String outputFileName = DB_PATH + DB_NAME;
        OutputStream output = new FileOutputStream(outputFileName);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = input.read(buffer)) > 0) {
            output.write(buffer, 0, length);
        }

        // Close the streams
        output.flush();
        output.close();
        input.close();
        // System.out.println(DB_NAME + "Database Copied !");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

    public void openDataBase() throws SQLException {
        // Open the database
        String myPath = DB_PATH + DB_NAME;
        db = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READWRITE);
    }

    public boolean isOpen() {
        if (db != null)
            return db.isOpen();
        return false;
    }

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

    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String myPath = DB_PATH + DB_NAME;
            // System.out.println("My Pathe is:- " + myPath);
            // System.out.println("Open");
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READWRITE);
            // System.out.println("checkDB value:" + checkDB);
            // System.out.println("My Pathe is:- " + myPath);
        } catch (Exception e) {
            // database does't exist yet.
        }

        if (checkDB != null) {
            // System.out.println("Closed");
            checkDB.close();
            // System.out.println("My db is:- " + checkDB.isOpen());
        }

        return checkDB != null ? true : false;
    }

    public Cursor execCursorQuery(String sql) {
        Cursor cursor = null;
        try {
            cursor = db.rawQuery(sql, null);
            GetCursor = cursor.getCount();
            Log.i("Inside execCursorQuery try", sql);
        } catch (Exception e) {
            Log.i("Inside execCursorQuery exception", e.getMessage());
        }
        return cursor;
    }

    public void execNonQuery(String sql) {
        try {
            db.execSQL(sql);
            // Log.d("SQL", sql);
        } catch (Exception e) {
            // Log.e("Err", e.getMessage());
        } finally {
            // closeDb();
        }
    }

    public ArrayList<String> GetchapterID(){
        String sql="";
            //System.out.println("Inside Database");
            sql="select distinct(ChapterId) from contents";
        
        ArrayList<String> list = new ArrayList<String>();
        Cursor cursor=db.rawQuery(sql, null);
        
        try{
        if(cursor != null){
        if (cursor.moveToFirst()) {
            do {
                list.add(cursor.getString(0));
            }
            while (cursor.moveToNext());
        }
        if (cursor != null && !cursor.isClosed()) {
            cursor.close();
        }
        }
     else
            Toast.makeText(myContext, "No values in DB", Toast.LENGTH_SHORT).show();
        }
        catch(Exception e){
            System.out.println("GetGradeNames(): " +e);
        }
        return list;
    }
}

Answer 2

1. 尝试卸载应用并重新安装应用
2. 检查创建数据库时使用的 SQLite 版本是否与当前版本相同
3. 检查您是否尝试从代码中的多个线程访问数据库。它可能被其中一个线程阻塞。
   • 你必须先close与进程A的数据库的连接，然后才能开始使用进程B的数据库。
   • 这将解决您的concurrency。
   • 使用db.close();关闭此类连接

Answer 3

没办法

打开位于 assets 文件夹中的数据库文件。始终正确答案的要点是：databases located in assets cannot be opened，因为此类文件夹（作为 APK 的全部内容）是只读的。

但是，如果实际上不必修改数据库文件怎么办？在这种情况下，资产文件夹是只读的限制无关紧要。

所以将你的 db 文件复制到其他位置，例如 sdcard,data\data folder，然后它将是可读的

Answer 4

试试这个，它会帮助你：-

http://blog.softeq.com/2012/12/using-pre-populated-sqlite-database-in.html

只需从 assets 文件夹中获取数据库文件，然后使用 sqlite 浏览器插入您的数据，然后再次将该文件粘贴到该文件夹​​中

注意：- 并且不要忘记根据您更改列名..

Answer 5

尝试改变这个：

   private static String DB_NAME = "dbtest.sqlite";

为此

   private static String DB_NAME = "dbtest.db";

Answer 6

DB_NAME 应该是 -

DB_NAME="dbtest";

对于 DB_PATH，您使用了包 com.exasmple.dbexam，

DB_PATH = "/data/data/com.exasmple.dbexam/databases/";

可能是错误的。

注意： 输入正确的包名（您可以从清单文件中查看）。

更新：

喜欢-

 public void createDataBase() throws IOException {
            // System.out.println("Creating database");
            boolean dbExist = checkDataBase();
            if (dbExist == true) {
                this.getReadableDatabase();

            try {
                  this.openDataBase();
            } catch (SQLException e) {

              e.printStackTrace();
            }

                try {
                    copyDataBase();
                } catch (IOException e) {
                    throw new Error("Error copying database");
                }
            }
        }

有关handling Sqlite database on Android的更多信息。