Get LinearLayout reference at custom view

Question

My question is about Android/Java.

I wanna access to other views from my custom view.

My main.xml:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/mainLinearLayout1">

    <org.javaforum.input
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textEmailAddress"
        required=""
        android:hint="Enter your E-Mail"
        oninvalid="this.setCustomValidity('SO - Please enter a correct E-Mail!!!')"/>

    <org.javaforum.input
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        inputType="submit"/>

</LinearLayout>

So when the second "input" view is clicked, I wanna check if there exists an attribute named "required" at the first "input" view.

I tried this in my input.java:

public class input extends TextView{
    public input(Context context, AttributeSet attr) {
        super(context, attr, getIdentifier(context,attr));
    }

    @Override
    public void onFinishInflate() {
        setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                LinearLayout layout = (LinearLayout)findViewById(R.id.mainLinearLayout1);
                View v = null;
                for(int i=0; i<layout.getChildCount(); i++) {//Error
                    //Code
                }
            }
        });
    }
}

But I get the following error:

java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.LinearLayout.getChildCount()' on a null object reference

I don't understand why it's null. It should be already created, right?

So how can I get an LinearLayout reference of my main.xml at my custom view correctly?

Answer 1

To solve the null pointer exception, you will need to search for the other widget in the parent LinearLayout. You can use View.getParent() to identify the parent. Since the view you are looking for is a sibling of the current view, you will find it in the parent.

As for determining if a certain attribute is set, I recommend that the value be captured by its view and a method provided to present that value upon request. Say the value is your "required" value then capture that value locally and provide a method, getRequiredValue(), for instance, to expose it.