如何將數據從Java類傳遞到片段

Question

我想將數據（字符串mFilePath ）從我的Java類RecordingService.java傳遞給RecordingFragment.java 。 這是我的RecordingService.java

    public class RecordingService extends Service {

    private static final String LOG_TAG = "RecordingService";

    private String mFileName = null;
    private String mFilePath = null;

    private MediaRecorder mRecorder = null;

    private DBHelper mDatabase;

    private long mStartingTimeMillis = 0;
    private long mElapsedMillis = 0;
    private int mElapsedSeconds = 0;
    private OnTimerChangedListener onTimerChangedListener = null;
    private static final SimpleDateFormat mTimerFormat = new SimpleDateFormat("mm:ss", Locale.getDefault());

    private Timer mTimer = null;
    private TimerTask mIncrementTimerTask = null;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    public interface OnTimerChangedListener {
        void onTimerChanged(int seconds);
    }

    @Override
    public void onCreate() {
        super.onCreate();
        mDatabase = new DBHelper(getApplicationContext());
    }



    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        startRecording();
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        if (mRecorder != null) {
            stopRecording();
        }

        super.onDestroy();
    }

    public void startRecording() {
        setFileNameAndPath();

        mRecorder = new MediaRecorder();
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
        mRecorder.setOutputFile(mFilePath);
        mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
        mRecorder.setAudioChannels(1);
        if (MySharedPreferences.getPrefHighQuality(this)) {
            mRecorder.setAudioSamplingRate(44100);
            mRecorder.setAudioEncodingBitRate(192000);
        }

        try {
            mRecorder.prepare();
            mRecorder.start();
            mStartingTimeMillis = System.currentTimeMillis();

            //startTimer();
            //startForeground(1, createNotification());

        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }
    }

    public void setFileNameAndPath(){
        int count = 0;
        File f;

        do{
            count++;

            mFileName = getString(R.string.default_file_name)
                    + "_" + (mDatabase.getCount() + count) + ".mp4";
            mFilePath = Environment.getExternalStorageDirectory().getAbsolutePath();
            mFilePath += "/SoundRecorder/" + mFileName;

            f = new File(mFilePath);
        }while (f.exists() && !f.isDirectory());
    }

    public String getFileNameAndPath(){
        return mFilePath;
    }

    public void stopRecording() {
        mRecorder.stop();
        mElapsedMillis = (System.currentTimeMillis() - mStartingTimeMillis);
        mRecorder.release();
        Toast.makeText(this, getString(R.string.toast_recording_finish) + " " + mFilePath, Toast.LENGTH_LONG).show();

        //remove notification
        if (mIncrementTimerTask != null) {
            mIncrementTimerTask.cancel();
            mIncrementTimerTask = null;
        }

        mRecorder = null;

        try {
            mDatabase.addRecording(mFileName, mFilePath, mElapsedMillis);
            Log.v("RecordingService", mFilePath);
            Bundle bundle = new Bundle();
            RecordFragment recordFragment = new RecordFragment();
            bundle.putString("filepath", mFilePath);
            recordFragment.setArguments(bundle);
        } catch (Exception e){
            Log.e(LOG_TAG, "exception", e);
        }
    }

    private void startTimer() {
        mTimer = new Timer();
        mIncrementTimerTask = new TimerTask() {
            @Override
            public void run() {
                mElapsedSeconds++;
                if (onTimerChangedListener != null)
                    onTimerChangedListener.onTimerChanged(mElapsedSeconds);
                NotificationManager mgr = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
                mgr.notify(1, createNotification());
            }
        };
        mTimer.scheduleAtFixedRate(mIncrementTimerTask, 1000, 1000);
    }

    //TODO:
    private Notification createNotification() {
        NotificationCompat.Builder mBuilder =
                new NotificationCompat.Builder(getApplicationContext())
                        .setSmallIcon(R.drawable.ic_mic_white_36dp)
                        .setContentTitle(getString(R.string.notification_recording))
                        .setContentText(mTimerFormat.format(mElapsedSeconds * 1000))
                        .setOngoing(true);

        mBuilder.setContentIntent(PendingIntent.getActivities(getApplicationContext(), 0,
                new Intent[]{new Intent(getApplicationContext(), MainActivity.class)}, 0));

        return mBuilder.build();
    }
}

這是我的RecordingFragment.java：

    public class RecordFragment extends Fragment {
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_POSITION = "position";
    private static final String LOG_TAG = RecordFragment.class.getSimpleName();

    private int position;

    //Recording controls
    private FloatingActionButton mRecordButton = null;

    // evaluation button
    private FloatingActionButton mEvalButton = null;

    private Button mPauseButton = null;

    private TextView mRecordingPrompt;
    private int mRecordPromptCount = 0;

    private boolean mStartRecording = true;
    private boolean mPauseRecording = true;

    private Chronometer mChronometer = null;
    long timeWhenPaused = 0; //stores time when user clicks pause button

    String filePath;

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @return A new instance of fragment Record_Fragment.
     */
    public static RecordFragment newInstance(int position) {
        RecordFragment f = new RecordFragment();
        Bundle b = new Bundle();
        b.putInt(ARG_POSITION, position);
        f.setArguments(b);

        return f;
    }



    public RecordFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        position = getArguments().getInt(ARG_POSITION);
        Log.d("Position Nilai", "" + position);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View recordView = inflater.inflate(R.layout.fragment_record, container, false);
        if (getArguments() != null) {
            filePath = getArguments().getString("filepath");
        }

        mChronometer = (Chronometer) recordView.findViewById(R.id.chronometer);
        //update recording prompt text
        mRecordingPrompt = (TextView) recordView.findViewById(R.id.recording_status_text);

        mRecordButton = (FloatingActionButton) recordView.findViewById(R.id.btnRecord);
        mRecordButton.setColorNormal(getResources().getColor(R.color.primary));
        mRecordButton.setColorPressed(getResources().getColor(R.color.primary_dark));
        mRecordButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onRecord(mStartRecording);
                mStartRecording = !mStartRecording;
            }
        });

        mEvalButton = (FloatingActionButton) recordView.findViewById(R.id.btnEval);
        mEvalButton.setColorNormal(getResources().getColor(R.color.primary));
        mEvalButton.setColorPressed(getResources().getColor(R.color.primary_dark));
        mEvalButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                evaluation();
            }
        });

        mPauseButton = (Button) recordView.findViewById(R.id.btnPause);
        mPauseButton.setVisibility(View.GONE); //hide pause button before recording starts
        mPauseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onPauseRecord(mPauseRecording);
                mPauseRecording = !mPauseRecording;
            }
        });

        return recordView;
    }

    // Recording Start/Stop
    //TODO: recording pause
    private void onRecord(boolean start){

        Intent intent = new Intent(getActivity(), RecordingService.class);

        if (start) {
            // start recording
            mRecordButton.setImageResource(R.drawable.ic_media_stop);
            //mPauseButton.setVisibility(View.VISIBLE);
            Toast.makeText(getActivity(),R.string.toast_recording_start,Toast.LENGTH_SHORT).show();
            File folder = new File(Environment.getExternalStorageDirectory() + "/SoundRecorder");
            if (!folder.exists()) {
                //folder /SoundRecorder doesn't exist, create the folder
                folder.mkdir();
            }

            //start Chronometer
            mChronometer.setBase(SystemClock.elapsedRealtime());
            mChronometer.start();
            mChronometer.setOnChronometerTickListener(new Chronometer.OnChronometerTickListener() {
                @Override
                public void onChronometerTick(Chronometer chronometer) {
                    if (mRecordPromptCount == 0) {
                        mRecordingPrompt.setText(getString(R.string.record_in_progress) + ".");
                    } else if (mRecordPromptCount == 1) {
                        mRecordingPrompt.setText(getString(R.string.record_in_progress) + "..");
                    } else if (mRecordPromptCount == 2) {
                        mRecordingPrompt.setText(getString(R.string.record_in_progress) + "...");
                        mRecordPromptCount = -1;
                    }

                    mRecordPromptCount++;
                }
            });

            //start RecordingService
            getActivity().startService(intent);
            //keep screen on while recording
            getActivity().getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

            mRecordingPrompt.setText(getString(R.string.record_in_progress) + ".");
            mRecordPromptCount++;

        } else {
            //stop recording
            mRecordButton.setImageResource(R.drawable.ic_mic_white_36dp);
            //mPauseButton.setVisibility(View.GONE);
            mChronometer.stop();
            mChronometer.setBase(SystemClock.elapsedRealtime());
            timeWhenPaused = 0;
            mRecordingPrompt.setText(getString(R.string.record_prompt));

            getActivity().stopService(intent);
            //allow the screen to turn off again once recording is finished
            getActivity().getWindow().clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        }
    }

    //TODO: implement pause recording
    private void onPauseRecord(boolean pause) {
        if (pause) {
            //pause recording
            mPauseButton.setCompoundDrawablesWithIntrinsicBounds
                    (R.drawable.ic_media_play ,0 ,0 ,0);
            mRecordingPrompt.setText((String)getString(R.string.resume_recording_button).toUpperCase());
            timeWhenPaused = mChronometer.getBase() - SystemClock.elapsedRealtime();
            mChronometer.stop();
        } else {
            //resume recording
            mPauseButton.setCompoundDrawablesWithIntrinsicBounds
                    (R.drawable.ic_media_pause ,0 ,0 ,0);
            mRecordingPrompt.setText((String)getString(R.string.pause_recording_button).toUpperCase());
            mChronometer.setBase(SystemClock.elapsedRealtime() + timeWhenPaused);
            mChronometer.start();
        }
    }

    private void evaluation(){
        Toast.makeText(getActivity(), "Filepath " + filePath, Toast.LENGTH_SHORT).show();
    }
}

我想要將數據（ stopRecording方法內的字符串mFilePath ）從RecordingService傳遞給RecordingFragment 。 當我嘗試從（ onCreateView方法和evaluation方法） RecordingFragment訪問時，結果是NPE，但是當我在內部登錄（ stopRecording方法） RecordingService類時，結果是我想要的，您可以看到下面帶有紅色邊框的圖片。

我看到從另一個問題本 。 老實說，我還是不明白，也不使用BroadCastReceiver。 我仍然感到困惑。

我的問題是：該問題的解決方案是什么？

謝謝

Answer 1

為此，您可以在Activity使用BroadcastReceiver 。

這是一個很好的示例，我可以使用BroadcastReceivers在Service <> Activity <> Fragment之間進行連續通信。

這是 Service <> Activity之間通信的另一個很好的例子 。 它使用Messenger和IncomingHandler 。

廣播接收器

我將為您提供一個簡單的例子。

這是您的Activity的BroadcastReceiver。 它會收到您的字符串：

//Your activity will respond to this action String
public static final String RECEIVE_PATH = "com.your.package.RECEIVE_JSON";

private BroadcastReceiver bReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        if(intent.getAction().equals(RECEIVE_PATH)) {
            String path = intent.getStringExtra("path");
            //Do something with the string
        }
    }
};
LocalBroadcastManager bManager;

在片段的onCreateView()中

bManager = LocalBroadcastManager.getInstance(getActivity());
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(RECEIVE_PATH);
bManager.registerReceiver(bReceiver, intentFilter);

確保在片段的onDestroyView()中，取消注冊broadcastReceiver。

bManager.unregisterReceiver(bReceiver);

最后，在您的Service onStart() ，執行以下操作：

System.out.println("intent Received");
Intent RTReturn = new Intent(YourActivity.RECEIVE_PATH);
RTReturn.putExtra("path", yourPath);
LocalBroadcastManager.getInstance(this).sendBroadcast(RTReturn);

並且您的Fragment會收到其中包含該路徑的意圖。