Android 底部导航

Question

我一直在我的应用程序中实现底部导航栏，问题是无论哪个 activity 我在仪表板上的图标都是突出显示的。我怎样才能得到它，所以我所在的 activity 是突出显示的那个？

public class Dashboard extends AppCompatActivity
    implements View.OnClickListener
{

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener()
{
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.navigation_request:
                Intent r = new Intent(Dashboard.this, Request.class);
                startActivity(r);
                finish();
                break;
            case R.id.navigation_settings:
                Intent s = new Intent(Dashboard.this, AppSettings.class);
                startActivity(s);
                finish();
                break;
        }
        return false;
    }
};

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dashboard);

BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}

这是我的XML菜单文件

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
    android:id="@+id/navigation_home"
    android:icon="@drawable/ic_home_black_24dp"
    android:title="@string/title_home" />

<item
    android:id="@+id/navigation_request"
    android:icon="@drawable/ic_request_icon"
    android:title="@string/title_request" />

<item
    android:id="@+id/navigation_settings"
    android:icon="@drawable/ic_icon_settings"
    android:title="@string/title_settings" />

</menu>

这是我在 activity_dashboard

中使用导航的方式

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">

<FrameLayout
    android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1">

<!-- ONLY TEXTVIEWS ARE HERE -->

</FrameLayout>



<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom"
    android:background="?android:attr/windowBackground"
    app:menu="@menu/navigation" />

</LinearLayout>

Answer 1

只需使用方法 setSelectedItemId(int id) 即可将项目标记为选中状态，就好像它已被点击一样。

像这样：

BottomNavigationView bottomNavigationView;
bottomNavigationView = (BottomNavigationView) 
findViewById(R.id.bottomNavigationView);
bottomNavigationView.setSelectedItemId(R.id.my_menu_item_id);

Answer 2

不推荐使用许多不同的 Activity 实例来复制 BottomNavigationView 及其相关代码（如 OnNavigationItemSelectedListener 等）。相反，您通常会使用一个 Activity 托管 BottomNavigationView 以及多个 Fragment 实例，当用户与 .replace()d 进入您的内容区域时=12=].

话虽这么说，让我们看看能否解决您的问题。

这个谜题有两个部分。第一个很简单：您必须指出应该选择 BottomNavigationView 中的哪个项目。这可以通过调用 setSelectedItemId() 来实现。将类似的内容添加到您的 onCreate() 方法中。

    navigation.setSelectedItemId(R.id.navigation_settings);

第二个有点复杂。当您调用 setSelectedItemId() 时，系统的行为就像用户点击了该项目一样。也就是说，你的OnNavigationItemSelectedListener会被触发。

看着你发布的监听器，我注意到你总是 return false。如果您查看 onNavigationItemSelected() 的文档，您会发现

Returns: true to display the item as the selected item and false if the item should not be selected

因此，如果不将您的侦听器也更改为 return true。

，那么对 setSelectedItemId() 的调用将无法正常工作

如果您将 调用放在 之前 setOnNavigationItemSelectedListener() 调用，您仍然可以仅通过 setSelectedItemId() 调用来解决问题，但这只是掩盖了问题.在您希望点击的项目显示为选中状态的情况下，最好将您的侦听器固定为 return true。

Answer 3

步骤 - 1 将以下代码放入应用级别 Build.gradle

implementation 'androidx.navigation:navigation-fragment:2.3.0'

implementation 'com.google.android.material:material:1.2.1'

implementation 'androidx.navigation:navigation-ui:2.3.0'

步骤 - 2 将下面的代码放入 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_nav_menu" />

    <fragment
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@id/nav_view"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

步骤 - 3 将下面的代码放入 menu/bottom_nav_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_home_black_24dp"
        android:title="@string/title_home" />
    <item
        android:id="@+id/navigation_dashboard"
        android:icon="@drawable/ic_dashboard_black_24dp"
        android:title="Orders" />
    <item
        android:id="@+id/navigation_notifications"
        android:icon="@drawable/ic_notifications_black_24dp"
        android:title="Services" />
    <item
        android:id="@+id/navigation_account"
        android:icon="@drawable/ic_notifications_black_24dp"
        android:title="Account" />
</menu>

步骤 - 4 将下面的代码放入 MainActivity.java

import android.os.Bundle;
import android.view.MenuItem;

import com.example.bottomnavigationdemo.ui.account.AccountFragment;
import com.example.bottomnavigationdemo.ui.dashboard.DashboardFragment;
import com.example.bottomnavigationdemo.ui.home.HomeFragment;
import com.example.bottomnavigationdemo.ui.notifications.NotificationsFragment;
import com.google.android.material.bottomnavigation.BottomNavigationView;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentTransaction;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

public class MainActivity extends AppCompatActivity {

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

        BottomNavigationView navView = findViewById(R.id.nav_view);
        navView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()) {
                    case R.id.navigation_home:
                        Fragment fragment = new HomeFragment();
                        getSupportFragmentManager().beginTransaction()
                                .replace(R.id.nav_host_fragment, fragment, fragment.getClass().getSimpleName())
                                .commit();
                        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                        transaction.replace(R.id.nav_host_fragment, fragment, fragment.getClass().getSimpleName());
                        transaction.commit();
                        return true;

                    case R.id.navigation_dashboard:
                        Fragment fragment2 = new DashboardFragment();
                        transaction = getSupportFragmentManager().beginTransaction();
                        transaction.replace(R.id.nav_host_fragment, fragment2, fragment2.getClass().getSimpleName());

                        transaction.commit();
                        return true;

                    case R.id.navigation_notifications:
                        Fragment fragment3 = new NotificationsFragment();
                        transaction = getSupportFragmentManager().beginTransaction();
                        transaction.replace(R.id.nav_host_fragment, fragment3, fragment3.getClass().getSimpleName());
                        transaction.commit();
                        return true;

                    case R.id.navigation_account:
                        Fragment fragment4 = new AccountFragment();
                        transaction = getSupportFragmentManager().beginTransaction();
                        transaction.replace(R.id.nav_host_fragment, fragment4, fragment4.getClass().getSimpleName());
                        transaction.commit();
                        return true;
                }
                return true;
            }

        });
    }

}

步骤 - 5 将下面的代码放入 HomeFragment.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;

import com.example.bottomnavigationdemo.R;
import com.example.bottomnavigationdemo.ui.dashboard.DashboardFragment;

public class HomeFragment extends Fragment {

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_home, container, false);
        return root;
    }
}

Android 底部导航

Android Bottom Navigation

android

bottomnavigationview