Java 我需要在单击底部导航栏中的菜单时启动新活动。如何实施。请帮帮我。提前谢谢

让我在这里添加代码 请通读代码并帮助我解决问题 这是我的主要活动

package com.learning.easyenglish;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.material.bottomnavigation.BottomNavigationView;

public class mainpage extends AppCompatActivity {

    private BottomNavigationView bottomNavigationView;

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

        bottomNavigationView = findViewById(R.id.navigationbar);

        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener(
        ) {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                Toast.makeText(mainpage.this, ""+item.getTitle(), Toast.LENGTH_SHORT).show();
                return true;
            }
        });
    }
}

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".mainpage">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/navigationbar"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:background="#EEEEEE"
        app:menu="@menu/drawer_menu"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

这是我的活动xml文件 与主要活动相关联

package com.learning.easyenglish;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.material.bottomnavigation.BottomNavigationView;

public class mainpage extends AppCompatActivity {

    private BottomNavigationView bottomNavigationView;

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

        bottomNavigationView = findViewById(R.id.navigationbar);

        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener(
        ) {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                Toast.makeText(mainpage.this, ""+item.getTitle(), Toast.LENGTH_SHORT).show();
                return true;
            }
        });
    }
}

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".mainpage">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/navigationbar"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:background="#EEEEEE"
        app:menu="@menu/drawer_menu"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

这是抽屉菜单

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:title="Profile"
        android:icon="@drawable/ic_baseline_person_24"
        />

    <item
        android:title="Home"
        android:icon="@drawable/home"
        />

    <item
        android:title="Help"
        android:icon="@android:drawable/ic_menu_help"
        />
</menu>

单击菜单时，我需要它来启动新活动。 `我正试图通过单击“打开新活动”