Question

我正在使用SQLiteOpenHelper来编写我的所有查询等。当我在内部编写和读取数据库时，一切正常。但如果我想将数据库保存到手机上的文件夹中，我会得到以下内容：

01-03 07:12:24.786 16097-16097/com.myApp.app E/SQLiteLog: (14) cannot open file at line 31278 of [2ef4f3a5b1]
01-03 07:12:24.786 16097-16097/com.myApp.app E/SQLiteLog: (14) os_unix.c:31278: (2) open(/storage/emulated/0/myApp/db/app) - 
01-03 07:12:24.787 16097-16097/com.myApp.app E/SQLiteDatabase: Failed to open database '/storage/emulated/0/myApp/db/app'.
    android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
    at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:207)
    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:191)
    at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
    at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:806)
    at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:791)
    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
    at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:571)
    at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:269)
    at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
    at com.myApp.db.DbMain.getCountValueForMainMenu(DbMain.java:576)
    at com.myApp.app.Beginner.openApp(Beginner.java:672)
    at com.myApp.app.Beginner.checkfilepermission(Beginner.java:341)
    at com.myApp.app.Beginner.onCreate(Beginner.java:332)
    at android.app.Activity.performCreate(Activity.java:6251)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
    at android.app.ActivityThread.-wrap11(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

DBhelper类文件：

 public DbMain(Context context)
    {
        // code to create database in internal storage
       //super(context, DATABASE_NAME, null, DATABASE_VERSION);

        //code to create database in External SD card
       super(context, Environment.getExternalStorageDirectory()
                + File.separator + "/myApp/db/"
                + File.separator
                + DATABASE_NAME, null, DATABASE_VERSION);
    }

@Override
    public void onCreate(SQLiteDatabase db) 
    {
        //1
        String CREATE_TABLE_MENU = "CREATE TABLE IF NOT EXISTS " + TABLE_MENU_LOCAL +"("
                +KEY_MENUID_LOCAL + " TEXT,"
                +KEY_MENUNAME_LOCAL + " TEXT,"
                +KEY_ISCHILD_LOCAL + " TEXT,"
                +KEY_CATEGORYURL_LOCAL + " TEXT,"
                +KEY_IMAGEID_LOCAL + " TEXT,"
                +KEY_MENUNAME_DESCRIPTION_LOCAL + " TEXT"
                + ")";

        db.execSQL(CREATE_TABLE_MENU);
     }

    //to get totalcount
public int getCountValueForMainMenu()
    {
        SQLiteDatabase db = this.getWritableDatabase();
        int count = 0;
        Cursor cursor = db.rawQuery("SELECT COUNT (*) FROM " + TABLE_MENU_LOCAL, null);

        if(null != cursor)
        {
            if(cursor.moveToFirst() && 0 < cursor.getCount())
            {
                count = cursor.getInt(0);
            }

            cursor.close();
        }

        return count;
    }

在内部创建DB时调用相同的方法等，一切都很好。

可能出现什么问题？

谢谢！

Answer 1

检查这些要点

1.READ_EXTERNAL_STORAGE和WRITE_EXTERNAL_STORAGE在androidmanifest.xml中定义

2.创建外部存储目录。如果没有，db Helper之前调用的构造函数创建存储目录

尝试使用此dbHelper代码

public class DbHelper extends SQLiteOpenHelper {

private static final String TABLE_MENU_LOCAL = "menu";
private static final String KEY_MENUID_LOCAL ="menuid" ;
private static final String KEY_MENUNAME_LOCAL ="menuname" ;
private static final String KEY_ISCHILD_LOCAL ="ischild" ;
private static final String KEY_CATEGORYURL_LOCAL ="categoryurl" ;
private static final String KEY_IMAGEID_LOCAL ="imageid" ;
private static final String KEY_MENUNAME_DESCRIPTION_LOCAL ="description" ;

private static String DATABASE_NAME="dbtest.db";
private static int DATABASE_VERSION=1;

public DbHelper(Context context)
{
    // code to create database in internal storage
    //super(context, DATABASE_NAME, null, DATABASE_VERSION);

    //code to create database in External SD card


    super(context, Environment.getExternalStorageDirectory()
            + File.separator + "/myapp/db/"
            + File.separator
            + DATABASE_NAME, null, DATABASE_VERSION);

     }

@Override
public void onCreate(SQLiteDatabase db) {
    //1
    String CREATE_TABLE_MENU = "CREATE TABLE IF NOT EXISTS " + TABLE_MENU_LOCAL +"("
            +KEY_MENUID_LOCAL + " TEXT,"
            +KEY_MENUNAME_LOCAL + " TEXT,"
            +KEY_ISCHILD_LOCAL + " TEXT,"
            +KEY_CATEGORYURL_LOCAL + " TEXT,"
            +KEY_IMAGEID_LOCAL + " TEXT,"
            +KEY_MENUNAME_DESCRIPTION_LOCAL + " TEXT"
            + ")";

    db.execSQL(CREATE_TABLE_MENU);
}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

}

public void insertValues(){
    SQLiteDatabase db=this.getWritableDatabase();

    for(int count=0;count<5;count++) {
        ContentValues insertValues = new ContentValues();
        insertValues.put(KEY_MENUID_LOCAL, "1");
        insertValues.put(KEY_MENUNAME_LOCAL, "Food1");
        insertValues.put(KEY_ISCHILD_LOCAL, "No");
        insertValues.put(KEY_CATEGORYURL_LOCAL, "Demo");
        insertValues.put(KEY_IMAGEID_LOCAL, "imageid");
        insertValues.put(KEY_MENUNAME_DESCRIPTION_LOCAL, "Description");
        db.insert(TABLE_MENU_LOCAL, null, insertValues);
    }
}

//to get totalcount
public int getCountValueForMainMenu()
{
    SQLiteDatabase db = this.getWritableDatabase();
    int count = 0;
    Cursor cursor = db.rawQuery("SELECT COUNT (*) FROM " + TABLE_MENU_LOCAL, null);

    if(null != cursor)
    {
        if(cursor.moveToFirst() && 0 < cursor.getCount())
        {
            count = cursor.getInt(0);
        }

        cursor.close();
    }

    return count;
}

}

并从您的活动或此类任何地方调用此

 String storage_folder = "/myapp/db";

    File f = new File(Environment.getExternalStorageDirectory(), storage_folder);
    if (!f.exists()) {
        f.mkdirs();
    }
    DbHelper lDbHeper=new DbHelper(MainActivity.this);
    lDbHeper.insertValues();
    int count=lDbHeper.getCountValueForMainMenu();

    Log.i("Count is:",""+count);

让我知道它对你有帮助

Answer 2

确保您在清单中声明了写入权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

如果您的目标是API 23或更高版本，则还需要request the permission at runtime。

未知错误（代码14）：在android中外部写入时无法打开数据库

2 个答案: