android使用导航抽屉加载片段

问题描述

我正在使用NavigationDrawer创建菜单，并且我使用片段加载菜单项，当我打开我的应用程序时，我位于家庭片段中，而当我单击另一个项目时，相应的片段将出现在屏幕上但是，如果我再次单击房屋，它将不收费，但对其他房屋有效，只有房屋碎片不再出现

i'm using navigationdrawer to create a menu, and i use fragment to load my menu items , when i open my app i am in the home fragment, and when i click on another item ,the corresponding fragment appears on the screen but if i click on the home again it doesn't charge, it works for the others only the home fragment doesn't appear again

here is my MenuActivity
/**
 * Created by SADA INFO on 10/03/2018.
 */
package com.android.pfe.activity;

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.support.design.widget.NavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.android.pfe.fragment.ArticleFragment;
import com.android.pfe.fragment.ContactFragment;

import com.android.pfe.R;
import com.android.pfe.fragment.HomeFragment;
import com.android.pfe.fragment.NotificationsFragment;
import com.android.pfe.fragment.RechercheFragment;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MenuActivity extends AppCompatActivity {

    private NavigationView navigationView;
    private DrawerLayout drawer;
    private View navHeader;
    private ImageView imgNavHeaderBg, imgProfile;
    private TextView txtName, txtWebsite,profil;
    private Toolbar toolbar;
    private DatabaseReference mDatabase;


    // urls to load navigation header background image
    // and profile image
   // private static final String urlNavHeaderBg = "http://api.androidhive.info/images/nav_header_img.jpg";

        // index to identify current nav menu item
    public static int navItemIndex = 0;

    // tags used to attach the fragments
    private static final String TAG_HOME = "home";
    private static final String TAG_PHOTOS = "photos";
    private static final String TAG_MOVIES = "movies";
    private static final String TAG_NOTIFICATIONS = "notifications";
    private static final String TAG_SETTINGS = "settings";
    public static String CURRENT_TAG = TAG_HOME;

    // toolbar titles respected to selected nav menu item
    private String[] activityTitles;

    // flag to load home fragment when user presses back key
    private boolean shouldLoadHomeFragOnBackPress = true;
    private Handler mHandler;
    private FirebaseAuth auth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu);
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        //get firebase auth instance
        auth = FirebaseAuth.getInstance();
        mHandler = new Handler();
        //databse
        mDatabase = FirebaseDatabase.getInstance().getReference();
        drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        navigationView = (NavigationView) findViewById(R.id.nav_view);

        // Navigation view header
        navHeader = navigationView.getHeaderView(0);
        txtName = (TextView) navHeader.findViewById(R.id.name);
        txtWebsite = (TextView) navHeader.findViewById(R.id.job);
     //   imgNavHeaderBg = (ImageView) navHeader.findViewById(R.id.img_header_bg);
        imgProfile = (ImageView) navHeader.findViewById(R.id.img_profile);

        if(auth.getCurrentUser()!=null) {
            if(auth.getCurrentUser().getDisplayName()!=null) {
                txtName.setText(auth.getCurrentUser().getDisplayName().toString().trim());
            }
            txtWebsite.setText(auth.getCurrentUser().getEmail().toString().trim());

        }
        profil=(TextView) navHeader.findViewById(R.id.Profil);
        profil.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent insc = new Intent(MenuActivity.this,ProfilActivity.class);
                startActivity(insc);

            }
        });
        // load toolbar titles from string resources
        activityTitles = getResources().getStringArray(R.array.nav_item_activity_titles);


        // load nav menu header data
        //loadNavHeader();


        navigationView.getMenu().getItem(4).setActionView(R.layout.menu_dot);
        // initializing navigation menu
        setUpNavigationView();

        if (savedInstanceState == null) {
            navItemIndex = 0;
            CURRENT_TAG = TAG_HOME;
            loadHomeFragment();
        }
    }

    /***
     * Load navigation menu header information
     * like background image, profile image
     * name, website, notifications action view (dot)
     */
    private void loadNavHeader() {
        // name, email
        // loading header background image
      /*  Glide.with(this).load(urlNavHeaderBg)
                .crossFade()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(imgNavHeaderBg);

         Loading profile image
        Glide.with(this).load(urlProfileImg)
                .crossFade()
                .thumbnail(0.5f)
                .bitmapTransform(new CircleTransform(this))
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(imgProfile);*/

        // showing dot next to notifications label
     //   navigationView.getMenu().getItem(4).setActionView(R.layout.menu_dot);
    }

    /***
     * Returns respected fragment that user
     * selected from navigation menu
     */
    private void loadHomeFragment() {
        // selecting appropriate nav menu item
        selectNavMenu();

        // set toolbar title
        setToolbarTitle();

        // if user select the current navigation menu again, don't do anything
        // just close the navigation drawer
        if (getSupportFragmentManager().findFragmentByTag(CURRENT_TAG) != null) {
            drawer.closeDrawers();

            return;
        }

        // Sometimes, when fragment has huge data, screen seems hanging
        // when switching between navigation menus
        // So using runnable, the fragment is loaded with cross fade effect
        // This effect can be seen in GMail app
        Runnable mPendingRunnable = new Runnable() {
            @Override
            public void run() {
                // update the menu content by replacing fragments
                Fragment fragment = getHomeFragment();
                FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                fragmentTransaction.setCustomAnimations(android.R.anim.fade_in,
                        android.R.anim.fade_out);
                fragmentTransaction.replace(R.id.frame, fragment, CURRENT_TAG);
                fragmentTransaction.commitAllowingStateLoss();
            }
        };

        // If mPendingRunnable is not null, then add to the message queue
        if (mPendingRunnable != null) {
            mHandler.post(mPendingRunnable);
        }



        //Closing drawer on item click
        drawer.closeDrawers();

        // refresh toolbar menu
        invalidateOptionsMenu();
    }

    private Fragment getHomeFragment() {
        switch (navItemIndex) {
            case 0:
                // home
                HomeFragment homeFragment = new HomeFragment();
                return homeFragment;
            case 1:
                // Contact
                ContactFragment contactFragment = new ContactFragment();
                return contactFragment;
            case 2:
                // Article
                ArticleFragment articleFragment = new ArticleFragment();
                return articleFragment;
            case 3:
                //  recherche
                RechercheFragment rechercheFragment = new RechercheFragment();
                return rechercheFragment;

            case 4:
                // notifications fragment
                NotificationsFragment notificationsFragment = new NotificationsFragment();
                return notificationsFragment;


            default:
                return new HomeFragment();
        }
    }

    private void setToolbarTitle() {
        getSupportActionBar().setTitle(activityTitles[navItemIndex]);
    }

    private void selectNavMenu() {
        navigationView.getMenu().getItem(navItemIndex).setChecked(true);
    }

    private void setUpNavigationView() {
        //Setting Navigation View Item Selected Listener to handle the item click of the navigation menu
        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

            // This method will trigger on item Click of navigation menu
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {

                //Check to see which item was being clicked and perform appropriate action
                switch (menuItem.getItemId()) {
                    //Replacing the menu content with ContentFragment Which is our Inbox View;
                    case R.id.home:
                        navItemIndex = 0;
                        CURRENT_TAG = TAG_HOME;

                        break;
                    case R.id.nav_contact:
                        navItemIndex = 1;
                        CURRENT_TAG = TAG_PHOTOS;
                        break;
                    case R.id.nav_article:
                        navItemIndex = 2;
                        CURRENT_TAG = TAG_MOVIES;
                        break;

                    case R.id.nav_recherche:
                        navItemIndex = 3;
                        CURRENT_TAG = TAG_SETTINGS;
                        break;
                    case R.id.nav_notifications:
                        navItemIndex = 4;
                        CURRENT_TAG = TAG_NOTIFICATIONS;
                        break;
                    default:
                        navItemIndex = 0;
                }

                //Checking if the item is in checked state or not, if not make it in checked state
                if (menuItem.isChecked()) {
                    menuItem.setChecked(false);
                } else {
                    menuItem.setChecked(true);
                }
                menuItem.setChecked(true);

                loadHomeFragment();

                return true;
            }
        });


        ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.openDrawer, R.string.closeDrawer) {

            @Override
            public void onDrawerClosed(View drawerView) {
                // Code here will be triggered once the drawer closes as we dont want anything to happen so we leave this blank
                super.onDrawerClosed(drawerView);
            }

            @Override
            public void onDrawerOpened(View drawerView) {
                // Code here will be triggered once the drawer open as we dont want anything to happen so we leave this blank
                super.onDrawerOpened(drawerView);
            }
        };

        //Setting the actionbarToggle to drawer layout
        drawer.setDrawerListener(actionBarDrawerToggle);

        //calling sync state is necessary or else your hamburger icon wont show up
        actionBarDrawerToggle.syncState();
    }

    @Override
    public void onBackPressed() {
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawers();
            return;
        }

        // This code loads home fragment when back key is pressed
        // when user is in other fragment than home
        if (shouldLoadHomeFragOnBackPress) {
            // checking if user is on other navigation menu
            // rather than home
            if (navItemIndex != 0) {
                navItemIndex = 0;
                CURRENT_TAG = TAG_HOME;
                loadHomeFragment();
                return;
            }
        }

        super.onBackPressed();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.

        // show menu only when home fragment is selected
        if (navItemIndex == 0) {
            getMenuInflater().inflate(R.menu.menu, menu);
        }

        // when fragment is notifications, load the menu created for notifications
        if (navItemIndex == 4) {
            getMenuInflater().inflate(R.menu.notifications, menu);
        }
        return true;
    }

    @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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_logout) {
            Toast.makeText(getApplicationContext(), "vous allez vous déconnecter", Toast.LENGTH_LONG).show();
            auth.signOut();
            finish();
            startActivity(new Intent(getApplicationContext(),LoginActivity.class));
          //  return true;
        }

        // user is in notifications fragment
        // and selected 'Mark all as Read'
        if (id == R.id.action_mark_all_read) {
            Toast.makeText(getApplicationContext(), " Marquer comme lue", Toast.LENGTH_LONG).show();
        }

        // user is in notifications fragment
        // and selected 'Clear All'
        if (id == R.id.action_clear_notifications) {
            Toast.makeText(getApplicationContext(), "Supprimer toute les notifications", Toast.LENGTH_LONG).show();
        }

        return super.onOptionsItemSelected(item);
    }



}

推荐答案

根据Java文档

您可以在此处查找更多，而且我会建议您这样做:

You can look here for more and also I would suggest you do to it smth like this:

@Override
        public boolean onNavigationItemSelected(MenuItem item) {
            int id = item.getItemId();
            Fragment fragment = null;
            if (id == R.id.home) {
           fragment = new HomeFragment();
            } else if (id == R.id.nav_contact) {
           fragment = new ContactFragment();
            } else if (id == R.id.nav_article) {
               fragment = new ArticleFragment();
            } else if (id == R.id.nav_notifications) {
             fragment= new NotificationsFragment();
            }  else if (id == R.id.research) {
             fragment= new RechercheFragment();
            }

            if (fragment != null) {

                myFragmentTransaction = fragmentManager.beginTransaction();
                myFragmentTransaction.replace(R.id.frame, fragment);
                myFragmentTransaction.addToBackStack(null);
                myFragmentTransaction.commit();

            }

                item.setChecked(true);
            setTitle(item.getTitle());

            DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
            drawer.closeDrawer(GravityCompat.START);

            return super.onOptionsItemSelected(item);

        }
    }

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