在启动时设置初始片段 [英] Set Initial Fragment on startup

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本文介绍了在启动时设置初始片段的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我想设置哪些片段要在启动时首先显示。为了确定这一点，我检查用户是否与ParseUser.getCurrentUser登录（），如果一个文件是在设备上present。在启动时，我想设置要显示的片段。这样做，我把这个code初始片段onCreate方法。

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();
        }

我能够确定哪些片段被显示在启动时。但在我的抽屉式导航当我选择我的信息我的显示屏只与我的显示替换片段，我不能够显示从抽屉式导航我的信息。出于某种原因，它只是忽略CollectionFragment。

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.

主要活动：

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));
    }
}

}

抽屉式导航片段：

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);
}
}

任何帮助将非常AP preciated！

Any Help would be much appreciated!!!

推荐答案

你设置你的抽屉后写这在的onCreate（捆绑savedInstanceState）方法：

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"
}

注意，你的片段的数量为2的号码从onSectionAttached你的公共无效（INT数）方法。如果案例2：打开 Col​​lectionFragment ，所以你的片段的数量是2（因为情况数为2）。然后，改变你的 onSectionAttached（）略：

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");
    }
}

所以，现在，你只需要调用 onSectionAttached（您片段的数量）; 来显示你的片段你想

这篇关于在启动时设置初始片段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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