How can I get a Dialog style activity window to fill the screen?

I just want to fill only 80% of the screen for that I did like this below

        DisplayMetrics metrics = getResources().getDisplayMetrics();
        int screenWidth = (int) (metrics.widthPixels * 0.80);

        setContentView(R.layout.mylayout);

        getWindow().setLayout(screenWidth, LayoutParams.WRAP_CONTENT); //set below the setContentview

it works only when I put the getwindow().setLayout... line below the setContentView(..)

thanks @Matthias

I found the solution:

In your activity which has the Theme.Dialog style set, do this:

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

    setContentView(R.layout.your_layout);

    getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
}

It's important that you call Window.setLayout() after you call setContentView(), otherwise it won't work.

You may add this values to your style android:windowMinWidthMajor and android:windowMinWidthMinor

<style name="Theme_Dialog" parent="android:Theme.Holo.Dialog">
    ...
    <item name="android:windowMinWidthMajor">97%</item>
    <item name="android:windowMinWidthMinor">97%</item>
</style>