当从主UI线程向其他线程发送消息时，应用程序崩溃

Question

我正在尝试从onCreate()的MainActivity方法向Connection线程发送消息，然后该线程通过udp socket将数据发送到服务器。但是该应用程序连续崩溃。请告诉我如何将数据从UI线程发送到非UI线程。

MainActivity的onCreate（）方法。

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Looper.prepare();
        Thread connection = new Thread(new Connection());
        connection.start();
        Message msg = Message.obtain();
        Bundle bundle = new Bundle();
        bundle.putString("NAVIGATION", "Message");
        msg.setData(bundle);
        if(Connection.getHandler() == null){
            Connection.getHandler().sendMessage(msg);
        }
        Looper.loop();
    }

连接类别

public class Connection implements Runnable {

    private DatagramSocket client_socket = null;
    private InetAddress host = null;
    private byte[] buffer = null;
    private static Handler handler = null;
    private String data = null;

    @Override
    public void run() {
        boolean status = this.create();
        if(status) {
            while (true) {
                Looper.prepare();
                Connection.handler = new Handler(){
                    @Override
                    public void handleMessage(Message msg) {
                        super.handleMessage(msg);
                        Connection.handler.obtainMessage();
                        String data = msg.getData().getString("NAVIGATION");
                        send(data);
                    }
                };
                Looper.loop();
            }
        }
    }
    private boolean create(){
        try{
            this.client_socket = new DatagramSocket();
        } catch(Exception e){
            Log.e("Connection", e.getMessage());
            return false;
        }
        try{
            this.host = InetAddress.getByName("192.168.0.107");
        } catch (Exception e){
            Log.e("Connection", e.getMessage());
            return false;
        }
        return true;
    }

    private void send(String nav){
        this.buffer = nav.getBytes();

        DatagramPacket packet = new DatagramPacket(buffer, buffer.length, this.host, 12345);

        try{
            this.client_socket.send(packet);
        } catch (Exception e){
            Log.e("Connection", e.getMessage());
        }
    }

    public static Handler getHandler() {
        return Connection.handler;
    }
}

Answer 1

 if(Connection.getHandler() == null){
     Connection.getHandler().sendMessage(msg);
  }

这似乎是罪魁祸首-您说“如果为空，请使用它”

也许你打算写Connection.getHandler() != null

还请在onCreate以及您的连接初始化中添加日志消息，以确保在onCreate运行之前已创建连接