CODEWITHSUNDEEP
androidperformance
Nickmccomb
Nickmccomb

Reputation: 1527

Android - Class variable vs method variable for Views

Which way is better programming for memory management when dealing with Android Views? I believe the second way is better because the TextView is only accessed when needed and then, hopefully, garbage collected. Would love to hear your views!

  public class MainActivity extends Activity {
     TextView tvHelp; 

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main); 

        tvHelp = (TextView) layout.findViewById(R.id.ivHelp);
        tvHelp.setText("Started"); 
     }


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

        tvHelp.setText("Resumed");
     }
  }

Or this

  public class MainActivity extends Activity { 

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main); 

        TextView tvHelp = (TextView) findViewById(R.id.ivHelp);
        tvHelp.setText("Started"); 
     }


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

        TextView tvHelp = (TextView) findViewById(R.id.ivHelp);
        tvHelp.setText("Resumed");
     }
  }

Upvotes: 0

Views: 55

Answers (2)

Kevin Coppock
Kevin Coppock

Reputation: 134664

In your case, it won't really make any difference as far as memory consumption. The Activity is going to hold a reference to that view through its hierarchy until it's destroyed whether you keep a reference to it or not. Releasing your reference to it won't make it be garbage collected.

Once the Activity goes through onDestroy(), it and its view hierarchy will be garbage collected anyway, so for this case I wouldn't worry about the difference.

One case where this can make a difference is in Fragments where the View lifecycle differs from the component lifecycle. Holding a reference to a View from onCreateView() or onViewCreated() can temporarily cause additional memory usage once they go on the backstack. You can release the references in onDestroyView() since they won't be valid anyway -- unless you are keeping the whole view hierarchy around manually.

For more info: https://stackoverflow.com/a/26370042/321697

Upvotes: 1

E-Kami
E-Kami

Reputation: 2669

It doesn't make that much difference. The first one will help you avoid multiple calls of findViewById() which is CPU consuming. The second one will help you preserve some bytes on the heap. But by doing this you will also create unreferenced objects which will stack on the heap until the GC passes (which is CPU consuming). GC will also starts when the memory is running out (when you create unreferenced objects for example). So the first solution is definitely the best one to use. You'll avoid:

  • Code repetition
  • Multiples calls to findViewById
  • Unreferenced objects which will stack in the heap until the GC passes

Upvotes: 1

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