Inflate your fragment like this

   @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_timer, container, false);
}

My code worked when I had it in MainActivity but then when I tried to use it in a fragment it wont work because I can’t extend AppCompatActivity. Is there anyway I can fix my code for it to work in this fragment without extending AppCompatActivity and if so, how?

Timer.java

public class Timer extends Fragment {
    private static final long START_TIME_IN_MILLIS = 600000;

    private TextView mTextViewCountDown;
    private Button mButtonStartPause;
    private Button mButtonReset;

    private CountDownTimer mCountDownTimer;

    private boolean mTimerRunning;

    private long mTimeLeftInMillis = START_TIME_IN_MILLIS;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_timer);

        mTextViewCountDown = findViewById(R.id.text_view_countdown);

        mButtonStartPause = findViewById(R.id.button_start_pause);
        mButtonReset = findViewById(R.id.button_reset);

        mButtonStartPause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mTimerRunning) {
                    pauseTimer();
                } else {
                    startTimer();
                }
            }
        });

        mButtonReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                resetTimer();
            }
        });

        updateCountDownText();
    }