我知道这个问题已经讨论过了，但我在片段之间实现导航时遇到了困难。我想使用后退按钮返回上一个片段或主要活动。现在，后退按钮仅关闭导航抽屉或退出应用程序。我知道我应该使用addToBackStack，但我不确切知道如何。
我的主要活动：
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
setTitle("infoGmina");
ImageView gminaImageView = (ImageView) findViewById(R.id.gminaImageView);
ImageView weatherImageView = (ImageView) findViewById(R.id.weatherImageView);
ImageView partlyCloudImageView = (ImageView) findViewById(R.id.partlyCloudImageView);
partlyCloudImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
PogodaFragment fragment = new PogodaFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.replacableConstraintLayout, fragment);
transaction.commit();
}
});
weatherImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
WeatherFragment fragment = new WeatherFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.replacableConstraintLayout, fragment);
transaction.commit();
}
});
gminaImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
AnnouncementListFragment fragment = new AnnouncementListFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.replacableConstraintLayout, fragment);
transaction.commit();
}
});
ParseAnalytics.trackAppOpenedInBackground(getIntent());
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
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);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_gmina) {
AnnouncementListFragment listFragment = new AnnouncementListFragment();
FragmentManager manager = getFragmentManager();
manager.beginTransaction().replace(R.id.replacableConstraintLayout, listFragment).commit();
setTitle("Gmina");
} else if (id == R.id.nav_restauracja) {
} else if (id == R.id.nav_sklep) {
} else if (id == R.id.nav_weather) {
WeatherFragment weatherFragment = new WeatherFragment();
FragmentManager manager = getFragmentManager();
manager.beginTransaction().replace(R.id.replacableConstraintLayout, weatherFragment).commit();
setTitle("Jakość powietrza");
} else if (id == R.id.nav_pogoda) {
PogodaFragment pogodaFragment = new PogodaFragment();
FragmentManager manager = getFragmentManager();
manager.beginTransaction().replace(R.id.replacableConstraintLayout, pogodaFragment).commit();
setTitle("Pogoda");
} else if (id == R.id.nav_onas) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}