Fragment on top of an Activity
<p>I have a main Activity with some elements. One of them is a Button. I want to load a Fragment when the button is clicked. I want the Fragment to cover the whole Activity, not just be in a layout in it. Then in the Fragment there is also a Button that has to load another Fragment that covers everything, then another one and so on.</p>

<p>So I set an OnClickListener on the Activity to load the first of the Fragments. The Activity loads just fine. If I click buttons for other Activities everything is good. But no matter what I tried it always crashes when I click the Button that is supposed to load the Fragment.</p>

<p>Here's the main Activity's code:</p>

<pre><code>public class SignUpActivity extends AppCompatActivity {

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

    Button next = (Button) findViewById(R.id.button_next_name);
    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            SignNameFragment nameFragment = new SignNameFragment();
            fragmentTransaction.add(PROBABLY_WHAT_I_AM_DOING_WRONG,nameFragment);
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
        }
    });
}
}
</code></pre>

<p>All the xml are pretty much the same. RelativeLayout for the Activity, FrameLayout for the Fragments and ScrollView, ImageView, EditText, TextView and Button for all of them.</p>

<p>Things I tried so far according to suggestions on the web:</p>

<ul>
<li>The main Activity's xml uses a RelativeLayout. I tried to load the Fragment in it, but it failed</li>
<li>I changed it to FrameLayout</li>
<li>I used fragmentTransaction.add(R.id.fragment_container,nameFragment)</li>
<li>Instead of using add(), I tried replace(R.id.activity_sign_up,nameFragment)</li>
<li>Extending to FragmentActivity</li>
<li>Setting a FrameLayout as a Fragment container in my main Activity's xml</li>
</ul>

<p>I believe my mistake is that I don't set where I want to add the Fragment in the right way. </p>

<p>I am pretty sure it's gonna be a rookie mistake, but I've never used Fragments before. So any suggestions?</p>

<p>Thanks </p>

<p><strong>EDIT:</strong>
That's the error when I click the button</p>

<blockquote>
  <p>E/AndroidRuntime: FATAL EXCEPTION: main
                    Process: be.test.test, PID: 16763
                    java.lang.RuntimeException: be.test.test.SignUpActivity@276634a3 must implement OnFragmentInteractionListener
                        at layout.SignNameFragment.onAttach(SignNameFragment.java:84)
                        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1043)
                        at android.support.v4.app.BackStackRecord.setLastIn(BackStackRecord.java:838)
                        at android.support.v4.app.BackStackRecord.calculateFragments(BackStackRecord.java:861)
                        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:719)
                        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
                        at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:536)
                        at android.os.Handler.handleCallback(Handler.java:739)
                        at android.os.Handler.dispatchMessage(Handler.java:95)
                        at android.os.Looper.loop(Looper.java:145)
                        at android.app.ActivityThread.main(ActivityThread.java:6145)
                        at java.lang.reflect.Method.invoke(Native Method)
                        at java.lang.reflect.Method.invoke(Method.java:372)
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)</p>
</blockquote>