Is it good to call findViewById every time in Activity lifecycle whenever required?

Question

Whenever we need a reference to the widget, we uses findByViewById.

When we are referring the widget lots of time in the code of the same Activity class, we can fol

Answer 1

I may be wrong since i am new to Android, but i prefer storing a a variable; it's less coding to write.

for example: if you have to access an imageview that is nested in layouts how would you wish to access it and get its tag.

Access 1:

public Integer getTag(){
       FrameLayout frame1 = (FrameLayout) findViewById(R.id.frame_1);
       LinearLayout linear3 = (LinearLayout) frame1.findViewById(R.id.linear_3);
       ImageView imgView = (ImageView) linear3.findViewById(R.id.myImg);
       return Integer.valueOf( imgView.getTag().ToString());
}

Access 2:

 private ImageView myImageView;
 @Override
 public void onCreate( Bundle savedInstanceState){
       //set access to variable
 }   

 public Integer getTag(){
       //return Integer.valueOf( myImageView.getTag().ToString());
       //can be written
       Integer mTag = Integer.valueOf(myImageView.getTag().ToString());
       return mTag;
 }

Answer 2

Accessing a member variable is always faster than any function call. The used space for that variable is insignificant. By the way: The code looks much cleaner!

Answer 3

You should decide this according to your purpose. Holding an object for your views are faster than getting your view with an activity method. But this also means that you are using a memory for your reference and it can cause a memory leak.

Answer 4

The second possibility is clearly the better.

findViewById iterates through the whole view hierachy, which of course costs much more time than a reference.

Dianne Hackborn (Android engineer) gave some details about the topic here: https://groups.google.com/forum/#!topic/android-developers/_22Z90dshoM

Answer 5

Both approaches have their risks. In general, you should call findViewById() the less times you can, by the other hand, storing a reference on the Activity class may lead to memory leaks. It depends so much on what you want to do, how much times are you calling it and basing on it choose one of the approaches. For that, you'll need to analyze your code and if you're not clear about which is better, just try both and choose the "less bad", but generally the first approach is worse than the second one because you know you'll always have to find across ALL elements you've defined an id.

Answer 6

Most developers use method 2, mostly because its more effective. If your layout is complicated then findViewById must traverse its tree to find given widget which takes time. In list views you mostly use ViewHolder pattern which allows you to store references to list item widgets. Since lists are redrawn very ofthen this greatly speeds up its rendering.

Storing widgets in private references is quite safe, those references gets invalidated on configuration changes, but your activity is also destroyed then.