Android - FATAL EXCEPTION：main - 无法启动活动ComponentInfo NullPointerException

Question

我是一个Android新手并使用asynctask和java我正在尝试创建一个即时消息系统。 但这就是我得到的。

我已经被困了几个星期了。 任何人都可以找出我出错的地方以及为什么会出现错误？

IndividualActivity.java

package com.example.soc;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;
import android.widget.Toast;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
public class IndividualActivity  extends Activity {

    private ProgressDialog pDialog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getLayoutInflater().inflate(R.layout.individual, null);
        Intent intent = getIntent();
        int uuid = intent.getIntExtra("uuid",0); //if it's a string you stored.
        new openMsg(IndividualActivity.this).execute();

    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
    }
    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }   
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }       

}

openMsg.java

package com.example.soc;


import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

import com.example.soc.adater.msgAdapter;
import com.example.soc.model.MSList;
import com.example.soc.util.JSONParser;



public class openMsg extends AsyncTask<Object, Object, JSONArray>{
    final IndividualActivity main;

    public openMsg(IndividualActivity indv) {
        this.main = indv;
    }   

    private JSONParser jsonParser = new JSONParser();    
    //private static final String TAG = MainActivity.class.getSimpleName();

    private ProgressDialog pDialog;
    private List<MSList> imlist = new ArrayList<MSList>();
    private ListView listView;
    private msgAdapter adapter;
    String myip = "10.0.2.2";
    private JSONArray json = null;
    ArrayList<Integer> uidList = new ArrayList<Integer>(); 

    @Override
    protected void onPreExecute() {
         super.onPreExecute();  

            listView = (ListView)main.findViewById(R.id.listx);
            adapter = new msgAdapter(main, imlist);
            listView.setAdapter(adapter);       
    }   

    protected JSONArray doInBackground(Object... v) {
        List<NameValuePair> pairs = new ArrayList<NameValuePair>();
        json = jsonParser.getJSONFromUrl("http://"+myip+"/resource/android/MSG.php", pairs);
        return json;
    }

    protected void onPostExecute(JSONArray json) {

        for (int i = 0; i < json.length(); i++) { 
            try {
                JSONObject c = json.getJSONObject(i);
                MSList iml = new MSList();
                iml.setpname(c.getString("name"));
                //iml.setuname(c.getString("username"));
                iml.setppUrl("http://"+myip+"/"+c.getString("img"));
                iml.setmsgcon(c.getString("content"));
                iml.setmsgtime(c.getString("time"));
                int uuid = Integer.parseInt(c.getString("user_id"));
                iml.setUid(uuid);
                iml.setme(Integer.parseInt(c.getString("me")));

                imlist.add(iml);

                uidList.add(uuid);
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        adapter.notifyDataSetChanged();     
    }   

}

Individual.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".IndividualActivity" >

    <ListView
        android:id="@+id/listx"
        android:layout_width="fill_parent"
        android:layout_height="350dp"
        android:layout_above="@+id/individual_bottomAction"
        android:divider="@color/list_divider"
        android:dividerHeight="1dp"
        android:listSelector="@drawable/list_row_selector" />

    <LinearLayout
        android:id="@+id/individual_bottomAction"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true" >

        <EditText
            android:id="@+id/msgTypeBox"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginBottom="16dp"
            android:layout_weight=".70"
            android:ems="10"
            android:hint="Write a message"
            android:inputType="textMultiLine" />

        <Button
            android:id="@+id/msgSend"
            style="?android:attr/buttonStyleSmall"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginLeft="14dp"
            android:layout_weight=".2"
            android:text="Send" />
    </LinearLayout>

</RelativeLayout>

logcat的

02-24 19:22:47.399: E/AndroidRuntime(6255): FATAL EXCEPTION: main
02-24 19:22:47.399: E/AndroidRuntime(6255): Process: com.example.soc, PID: 6255
02-24 19:22:47.399: E/AndroidRuntime(6255): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.soc/com.example.soc.IndividualActivity}: java.lang.NullPointerException
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.os.Handler.dispatchMessage(Handler.java:102)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.os.Looper.loop(Looper.java:136)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread.main(ActivityThread.java:5021)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at java.lang.reflect.Method.invokeNative(Native Method)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at java.lang.reflect.Method.invoke(Method.java:515)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:827)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at dalvik.system.NativeStart.main(Native Method)
02-24 19:22:47.399: E/AndroidRuntime(6255): Caused by: java.lang.NullPointerException
02-24 19:22:47.399: E/AndroidRuntime(6255):     at com.example.soc.openMsg.onPreExecute(openMsg.java:60)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.os.AsyncTask.execute(AsyncTask.java:535)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at com.example.soc.IndividualActivity.onCreate(IndividualActivity.java:37)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.Activity.performCreate(Activity.java:5231)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1090)
02-24 19:22:47.399: E/AndroidRuntime(6255):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
02-24 19:22:47.399: E/AndroidRuntime(6255):     ... 11 more

Answer 1

尝试改变

getLayoutInflater().inflate(R.layout.individual, null);

至

setContentView(R.layout.individual);

如果有效，请告诉我