[英]NullPointer exception in Jsoup Element
I want to show newspapers headline and news in android application. 我想在Android应用程序中显示报纸头条和新闻。 So at first I create a Java project and did my task perfectly.
因此,首先,我创建一个Java项目并完美地完成了我的任务。 here is my java projects classes
这是我的java项目类
Main.java Main.java
package com.emon.newsportal;
import java.io.ObjectInputStream.GetField;
import java.util.List;
public class Main {
public static void main(String[] args) {
newspaperTest(new NewAge());
}
private static void newspaperTest(Newspaper newspaper) {
List<Headline>headlines=newspaper.getAllSportsHeadLines();
System.out.println(newspaper.getSportsNews(headlines.get(0)));
System.out.println(headlines.get(0).getHeading());
}
}
NewAge.java NewAge.java
package com.emon.newsportal;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
public class NewAge extends Newspaper{
protected List<Headline> getHeadlines(String baseUrl) {
List<Headline> headlines = new ArrayList<Headline>();
Document document = connectToTheWebpage(baseUrl);
Elements elements = document.select("h2 a");
for (Element element : elements) {
Headline headline = new Headline(element.text(),
element.attr("href"));
headlines.add(headline);
}
// System.out.println(""+headlines);
return headlines;
}
protected String getNews(Headline headline) {
Document document = connectToTheWebpage(headline.getUrl());
return document.select("body p").get(0).text();
}
@Override
public List<Headline> getAllSportsHeadLines() {
// TODO Auto-generated method stub
return getHeadlines("http://newagebd.net/category/sport/");
}
@Override
public List<Headline> getALLPoliticalHeadlines() {
// TODO Auto-generated method stub
return getHeadlines("http://newagebd.net/category/politics/");
}
@Override
public List<Headline> getALLEntertainmentHeadlines() {
// TODO Auto-generated method stub
return getHeadlines("http://newagebd.net/category/entertain/");
}
@Override
public List<Headline> getALLBusinessHeadlines() {
// TODO Auto-generated method stub
return getHeadlines("http://newagebd.net/category/bizn/");
}
}
But when I try to implement this same project in Android this gives a Nullpointer exception in the NewAge.java class 但是,当我尝试在Android中实现同一项目时,NewAge.java类中出现了Nullpointer异常
Elements elements = document.select("h2 a");
here is my error log 这是我的错误日志
03-18 14:49:53.974 1056-1070/com.songkeet.news_a W/System.err﹕ java.lang.NullPointerException
03-18 14:49:53.974 1056-1070/com.songkeet.news_a W/System.err﹕ at com.songkeet.news_a.NewAge.getHeadlines(NewAge.java:27)
03-18 14:49:53.974 1056-1070/com.songkeet.news_a W/System.err﹕ at com.songkeet.news_a.NewAge.getAllSportsHeadLines(NewAge.java:50)
03-18 14:49:53.974 1056-1070/com.songkeet.news_a W/System.err﹕ at com.songkeet.news_a.MainActivity$1.run(MainActivity.java:36)
03-18 14:49:53.984 1056-1070/com.songkeet.news_a W/System.err﹕ at java.lang.Thread.run(Thread.java:856)
Can you suggest me I can I fix this error? 你能建议我我可以解决这个错误吗? Thank you
谢谢
If you have a NullPointerException
on 如果您有
NullPointerException
Elements elements = document.select("h2 a");
It means the document
is null. 这意味着
document
为空。 You have to look at the connectToTheWebpage(baseUrl)
method (you don't provide). 您必须查看
connectToTheWebpage(baseUrl)
方法(您未提供)。
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