UI组件在UI线程的处理程序中变为null

Question

在我的Android应用程序中，我有UI线程和子线程。子线程将消息发送到需要在TextView上打印的UI线程。我初始化UI线程中的TextView，我生成子线程，子线程将消息发送到UI线程，但UI线程在handleMessage（）中失败。调试后，我发现HandleMessage（）中的TextView为null。下面我展示了UI和子线程的代码。你能告诉我我做错了吗？

在UI主题中：

public class Example extends Activity {
    public TextView mMatchesText;
    public Handler mHandler;  
    private ServerConnection conn;
    private String mProfile;

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mMatchesText = (TextView) Example.this.findViewById(R.id.matches);
        mMatchesText.setText("Matches:\n");     /*this text appears when I run the app*/


    Example.this.runOnUiThread(new Runnable() {
        public void run() {

            if(mMatchesText == null)
                Log.e("MY APP", "Before creating thread: mMatchesText is null");
            else
                Log.e("MY APP", "Before creating thread: mMatchesText is not null");    

            mProfile = FileReader.readFileAsString(getApplicationContext(), "profile.txt"));
            conn = new ServerConnection(mProfile);

            if(mMatchesText == null)
                Log.e("MY APP", "After creating thread: mMatchesText is null");
            else
                Log.e("MY APP", "After creating thread: mMatchesText is not null");
        }
    });
}        

Handler mHandler = new Handler(){
            public void handleMessage(Message msg)
            {
                 Log.e("MY APP", "In handler: Thread = " + Thread.currentThread().getName());

                 if(mMatchesText == null)
                     Log.e("MY APP", "In handler: mMatchesText is null");
                 else
                     Log.e("MY APP", "In handler: mMatchesText is not null");

                Log.e("MY APP", "In handler: " + (String)msg.obj);
                mMatchesText.setText((String)msg.obj);
            }
};

请注意，在生成子线程之前和之后，TextView不为null。在Handler中，消息被正确接收，但TextView为null，即使它是正在执行处理程序的UI线程。

在子线程中：

public class ServerConnection extends Example implements Runnable
{
    /* constructor */
    public ServerConnection()
    {
       runner = new Thread(this);
       runner.start();
    }

    public void run()
    {
        String fromServer;

        /** Establish connection to the server */

        /** Wait for messages from the server */
        while((fromServer = inFromServer.readLine()) != null)
        {
            Message toMain = mHandler.obtainMessage();
            toMain.obj = fromServer;
            mHandler.sendMessage(toMain);   
        }
    }
}

你能帮帮我吗。