ANDROID：强制关闭 - java.lang.ClassCastException：com.example.httpgetandroidexample.HttpGetAndroidExample不能转换为android.app

Question

我收到以下强制关闭错误：java.lang.ClassCastException：com.example.httpgetandroidexample。 HttpGetAndroidExample不能转换为android.app

当试图执行下面的代码，我不清楚为什么。

package com.example.httpgetandroidexample; 

import java.io.IOException; 

import org.jsoup.Jsoup; 
import org.jsoup.nodes.Document; 
import org.jsoup.nodes.Element; 
import org.jsoup.select.Elements; 

public class HttpGetAndroidExample { 

public static void main(String[] args) { 

    Document doc; 
    try { 

     // need http protocol 
     doc = Jsoup.connect("http://www.sheriff.org/apps/arrest/results.cfm?lname=smith&fname=").get(); 

     // get page title 
     String title = doc.title(); 
     System.out.println("Arrest # : " + title); 

     // get all links 
     Elements links = doc.select("a[href]"); 
     for (Element link : links) { 

      // get the value from href attribute 
      System.out.println("\nlink : " + link.attr("href")); 
      System.out.println("text : " + link.text()); 

     } 

    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

} 

} 

的logcat：

07-18 15:41:43.330: D/ActivityThread(8349): setTargetHeapUtilization:0.25 
07-18 15:41:43.330: D/ActivityThread(8349): setTargetHeapIdealFree:8388608 
07-18 15:41:43.330: D/ActivityThread(8349): setTargetHeapConcurrentStart:2097152 
07-18 15:41:43.350: W/dalvikvm(8349): threadid=1: thread exiting with uncaught exception (group=0x41e1f438) 
07-18 15:41:43.350: E/AndroidRuntime(8349): FATAL EXCEPTION: main 
07-18 15:41:43.350: E/AndroidRuntime(8349): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.httpgetandroidexample/com.example.httpgetandroidexample.HttpGetAndroidExample}: java.lang.ClassCastException: com.example.httpgetandroidexample.HttpGetAndroidExample cannot be cast to android.app.Activity 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2012) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread.access$700(ActivityThread.java:139) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1224) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.os.Looper.loop(Looper.java:137) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread.main(ActivityThread.java:4918) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at dalvik.system.NativeStart.main(Native Method) 
07-18 15:41:43.350: E/AndroidRuntime(8349): Caused by: java.lang.ClassCastException: com.example.httpgetandroidexample.HttpGetAndroidExample cannot be cast to android.app.Activity 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.Instrumentation.newActivity(Instrumentation.java:1068) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2003) 
07-18 15:41:43.350: E/AndroidRuntime(8349):  ... 11 more 
07-18 15:42:53.765: D/ActivityThread(8635): setTargetHeapUtilization:0.25 
07-18 15:42:53.765: D/ActivityThread(8635): setTargetHeapIdealFree:8388608 
07-18 15:42:53.765: D/ActivityThread(8635): setTargetHeapConcurrentStart:2097152 
07-18 15:42:53.785: W/dalvikvm(8635): threadid=1: thread exiting with uncaught exception (group=0x41e1f438) 
07-18 15:42:53.785: E/AndroidRuntime(8635): FATAL EXCEPTION: main 
07-18 15:42:53.785: E/AndroidRuntime(8635): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.httpgetandroidexample/com.example.httpgetandroidexample.HttpGetAndroidExample}: java.lang.ClassCastException: com.example.httpgetandroidexample.HttpGetAndroidExample cannot be cast to android.app.Activity 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2012) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread.access$700(ActivityThread.java:139) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1224) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.os.Looper.loop(Looper.java:137) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread.main(ActivityThread.java:4918) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at dalvik.system.NativeStart.main(Native Method) 
07-18 15:42:53.785: E/AndroidRuntime(8635): Caused by: java.lang.ClassCastException: com.example.httpgetandroidexample.HttpGetAndroidExample cannot be cast to android.app.Activity 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.Instrumentation.newActivity(Instrumentation.java:1068) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2003) 
07-18 15:42:53.785: E/AndroidRuntime(8635):  ... 11 more 

清单：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example.httpgetandroidexample" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="17" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="com.example.httpgetandroidexample.HttpGetAndroidExample" 
      android:label="@string/app_name" > 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

    <uses-permission android:name="android.permission.INTERNET"></uses-permission> 

</manifest> 

Answer 1

您尝试运行在Android上一个 “简单” 的Java应用程序至极你不能。首先阅读android documentation。您的申请必须至少包含一个活动课程，并且您不能将public static void main(String[] args)放在您的任何课程中。