How to change the text on the action bar

Kotlin

You can do it programmatically in Kotlin this way. You just ignore it if "supportActionBar" is null:

    supportActionBar?.setTitle(R.string.my_text)
    supportActionBar?.title = "My text"

Or this way. It throws an exception if "supportActionBar" is null.

    supportActionBar!!.setTitle(R.string.my_text)
    supportActionBar!!.title = "My text"

You just add this code in the onCreate method.

setTitle("new title");

getSupportActionBar().setTitle("title");

The below code worked well for me inside the Oncreate method

    getSupportActionBar().setTitle("Text to display");

For future developers that are using AndroidX and the navigation architectural component.

Instead of setting the toolbar title using one of the solutions above, which can be very painful if you want to set it dynamically on a back stack change, you can set a placeholder for the title of the fragment in the navigation graph like the following:

<fragment
    android:id="@+id/some_fragment"
    android:name="package.SomeFragment"
    android:label="Hello {placeholder}"
    tools:layout="@layout/fragment_some">
    <argument
        android:name="placeholder"
        app:argType="string" />
</fragment>

The placeholder value has to be provided using the FragmentDirections (via the action method).

It is then replaced in the title and show like Hello World (when placeholder = "World").

if u r using navigation bar to change fragment then u can add change it where u r changing Fragment like below example :

 public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.clientsidedrawer:
                    //    Toast.makeText(getApplicationContext(),"Client selected",Toast.LENGTH_SHORT).show();
                    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new clients_fragment()).commit();
                    break;
    
                case R.id.adddatasidedrawer:
                    getSupportActionBar().setTitle("Add Client");
                    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new addclient_fragment()).commit();
                    break;
    
                case R.id.editid:
                    getSupportActionBar().setTitle("Edit Clients");
                    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new Editclient()).commit();
                    break;
    
                case R.id.taskid:
                    getSupportActionBar().setTitle("Task manager");
                    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new Taskmanager()).commit();
                    break;

if u r using simple activity then just call :

getSupportActionBar().setTitle("Contact Us");

to change actionbar/toolbar color in activity use :

getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#06023b")));

to set gradient to actionbar first create gradient : Example directry created > R.drawable.gradient_contactus

<?xml version="1.0" encoding="utf-8"?>
<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle"
    >

    <gradient
        android:angle="90"
        android:startColor="#2980b9"
        android:centerColor="#6dd5fa"
        android:endColor="#2980b9">
    </gradient>


</shape>

and then set it like this :

getSupportActionBar().setBackgroundDrawable(getResources().getDrawable(R.drawable.gradient_contactus));

In onCreateView add this:

(activity as AppCompatActivity).supportActionBar?.title ="My APP Title"