How to Programmatically Set Style Attribute in a View

How to programmatically set style attribute in a view

Generally you can't change styles programmatically; you can set the look of a screen, or part of a layout, or individual button in your XML layout using themes or styles. Themes can, however, be applied programmatically.

There is also such a thing as a StateListDrawable which lets you define different drawables for each state the your Button can be in, whether focused, selected, pressed, disabled and so on.

For example, to get your button to change colour when it's pressed, you could define an XML file called res/drawable/my_button.xml directory like this:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item
    android:state_pressed="true"
    android:drawable="@drawable/btn_pressed" />
  <item
    android:state_pressed="false"
    android:drawable="@drawable/btn_normal" />
</selector>

You can then apply this selector to a Button by setting the property android:background="@drawable/my_button".

how to set the Style Attribute Programmatically in Android?

Dynamic style change is not currently supported. You must set the style before the view is create (in xml).

Android: set view style programmatically

Technically you can apply styles programmatically, with custom views anyway:

private MyRelativeLayout extends RelativeLayout {
  public MyRelativeLayout(Context context) {
     super(context, null, R.style.LightStyle);
  }
}

The one argument constructor is the one used when you instantiate views programmatically.

So chain this constructor to the super that takes a style parameter.

RelativeLayout someLayout = new MyRelativeLayout(new ContextThemeWrapper(this,R.style.RadioButton));

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Or as @Dori pointed out simply:

RelativeLayout someLayout = new RelativeLayout(new ContextThemeWrapper(activity,R.style.LightStyle));

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Now in Kotlin:

class MyRelativeLayout @JvmOverloads constructor(
    context: Context, 
    attributeSet: AttributeSet? = null, 
    defStyleAttr: Int = R.style.LightStyle,
) : RelativeLayout(context, attributeSet, defStyleAttr)

or

 val rl = RelativeLayout(ContextThemeWrapper(activity, R.style.LightStyle))

Programmatically change one attribute on custom style

What about group these TextView in only one Layout? Then change it programmatically.
In my example I group all of TextViews in only one LinearLayout.

LinearLayout ll = (LinearLayout) findViewById(R.id.layout);
int childCount = ll.getChildCount();
for (int i=0; i<childCount; i++){
    ((TextView)ll.getChildAt(i)).setTextSize(20);
}

Be sure that you only have TextViews in your layout.

Add Style after creating a View programmatically

You can't apply a style after constructing a view. The correct way to do this is to use the 4-argument constructor on Android 5.0+ or to create a theme attribute that references your style and use the 3-argument constructor.

// Works on versions prior to Android 5.0
RelativeLayout rl = new RelativeLayout(this, null, R.attr.myRelativeLayoutStyle);

// Works on Android 5.0 and above
RelativeLayout r2 = new RelativeLayout(this, null, 0, R.style.MyRelativeLayout);

res/values/attrs.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <attr name="myRelativeLayoutStyle" format="reference" />
    ...

res/values/styles.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="MyRelativeLayout">
        ...
    </style>
    ...

res/values/themes.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="MyAppTheme" parent="...">
        <item name="myRelativeLayoutStyle">@style/MyRelativeLayout</item>
        ...

Android - How to programmatically set the button style in a Linearlayout?

Hope I'm not too late to join the party :)

Well, Styles can be applied to a View at initialization phase. For example:

LinearLayout button = new LinearLayout(context, null, android.R.style.ButtonBar);

How can I set a textview's style programmatically?

You may find this answer by Benjamin Piette handy. To change this into working code for a TextView just change it up a bit:

TextView tv = new TextView (new ContextThemeWrapper(this, R.style.mystyle), null, 0);

EDIT: to set other things like margins, height & width and others, use LayoutParams. To set the params throrin19's answer can be helpful.

LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
        LinearLayout.LayoutParams.WRAP_CONTENT,      
        LinearLayout.LayoutParams.WRAP_CONTENT
);
params.setMargins(left, top, right, bottom);
tv.setLayoutParams(params);

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