應用程序AndroidAspect已意外停止。請再試一次

Question

我剛剛從上週開始學習android，我也非常享受。但我從過去兩天面臨一個問題，我找不到任何解決方案。其實我甚至不知道問題是什麼。所以我在這裏張貼代碼和一切。我希望你們幫助我。

這是活動。

package com.example.androidaspect; 

import java.io.BufferedReader; 
import java.io.InputStreamReader; 

import org.apache.http.HttpResponse; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.impl.client.DefaultHttpClient; 

import android.app.Activity; 
import android.os.Bundle; 
import android.widget.TextView; 

public class MainActivity extends Activity { 

    TextView tv = (TextView)findViewById(R.id.tvRes); 
    HttpClient httpclient; 
    HttpGet request; 
    HttpResponse response; 
    String url; 

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

     url = "https://www.google.co.in/?gfe_rd=cr&ei=o7s5U8fxBIrV8gfbzIHYCw"; 

     try { 
      httpclient = new DefaultHttpClient(); 
      request = new HttpGet(url); 
      response = httpclient.execute(request); 
     } catch (Exception e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 

     try { 
      BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent())); 
      String line = ""; 
      while((line=rd.readLine())!=null){ 
       tv.append(line); 
      } 
     } catch (Exception e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 

    } 

} 

這是xml文件。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 

    <TextView 
     android:id="@+id/tvRes" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="TextView" /> 

</LinearLayout> 

這裏是清單文件

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

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="19" /> 
    <uses-permission android:name="android.permission.INTERNET"/> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="com.example.androidaspect.MainActivity" 
      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> 

</manifest> 

這裏是日誌文件

04-01 01:52:51.291: D/AndroidRuntime(457): Shutting down VM 
04-01 01:52:51.291: W/dalvikvm(457): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
04-01 01:52:51.402: E/AndroidRuntime(457): FATAL EXCEPTION: main 
04-01 01:52:51.402: E/AndroidRuntime(457): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.androidaspect/com.example.androidaspect.MainActivity}: java.lang.NullPointerException 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.os.Looper.loop(Looper.java:123) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread.main(ActivityThread.java:4627) 
04-01 01:52:51.402: E/AndroidRuntime(457): at java.lang.reflect.Method.invokeNative(Native Method) 
04-01 01:52:51.402: E/AndroidRuntime(457): at java.lang.reflect.Method.invoke(Method.java:521) 
04-01 01:52:51.402: E/AndroidRuntime(457): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
04-01 01:52:51.402: E/AndroidRuntime(457): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
04-01 01:52:51.402: E/AndroidRuntime(457): at dalvik.system.NativeStart.main(Native Method) 
04-01 01:52:51.402: E/AndroidRuntime(457): Caused by: java.lang.NullPointerException 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.Activity.findViewById(Activity.java:1637) 
04-01 01:52:51.402: E/AndroidRuntime(457): at com.example.androidaspect.MainActivity.<init>(MainActivity.java:17) 
04-01 01:52:51.402: E/AndroidRuntime(457): at java.lang.Class.newInstanceImpl(Native Method) 
04-01 01:52:51.402: E/AndroidRuntime(457): at java.lang.Class.newInstance(Class.java:1429) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
04-01 01:52:51.402: E/AndroidRuntime(457): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 
04-01 01:52:51.402: E/AndroidRuntime(457): ... 11 more 

Answer 1

你應該張貼您的logcat輸出任何時候應用程序崩潰。它使查找錯誤變得容易很多。無論如何，我立即發現了兩件大事。你不能初始化你的View s直到之後你膨脹了你的佈局，這意味着它應該在setContentView()之後去。

public class MainActivity extends Activity { 

TextView tv; // you can declare here 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    tv = (TextView)findViewById(R.id.tvRes); // but initialize here 

你有它的樣子，你會得到一個NPE當您嘗試調用一個方法對你View。

我看到的另一個大問題是，你需要在背景Thread上做你的網絡東西。 AsyncTask可以非常方便。

Example of setting up an AsyncTask

AsyncTask Docs