当我的应用程序打开时，首先显示了主屏幕。在主屏幕上，我有NavigationDrawer，在按HamburgerIcon之后打开。主页Activity我需要在 Toolbar上显示回到按钮才能到达以前的片段。但是每次显示汉堡偶像。这是用于在XML中设置Toolbar的代码
<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:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/drawerLayout"
tools:context="biz.fyra.myApp.ActivityTwo">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#ccc"
android:minHeight="?attr/actionBarSize">
<ImageView
android:id="@+id/tooImage"
android:src="@drawable/latest"
android:layout_width="match_parent"
android:layout_gravity="center_horizontal"
android:layout_height="40dp" />
</android.support.v7.widget.Toolbar>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/frame">
</FrameLayout>
</LinearLayout>
<android.support.design.widget.NavigationView
android:layout_width="300dp"
android:layout_height="match_parent"
android:layout_gravity="start"
app:headerLayout="@layout/nav_header"
android:id="@+id/navigationView"
app:menu="@menu/actionmenu"
android:background="@android:color/white">
</android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>
如何实现这一目标？
如果我理解正确，则使用一个片段更换的活动。因此，看着您会有这样的东西：
重要：活动主题应扩展主题。
活动：
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;
private Toolbar toolbar;
private ActionBarDrawerToggle toggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
drawer = findViewById(R.id.drawer);
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
toggle = new ActionBarDrawerToggle(
this,
drawer,
toolbar,
R.string.navigation_drawer_open,
R.string.navigation_drawer_close
);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
// First creation
if (savedInstanceState == null)
showFragment(StartFragment.newInstance());
}
/**
* Using in Base Fragment
*/
protected ActionBarDrawerToggle getToggle() {
return toggle;
}
@Override
public void onBackPressed() {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.frame);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else if (fragment instanceof OnBackPressedListener) {
((OnBackPressedListener) fragment).onBackPressed();
} else {
super.onBackPressed();
}
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
drawer.closeDrawer(GravityCompat.START);
switch (item.getItemId()) {
case R.id.start: {
showFragment(StartFragment.newInstance());
break;
}
case R.id.orders: {
showFragment(OrdersFragment.newInstance());
break;
}
case R.id.category: {
showFragment(CategoryFragment.newInstance());
break;
}
case R.id.calendar: {
showFragment(CalendarFragment.newInstance());
break;
}
case R.id.settings: {
showFragment(SettingsFragment.newInstance());
break;
}
case R.id.about: {
showFragment(AboutFragment.newInstance());
break;
}
return true;
}
private void showFragment(Fragment fragment) {
getSupportFragmentManager().beginTransaction().replace(R.id.frame, fragment).commit();
}
}
用于发送从活动到片段的背压事件的接口：
public interface OnBackPressedListener {
void onBackPressed();
}
和抽象基础片段，您应该扩展并实现方法：
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.widget.Toolbar;
import ...
/**
* Abstract fragment with FAB button, Toolbar and 2 interfaces:
OnClick, OnBackPress
*
*/
public abstract class BaseFragment extends Fragment implements
View.OnClickListener, OnBackPressedListener {
protected FloatingActionButton fab;
protected Toolbar toolbar;
protected ActionBar actionBar;
protected ActionBarDrawerToggle toggle;
protected DrawerLayout drawer;
protected boolean mToolBarNavigationListenerIsRegistered = false;
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
fab = ((MainActivity)getActivity()).findViewById(R.id.fab);
toolbar = ((MainActivity) getActivity()).findViewById(R.id.toolbar);
actionBar = ((MainActivity) getActivity()).getSupportActionBar();
drawer = ((MainActivity) getActivity()).findViewById(R.id.drawer_layout);
toggle = ((MainActivity) getActivity()).getToggle();
fab.setOnClickListener(this);
}
/**
* Simplify fragment replacing in child fragments
*/
protected void replaceFragment(@NonNull Fragment fragment) {
FragmentManager fm = getActivity().getSupportFragmentManager();
fm.beginTransaction().replace(R.id.container, fragment).commit();
}
// hide FAB button
protected void hideFab() {
fab.hide();
}
//show FAB button
protected void showFab() {
fab.show();
}
/**
* Shows Home button as Back button
* Took from here {@link}https://stackoverflow.com/a/36677279/9381524
* <p>
* 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 disable first, then enable - VERY VERY IMPORTANT!!!
*
* @param show = true to show <showHomeAsUp> or show = false to show <Hamburger> button
*/
protected void showBackButton(boolean show) {
if (show) {
// Remove hamburger
toggle.setDrawerIndicatorEnabled(false);
// Show back button
actionBar.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.
if (!mToolBarNavigationListenerIsRegistered) {
toggle.setToolbarNavigationClickListener(v -> onBackPressed());
mToolBarNavigationListenerIsRegistered = true;
}
} else {
// Remove back button
actionBar.setDisplayHomeAsUpEnabled(false);
// Show hamburger
toggle.setDrawerIndicatorEnabled(true);
// Remove the/any drawer toggle listener
toggle.setToolbarNavigationClickListener(null);
mToolBarNavigationListenerIsRegistered = false;
}
// 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.
}
/**
* Simplify setTitle in child fragments
*/
protected void setTitle(int resId) {
getActivity().setTitle(getResources().getString(resId));
}
//
@Override
public abstract void onClick(View v);
// Handles BackPress events from MainActivity
@Override
public abstract void onBackPressed();
}
所有带有主攻击中使用的背面按钮的片段应从此底层范围内延伸。
您可以尝试
之类的东西 @Override
protected void onCreate(Bundle savedInstanceState)
{ super.onCreate(savedInstanceState);
[...]
if (getSupportActionBar() != null)
{ getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
}
[...]
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{ if (getSupportFragmentManager().getBackStackEntryCount() > 0)
{ switch (item.getItemId())
{ case android.R.id.home:
onBackPressed();
return true;
}
}
[...]
}