由网友(马儿渴死的告白)分享简介：我有以下DBAdapter（这不是全部，但它的相关的code）。I have the following DBAdapter (this isn't all of it, but it's the relevant code).private final String DATABASE_NAME = "seller...

我有以下DBAdapter（这不是全部，但它的相关的code）。

I have the following DBAdapter (this isn't all of it, but it's the relevant code).

private final String DATABASE_NAME = "seller";
private final String DATABASE_MY_TABLE = "sellertable";
private final Integer DATABASE_VERSION = 1
private final String CREATE_TABLE = "CREATE TABLE seller ........";

public DBAdapter( Context c )
{
    this.context = c;
    DBHelper = new DatabaseHelper(context);
}

private static class DatabaseHelper extends SQLiteOpenHelper
{
    public DatabaseHelper( Context context )
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate( SQLiteDatabase db )
    {
        MyLog.d("Creating Tables");
        try
        {
            db.execSQL(CREATE_TABLE);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    @Override
    public void onUpgrade( SQLiteDatabase db, int oldVersion, int newVersion )
    {
        MyLog.w("Upgrading database from version " + oldVersion + " to " + newVersion + ". Destroying old data.");
        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_MY_TABLE);
        onCreate(db);
    }
}

// Opens the database
public DBAdapter open() throws SQLException
{
    db = DBHelper.getWritableDatabase();
    return this;
}

当我尝试 db.open（）我得到了以下内容：

When I try to db.open() I get the following:

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate application com.company.app.MyApp: java.lang.NullPointerException
    at android.app.LoadedApk.makeApplication(LoadedApk.java:466)
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:3260)
    at android.app.ActivityThread.access$2200(ActivityThread.java:117)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:969)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:130)
    at android.app.ActivityThread.main(ActivityThread.java:3683)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:118)
    at com.company.app.DBAdapter.open(DBAdapter.java:74)
    at com.company.app.MyApp.<init>(MyApp.java:106)
    at java.lang.Class.newInstanceImpl(Native Method)
    at java.lang.Class.newInstance(Class.java:1409)
    at android.app.Instrumentation.newApplication(Instrumentation.java:957)
    at android.app.Instrumentation.newApplication(Instrumentation.java:942)
    at android.app.LoadedApk.makeApplication(LoadedApk.java:461)

看来它越来越某种异常，与当帮手是决定是否创建或更新数据库...

It appears it's getting some kind of exception, related to when the helper is deciding whether or not to create or update the database...

推荐答案

尝试添加如.db的延伸到你的数据库名称末尾。

Try adding an extension like ".db" to the end of your database name.