Set Initial Fragment on startup

2019-01-29 00:15发布

站内文章 / Android
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问题:

I am trying to set which fragment should be displayed first on start up. To determine this I check whether the user is logged in with ParseUser.getCurrentUser() and if a file is present on the device. On start up, I want to set which fragment to display. to do so i put this code in the initial fragments onCreate Method.

if (ParseUser.getCurrentUser() != null) {
            File f = new File(getActivity().getFilesDir() + "/display_store.bin");
            if (f.exists() && !f.isDirectory()) {
                ft.replace(R.id.container, new Display()).commit();

            } else {
                ft.replace(R.id.container, new CollectionFragment()).commit();

            }
        } else {
            ft.replace(R.id.container, new Authentication()).commit();
        }

I am able to determine which fragment is displayed on start up. But in my Navigation Drawer When I select My information and My display it only replaces the fragment with my Display and I am not able to display My information from the Navigation Drawer. For some reason it is just ignoring CollectionFragment.

Main Activity:

import android.app.Activity;

import android.app.ActionBar;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;

import com.microsoft.windowsazure.mobileservices.*;
import com.parse.Parse;
import com.parse.ParseUser;

import java.io.File;
import java.net.MalformedURLException;

public class MainActivity extends Activity
    implements NavigationDrawerFragment.NavigationDrawerCallbacks {

/**
 * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
 */
private NavigationDrawerFragment mNavigationDrawerFragment;

/**
 * Used to store the last screen title. For use in {@link #restoreActionBar()}.
 */
private CharSequence mTitle;

private static MobileServiceClient mClient;

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

    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getFragmentManager().findFragmentById(R.id.navigation_drawer);
    mTitle = getTitle();

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));

    Parse.enableLocalDatastore(this);
    Parse.initialize(this, "api", "key");

    try {
        mClient = new MobileServiceClient("url", "key", this);

    } catch (MalformedURLException e) {
        e.printStackTrace();
    }
}

public static MobileServiceClient getmClient() {
    return mClient;
}


@Override

//Sets fragment 
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
            .commit();
}


public void onSectionAttached(int number) {
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction ft = fragmentManager.beginTransaction();

    switch (number) {
        case 1:
            mTitle = "Home";
            break;
        case 2:
            mTitle = "My Information";
            ft.replace(R.id.container, new CollectionFragment()).commit();
            break;
        case 3:
            mTitle = "My Display";
            ft.replace(R.id.container, new Display()).commit();
            break;
        case 4:
            mTitle = "Donate";
            Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.org"));
            startActivity(browserIntent);
            break;
        case 5:
            mTitle = "Settings";
            break;
        case 6:
            mTitle = "Log Out";
            ParseUser.logOut();
            ft.replace(R.id.container, new Authentication()).commit();
            break;

    }
}

public void restoreActionBar() {
    ActionBar actionBar = getActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    if (!mNavigationDrawerFragment.isDrawerOpen()) {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.main, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";
    private boolean runOnce = false;

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.form_welcome_screen_fragment, container, false);
        return rootView;
    }

    @Override
    public void onStart() {
        super.onStart();
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();


            if (ParseUser.getCurrentUser() != null) {
                File f = new File(getActivity().getFilesDir() + "/display_store.bin");
                if (f.exists() && !f.isDirectory()) {
                    ft.replace(R.id.container, new Display()).commit();

                } else {
                    ft.replace(R.id.container, new CollectionFragment()).commit();

                }
            } else {
                ft.replace(R.id.container, new Authentication()).commit();
            }

    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        ((MainActivity) activity).onSectionAttached(
                getArguments().getInt(ARG_SECTION_NUMBER));
    }
}

}

Navigation Drawer Fragment:

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.content.SharedPreferences;
import android.content.res.Configuration;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
/**
 * Fragment used for managing interactions for and presentation of a navigation drawer.
 * See the <a href="https://developer.android.com/design/patterns/navigation-drawer.html#Interaction">
 * design guidelines</a> for a complete explanation of the behaviors implemented here.
 */
public class NavigationDrawerFragment extends Fragment {

/**
 * Remember the position of the selected item.
 */
private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";

/**
 * Per the design guidelines, you should show the drawer on launch until the user manually
 * expands it. This shared preference tracks this.
 */
private static final String PREF_USER_LEARNED_DRAWER = "navigation_drawer_learned";

/**
 * A pointer to the current callbacks instance (the Activity).
 */
private NavigationDrawerCallbacks mCallbacks;

/**
 * Helper component that ties the action bar to the navigation drawer.
 */
private ActionBarDrawerToggle mDrawerToggle;

private DrawerLayout mDrawerLayout;
private ListView mDrawerListView;
private View mFragmentContainerView;

private int mCurrentSelectedPosition = 0;
private boolean mFromSavedInstanceState;
private boolean mUserLearnedDrawer;

public NavigationDrawerFragment() {
}

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

    // Read in the flag indicating whether or not the user has demonstrated awareness of the
    // drawer. See PREF_USER_LEARNED_DRAWER for details.
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
    mUserLearnedDrawer = sp.getBoolean(PREF_USER_LEARNED_DRAWER, false);

    if (savedInstanceState != null) {
        mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
        mFromSavedInstanceState = true;
    }

    // Select either the default item (0) or the last selected item.
    selectItem(mCurrentSelectedPosition);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    // Indicate that this fragment would like to influence the set of actions in the action bar.
    setHasOptionsMenu(true);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    mDrawerListView = (ListView) inflater.inflate(
            R.layout.fragment_navigation_drawer, container, false);
    mDrawerListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectItem(position);
        }
    });
    mDrawerListView.setAdapter(new ArrayAdapter<String>(
            getActionBar().getThemedContext(),
            android.R.layout.simple_list_item_activated_1,
            android.R.id.text1,
            new String[]{
                    getString(R.string.title_section1),
                    getString(R.string.title_section2),
                    getString(R.string.title_section3),
                    getString(R.string.title_section4),
                    getString(R.string.title_section5),
                    getString(R.string.title_section6),

            }));
    mDrawerListView.setItemChecked(mCurrentSelectedPosition, true);
    return mDrawerListView;
}

public boolean isDrawerOpen() {
    return mDrawerLayout != null && mDrawerLayout.isDrawerOpen(mFragmentContainerView);
}

/**
 * Users of this fragment must call this method to set up the navigation drawer interactions.
 *
 * @param fragmentId   The android:id of this fragment in its activity's layout.
 * @param drawerLayout The DrawerLayout containing this fragment's UI.
 */
public void setUp(int fragmentId, DrawerLayout drawerLayout) {
    mFragmentContainerView = getActivity().findViewById(fragmentId);
    mDrawerLayout = drawerLayout;

    // set a custom shadow that overlays the main content when the drawer opens
    mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
    // set up the drawer's list view with items and click listener

    ActionBar actionBar = getActionBar();
    actionBar.setDisplayHomeAsUpEnabled(true);
    actionBar.setHomeButtonEnabled(true);

    // ActionBarDrawerToggle ties together the the proper interactions
    // between the navigation drawer and the action bar app icon.
    mDrawerToggle = new ActionBarDrawerToggle(
            getActivity(),                    /* host Activity */
            mDrawerLayout,                    /* DrawerLayout object */
            R.drawable.ic_drawer,             /* nav drawer image to replace 'Up' caret */
            R.string.navigation_drawer_open,  /* "open drawer" description for accessibility */
            R.string.navigation_drawer_close  /* "close drawer" description for accessibility */
    ) {
        @Override
        public void onDrawerClosed(View drawerView) {
            super.onDrawerClosed(drawerView);
            if (!isAdded()) {
                return;
            }

            getActivity().invalidateOptionsMenu(); // calls onPrepareOptionsMenu()
        }

        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
            if (!isAdded()) {
                return;
            }

            if (!mUserLearnedDrawer) {
                // The user manually opened the drawer; store this flag to prevent auto-showing
                // the navigation drawer automatically in the future.
                mUserLearnedDrawer = true;
                SharedPreferences sp = PreferenceManager
                        .getDefaultSharedPreferences(getActivity());
                sp.edit().putBoolean(PREF_USER_LEARNED_DRAWER, true).apply();
            }

            getActivity().invalidateOptionsMenu(); // calls onPrepareOptionsMenu()
        }
    };

    // If the user hasn't 'learned' about the drawer, open it to introduce them to the drawer,
    // per the navigation drawer design guidelines.
    if (!mUserLearnedDrawer && !mFromSavedInstanceState) {
        mDrawerLayout.openDrawer(mFragmentContainerView);
    }

    // Defer code dependent on restoration of previous instance state.
    mDrawerLayout.post(new Runnable() {
        @Override
        public void run() {
            mDrawerToggle.syncState();
        }
    });

    mDrawerLayout.setDrawerListener(mDrawerToggle);
}

private void selectItem(int position) {
    mCurrentSelectedPosition = position;
    if (mDrawerListView != null) {
        mDrawerListView.setItemChecked(position, true);
    }
    if (mDrawerLayout != null) {
        mDrawerLayout.closeDrawer(mFragmentContainerView);
    }
    if (mCallbacks != null) {
        mCallbacks.onNavigationDrawerItemSelected(position);
    }
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mCallbacks = (NavigationDrawerCallbacks) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException("Activity must implement NavigationDrawerCallbacks.");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mCallbacks = null;
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt(STATE_SELECTED_POSITION, mCurrentSelectedPosition);
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    // Forward the new configuration the drawer toggle component.
    mDrawerToggle.onConfigurationChanged(newConfig);
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    // If the drawer is open, show the global app actions in the action bar. See also
    // showGlobalContextActionBar, which controls the top-left area of the action bar.
    if (mDrawerLayout != null && isDrawerOpen()) {
        inflater.inflate(R.menu.main, menu);
        showGlobalContextActionBar();
    }
    super.onCreateOptionsMenu(menu, inflater);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }

   // if (item.getItemId() == R.id.sort) {
    //    Toast.makeText(getActivity(), "Example action.", Toast.LENGTH_SHORT).show();
    //    return true;
   // }

    return super.onOptionsItemSelected(item);
}

/**
 * Per the navigation drawer design guidelines, updates the action bar to show the global app
 * 'context', rather than just what's in the current screen.
 */
private void showGlobalContextActionBar() {
    ActionBar actionBar = getActionBar();
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setTitle(R.string.app_name);
}

private ActionBar getActionBar() {
    return getActivity().getActionBar();
}



/**
 * Callbacks interface that all activities using this fragment must implement.
 */
public static interface NavigationDrawerCallbacks {
    /**
     * Called when an item in the navigation drawer is selected.
     */
    void onNavigationDrawerItemSelected(int position);
}
}

Any Help would be much appreciated!!!

回答1:

Write this in the onCreate(Bundle savedInstanceState) method after you set your drawer up:

mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
        (DrawerLayout) findViewById(R.id.drawer_layout));

if (savedInstanceState == null) {
    // on first time to display view for first navigation item based on the number
    onSectionAttached(2); // 2 is your fragment's number for "CollectionFragment"
}

Notice that your Fragment's number is 2. The number is got from your public void onSectionAttached(int number) method. If case 2: opens the CollectionFragment, so your Fragment's number is 2 (because of case number is 2). Then, alter your onSectionAttached() slightly:

public void onSectionAttached(int number) {
    // update the main content by replacing fragments
    Fragment fragment = null;

    switch (number) {
        case 1:
            mTitle = "Home";
            break;
        case 2:
            mTitle = "My Information";
            fragment = new CollectionFragment();
            break;
        case 3:
            mTitle = "My Display";
            fragment = new Display();
            break;
        case 4:
            mTitle = "Donate";
            Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.org"));
            startActivity(browserIntent);
            break;
        case 5:
            mTitle = "Settings";
            break;
        case 6:
            mTitle = "Log Out";
            ParseUser.logOut();
            fragment = new Authentication();
            break;
        default:
            break;
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction()
                .replace(R.id.container, fragment).commit();

        } else {
        // error in creating fragment
        Log.e("MainActivity", "Error in creating fragment");
    }
}

So now, you just need to call onSectionAttached(your fragment's number); to display your Fragment you want.



回答2:

To handle the default selection of the fragment in Your MainActivity, you need to do the following:

  • In the MainActivity 
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
    mTitle = getTitle();

    int selectedSection = getIntent().getIntExtra(EXTRA_PARAMS_ID, 0);

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout), selectedSection);
    mNavigationDrawerFragment.selectItem(selectedSection);
}


@Override
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
    // You could switch over different positions to show the right fragment
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.container, YourFragment.newInstance(position))
                    .commit();
}

public void onSectionAttached(int position) {
    final String[] sections = getResources().getStringArray(R.array.sections);
    if (sections.length > position)
        mTitle = sections[position];
    getSupportActionBar().setTitle(mTitle);
}
  • In the NavigationDrawerFragment remove the selectItem(mCurrentSelectedPosition); from the onCreate()


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