android - fragment 中的抽屉导航后退按钮

Question

我开始创建使用一个 Activity (抽屉导航)和许多 fragment 的应用程序。 但是我无法使用工具栏后退按钮从 fragment 中导航回来。硬件后退按钮完美运行。我知道我需要覆盖 onOptionsItemSelected，捕获 android.R.id.home，检查返回堆栈中是否有内容，然后将其弹出。更改 fragment 后，“汉堡”按钮变为“后退箭头”，但是当我点击它时 onOptionsItemSelected 从未触发，只是打开了 NavigationDrawer 菜单。

这里是 Activity 的代码:

public class NavDrawerActivity extends AppCompatActivity implements ... {

    NavigationView navigationView;
    BottomNavigationView bottomNavigationView;
    ActionBarDrawerToggle toggle;
    FragmentManager fragmentManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_nav_drawer);

        fragmentManager = getSupportFragmentManager();

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        final DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);

        toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);

        drawer.addDrawerListener(toggle);

        toggle.syncState();

        // Set back button
        fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
            @Override
            public void onBackStackChanged() {
                if (fragmentManager.getBackStackEntryCount() > 0) {
                    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
                } else {
                    getSupportActionBar().setDisplayHomeAsUpEnabled(false);
                    toggle.syncState();
                }
            }
        });

        // Load default fragment
        changeFragment(new HomeFragment(), false);

        navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        View headerLayout = navigationView.getHeaderView(0);

        bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener(this);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                Toast.makeText(this, "Back pressed", Toast.LENGTH_SHORT)
                        .show();
                onBackPressed();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);

        if (drawer.isDrawerOpen(GravityCompat.START))
            drawer.closeDrawer(GravityCompat.START);

        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else if (fragmentManager.getBackStackEntryCount() > 0) {
            fragmentManager.popBackStack();
        } else {
            super.onBackPressed();
        }
    }

    private void changeFragment(Fragment fm, boolean addToBackStack)
    {
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.replace(R.id.frame_layout_content, fm);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        if (addToBackStack) ft.addToBackStack(null);
        ft.commit();
    }

}

以及我如何更改(替换)HomeFragment 中的 fragment :

IndexDetailFragment newFragment = new IndexDetailFragment();
Bundle args = new Bundle();

args.putString(IndexDetailFragment.ARG_INDEX_ID, id);

newFragment.setArguments(args);

FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left);
transaction.replace(R.id.frame_layout_content, newFragment);
transaction.addToBackStack(null);

transaction.commit();

Answer 1

setSupportActionBar(toolbar) 之后的 toolbar 上的

setNavigationOnClick() :

setSupportActionBar(toolbar);
toolbar.setNavigationOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                Toast.makeText(getActivity(), "Back clicked!",     
                Toast.LENGTH_SHORT).show();
            }
        });

我做了一个小程序供引用

第一个 fragment

 public class FirstFragment extends Fragment {


public FirstFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_first, container, false);
}

}

第二个 fragment

public class SecondFragment extends Fragment {


public SecondFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_second, container, false);
}

}

主要 Activity

public class MainActivity extends AppCompatActivity {
private Toolbar mToolbar;
private ActionBarDrawerToggle drawerToggle;
private DrawerLayout mDrawerLayout;
private String TAG = "MainActivity";
private FragmentManager mFragmentManager;
private NavigationView mNavigationView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mToolbar = (Toolbar) findViewById(R.id.toolbar);
    if (mToolbar != null) {
        setSupportActionBar(mToolbar);
    }
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer);
    drawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.drawer_open, R.string.drawer_close) {
        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
        }

        @Override
        public void onDrawerClosed(View drawerView) {
            super.onDrawerClosed(drawerView);
        }
    };
    mDrawerLayout.addDrawerListener(drawerToggle);
    mNavigationView = findViewById(R.id.navigation);
    mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.first:
                    changeFragment(new FirstFragment(), true);
                    return true;
                case R.id.second:
                    changeFragment(new SecondFragment(), true);
                    return true;
            }
            return false;
        }
    });
    mFragmentManager = getSupportFragmentManager();
    changeFragment(new FirstFragment(), true);
}

@Override
protected void onPostCreate(@Nullable Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    if (drawerToggle != null) {
        drawerToggle.syncState();
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home) {
        Log.i(TAG, "onOptionsItemSelected: Home Button Clicked");
        if (mDrawerLayout.isDrawerOpen(Gravity.START)) {
            mDrawerLayout.closeDrawer(Gravity.START);
        } else {
            mDrawerLayout.openDrawer(Gravity.START);
        }
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onBackPressed() {
    if (mDrawerLayout.isDrawerOpen(Gravity.START)) {
        mDrawerLayout.closeDrawer(Gravity.START);
    }
    if (mDrawerLayout.isDrawerOpen(Gravity.START)) {
        mDrawerLayout.closeDrawer(Gravity.START);
    } else if (mFragmentManager.getBackStackEntryCount() > 0) {
        mFragmentManager.popBackStack();
    } else {
        super.onBackPressed();
    }
}

private void changeFragment(Fragment fragment, boolean needToAddBackstack) {
    FragmentTransaction mFragmentTransaction = mFragmentManager.beginTransaction();
    mFragmentTransaction.replace(R.id.FRAME_CONTENT, fragment);
    mFragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
    if (needToAddBackstack)
        mFragmentTransaction.addToBackStack(null);
    mFragmentTransaction.commit();
}
}

Activity 主线

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
            

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="@dimen/abc_action_bar_default_height_material"
        android:background="@color/colorPrimaryDark"
        />

    <FrameLayout
        android:id="@+id/FRAME_CONTENT"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="@dimen/abc_action_bar_default_height_material" />
</FrameLayout>

<android.support.design.widget.NavigationView
    android:id="@+id/navigation"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:layout_marginTop="@dimen/abc_action_bar_default_height_material"
    app:menu="@menu/drawermenu" />
  </android.support.v4.widget.DrawerLayout>