Kai Y Kai Y - 6 months ago 41
Android Question

Fragment vs. Custom View in Android

The Fragment and Custom View can achieve the similar function, I know that fragment is more re-usable comparing with custom view, any other benefits/enhancements for using Fragment ? Is fragment supposed to replace Custom View, or just a enhancement for some specific purpose ?

For instance, the code below is fragment:

public class TestFragment extends Fragment {

private TextView tv_name;
private Button btn_play;
private Button btn_delete;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.testfragment, container, false);
}

@Override
public void onStart() {
super.onStart();

tv_name = (TextView)getView().findViewById(R.id.tv_name);
btn_play = (Button)getView().findViewById(R.id.btn_play);
btn_delete = (Button)getView().findViewById(R.id.btn_delete);

}
}


The code for custom view:

public class TestCustomView extends LinearLayout {

private TextView tv_name;
private Button btn_play;
private Button btn_delete;

public TestCustomView(Context context, AttributeSet attrs){
super(context, attrs);

setOrientation(LinearLayout.HORIZONTAL);
setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));

tv_name = new TextView(context);
addView(tv_name);

btn_play = new Button(context);
addView(btn_play);

btn_delete = new Button(context);
addView(btn_delete);
}

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.testfragment, container, false);
}
}


Both "TestFragment" & "TestCustomView" can create a view consisting of TextView & Buttons, and use tags of
Framelayout/fragment
and
com.packagename.TestCustomView
to declare in the activity's xml layout file, but what's the advantages to use Fragment ?

Thanks in advance :)

Answer

Fragment can be used in different scenarios but most used are:

  • wrapper around a view
  • headless fragment - i.e. no view => not very helpful in general but can be used
  • retainable fragment - can be any of above. By using Fragment.setRetainInstance(true) you can bypass Fragment.onDestroy(), i.e. can keep fragment data on configuration changes but fragment view structure is still destroyed/recreated
  • can be added to activity back stack, i.e. easy Back button previous state restore

There are cases where fragment are complete pain in the neck, then there are cases where they can achieve results quicker.

For some custom and more flexible situations fragments can get cluttered and managing them would be difficult. So dealing with views directly can be really handy and more helpful for some cases. But everything is based on requirements.

Note View has its own life cycle too and can store/recreate saved instance state. A little bit more work but it has the option too.