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junior
Asked: 2020-07-24 12:21:47 +0800 CST 2020-07-24 12:21:47 +0800 CST

get actionViewClass from menuitem android studio

  • 772

I am trying to make a custom menuitem but trying to get a property from the custom class gives mejava.lang.NullPointerException

this is my code:

activity_main.xml

<android.support.design.widget.NavigationView
     android:id="@+id/nav_view"
     android:layout_width="wrap_content"
     android:layout_height="match_parent"
     android:layout_gravity="start"
     android:fitsSystemWindows="true"
     app:headerLayout="@layout/nav_header_main"
     app:menu="@menu/main.xml" />

main.xml

<menu>
    
      <item
           android:id="@+id/nav_newversion"
           tools:ignore="MenuTitle"
           app:actionViewClass="com.package.meteorocorte.customitem" />
</menu>

customitem.java

public class customitem extends LinearLayout {
    TextView text=new TextView(getContext());

    public customitem(Context context) {
        super(context);
        setOrientation(VERTICAL);
        setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        setBackgroundColor(Color.GREEN);
        setPadding(0,12,0,12);
        text.setText(("hola"));
        text.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        text.setTextColor(Color.BLACK);
        addView(text);
    }

    public TextView getText() {
        return text;
    }
}

MainActivity.java

MenuItem item=((NavigationView)findViewById(R.id.nav_view)).getMenu().getItem(0);
item.setVisible(true);
TextView text= ((customitem) item.getActionView()).getText();//aqui me da java.lang.NullPointerException

And if you were wondering if customization would work, I leave you the image:

enter image description here

java

1 Answers

  1. Best Answer

    Most of what you do is correct, you get the element from the NavigationView, this should work without problem:

    MenuItem item=((NavigationView)findViewById(R.id.nav_view)).getMenu().getItem(0);
TextView text= ((customitem) item.getActionView()).getText();

    But it is super important that in the menu file main.xmlthe element is actually the first (index 0)

    <?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    
    <item
        android:id="@+id/nav_newversion"
        tools:ignore="MenuTitle"
        app:actionViewClass="com.package.meteorocorte.customitem" />


</menu>

    and the class customitemis actually in the package: "com.package.meteorocorte", ensure these two things and I assure you that you will do what you want without any problem.

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