Question

While clicking the popup button it’s not showing popup box and it’s force close the application. Here i included my code (xml and java) for my native android application.

popup.xml

<Button
    android:id="@+id/ButtonPopup"
    android:layout_marginTop="20dip"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="onButtonInPopup"
    android:text="Dismiss this PopupWindow">
</Button>

Java code

public void onButtonPopup (View target) {
       // Make a View from our XML file
       LayoutInflater inflater = (LayoutInflater)
             this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
       View layout = inflater.inflate(R.layout.popup,(ViewGroup) findViewById(R.id.ButtonPopup));

       m_pw = new PopupWindow( layout,  350,  250,  true);
       m_pw.showAtLocation(layout, Gravity.CENTER, 0, 0);
    }

Answer 1

You are inflating popup.xml and defined the parent as (ViewGroup) findViewById(R.id.ButtonPopup). This ViewGroup will not create until you inflate the layout. and findViewById will work only after you set the layout in setContentView.
Try inflating using this –

View layout = inflater.inflate(R.layout.popup, null);