我创建了一个使用一个活动（导航抽屉）和一个片段的应用程序。但是我无法使用工具栏的后退按钮从片段导航回到主要活动。硬件后退按钮可以完美工作。我知道我需要重写onOptionsItemSelected，捕获android.R.id.home，检查是否在堆栈中有东西，然后将其弹出。更改片段后，“汉堡”按钮变为“后退箭头”，但是当我单击它时，永远不会调用覆盖的方法“ onOptionsItemSelected”，而是单击后退按钮，NavigationDrawer菜单打开。
注意：我已经在StackOverflow中引用了许多答案，包括THIS，它与我的问题相同，但对我不起作用。我已经为此工作了一个星期，非常感谢您的帮助。请不要拒绝投票。 1
这是我的代码
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
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);
}
public void init() {
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
mDrawerLayout.addDrawerListener(mDrawerToggle);
mDrawerToggle.syncState();
getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
@Override
public void onBackStackChanged() {
Log.d("Backstack Count", String.valueOf(getSupportFragmentManager().getBackStackEntryCount()));
if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
showUpButton(false);
} else {
showUpButton(true);
}
}
});
}
private void showUpButton(boolean show) {
// To keep states of ActionBar and ActionBarDrawerToggle synchronized,
// when you enable on one, you disable on the other.
// And as you may notice, the order for this operation is disabled first, then enable - VERY VERY IMPORTANT.
if (show) {
// Remove hamburger
mDrawerToggle.setDrawerIndicatorEnabled(false);
// Show back button
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// when DrawerToggle is disabled i.e. setDrawerIndicatorEnabled(false), navigation icon
// clicks are disabled i.e. the UP button will not work.
// We need to add a listener, as in below, so DrawerToggle will forward
// click events to this listener.
} else {
// Show hamburger
mDrawerToggle.setDrawerIndicatorEnabled(true);
invalidateOptionsMenu();
}
// So, one may think "Hmm why not simplify to:
// .....
// getSupportActionBar().setDisplayHomeAsUpEnabled(enable);
// mDrawer.setDrawerIndicatorEnabled(!enable);
// ......
// To re-iterate, the order in which you enable and disable views IS important #dontSimplify.
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// super.onCreateOptionsMenu(menu);
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// onBackPressed();
if (getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
}
return true;
}
// return false;
// return super.onOptionsItemSelected(item);
return true;
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
displayImportFrag();
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
public void displayImportFrag() {
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
Log.d("called", "new frag");
ImportFragment importFragment = new ImportFragment();
ft.add(R.id.fragment_frame, importFragment).addToBackStack(null).commit();
}
}
ImportFragment.java
public class ImportFragment extends Fragment {
View rootView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.import_fragment, container, false);
return rootView;
}
}