Question

正常情况下，我正在尝试将我的位置名称存储在一个包上并在热启动时使用它：

    public class LocFragment extends Fragment {
      private static final String KEY_LOCATION_NAME = "location_name";
      public String location;//="No location name found";

       //to be called by the MainActivity as:
       //@Override
       //public Fragment getItem(int pos) {
        //switch (pos) {
        //    case 0:
        //      return new LocFragment();
        //    case 2:....
      public LocFragment() {
      // Required empty public constructor
      }
      @Override
      public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Retrieve location and camera position from saved instance state.
        if (savedInstanceState != null) {
          location = savedInstanceState.getCharSequence(KEY_LOCATION_NAME).toString();
    //      Snackbar.make(getView(), location, Snackbar.LENGTH_LONG).show();
            System.out.println("location  "+location);

          //mCameraPosition = savedInstanceState.getParcelable(KEY_CAMERA_POSITION);
        }else{
          System.out.println("NULL SI");
        }
      }

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
                           Bundle savedInstanceState) {
     ....
     List<Address> addresses = null;
     Geocoder geocoder = new Geocoder(getContext(), Locale.getDefault());
     try {
      addresses = geocoder.getFromLocation(
       latlang.Lat,
       latlang.Lang,
       1);
     } catch (IOException ioException) {
     // Catch network or other I/O problems.
     errorMessage = getString(R.string.service_not_available);
     // Log.e(TAG, errorMessage, ioException);
     Snackbar.make(getView(), errorMessage, Snackbar.LENGTH_LONG).show();
     } catch (IllegalArgumentException illegalArgumentException) {
    // Catch invalid latitude or longitude values.
    errorMessage = getString(R.string.invalid_lat_long_used);
    Snackbar.make(getView(),
      "Illegal Latitude = " + latlang.Lat + ", Longitude = " +
          latlang.Lang, Snackbar.LENGTH_LONG).show();
   }
   if (addresses == null || addresses.size() == 0) {
     if (errorMessage.isEmpty()) {
       System.out.println("Adress Empty No Adress Found");// Snackbar.LENGTH_LONG).show();
       location = "Restart the app";
     }
  } else {
  location = addresses.get(0).getLocality();
  System.out.println("AM I GETTING Location"+location);
}


  @Override
  public void onSaveInstanceState(Bundle outState) {
    if (location != null) {
      outState.putCharSequence(KEY_LOCATION_NAME, location);
      super.onSaveInstanceState(outState);
    }
  }

现在，我希望这种情况：

在应用程序冷启动时，savedInstanceState将为null并打印"NULL SI"。在此步骤中，当它获得位置名称时，该名称将添加到"KEY_LOCATION_NAME"上的onSaveInstanceState
第二次，在热启动时，会将其添加到该位置。

但这不是我得到的。

从日志开始，冷启动：

I/System.out: NULL SI
I/System.out: Adress Empty No Adress Found

它在此步骤中获取地址，然后： @ 1st热门开始

 I/System.out: NULL SI
 I/System.out: AM I GETTING LocationMountain View

@ 2nd Hot start （只是为了确认，即使知道位置也会显示相同的内容）：

 I/System.out: NULL SI
 I/System.out: AM I GETTING LocationMountain View

我在这里缺少什么？

更新只需检查代码调用的onSaveInstanceState实际上是从不。可能这是原因吗？我怎么称呼这个？

更新：MainActivity.java

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener{

    private DrawerLayout drawer;
    private ListView mDrawerList;
    private String[] mPlanetTitles;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        drawer =  findViewById(R.id.drawerLayout);

        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar,
                R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        final ViewPager pager = (ViewPager) findViewById(R.id.viewPager);
        pager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));

       /*
        NavigationView
        */
        ImageButton leftNav = (ImageButton) findViewById(R.id.left_nav);
        ImageButton rightNav = (ImageButton) findViewById(R.id.right_nav);
            leftNav.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              int tab = pager.getCurrentItem();
                if (tab > 0) {
                    tab--;
                    pager.setCurrentItem(tab);
                } else if (tab == 0) {
                    pager.setCurrentItem(tab);
                }
                }
            });

            rightNav.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int tab = pager.getCurrentItem();
                tab++;
                pager.setCurrentItem(tab);
                }
            });

    }


    public void showDateDialog() {
        DialogFragment CalFragment = new CalFragment();
        CalFragment.show(getSupportFragmentManager(), "timePicker");
    }

 /*   @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
//        int id = menu.getItem(int );
//        if (id = )
        return true;
    }*/

    private class MyPagerAdapter extends FragmentPagerAdapter {

        public MyPagerAdapter(FragmentManager fm) {
            super(fm);
        }


        @Override
        public Fragment getItem(int pos) {
            switch (pos) {
                case 0:
                  //invalidateOptionsMenu();
                  return new LocFragment();
                case 2:
                    return ThirdFragment.newInstance("ThirdFragment, instance 1");
                case 1:
                    return SecondFragment.newInstance();
                case 3:
                    return FirstFragment.newInstance("FirstFragment, Instance 1");
                default:
                    return ThirdFragment.newInstance("ThirdFragment, default");
            }
        }


        @Override
        public int getCount() {
            return 4;
        }
    }

Bundle不会在重启时存储和更新值

0 个答案: