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

I am using an activity with the dialog theme set, and I want it to be full screen. I tried all sorts of things, even going through the WindowManager to expand the window to full width and height manually, but nothing works.

Apparently, a dialog window (or an activity with the dialog theme) will only expand according to its contents, but even that doesn't always work. For instance, I show a progress bar circle which has width and height set to FILL_PARENT (so does its layout container), but still, the dialog wraps around the much smaller progress bar instead of filling the screen.

There must be a way of displaying something small inside a dialog window but have it expand to full screen size without its content resizing as well?

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>

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

Wrap your dialog_custom_layout.xml into RelativeLayout instead of any other layout.That worked for me.

For Dialog This may helpful for someone. I want a dialog to take full width of screen. searched a lot but nothing found useful. Finally this worked for me:

mDialog.setContentView(R.layout.my_custom_dialog);
mDialog.getWindow().setBackgroundDrawable(null);

after adding this, my dialog appears in full width of screen.

This answer is a workaround for those who use "Theme.AppCompat.Dialog" or any other "Theme.AppCompat.Dialog" descendants like "Theme.AppCompat.Light.Dialog", "Theme.AppCompat.DayNight.Dialog", etc. I myself has to use AppCompat dialog because i use AppCompatActivity as extends for all my activities. There will be a problem that make the dialog has padding on every sides(top, right, bottom and left) if we use the accepted answer.

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

    setContentView(R.layout.your_layout);

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

On your Activity's style, add these code

<style name="DialogActivityTheme" parent="Theme.AppCompat.Dialog">
    <item name="windowNoTitle">true</item>
    <item name="android:windowBackground">@null</item>
</style>

As you may notice, the problem that generate padding to our dialog is "android:windowBackground", so here i make the window background to null.

Set a minimum width at the top most layout.

android:minWidth="300dp"

For example:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"
  xmlns:android="http://schemas.android.com/apk/res/android" android:minWidth="300dp">

<!-- Put remaining contents here -->

</LinearLayout>

Matthias' answer is mostly right but it's still not filling the entire screen as it has a small padding on each side (pointed out by @Holmes). In addition to his code, we could fix this by extending Theme.Dialog style and add some attributes like this.

<style name="MyDialog" parent="@android:style/Theme.Dialog">
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:windowNoTitle">true</item>
</style>

Then we simply declare Activity with theme set to MyDialog:

<activity
    android:name=".FooActivity"
    android:theme="@style/MyDialog" />

This would be helpful for someone like me. Create custom dialog style:

<style name="MyDialog" parent="Theme.AppCompat.Light.Dialog">
    <item name="windowNoTitle">true</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowIsFloating">false</item>
</style>

In AndroidManifest.xml file set theme for wanted activity:

<activity
        android:name=".CustomDialog"
        ...
        android:theme="@style/MyDialog"/>

That is all, no need to call methods programaticaly.

In your manifest file where our activity is defined

<activity
        android:name=".YourPopUpActivity"
        android:theme="@android:style/Theme.Holo.Dialog" >
    </activity>

without action bar

<activity android:name=".YourPopUpActivity"
            android:theme="@android:style/Theme.Holo.Dialog.NoActionBar"/>