public class MainActivity extends Activity {
private Button btn1,btn2;
private TextView tv1;
private EditText et1;
private Socket socket;
private BufferedReader br;
private PrintWriter pw;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = (Button)findViewById(R.id.btn1);
btn2 = (Button)findViewById(R.id.btn2);
tv1 = (TextView)findViewById(R.id.tv1);
et1 = (EditText)findViewById(R.id.et1);
try {
socket = new Socket("10.0.0.2", 54321);
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream());
} catch (IOException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
btn1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new Thread(){
public void run() {
try {
String str = br.readLine();
tv1.setText(str);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
};
};
}
});
btn2.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String str = et1.getText().toString();
pw.print(str);//这一行报错空指针,为什么...
pw.flush();
}
});
}
}
为什么报错空指针的:
报错如下:
10-29 02:06:21.898: E/AndroidRuntime(487): FATAL EXCEPTION: main
10-29 02:06:21.898: E/AndroidRuntime(487): java.lang.NullPointerException
10-29 02:06:21.898: E/AndroidRuntime(487): at com.example.androidsocket.MainActivity$2.onClick(MainActivity.java:66)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.view.View.performClick(View.java:2485)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.view.View$PerformClick.run(View.java:9080)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Handler.handleCallback(Handler.java:587)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Handler.dispatchMessage(Handler.java:92)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Looper.loop(Looper.java:123)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.app.ActivityThread.main(ActivityThread.java:3683)
10-29 02:06:21.898: E/AndroidRuntime(487): at java.lang.reflect.Method.invokeNative(Native Method)
10-29 02:06:21.898: E/AndroidRuntime(487): at java.lang.reflect.Method.invoke(Method.java:507)
10-29 02:06:21.898: E/AndroidRuntime(487): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-29 02:06:21.898: E/AndroidRuntime(487): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-29 02:06:21.898: E/AndroidRuntime(487): at dalvik.system.NativeStart.main(Native Method)
private Button btn1,btn2;
private TextView tv1;
private EditText et1;
private Socket socket;
private BufferedReader br;
private PrintWriter pw;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = (Button)findViewById(R.id.btn1);
btn2 = (Button)findViewById(R.id.btn2);
tv1 = (TextView)findViewById(R.id.tv1);
et1 = (EditText)findViewById(R.id.et1);
try {
socket = new Socket("10.0.0.2", 54321);
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream());
} catch (IOException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
btn1.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new Thread(){
public void run() {
try {
String str = br.readLine();
tv1.setText(str);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
};
};
}
});
btn2.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String str = et1.getText().toString();
pw.print(str);//这一行报错空指针,为什么...
pw.flush();
}
});
}
}
为什么报错空指针的:
报错如下:
10-29 02:06:21.898: E/AndroidRuntime(487): FATAL EXCEPTION: main
10-29 02:06:21.898: E/AndroidRuntime(487): java.lang.NullPointerException
10-29 02:06:21.898: E/AndroidRuntime(487): at com.example.androidsocket.MainActivity$2.onClick(MainActivity.java:66)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.view.View.performClick(View.java:2485)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.view.View$PerformClick.run(View.java:9080)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Handler.handleCallback(Handler.java:587)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Handler.dispatchMessage(Handler.java:92)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.os.Looper.loop(Looper.java:123)
10-29 02:06:21.898: E/AndroidRuntime(487): at android.app.ActivityThread.main(ActivityThread.java:3683)
10-29 02:06:21.898: E/AndroidRuntime(487): at java.lang.reflect.Method.invokeNative(Native Method)
10-29 02:06:21.898: E/AndroidRuntime(487): at java.lang.reflect.Method.invoke(Method.java:507)
10-29 02:06:21.898: E/AndroidRuntime(487): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-29 02:06:21.898: E/AndroidRuntime(487): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-29 02:06:21.898: E/AndroidRuntime(487): at dalvik.system.NativeStart.main(Native Method)
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socket = new Socket("10.0.0.2", 54321);
br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
pw = new PrintWriter(socket.getOutputStream());
} catch (IOException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}你看下这段有没有抛异常,有没有运行到pw = new PrintWriter(socket.getOutputStream());