单击按钮时从“活动”移动到“片段”

Question

I used this code to move from Activity to Fragment when button clicked but when I run this code I find Activity is still in background.

 TopicsFragment fragment = new TopicsFragment();
            android.support.v4.app.FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.welcome_id, fragment);
            transaction.commit();

Answer 1

First of all, you need to understand what Activity and Fragments are. You cannot move from Activity to Fragment.

You can inflate a Fragment or Fragments into an Activity. Fragments cannot be independent from an activity.

A fragment must always be hosted in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle. For example, when the activity is paused, so are all fragments in it, and when the activity is destroyed, so are all fragments. However, while an activity is running (it is in the resumed lifecycle state), you can manipulate each fragment independently, such as add or remove them. When you perform such a fragment transaction, you can also add it to a back stack that's managed by the activity—each back stack entry in the activity is a record of the fragment transaction that occurred. The back stack allows the user to reverse a fragment transaction (navigate backwards), by pressing the Back button.

Source: https://developer.android.com/guide/components/fragments

Answer 2

If you don't want to see the activity after entering into fragment, you could extend from DialogFragment and make it fullscreen, there are many examples, google it using "android fullscreen dialogfragment".

and here is DialogFragment doc .