使用线程从 Activity 更新 Fragment

Question

First, I'm sorry for my poor English, I hope you could understand me even so.

The APP :

• 1 Activity with 3 Fragments and PageAdaptater OK

• Collect data from an Bluetooth device. OK

• Update TextView in an fragment each time data is collected in the MainActivity via Handler.

Below my code :

MainActivity :

public class MainActivity extends FragmentActivity {

    private PagerAdapter mPagerAdapter;
    private static final String TAG = "bluetooth2";
    private String btaddr = "20:14:09:17:00:40";
    Handler h;
    final int RECIEVE_MESSAGE = 1;        // Status  for Handler
    private BluetoothAdapter btAdapter = null;
    private BluetoothSocket btSocket = null;
    private StringBuilder sb = new StringBuilder();
    private ConnectedThread mConnectedThread;
    private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.viewpager);

        // Création de la liste de Fragments que fera défiler le PagerAdapter
        List<Fragment> fragments = new Vector<Fragment>();

        // Ajout des Fragments dans la liste
        fragments.add(Fragment.instantiate(this,HomeFragment.class.getName()));
        fragments.add(Fragment.instantiate(this,NormalFragment.class.getName()));
        fragments.add(Fragment.instantiate(this,ConfigFragment.class.getName()));

        // Création de l'adapter qui s'occupera de l'affichage de la liste de
        // Fragments
        this.mPagerAdapter = new MyPagerAdapter(super.getSupportFragmentManager(), fragments);

        ViewPager pager = (ViewPager) super.findViewById(R.id.viewpager);
        // Affectation de l'adapter au ViewPager
        pager.setAdapter(this.mPagerAdapter);

        h = new Handler() {
            public void handleMessage(android.os.Message msg)  {
                switch (msg.what) {
                case RECIEVE_MESSAGE:                                                   // if receive massage
                    byte[] readBuf = (byte[]) msg.obj;
                    String strIncom = new String(readBuf, 0, msg.arg1);                 // create string from bytes array
                    sb.append(strIncom);                                                // append string
                    int endOfLineIndex = sb.indexOf("\r\n");                            // determine the end-of-line
                    if (endOfLineIndex > 0) {                                            // if end-of-line,
                        String sbprint = sb.substring(0, endOfLineIndex);               // extract string
                        sb.delete(0, sb.length());                                      // and clear

                        Log.d(TAG, "...String:"+ sb.toString() +  "Byte:" + msg.arg1 + "...");
                        //My question : How to send data to fragment from here ?

                        break;
                    }
                }
            };
        };

        btAdapter = BluetoothAdapter.getDefaultAdapter();       // get Bluetooth adapter

        checkBTState();


      }

      private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
          if(Build.VERSION.SDK_INT >= 10){
              try {
                  final Method  m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", new Class[] { UUID.class });
                  return (BluetoothSocket) m.invoke(device, MY_UUID);
              } catch (Exception e) {
                  Log.e(TAG, "Could not create Insecure RFComm Connection",e);
              }
          }
          return  device.createRfcommSocketToServiceRecord(MY_UUID);
      }

      @Override
      public void onResume() {
        super.onResume();

        Log.d(TAG, "...onResume - try connect...");

        // Set up a pointer to the remote node using it's address.
        BluetoothDevice device = btAdapter.getRemoteDevice(btaddr);

        // Two things are needed to make a connection:
        //   A MAC address, which we got above.
        //   A Service ID or UUID.  In this case we are using the
        //     UUID for SPP.

        try {
            btSocket = createBluetoothSocket(device);
        } catch (IOException e) {
            errorExit("Fatal Error", "In onResume() and socket create failed: " + e.getMessage() + ".");
        }

        // Discovery is resource intensive.  Make sure it isn't going on
        // when you attempt to connect and pass your message.
        btAdapter.cancelDiscovery();

        // Establish the connection.  This will block until it connects.
        Log.d(TAG, "...Connecting...");
        try {
          btSocket.connect();
          Log.d(TAG, "....Connection ok...");
        } catch (IOException e) {
          try {
            btSocket.close();
          } catch (IOException e2) {
            errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
          }
        }

        // Create a data stream so we can talk to server.
        Log.d(TAG, "...Create Socket...");

        mConnectedThread = new ConnectedThread(btSocket);
        mConnectedThread.start();
      }

      @Override
      public void onPause() {
        super.onPause();

        Log.d(TAG, "...In onPause()...");

        try     {
          btSocket.close();
        } catch (IOException e2) {
          errorExit("Fatal Error", "In onPause() and failed to close socket." + e2.getMessage() + ".");
        }
      }

      private void checkBTState() {
        // Check for Bluetooth support and then check to make sure it is turned on
        // Emulator doesn't support Bluetooth and will return null
        if(btAdapter==null) {
          errorExit("Fatal Error", "Bluetooth not support");
        } else {
          if (btAdapter.isEnabled()) {
            Log.d(TAG, "...Bluetooth ON...");
          } else {
            //Prompt user to turn on Bluetooth
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, 1);
          }
        }
      }

      private void errorExit(String title, String message){
        Toast.makeText(getBaseContext(), title + " - " + message, Toast.LENGTH_LONG).show();
        finish();
      }

      public class ConnectedThread extends Thread {
            private final InputStream mmInStream;
            private final OutputStream mmOutStream;

            public ConnectedThread(BluetoothSocket socket) {
                InputStream tmpIn = null;
                OutputStream tmpOut = null;

                // Get the input and output streams, using temp objects because
                // member streams are final
                try {
                    tmpIn = socket.getInputStream();
                    tmpOut = socket.getOutputStream();
                } catch (IOException e) { }

                mmInStream = tmpIn;
                mmOutStream = tmpOut;
            }

            public void run() {
                byte[] buffer = new byte[256];  // buffer store for the stream
                int bytes; // bytes returned from read()

                // Keep listening to the InputStream until an exception occurs
                while (true) {
                    try {
                        // Read from the InputStream
                        bytes = mmInStream.read(buffer);        // Get number of bytes and message in "buffer"
                        h.obtainMessage(RECIEVE_MESSAGE, bytes, -1, buffer).sendToTarget();     // Send to message queue Handler
                    } catch (IOException e) {
                        break;
                    }
                }
            }

            /* Call this from the main activity to send data to the remote device */
            public void write(String message) {
                Log.d(TAG, "...Data to send: " + message + "...");
                byte[] msgBuffer = message.getBytes();
                try {
                    mmOutStream.write(msgBuffer);
                } catch (IOException e) {
                    Log.d(TAG, "...Error data send: " + e.getMessage() + "...");
                  }
            }
        }

}

HomeFragment (receiver) :

public class HomeFragment extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        View myInflatedView = inflater.inflate(R.layout.home_layout, container, false);

        return myInflatedView;
    }

}

Home Layout :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/data"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="20dp"
        android:text="DATA" />

</LinearLayout>

In this situation, for you, how can I send data easly from handler in activity to the HomeFragment and update the textview inside?

I'm very new in Java, and most tutorials are in English, same thing about documentation so it's hard to learn alone correctly...

I tried many snippets found on stackoverflow without success, and now I am a bit lost..

EDIT 1:
As requested, here the code for PagerAdaptater :

public class MyPagerAdapter extends FragmentPagerAdapter {

    private final List<Fragment> fragments;

    //On fournit à l'adapter la liste des fragments à afficher
    public MyPagerAdapter(FragmentManager fm, List<Fragment> fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int position) {
        return this.fragments.get(position);
    }

    @Override
    public int getCount() {
        return this.fragments.size();
    }
}

EDIT 2:
Updated HomeFragment :

public class HomeFragment extends Fragment {

    TextView data;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        View myInflatedView = inflater.inflate(R.layout.home_layout, container, false);
        data= (TextView) myInflatedView.findViewById(R.id.data);

        return myInflatedView;
    }
      public void change(String txt){
          data.setText(txt); //Don't WORK "NullPointerException"
          Log.d("TEST", "...String:"+ txt +  "..."); //Work
        }

}

EDIT 3 :

The solution, check if data is not null before do setText.

public void change(String txt){
            if(data != null){
                data.setText(str);
            }
          Log.d("TEST", "...String:"+ txt +  "..."); //Work
        }

Answer 1

You could keep a reference to your HomeFragment in your MainActivity like this and add it to your pager adapter:

public class MainActivity extends FragmentActivity {
    // instanciate other variables
    private HomeFragment myHomeFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.

        List<Fragment> fragments = new Vector<Fragment>();

        this.myHomeFragment = fragment.instantiate(this,HomeFragment.class.getName());

        fragments.add(myHomeFragment);
        fragments.add(Fragment.instantiate(this,NormalFragment.class.getName()));
        fragments.add(Fragment.instantiate(this,ConfigFragment.class.getName()));

        ...
    }
}

Then, in your HomeFragment, declare a public method that takes a string and sets the text of the TextView and call it in your handler:

myHomeFragment.setTextView(sb.toString());