All custom view instance variables are null

Question

I created a custom view that extends LinearLayout and contains two TextViews. Even though I set the text views in onFinishInflate(), I get null pointer exceptions when I call setText() on these textviews later.

Here's the code for the custom view:

public class MyCustomView extends LinearLayout{
    private TextView textView1; 
    private TextView textView2; 

    public MyCustomView(Context context){
        super(context);
        LayoutInflater layoutInflater = LayoutInflater.from(context); 
        layoutInflater.inflater(R.layout.my_custom_view, this); 
    }

    public MyCustomView(Context context, AttributeSet attrs){
        super(context, attrs); 
    }

    public MyCustomView(Context context, AttributeSet attrs, int defStyle){
        super(context, attrs, defStyle); 
    }

    @Override
    protected void onFinishInflate(){
        super.onFinishInflate();
        textView1 = (TextView)findViewById(R.id.tv1); 
        textView2 = (TextView)findViewById(R.id.tv2); 
    }

    // here's where I get the null pointer for textView1
    public void setTitle(String title){
        textView1.setText(title);
    } 
}

my_custom_view.xml looks like this:

<?xml version="1.0" encoding="utf-8">
<my_package.myapp.MyCustomView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
    <TextView
        android:id="@+id/tv1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/tv2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</my_package.myapp.MyCustomView>

I later use the custom view like so:

View view = new MyCustomView(context); 
((MyCustomView)view).setTitle("Title");   // null pointer exception here
return view;

Any ideas what I'm misunderstanding or doing wrong? I'd really appreciate any help.

I also noticed that if I modified the first constructor to take some other object and then later try to use this object, that instance variable is also null. Eg:

public MyCustomView(Context context, SomeObject object){
    this.object = object;
}

// as with the textviews, object would be null here
public int getObjectValue(){
    return object.getValue(); 
}

Thanks!

Gabe Sechan · Accepted Answer · 2015-07-08 00:34:43Z

4

Ok, multiple problems here.

1)Your xml is wrong. It should start with a merge, not a reference to your class, if you're inflating it into your class.

2)All 3 of your contructors need to do the inflation stuff. (this is prt of why it failed- the 2 or 3 param constructor would be called here).

3)You do not want or need to override onFinishInflate. Put that code in the constructor. Inflation is not asynchronous, so there's no reason not to.

answered Jul 8, 2015 at 0:34

Gabe Sechan

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