[java] How to set background color of an Activity to white programmatically?

How can I set the background color of an Activity to white programatically?

View randview = new View(getBaseContext());
randview = (View)findViewById(R.id.container);
randview.setBackgroundColor(Color.BLUE);

worked for me. thank you.

Add this single line in your activity, after setContentView() call

getWindow().getDecorView().setBackgroundColor(Color.WHITE);

I prefer coloring by theme

<style name="CustomTheme" parent="android:Theme.Light">
    <item name="android:windowBackground">@color/custom_theme_color</item>
    <item name="android:colorBackground">@color/custom_theme_color</item>
</style>

Button btn;
View root;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn = (Button)findViewById(R.id.button);

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            root =findViewById(R.id.activity_main).getRootView();
            root.setBackgroundColor(Color.parseColor("#FFFFFF"));
        }
    });
}

The best method right now is of course

getWindow().getDecorView().setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.main_activity_background_color));

Please be aware though, if you have anything set as the background color in Designer, it will overwrite anything you try to set in your code.

To get the root view defined in your xml file, without action bar, you can use this:

View root = ((ViewGroup) findViewById(android.R.id.content)).getChildAt(0);

So, to change color to white:

root.setBackgroundResource(Color.WHITE);

final View rootView = findViewById(android.R.id.content);
rootView.setBackgroundResource(...);

In your onCreate() method:

getWindow().getDecorView().setBackgroundColor(getResources().getColor(R.color.main_activity_background_color));

Also you need to add to values folder a new XML file called color.xml and Assign there a new color property:

color.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="main_activity_background_color">#000000</color>
</resources>

Note that you can name the color.xml any name you want but you refer to it by code as R.color.yourId.

EDIT

Because getResources().getColor() is deprecated, use getWindow().getDecorView().setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.main_activity_background_color)); instead.

for activity

findViewById(android.R.id.content).setBackgroundColor(color)

You can use this to call predefined android colours:

element.setBackgroundColor(android.R.color.red);

If you want to use one of your own custom colours, you can add your custom colour to strings.xml and then use the below to call it.

element.setBackgroundColor(R.color.mycolour);

However if you want to set the colour in your layout.xml you can modify and add the below to any element that accepts it.

android:background="#FFFFFF"

?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#FFFFFF"
android:id="@+id/myScreen"
</LinearLayout>

In other words, "android:background" is the tag in the XML you want to change.

If you need to dynamically update the background value, see the following:

Exercise: Change background color, by SeekBar