Java 安卓工作室。没有指向我的项目的任何链接的NullPointerException
我使用jsoup从一个网站获取一些数据,并对其进行过滤,然后将其显示在ListView上,但无论我对代码做什么,每次都会收到一个奇怪的错误。它没有任何链接到我的项目,而是链接到Android库和一些奇怪的东西,比如zygote等等。 这是我的密码:Java 安卓工作室。没有指向我的项目的任何链接的NullPointerException,java,android,nullpointerexception,jsoup,Java,Android,Nullpointerexception,Jsoup,我使用jsoup从一个网站获取一些数据,并对其进行过滤,然后将其显示在ListView上,但无论我对代码做什么,每次都会收到一个奇怪的错误。它没有任何链接到我的项目,而是链接到Android库和一些奇怪的东西,比如zygote等等。 这是我的密码: package com.shapedhorizon.teymur.epiknovel; import android.content.Context; import android.content.Intent; import android.os
package com.shapedhorizon.teymur.epiknovel;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import java.io.IOException;
public class SeriInfo extends AppCompatActivity {
ListView listView ;
Context ncontext;
String[] tts;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_seri_info);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//something
}
});
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
ncontext = this;
listView = findViewById(R.id.seri_bolum);
Log.i("Message", message);
AsyncInternet task = new AsyncInternet();
task.execute(message);
Log.i("OMG", "You got to be kidding with me");
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
}
});
return;
}
private class AsyncInternet extends AsyncTask<String, Void, Void>{
@Override
protected Void doInBackground(String... strings) {
Elements els;
Document doc= null;
Log.e("try",strings[0]);
try {
int ttsi = 0;
doc = Jsoup.connect(strings[0]).get();
els = doc.getElementsByAttributeValueStarting("href","https://www.epiknovel.com/seri");
Integer size = 0;
for (Element e: els
) {
if(!(e==null)) {
if(!e.parent().tagName("span").text().contains("Premium")){
size++;
Log.i("e.text",e.text());
}
}
}
Log.e("size", size.toString());
tts = new String[size];
for (Element e: els
) {
if(!(e==null)) {
if(!e.parent().tagName("span").text().contains("Premium")){
Log.i("e.text",e.text());
tts[ttsi] = e.text();
}
}
}
} catch (IOException c) {
c.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
if(!(tts ==null)) {
Log.i("tts","IS NOT NULL");
ArrayAdapter adapter = new ArrayAdapter<String>(ncontext, R.layout.seri_view, tts);
Log.i("Adapter", "Check if we set up the adapter");
if(!(adapter==null)) {
listView.setAdapter(adapter);
Log.i("LW", "Weird that we passed that part");
}else{
Log.e("ADAPTER", "IS NULL");
}
}else{
Log.e("tts","IS NULL");
}
Log.i("OMG","Still?! What the hell is wrong with you?!");
return;
}
}
}
编辑1:我添加了
for (Object obj: tts
) {
if (obj.equals(null)){
Log.e("BIG ERROR", "There is null in tts");
}
}
在doInBackground函数中,我得到了一个新错误:
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #2
Process: com.shapedhorizon.teymur.epiknovel, PID: 30862
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:309)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Object.equals(java.lang.Object)' on a null object reference
at com.shapedhorizon.teymur.epiknovel.SeriInfo$AsyncInternet.doInBackground(SeriInfo.java:102)
at com.shapedhorizon.teymur.epiknovel.SeriInfo$AsyncInternet.doInBackground(SeriInfo.java:62)
at android.os.AsyncTask$2.call(AsyncTask.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818) `
and(serinfo.java:102)指的是if(obj.equals(null)){
编辑2:我将数组更改为列表。以下是在AsyncInternet函数中更改的内容:
private class AsyncInternet extends AsyncTask<String, Void, List<String>>{
@Override
protected List<String> doInBackground(String... strings) {
Elements els;
Document doc= null;
List<String> adapterData = new ArrayList<>();
Log.e("try",strings[0]);
try {
int ttsi = 0;
doc = Jsoup.connect(strings[0]).get();
els = doc.getElementsByAttributeValueStarting("href","https://www.epiknovel.com/seri");
for (Element e: els
) {
if(!e.parent().tagName("span").text().contains("Premium")){
if(e.text() != null) {
if(e.parent().parent().html().contains("td")) {
Log.i("e.text", e.text());
adapterData.add(e.text());
}
}
}
}
} catch (IOException c) {
c.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(List<String> result) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(ncontext, R.layout.seri_view, result);
Log.i("Adapter", "set up the adapter");
listView.setAdapter(adapter);
Log.i("LW", "Weird that we passed that part");
}
}
(serinfo.java:97)是
listView.setAdapter(adapter);
在尝试在onPostExecute方法中创建适配器之前,请检查tts数组是否有空元素。我猜在该方法的第三行中会触发异常:ArrayAdapter adapter=。。。。
您还可以将try/catch(Exception-ex)放在它周围,以查看它是否捕获了异常以及捕获了什么异常
编辑:
我想我发现了这个问题-你的doInBackground方法应该返回你的列表(或数组),而不是null。然后返回的值被onPostExecute用作输入参数。这是来自官方文档的
doInBackground(参数…)…此步骤必须返回计算结果,并将返回到最后一步
对于初学者来说,
==null
是一个正确的null检查。你可以用!=null
来否定它
但无论如何,我建议不要使用数组,而是为适配器使用列表
从
extends AsyncTask<String, Void, List<String>>
扩展异步任务
然后
@覆盖
受保护列表doInBackground(字符串…字符串){
元素els;
单据单据=空;
List adapterData=new ArrayList();
Log.e(“try”,字符串[0]);
试一试{
//向adapterData添加非空字符串
}捕获(IOC异常){
c、 printStackTrace();
}
返回适配器数据;
}
现在,在onPostExecute中有一个非空的列表对象。如果在此处初始化,则适配器不是空的
@Override
protected void onPostExecute(List<String> result) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(ncontext, R.layout.seri_view, result);
Log.i("Adapter", "set up the adapter");
listView.setAdapter(adapter);
Log.i("LW", "Weird that we passed that part");
}
@覆盖
受保护的void onPostExecute(列表结果){
ArrayAdapter=新的ArrayAdapter(ncontext,R.layout.seri_视图,结果);
Log.i(“适配器”,“设置适配器”);
setAdapter(适配器);
我(“LW”,“奇怪的是我们通过了那个部分”);
}
您还应该将适配器移动到活动中的某个字段,并在onCreate中使用空列表初始化它。
tts
看起来像什么?它可能包含空元素。if(!(adapter==null))
。更改为if(adapter!=null)
。您拥有更多。很快,这可能是因为e.text()
为null,这就是适配器在对元素obj(null)调用toString()时发送NullPointerException的原因。
如果trueI尝试用_try-catch(异常exc)包围它,它将始终抛出NullPointerException_但是没有什么新的事情发生。围绕适配器构造函数的try-catch无法解决问题。这不是当getView
被调用为djava.lang.NullPointerException:尝试调用接口方法'int java.util.List.size()'在一个空对象引用上,我得到了这个结果。如果你在try之前创建Arraylist,在catch之后返回,它就不能为空。……仔细看看你的代码。你有一个返回null;
。试着理解答案的作用,不要盲目复制粘贴它们
extends AsyncTask<String, Void, List<String>>
@Override
protected List<String> doInBackground(String... strings) {
Elements els;
Document doc= null;
List<String> adapterData = new ArrayList<>();
Log.e("try",strings[0]);
try {
// add non null strings to adapterData
} catch (IOException c) {
c.printStackTrace();
}
return adapterData;
}
@Override
protected void onPostExecute(List<String> result) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(ncontext, R.layout.seri_view, result);
Log.i("Adapter", "set up the adapter");
listView.setAdapter(adapter);
Log.i("LW", "Weird that we passed that part");
}