Facebook Popup using PopupWindow

fb_comments_list_item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="horizontal"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:padding="10dp"
              android:paddingLeft="5dp"
              android:paddingRight="5dp">
    <ImageView
        android:src="@drawable/ic_launcher"
        android:layout_width="30dp"
        android:layout_height="30dp"/>

    <TextView
        android:id="@android:id/text1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="@android:style/TextAppearance.Small"
        android:gravity="center_vertical"
        android:textColor="@color/black"/>

</LinearLayout>

fb_popup_bg.xml

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/white"/>
    <corners android:radius="5dp"/>
</shape>

fb_popup_layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/headerLayout"
        android:layout_width="match_parent"
        android:layout_height="30dp"
        android:orientation="horizontal"
        android:layout_alignParentTop="true"
        android:gravity="center">

        <TextView
            android:layout_gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Some One and 20 Others Like this"
            android:textColor="@color/black"
            android:textStyle="bold"
            android:layout_margin="5dp"/>
    </LinearLayout>

    <ListView
        android:id="@+id/commentsListView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="5dp"
        android:layout_below="@id/headerLayout"
        android:paddingBottom="50dp"
        android:layout_marginBottom="0dp"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:orientation="vertical"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:src="@color/Gray"/>
        <EditText
            android:id="@+id/writeComment"
            android:hint="Write a Comment"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:textSize="12dp"
            android:textColor="@color/black"
            android:background="#00000000"/>
    </LinearLayout>

</RelativeLayout>

MainActivity.java

public class MainActivity extends
    private PopupWindow popWindow;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    // call this method when required to show popup
    public void onShowPopup(View v){

        LayoutInflater layoutInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        // inflate the custom popup layout
        final View inflatedView = layoutInflater.inflate(R.layout.fb_popup_layout, null,false);
        // find the ListView in the popup layout
        ListView listView = (ListView)inflatedView.findViewById(R.id.commentsListView);

        // get device size
        Display display = getWindowManager().getDefaultDisplay();
        final Point size = new Point();
        display.getSize(size);
        mDeviceHeight = size.y;


        // fill the data to the list items
        setSimpleList(listView);


        // set height depends on the device size
        popWindow = new PopupWindow(inflatedView, size.x - 50,size.y - 400, true );
        // set a background drawable with rounders corners
        popWindow.setBackgroundDrawable(getResources().getDrawable(R.drawable.fb_popup_bg));
        // make it focusable to show the keyboard to enter in `EditText`
        popWindow.setFocusable(true);
        // make it outside touchable to dismiss the popup window
        popWindow.setOutsideTouchable(true);

        // show the popup at bottom of the screen and set some margin at bottom ie,
        popWindow.showAtLocation(v, Gravity.BOTTOM, 0,100);
    }
    
    
    void setSimpleList(ListView listView){
        
        ArrayList<String> contactsList = new ArrayList<String>();

        for (int index = 0; index < 10; index++) {
            contactsList.add("I am @ index " + index + " today " + Calendar.getInstance().getTime().toString());
        }

        listView.setAdapter(new ArrayAdapter<String>(TryMeActivity.this,
            R.layout.fb_comments_list_item, android.R.id.text1,contactsList));
    }
    
}

Hi! I was linked to this example from a brilliant answer to a question on SO. However I'm a little confused as to how the sizing dependant on Device screen size works. Namely in curious about this variable 'mDeviceHeight'. When and how should it be declared and what does it do?

Kind regards, Johan

Any idea how to close it when it's dragged down like facebook comments?

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edittext is not showing while typing