为什么我保存的片段总是空的？

qxsslcnc  于 2021-08-20  发布在  Java
关注(0)|答案(1)|浏览(396)

我正在尝试在我的应用程序中保存我的片段示例（至少我想保存模型示例）。我有一个底部导航活动，这个片段从一个可编程设备获取一系列数据。我想让用户有机会在接收数据时在片段中导航。我可以做到，但当我回到采集片段时，它会创建另一个获取数据的对象示例，因此我无法控制当前正在工作的对象。所以我想保存片段示例。我尝试了这个和android开发者描述中的每一个答案。正如您可以从我的代码中看到的，我现在只保存一个布尔值，以尝试它是否有效。

@Override
public void onSaveInstanceState(@NonNull Bundle saved) {
    // call superclass to save any view hierarchy

    out.println("Saving...");
    out.println(start);
    if (!start)
    {
        /*Gson gson = new Gson();
        String json= gson.toJson(model);
        out.println(json);
        outState.putString("MODEL", json);*/
        saved.putBoolean("START", start);
    }
    super.onSaveInstanceState(saved);

}

无论如何，当我更改片段时，什么都不会发生，但我可以在ondestroy回调中调用此函数来保存它。

@Override
public void onDestroyView()
{
    super.onDestroyView();
    Bundle saved = new Bundle();
    this.onSaveInstanceState(saved);
    model.stop();
    model.disconnect();
    out.println("Destroy yourself");

}

但在oncreateview和oncreate中，我的包仍然为空。我不明白为什么。

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    out.println(savedInstanceState);
    super.onCreate(savedInstanceState);
    if (savedInstanceState != null) {
        start = savedInstanceState.getBoolean("START");
        out.println(start);
    } else {
        start = false;
    }
}

 @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    out.println(savedInstanceState);
    super.onCreate(savedInstanceState);
    if (savedInstanceState != null) {
        start = savedInstanceState.getBoolean("START");
        out.println(start);
    } else {
        start = false;
    }
    model = new ViewModelProvider(this).get(AcquisitionModel.class);

    model.getFreq().observe(getViewLifecycleOwner(), freq -> {
        updateFreq(freq);
    });
    model.getOrder().observe(getViewLifecycleOwner(), order -> {
        updateOrder(order);
    });
    model.getToDrawn().observe(getViewLifecycleOwner(),  toDrown-> {
        draw(toDrown);
    });
    View root = inflater.inflate(R.layout.fragment_acquisition, container, false);

    graph = (GraphView) root.findViewById(R.id.line_graph);
    graph.getViewport().setXAxisBoundsManual(true);
    GridLabelRenderer gridLabel = graph.getGridLabelRenderer();
    //gridLabel.setPadding(64);
    util = new AppUtilis(this.getContext());
    //graph.getViewport().setMaxX(5);

    series = new LineGraphSeries<>();
    graph.getViewport().setScalable(true);
    graph.getViewport().setScrollable(true);
    //series.setThickness(3);

    graph.addSeries(series);

    text= root.findViewById(R.id.frequenza);
    RG = (RadioGroup) root.findViewById(R.id.RG);
    RG.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener()
    {
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected

            String nonso = "";
            if (checkedId== R.id.ecg_switch) {
                TextView text= (TextView) root.findViewById(R.id.label);
                text.setText("Frequenza cardiaca (BPM)");
                nonso = "ecg";
            }
            else
            {
                TextView text= (TextView) root.findViewById(R.id.label);
                text.setText("Frequenza respiratoria");
                nonso = "resp";
            }
            model.scambio(nonso);
        }
    });

    B_start= (Button) root.findViewById(R.id.start_stop);
    B_start.setOnClickListener(new View.OnClickListener()
    { //utente pigia il bottone

        @Override

        public void onClick(View v) {

            //controllo se esiste il dispositivo
            if (model.isConnected() || disp != null) {
                boolean ans;
                if (start) {
                    ans = model.stop();
                    if (ans) {
                        start = false;//chiama lo stop
                        B_start.setText("Start");

                        //set colore standard
                        B_start.setBackgroundColor(Color.rgb(3, 218, 197));
                    }
                } else {
                    ans = model.start();
                    if (ans) {
                        start = true;
                        graph.removeAllSeries();
                        series = new LineGraphSeries<>();
                        series.setThickness(3);
                        graph2LastXValue = 0d;
                        graph.addSeries(series);
                        B_start.setText("Stop");
                        B_start.setBackgroundColor(Color.rgb(255, 0, 0));
                    }
                }
            }
            else
            {
                util.alert("Attenzione", "Non sei connesso!");
            }

        }

    });
    B_export = (Button) root.findViewById(R.id.exp);
    B_export.setOnClickListener(new View.OnClickListener()
    { //utente pigia il bottone
        @Override

        public void onClick(View v) {
            Log.d("saving", "premuto");
            if (model.isConnected() || disp != null) {

                util.loading("Sto salvando", false);
                model.stop();
                start = false;//chiama lo stop
                B_start.setText("Start");
                B_start.setBackgroundColor(Color.rgb(3, 218, 197));

                boolean ans = model.saveAll();
                analyzeCough(model.getResp().getFile(), model.fc);

                util.loadingFinished();
                if (ans)
                {
                    util.alert("Successo", "Esportazione avvenuta! Cerca nella cartella Registrazioni nella memoria interna del telefono");
                }
                else {
                    util.alert("Errore", "Esportazione fallita");
                }

            }
            else
            {
                util.alert("Attenzione", "Non sei connesso!");
            }
        }
    });
    share = root.findViewById(R.id.share);
    share.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (model.isConnected() || disp != null) {
                //funzione per condividere i file
                //controllo se non sia già stato fatto un export
                util.loading("Sto salvando", false);
                //model.disconnect();
                start = false;//chiama lo stop
                B_start.setText("Start");
                B_start.setBackgroundColor(Color.rgb(3, 218, 197));
                model.stop();
                boolean ansi = model.saveAll();
                analyzeCough(model.getResp().getFile(), model.fc);
                ArrayList<File> fil = model.getAllFiles();
                util.loadingFinished();
                if (ansi) {
                    StrictMode.VmPolicy.Builder builder = new StrictMode.VmPolicy.Builder();
                    StrictMode.setVmPolicy(builder.build());
                    //provo la condivisione
                    //prendi i path con una funzione dal model
                    try {
                        Intent sharingIntent = new Intent();
                        sharingIntent.setAction(Intent.ACTION_SEND_MULTIPLE);
                        sharingIntent.putExtra(Intent.EXTRA_SUBJECT, "Here are some files.");
                        sharingIntent.setType("text/*");
                        ArrayList<Uri> files = new ArrayList<Uri>();
                        for (int i = 0; i < fil.size(); i++) {
                            files.add(Uri.fromFile(fil.get(i)));
                        }
                        sharingIntent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, files);
                        startActivity(Intent.createChooser(sharingIntent, "Condividi con"));
                        out.println("Post sharing");
                    } catch (Exception e) {
                        e.printStackTrace();
                        util.alert("Errore", "Condivisione fallita!");
                    }

                } else {
                    util.alert("Errore", "Condivisione fallita");
                }
            }
            else
            {
                util.alert("Attenzione", "Non sei connesso!");
            }

        }
    });
    return root;
}

我还试图保存活动中的片段，正如有人在我之前发布的链接中提到的，作为答案，但它不起作用。有人知道吗？提前谢谢。
编辑这里是我的oncreate in活动

@Override
protected void onCreate(Bundle savedInstanceState) {
    model = new ViewModelProvider(this).get(ConnectionViewModel.class);
    ActivityCompat.requestPermissions(this,
            new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.INTERNET},
            REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
    if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.R && !Environment.isExternalStorageManager()) {
        // solo funzioni nuove e solo se non è già stato accettato
        Intent intent = new Intent();
        intent.setAction(Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION);
        Uri uri = Uri.fromParts("package", this.getPackageName(), null);
        intent.setData(uri);
        startActivity(intent);
    }
    try {
        setTheme(R.style.splashScreenTheme);
        super.onCreate(savedInstanceState);
        sleep(2000);
    } catch (Exception e) {
        e.printStackTrace();
    }
    setTheme(R.style.Theme_Ble);
    setContentView(R.layout.activity_main3);
    BottomNavigationView navView = findViewById(R.id.nav_view);
    // Passing each menu ID as a set of Ids because each
    // menu should be considered as top level destinations.
    AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
            R.id.tosse, R.id.grafici, R.id.elettrodi)
            .build();
    NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);

    util = new AppUtilis(this);
    NavigationUI.setupWithNavController(navView, navController);
    Button easter;
    easter = (Button) findViewById(R.id.easterEgg);
    easter.setOnClickListener(new View.OnClickListener()
    {

        @Override
        public void onClick(View v)
        {
            System.out.println("uovooooo");
            Intent intent = new Intent(util.getContext(), SettingsActivity.class);
            System.out.println("Vado a cercare roba");
            startActivityForResult(intent, 3);

        }
    });
    Ble = (ImageButton) findViewById(R.id.IconaBle);
    Ble.setOnClickListener(new View.OnClickListener()
    {

        @Override
        public void onClick(View v)
        {
            final BluetoothManager bluetoothManager =
                    (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
            BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();

            // Ensures Bluetooth is available on the device and it is enabled. If not,
            // displays a dialog requesting user permission to enable Bluetooth.
            final LocationManager manager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
            if (bluetoothAdapter == null || !bluetoothAdapter.isEnabled() ||  !manager.isProviderEnabled( LocationManager.GPS_PROVIDER ) ) {
                /*
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);*/
                util.alert("GPS e Bluetooth", "Per trovare dispositivi devi attivare GPS e Bluetooth");
            }
            else
            {
                Intent intent = new Intent(util.getContext(), BleScan.class);
                System.out.println("Vado a cercare roba");
                startActivityForResult(intent, 2);
            }

        }
    });

}
JavaandroidBundleandroid-fragmentsonsaveinstancestate

1条答案

按热度按时间
j2datikz

j2datikz1#

如果您将任何数据保存在 onDestoryView() 这意味着应用程序已关闭。及 savedInstanceState 除非系统自身强制关闭应用程序，否则应用程序无法关闭。所以 onCreate() 即使您保存了示例，也将打印null。加上 onDestroyView() 不必总是打电话。有时操作系统不调用 onDestroyView() . 您应该尝试将对象保存在内部 onPause() 或 onStop() 如果用户没有离开应用程序，而您正在加载保存的示例。

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