get XML's id from not linked activity-CodePudding

Want to do

I want to get android:id = "@ id/drawer_layout2" at activity which is not linked with SetContentView because I want to open navigation? DrawerLayout? with a button. I already know that drawer.OpenDrawer(GravityCompat.Start) open it but drawer is null.

Relation

MainActivity.cs - activity_main.xml

NaviDrawer.cs - drawer.xml

Error Message

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Code

MainActivity

public class MainActivity : AppCompatActivity, NavigationView.IOnNavigationItemSelectedListener, TabLayout.IOnTabSelectedListener
{
    private Context context;
    DrawerLayout m_drawer;

protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);
        SetContentView(Resource.Layout.activity_main);
        context = this;

        m_drawer = FindViewById<DrawerLayout>(Resource.Id.drawer_layout2);

        btn_drawer = FindViewById<Button>(Resource.Id.btn_drawer);
        btn_drawer.Click  = Btn_Drawer_Click;
    }

    private void Btn_Drawer_Click(object sender, EventArgs args)
    {
        m_drawer.OpenDrawer(GravityCompat.Start);
    }

Drawer.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.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:id="@ id/drawer_layout2"
                                    android:layout_width="match_parent"
                                    android:layout_height="match_parent"
                                    android:fitsSystemWindows="true"
                                    tools:openDrawer="start">

  <com.google.android.material.navigation.NavigationView
    android:id="@ id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@ id/test"
            android:layout_width="match_parent"
            android:layout_height="58dp"
            android:text="test"
            android:textSize="12dp"
            android:gravity="center">
        </TextView>
    </LinearLayout>

  </com.google.android.material.navigation.NavigationView>

</androidx.drawerlayout.widget.DrawerLayout>

CodePudding user response：

You may directly get the current drawer inside a view/fragment so that you won't get a NullPointerException，such like this:

m_drawer = (DrawerLayout) getActivity().findViewById(Resource.Id.drawer_layout2);

And then in your Button click event you may try to set like this:

private void Btn_Drawer_Click(object sender, EventArgs args)
{
    m_drawer.OpenDrawer(m_drawer);
}

These are just my suggestions and I hope they will help you. If there are follow-up questions, I may follow up.

CodePudding user response：

Linked file

ActivityMain.cs - activity_main.xml

FragmentEvent.cs - fragment_event.xml

(At this time, I access to drawerlayout's ID in activity_main from FragmentEvent)

Added Source

((ActivityMain)Activity).m_drawer.OpenDrawer(GravityCompat.Start);

Fixed Source

I change m_drawer from private to public

ActivityMain.cs

public class MainActivity : AppCompatActivity, NavigationView.IOnNavigationItemSelectedListener, TabLayout.IOnTabSelectedListener
{
    private Context context;
    //DrawerLayout m_drawer;
    public DrawerLayout m_drawer;