是什么导致此按钮崩溃？

Question

I'm writing an app that allows me to send a command through TCP/IP by clicking a button. However when I click to the button in the emulator it comes back with a message saying the button has stopped working. I was wondering if anyone could spot the error in my code.

CODE:

package button.test;  
import java.io.IOException;  
import java.io.OutputStream;  
import java.net.Socket;  
import java.net.UnknownHostException;  
import android.app.Activity;  
import android.os.Bundle;
import android.view.View;  

public class ButtonActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
    public void onClick(View view) throws UnknownHostException, IOException
    {
        Socket socket = new Socket("192.168.2.92", 60128);
        try{
            dataOutputStream.Object BUFFER = null;
            write(BUFFER);
            String buffer="ISCP000000100000000701000000!1PWR010D";
            OutputStream os=socket.getOutputStream();
            os.write(buffer.getBytes()); 
        } catch(IOException e)
        {
            //error code
        }

    }
    private void write(Object BUFFER) {
        // TODO Auto-generated method stub

    }
}

Answer 1

1. You missed declaring the button, and initializing it...

Eg:

public class ButtonActivity extends Activity {

Button mbutt;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mbutt = (Button)findViewById(R.id.Button_Click);
    }

- Make a note that you must initialize the views only after the setContentView() , else your views won't get the id and will make your App to crash.

2. Its always advisable to keep the UI work on UI thread, and Non-UI work on Non-UI thread , but that became a law with the arrival of HoneyComb android version.

3. You can use Thread with a Handler to sync UI and Non-UI thread.

4. AsyncTask which is known as Painless Threading was introduced specially in android for this.

See this link for tutorials on Threads, Handlers and AsyncTask:

http://www.vogella.com/articles/AndroidPerformance/article.html

Answer 2

It looks like the socket connection work is taking a long time. Suggest putting this functionality inside an AsyncTask.

Answer 3

您尚未在onCreate()声明按钮

Answer 4

You don't need to declare the button if you are inflating an xml. Your problem is that you run a Network connectivity on a main Thread which is not allowed since api 11. Use a asynctask or a thread for this.

eg

new Thread() {
public void run() {
    Socket socket = new Socket("192.168.2.92", 60128);
    try{
        dataOutputStream.Object BUFFER = null;
        write(BUFFER);
        String buffer="ISCP000000100000000701000000!1PWR010D";
        OutputStream os=socket.getOutputStream();
        os.write(buffer.getBytes()); 
    } catch(IOException e)
    {
        //error code
    }
  }
}.start();