Android中的java.lang.IllegalStateException

Question

我嘗試使用套接字連接將字符串從Java桌面程序發送到android。 當用戶單擊android應用程序中的按鈕時，它將顯示來自Java應用程序的消息。 當我單擊按鈕時，它將顯示java.lang.IllegalStateException。我可以在此站點中找到許多類似的問題，但是沒有人不符合我的要求。

Android代碼

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
public class MainActivity extends Activity 
{
    private Socket client;
    private InputStreamReader isr;
    private BufferedReader bf;
    private String message;
    private AsyncClass ac;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);   
    }
class AsyncClass extends AsyncTask<Void, Void,Void>
{
    protected Void doInBackground(Void... params)
    {
          hardtask();
          return null;
    }
    public void hardtask()
    {
          try 
          {
        client=new Socket("10.0.2.2",7777);
        isr=new InputStreamReader(client.getInputStream());
        bf=new BufferedReader(isr);
        message=bf.readLine();
        Log.v("Message", message);
       } 
           catch (IOException e) 
           {
        // TODO Auto-generated catch block
        e.printStackTrace();
       }
     }
}
public void onClick(View view)
{
    ac.execute();
}
@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;
}
}

logcat的

02-27 02:02:02.191: D/gralloc_goldfish(1445): Emulator without GPU emulation detected.
02-27 02:02:05.541: D/AndroidRuntime(1445): Shutting down VM
02-27 02:02:05.651: W/dalvikvm(1445): threadid=1: thread exiting with uncaught exception (group=0xb1a7eb90)
02-27 02:02:05.711: E/AndroidRuntime(1445): FATAL EXCEPTION: main
02-27 02:02:05.711: E/AndroidRuntime(1445): Process: andro.androreply, PID: 1445
02-27 02:02:05.711: E/AndroidRuntime(1445): java.lang.IllegalStateException: Could not execute method of the activity
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.view.View$1.onClick(View.java:3814)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.view.View.performClick(View.java:4424)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.view.View$PerformClick.run(View.java:18383)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.os.Handler.handleCallback(Handler.java:733)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.os.Handler.dispatchMessage(Handler.java:95)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.os.Looper.loop(Looper.java:137)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.app.ActivityThread.main(ActivityThread.java:4998)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at java.lang.reflect.Method.invokeNative(Native Method)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at java.lang.reflect.Method.invoke(Method.java:515)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at dalvik.system.NativeStart.main(Native Method)
02-27 02:02:05.711: E/AndroidRuntime(1445): Caused by: java.lang.reflect.InvocationTargetException
02-27 02:02:05.711: E/AndroidRuntime(1445):     at java.lang.reflect.Method.invokeNative(Native Method)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at java.lang.reflect.Method.invoke(Method.java:515)
02-27 02:02:05.711: E/AndroidRuntime(1445):     at android.view.View$1.onClick(View.java:3809)
02-27 02:02:05.711: E/AndroidRuntime(1445):     ... 11 more
02-27 02:02:05.711: E/AndroidRuntime(1445): Caused by: java.lang.NullPointerException
02-27 02:02:05.711: E/AndroidRuntime(1445):     at andro.androreply.MainActivity.onClick(MainActivity.java:52)
02-27 02:02:05.711: E/AndroidRuntime(1445):     ... 14 more

Java代碼

import java.io.*;
import java.net.*;
public class Server
{
private static String msg="Hai";
    private static Socket client;
private static PrintWriter pw;
private static ServerSocket socket;
public static void main(String args[])
{
     try {
     socket=new ServerSocket(7777);
         client= socket.accept();  //Server socket
         pw=new PrintWriter(client.getOutputStream(),true);
     pw.write(msg); 
     pw.flush();
     pw.close();
     client.close();
    } 
    catch (IOException e) 
    {
        System.out.println("Could not listen on port: 7676");
    }
  }
} 

任何人都可以幫助我解決這個問題。 提前致謝...

Answer 1

您需要instantiate ac，然后調用execute() 。 execute()是AsyncTask方法。

ac = new AsyncClass();

我看你有

private AsyncClass ac;

和

public void onClick(View view)
{
ac.execute();
}

但是你沒有在任何地方實例化ac

Answer 2

您有一個變量AsyncClass ac，但實際上並沒有對其進行初始化。 在您的onClick（）中，而不是：

ac.execute();

做：

new AsyncClass.execute();

或首先在onCreate（）中初始化您的ac變量：

ac = new AsyncClass();