我正在使用SQLiteDatabase在AsyncTask doInBackground（）方法中存储在后台购买的数据，有时如果接收到的数据不在数据库中，我会插入数据，如果接收到的数据已经存在且未读，我会标记为数据为未读... 但是它说在doInBackground Method（）中递归调用了getDatabase ... 是因为我在后台线程或其他某些线程上执行了操作而导致的问题吗？ 该应用程序从网站上抓取新闻并将其显示在应用程序中，如果看到的新闻标记为旧新闻，还将添加到sqlite数据库中。
2019-07-07 16:16:46.664 27223-27276/com.github.chillmonk2.mycollege E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.github.chillmonk2.mycollege, PID: 27223
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:365)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:257)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
at java.lang.Thread.run(Thread.java:784)
Caused by: java.lang.IllegalStateException: getDatabase called recursively
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:246)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:206)
at com.github.chillmonk2.mycollege.NewsDbHelper.insertUrl(NewsDbHelper.java:36)
at com.github.chillmonk2.mycollege.NewsDbHelper.onCreate(NewsDbHelper.java:26)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:310)
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:206)
at com.github.chillmonk2.mycollege.NewsDbHelper.urlExists(NewsDbHelper.java:59)
at com.github.chillmonk2.mycollege.NewsFragment$TaskLoader.doInBackground(NewsFragment.java:144)
at com.github.chillmonk2.mycollege.NewsFragment$TaskLoader.doInBackground(NewsFragment.java:111)
at android.os.AsyncTask$2.call(AsyncTask.java:345)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:257)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
at java.lang.Thread.run(Thread.java:784)
这里是Db助手类
package com.github.chillmonk2.mycollege;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class NewsDbHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "news.db";
public static final String TABLE_NAME = "newsIndex";
public String COL_0 = "URL";
public String COL_1 = "STATUS";
SQLiteDatabase db;
//SQLiteDatabase db = this.getWritableDatabase();
public NewsDbHelper(Context context) {
super(context, DATABASE_NAME, null ,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
String createTable = " CREATE TABLE " + TABLE_NAME + "(" +
COL_0 + " TEXT PRIMARY KEY ," +
COL_1 + " INT );";
db.execSQL(createTable);
insertUrl("EMPTY");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public int insertUrl(String url)
{
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COL_0,url);
values.put(COL_1,"0");//0 - Unread
int result = (int)db.insert(TABLE_NAME,null,values);
return result;
}
public int updateUrl(String Url)
{
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COL_0,Url);
values.put(COL_1,1);
int result = db.update(TABLE_NAME,values,COL_0 +"=?",new String[]{Url});
return result;
}
public int deleteUrl(String Url)
{
int result = db.delete(TABLE_NAME,COL_0 + "=?",new String[]{Url});
return result;
}
boolean urlExists(String Url){
db = this.getWritableDatabase();
String sql = "select * from "+TABLE_NAME + " where "+ COL_0 +"=?";
Cursor cursor = db.rawQuery(sql,new String[]{Url});
int count = cursor.getCount();
if (count>=1)
return true;
else
return false;
}
int getUrlStatus(String url)
{
//SQLiteDatabase db = this.getWritableDatabase();
String sql = "select "+COL_1+" from "+TABLE_NAME + " where "+ COL_0 +"=?";
Cursor cursor = db.rawQuery(sql,new String[]{url});
int status = -1;
while (cursor.moveToFirst())
{
status = cursor.getInt(cursor.getColumnIndex(COL_1));
}
return status;
}
}
这是NewsFragment.java类中的代码部分
@Override
protected ArrayList<NewsObject> doInBackground(Void... voids) {
String url = "http://rvrjc.ac.in/";
ArrayList<NewsObject> mList = new ArrayList<NewsObject>();
Document document;
try {
Log.d(MainActivity.class.getSimpleName(),"Main Activity");
document = Jsoup.connect(url).get();
Elements lnews = document.select("ul.newsticker li b");
Elements bnews = document.select("div#galleryimage p");
//Get the title of the website
for (Element news : lnews) {//latest news Section
String s = "New";
String descNews = news.select("p").text();
String newsUrl = news.select("a").attr("href");
if (newsUrl.startsWith("http")) {
//do nothing
if(!db.urlExists(newsUrl)){
db.insertUrl(newsUrl);
}
else
{
int status = db.getUrlStatus(newsUrl);
if(status==1){//read
s = "Old";
}
else
s = "New";
}
mList.add(new NewsObject(descNews, newsUrl,s));
} else
mList.add(new NewsObject(descNews, url ,s));
}
for(Element news:bnews){
String descNews = news.select("p").text();
String newsGif = news.select("p img").attr("src");
String newsStatus = "Old" ;
if(newsGif.equals("new.gif"))
{
newsStatus = "New";
//System.out.println("News Status changed");
}
String newsUrl = news.select("a").attr("href");
if(newsUrl.startsWith("http"))
{
if(!db.urlExists(newsUrl)){
db.insertUrl(newsUrl);
}
else
{
int status = db.getUrlStatus(newsUrl);
if(status==1){//read
newsStatus = "Old";
}
else
newsStatus = "New";
}
//do nothing
mList.add(new NewsObject(descNews,newsUrl,newsStatus));
}
else
mList.add(new NewsObject(descNews,url,newsStatus));
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Log.e("TAG",""+mList);
return mList;
}
@Override
protected void onPostExecute(ArrayList<NewsObject> newsArrayList) {
super.onPostExecute(newsArrayList);
progressDialog.dismiss();
Log.e("TAG","Inside onPostExecute"+newsArrayList);
mNewsAdapter.addAll(newsArrayList);
mNewsAdapter.notifyDataSetChanged();
}
}
答案 0 :(得分：1)
行
insertUrl("EMPTY");
这是您尝试使用 NewsDbHelper 实例打开数据库的原因，而它仍然是打开数据库的一部分。
this.getWritabaleDatabase，因为它仍在处理另一个{{ 1}}（或getReadableDatabase而不是getWritableDatabase ）您可以使用
this.getWritableDatabase