Question

您好，我正在尝试从android中的本地数据库查询数据。 1：m关系中有两个类别：Category和News。我想根据其类别ID搜索新闻列表。但是，当我这样做时，我会遵循以下异常。

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.infiniteloop.newsmobile/com.infiniteloop.newsmobile.NewsList}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/user/0/com.infiniteloop.newsmobile/databases/NEWS_DB
                                                                           at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                           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)
                                                                        Caused by: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/user/0/com.infiniteloop.newsmobile/databases/NEWS_DB
                                                                           at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55)
                                                                           at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1312)
                                                                           at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
                                                                           at com.infiniteloop.newsmobile.db.NewsDBAdapter.getNewsByCategory(NewsDBAdapter.java:105)
                                                                           at com.infiniteloop.newsmobile.data_models.NewsManager.getNewsByCategory(NewsManager.java:100)

这是我在NewsDBAdapter中的查询。

public Cursor getNewsByCategory(int Cat_ID){

    Cursor  c = db.rawQuery("SELECT * FROM " + TABLE_NEWS + " WHERE " +
            NEWS_CATEGORY_ID + " = " + Cat_ID + ";", null);

    return c;
}

我正在另一个类中调用此方法

public List<News> getNewsByCategory(int categoryID){

    List<News> newsList = new ArrayList<>();
    Cursor c = null;
    try {

        if(!adapter.isDBOpen()){
            adapter.openDB();
        }
        c = adapter.getNewsByCategory(categoryID);
        Log.i(TAG, "getNewsByCategory: " +  c);
        if (c.moveToFirst()) {
            do {
                int News_ID = c.getInt(c.getColumnIndex(NEWS_ID));
                String News_TITLE = c.getString(c.getColumnIndex(NEWS_TITLE));
                String News_Content = c.getString(c.getColumnIndex(NEWS_CONTENT));
                String News_Date = c.getString(c.getColumnIndex(NEWS_DATE));
                String News_IMGURL = c.getString(c.getColumnIndex(NEWS_IMGURL));
                int News_Category_ID = c.getInt(c.getColumnIndex(NEWS_CATEGORY_ID));
                News news = new News(News_ID, News_TITLE, News_Content, News_Date, News_IMGURL, News_Category_ID);
                newsList.add(news);
            } while (c.moveToNext());
        }
        return newsList;
    }finally {
        if (c!=null){
            c.close();
        }
        if(adapter.isDBOpen()){
            adapter.closeDB();
        }
    }


}

Answer 1

我认为这与该帖子有关：Attempt to reopen an already-closed object sqlitedatabase

但是您没有使用数据库的可读实例。尝试以下代码：

public Cursor getNewsByCategory(int Cat_ID){
    SQLiteDatabase db = adapter.getReadableDatabase(); // You need to call
    Cursor  c = db.rawQuery("SELECT * FROM " + TABLE_NEWS + " WHERE " +
            NEWS_CATEGORY_ID + " = " + Cat_ID + ";", null);

    return c;
}

java.lang.IllegalStateException：尝试重新打开一个已经关闭的对象：SQLiteDatabase？

1 个答案: