Question

当我使用SQLiteAssetHelper升级已发布的数据库时，我在各种设备上收到间歇性崩溃报告。当数据库尚未完成从assets / databases文件夹到设备文件系统的传输时，似乎会发生这种情况。我已经进行了一些检查以检查升级是否已完成，但仍然存在问题。

首先，我检查以确保数据库存在。这解决了在安装应用程序时初始加载数据库的任何问题，但对更新没有帮助：

public boolean databaseLoaded(Context context)  { 
    File dbFile = context.getDatabasePath(MyConstants.DEFAULT_DATABASE);
    return dbFile.exists();     
}

这是我的DatabaseHelper：

class DatabaseHelper extends SQLiteAssetHelper {

    public DatabaseHelper(Context context, String databaseName, int databaseVersion) {      
        super(context, databaseName, null, databaseVersion);
        if (databaseVersion>1 && databaseName.equals(MyConstants.DEFAULT_DATABASE)) {
            setForcedUpgradeVersion(databaseVersion);           
        }
    }
}

在我的内容提供商中，我用这种方式调用数据库：

@Override
public boolean onCreate() {


    DATABASE = constants.getDBName();
    db=new DatabaseHelper(getContext(), DATABASE, MyConstants.DATABASE_VERSION);
    return((db == null) ? false : true);
}

在我的内容提供程序查询中，如果数据库版本（我的常量 - 不是从数据库本身检索到的）高于存储的数据库版本，我首先做一些hacky事情给它一些时间。然后它偶尔会在db.getReadableDatabase（）崩溃。

@Override
public Cursor query(Uri url, String[] projection, String selection, String[] selectionArgs, String sort) {

    /**if updating the app, pause to wait for the database to transfer**/
    SharedPreferences sharedPreferences = getContext().getSharedPreferences(MyConstants.PREFS, 0);
    int lastDBVersion = sharedPreferences.getInt("db_version", MyConstants.STARTING_DB_VERSION);
    if (lastDBVersion<MyConstants.DATABASE_VERSION)  {
        try {
            Thread.sleep(5000);                 
        } catch(InterruptedException ex) {
            Thread.currentThread().interrupt();
        }
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putInt("db_version", MyConstants.DATABASE_VERSION);
        editor.commit();
    }       

    SQLiteQueryBuilder qb=new SQLiteQueryBuilder();

    qb.setTables(TABLE);

    String orderBy;

    if (TextUtils.isEmpty(sort)) {
      orderBy=_ID;
    }
    else {
      orderBy=sort;
    }
    Cursor c= null;
    if (db.getReadableDatabase()!=null) {
        c= qb.query(db.getReadableDatabase(), projection, selection,
                 selectionArgs, null, null, orderBy);
        c.setNotificationUri(getContext().getContentResolver(), url);
    }
    return c;
}

查看SQLiteAssetHelper库，问题是SQLiteDatabase getWritableDatabase() db.getVersion()返回null。

我在这里缺少什么？如何检查新数据库的传输是否完整？

这是我的stacktrace：

java.lang.RuntimeException: An error occured while executing doInBackground()
    at android.os.AsyncTask$3.done(AsyncTask.java:300)
    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
    at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
    at java.lang.Thread.run(Thread.java:841)
    Caused by: java.lang.NullPointerException
    at     com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getWritableDatabase(SQLiteAssetHelper.java:180)  //this is where db.getVersion() is null
    at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getReadableDatabase(SQLiteAssetHelper.java:257)
    at com.mypackage.Provider.query(Provider.java:84)  //this is if (db.getReadableDatabase()!=null) {...
    at android.content.ContentProvider.query(ContentProvider.java:857)
    at android.content.ContentProvider$Transport.query(ContentProvider.java:200)
    at android.content.ContentResolver.query(ContentResolver.java:477)
    at android.content.ContentResolver.query(ContentResolver.java:420)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:594)  //This is Cursor c = getActivity().getContentResolver().query...
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    ... 4 more
    java.lang.NullPointerException
    at   com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getWritableDatabase(SQLiteAssetHelper.java:180)
    at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.getReadableDatabase(SQLiteAssetHelper.java:257)
    at com.mypackage.Provider.query(Provider.java:84)
    at android.content.ContentProvider.query(ContentProvider.java:857)
    at android.content.ContentProvider$Transport.query(ContentProvider.java:200)
    at android.content.ContentResolver.query(ContentResolver.java:477)
    at android.content.ContentResolver.query(ContentResolver.java:420)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:594)
    at com.mypackage.MyClass$MyMethod.doInBackground(MyClass.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
    at java.lang.Thread.run(Thread.java:841)

升级数据库时，SQLiteAssetHelper db.getVersion（）为null

0 个答案: