无法打开数据库的Andr​​oid的Java的SQLite [英] Failed to open Database Android Java SQLite

问题描述

下面是我的code：

 保护无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.activity_main）;    SQLiteDatabase.openOrCreateDatabase（/ gregpeck.db，NULL）;}
 

显然，这是我的主要活动中。

我还添加了允许我的主要活动：

 ＆LT;清单的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android
        包=ie.callanan.dennis.testhw＆GT;        ＆LT;使用许可权的android：NAME =android.permission.WRITE_EXTERNAL_STORAG​​E/＆GT;        ＆lt;应用
            机器人：allowBackup =真
 

我收到错误消息是：

 无法打开数据库'gregpeck.db。
android.database.sqlite.SQLiteCantOpenDatabaseException：未知错误（code 14）：无法打开数据库
 

解决方案

我会建议使用 SQLiteOpenHelper ，如果您需要为您的应用程序专用数据库：

 公共类MyDatabaseHelper扩展SQLiteOpenHelper {    私有静态最后弦乐DATABASE_NAME =数据库名;
    私有静态最终诠释DATABASE_VERSION = 1;
    私有静态最后弦乐TABLE_CREATE =CREATE TABLE ......;    公共MyDatabaseHelper（上下文的背景下）{
        超（背景下，DATABASE_NAME，空，DATABASE_VERSION）;
    }    @覆盖
    公共无效的onCreate（SQLiteDatabase数据库）{
        database.execSQL（TABLE_CREATE）;
    }    @覆盖
    公共无效onUpgrade（SQLiteDatabase数据库，诠释oldVersion，诠释静态网页）{
        //做任何升级需要
    }
}
 

这里你找到一个完整的例子。如果你想打开从SD卡数据库，使用：

 文件文件=新的文件（/ SD卡/ db.sqlite）;
SQLiteDatabase DB = SQLiteDatabase.openOrCreateDatabase（文件，NULL）;
Log.d（MyApp的，成功打开：+ db.isOpen（））;
 

对于第一种情况下，你不需要任何特殊的权限。对于第二个你这样做。的注意的：Android的4.3和4.4做限制SD卡上的访问。所以它可能是，你不能在所有访问数据库文件（例如见该<一个href=\"http://www.theguardian.com/technology/askjack/2014/oct/09/how-can-i-get-android-kitkat-to-work-with-my-sd-cards\"相对=nofollow>文章）。

Here is my code:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    SQLiteDatabase.openOrCreateDatabase("/gregpeck.db", null);

}

Obviously this is inside my Main Activity.

I have also added the permission to my Main Activity:

    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="ie.callanan.dennis.testhw" >

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

        <application
            android:allowBackup="true"

The error message I receive is:

Failed to open database 'gregpeck.db'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database

解决方案

I would recommend to use a SQLiteOpenHelper, if you need a private database for your application:

public class MyDatabaseHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "DatabaseName";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_CREATE = "CREATE TABLE ....";

    public MyDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase database) {
        database.execSQL(TABLE_CREATE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase database,int oldVersion,int newVersion){
        // do whatever is required for the upgrade 
    }
}

Here you find a full example. If you want to open a database from SD card, use:

File file = new File("/sdcard/db.sqlite" ); 
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(file, null);
Log.d("MyApp", "Successfully opened: "  + db.isOpen());

For the first case you don't need any particular permissions. For the second one you do. Note: Android 4.3 and 4.4 do restrict the access on the SD card. So it might be that you cannot access the database file at all (see for instance this article).

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