我创建了一个主活动,在其中设置了一个片段容器,我在导航菜单选项选择时替换了许多片段。它运行良好,但问题是:
- 当我两次点击导航项目时,会打开两个相同的片段,我必须按两次返回按钮才能返回。
- 当所有片段在按下后被销毁后,我看到了一个空白页面(可能是主活动页面)。
layout_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_activity_page"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/pageBackgroundColor"
tools:context="co.sd.app.MainActivity">
<RelativeLayout
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="@+id/side_nav_drawer"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:padding="0sp"
app:menu="@menu/side_navigation_menu" />
</android.support.v4.widget.DrawerLayout>
MainActivity.java
public class MainActivity extends AppCompatActivity {
private Bundle bundle;
private SessionManager session;
private DrawerLayout drawerLayout;
private ActionBarDrawerToggle actionBarToggle;
private TextView cartItemCountDisplay;
private NavigationView sideNavView;
private Menu sideNavViewMenu;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
drawerLayout = (DrawerLayout) findViewById(R.id.main_activity_page);
actionBarToggle = new ActionBarDrawerToggle(this, drawerLayout, R.string.OPEN, R.string.CLOSE);
drawerLayout.addDrawerListener(actionBarToggle);
actionBarToggle.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
bundle = new Bundle();
sideNavView = ((NavigationView) findViewById(R.id.side_nav_drawer));
sideNavViewMenu = sideNavView.getMenu();
//To Display Home Fragment On Page Load
displaySelectedItemResult(sideNavViewMenu.findItem(R.id.nav_home));
//To Adjust Login or Logout option in side navigation menu
if (session.isUserLoggedIn()) {
sideNavViewMenu.findItem(R.id.nav_login).setVisible(false);
sideNavViewMenu.findItem(R.id.nav_logout).setVisible(true);
} else {
sideNavViewMenu.findItem(R.id.nav_login).setVisible(true);
sideNavViewMenu.findItem(R.id.nav_logout).setVisible(false);
}
//Operation on side navigation item click
sideNavView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem item) {
displaySelectedItemResult(item);
//navDrawerLayout.closeDrawers();
return true;
}
});
}
private void displaySelectedItemResult(MenuItem item) {
sideNavViewMenu.findItem(R.id.nav_home).setChecked(false);
sideNavViewMenu.findItem(R.id.nav_contactUs).setChecked(false);
sideNavViewMenu.findItem(R.id.nav_aboutUs).setChecked(false);
sideNavViewMenu.findItem(R.id.nav_login).setChecked(false);
sideNavViewMenu.findItem(R.id.nav_logout).setChecked(false);
Fragment fragment;
switch (item.getItemId()) {
case R.id.nav_user:
if (session.isUserLoggedIn()) {
item.setTitle(session.getUserDetails().get(SessionManager.KEY_NAME));
} else {
item.setTitle("Login First!");
}
drawerLayout.closeDrawer(GravityCompat.START);
break;
case R.id.nav_home:
fragment = new HomeFragment();
if (fragment != null) {
callNavMenuItemsFragment(fragment, "FRAG_HOME");
}
item.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
break;
case R.id.nav_contactUs:
fragment = new ContactUsFragment();
if (fragment != null) {
callNavMenuItemsFragment(fragment, "FRAG_CONTACT_US");
}
item.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
break;
case R.id.nav_aboutUs:
fragment = new AboutUsFragment();
if (fragment != null) {
callNavMenuItemsFragment(fragment, "FRAG_ABOUT_US");
}
item.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
break;
case R.id.nav_login:
new UserAuthentication(MainActivity.this, session).loginAndSignupDialog();
sideNavViewMenu.findItem(R.id.nav_login).setVisible(false);
sideNavViewMenu.findItem(R.id.nav_logout).setVisible(true);
item.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
break;
case R.id.nav_logout:
session.logoutUser();
sideNavViewMenu.findItem(R.id.nav_login).setVisible(true);
sideNavViewMenu.findItem(R.id.nav_logout).setVisible(false);
item.setChecked(true);
drawerLayout.closeDrawer(GravityCompat.START);
break;
default:
}
}
private FragmentTransaction callNavMenuItemsFragment(final Fragment fragment, final String fragmentTag) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.addToBackStack(null);
//if (!ACTIVE_FRAGMENT_ID.equals(String.valueOf(fragment.getId()))) {
if (!activeFragmentIDsList.contains(String.valueOf(fragment.getId()))) {
ft.replace(R.id.fragment_container, fragment, fragmentTag);
activeFragmentIDsList.add(String.valueOf(fragment.getId()));
}
ft.commit();
return ft;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (actionBarToggle.onOptionsItemSelected(item)) {
return true;
}
switch (item.getItemId()) {
case android.R.id.home:
finish();
break;
case R.id.cart:
if (session.isUserLoggedIn()) {
startActivity(new Intent(MainActivity.this, CartActivity.class));
} else if (new UserAuthentication(MainActivity.this, session).loginAndSignupDialog()) {
startActivity(new Intent(MainActivity.this, CartActivity.class));
}
break;
default:
}
return super.onOptionsItemSelected(item);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.actionbar_menu, menu);
final MenuItem menuItem = menu.findItem(R.id.cart);
MenuItemCompat.setActionView(menuItem, R.layout.cart_badge_layout);
final View actionView = MenuItemCompat.getActionView(menuItem);
cartItemCountDisplay = actionView.findViewById(R.id.cart_badge);
setupBadge();
actionView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setupBadge();
onOptionsItemSelected(menuItem);
}
});
return super.onCreateOptionsMenu(menu);
}
private void setupBadge() {
int itemCount = (((AppGlobalContent) getApplicationContext()).getSelectedItemsCount());
if (cartItemCountDisplay != null) {
if (itemCount == 0) {
if (cartItemCountDisplay.getVisibility() != View.GONE) {
cartItemCountDisplay.setVisibility(View.GONE);
}
} else {
cartItemCountDisplay.setText(String.valueOf(Math.min(itemCount, 99)));
if (cartItemCountDisplay.getVisibility() != View.VISIBLE) {
cartItemCountDisplay.setVisibility(View.VISIBLE);
}
}
}
}
@Override
public void onBackPressed() {
if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
drawerLayout.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
}
请在这个问题上给我建议。