Question

我对android很新，我正在尝试使用Jsoup从网站检索一些数据。这是我在Java项目中使用的确切代码，它起作用。但是当我将它转移到Android并将“println”更改为“setText（）”时，应用程序“意外停止”。

package com.ex.myschoolapp;
import java.io.IOException;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.select.Elements;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;
public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

Document doc = null;

    try {
        doc = Jsoup.connect("http://moisilonesti.licee.edu.ro/concursuri.php").get();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    Elements sElem = doc.select("div#olimpiade table tbody tr th");

    String str = sElem.text();
    TextView stv = (TextView) findViewById(R.id.textView2);
    stv.setText(str);}}

这是LogCat跟踪：

11-17 17:37:59.145: E/AndroidRuntime(23601): FATAL EXCEPTION: main
11-17 17:37:59.145: E/AndroidRuntime(23601): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ex.myschoolapp/com.ex.myschoolapp.MainActivity}: java.lang.NullPointerException
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread.access$1500(ActivityThread.java:121)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.os.Looper.loop(Looper.java:123)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread.main(ActivityThread.java:3701)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at java.lang.reflect.Method.invokeNative(Native Method)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at java.lang.reflect.Method.invoke(Method.java:507)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:862)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at dalvik.system.NativeStart.main(Native Method)
11-17 17:37:59.145: E/AndroidRuntime(23601): Caused by: java.lang.NullPointerException
11-17 17:37:59.145: E/AndroidRuntime(23601):    at com.ex.myschoolapp.MainActivity.onCreate(MainActivity.java:67)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-17 17:37:59.145: E/AndroidRuntime(23601):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1623)
11-17 17:37:59.145: E/AndroidRuntime(23601):    ... 11 more

我不知道如何使用AsyncTask但是从我在Jsoup食谱中看到的内容中我不需要任何繁琐的工作。

Answer 1

试试这段代码：

Document doc = Jsoup.connect("http://example.com/").get();
Elements divs = doc.select("div#test");
for(Element div : divs)
    System.out.println(div.text());

Answer 2

您的代码适合我，我可以在TextView中打印数据。

你有NullPointer，因为你没有正确设置setContentView，因为你的findViewById返回null ..，

setContentView(R.layout.your_activity_xml);

android app使用jsoup库意外停止

2 个答案: