package com.test.server;import android.app.Activity;
import android.os.Bundle;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.net.Socket;
import java.net.ServerSocket;
import android.widget.EditText;public class TestServerActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
receivedate();
}
EditText et=(EditText)findViewById(R.id.editText1);
ServerSocket server;
public void receivedate(){
try {
server=new ServerSocket(5556);
}catch(IOException e) {
e.printStackTrace();
}
beginlisten();
}
public void beginlisten(){
while(true){
try{
final Socket socket=server.accept();
new Thread(new Runnable(){
public void run(){
BufferedReader in;
try{
in=new BufferedReader(new InputStreamReader(socket.getInputStream(),"UTF-8"));
while(!socket.isClosed()){
String str;
str=in.readLine();
et.setText(str);
}
socket.close();
}catch(IOException e){
e.printStackTrace();
}
}
}).start();
}catch(IOException e){
e.printStackTrace();
}
}
}
}
LogCat显示：02-26 11:20:24.152: D/AndroidRuntime(266): Shutting down VM
02-26 11:20:24.152: W/dalvikvm(266): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
02-26 11:20:24.213: E/AndroidRuntime(266): FATAL EXCEPTION: main
02-26 11:20:24.213: E/AndroidRuntime(266): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.test.server/com.test.server.TestServerActivity}: java.lang.NullPointerException
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.os.Handler.dispatchMessage(Handler.java:99)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.os.Looper.loop(Looper.java:123)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread.main(ActivityThread.java:4627)
02-26 11:20:24.213: E/AndroidRuntime(266): at java.lang.reflect.Method.invokeNative(Native Method)
02-26 11:20:24.213: E/AndroidRuntime(266): at java.lang.reflect.Method.invoke(Method.java:521)
02-26 11:20:24.213: E/AndroidRuntime(266): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-26 11:20:24.213: E/AndroidRuntime(266): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-26 11:20:24.213: E/AndroidRuntime(266): at dalvik.system.NativeStart.main(Native Method)
02-26 11:20:24.213: E/AndroidRuntime(266): Caused by: java.lang.NullPointerException
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.Activity.findViewById(Activity.java:1637)
02-26 11:20:24.213: E/AndroidRuntime(266): at com.test.server.TestServerActivity.<init>(TestServerActivity.java:20)
02-26 11:20:24.213: E/AndroidRuntime(266): at java.lang.Class.newInstanceImpl(Native Method)
02-26 11:20:24.213: E/AndroidRuntime(266): at java.lang.Class.newInstance(Class.java:1429)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
02-26 11:20:24.213: E/AndroidRuntime(266): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
02-26 11:20:24.213: E/AndroidRuntime(266): ... 11 more
02-26 11:20:51.462: I/Process(266): Sending signal. PID: 266 SIG: 9
Caused by: java.lang.NullPointerException
at com.test.server.TestServerActivity.<init>(TestServerActivity.java:20)EditText et=(EditText)findViewById(R.id.editText1);
这个不是你这样写的，是需要放在方法中的，比如 onCreate中
如果你要全局可以这样 private EditText et;
@Override
public void onCreate(Bundle savedInstanceState) {
// some code....
this.et = (EditText)findViewById(R.id.editText1);
}