How can I assign an ID to a view programmatically

Question

In an XML file  we can assign an ID to a view like android id    id something  and then call findViewById    but when creating a view programmatically  how do I assign an ID   I think setId   is not the same as default assignment  setId   is extra   Can anybody correct me

User · Answer

Yes  you can call setId value  in any view with any  positive  integer value that you like and then find it in the parent container using findViewById value   Note that it is valid to call setId   with the same value for different sibling views  but findViewById   will return only the first one

User · Answer

Android id overview  An Android id is an integer commonly used to identify views  this id can be assigned via XML  when possible  and via code  programmatically   The id is most useful for getting references for XML-defined Views generated by an Inflater  such as by using setContentView    Assign id via XML   Add an attribute of android id    id somename  to your view  When your application is built  the android id will be assigned a unique int for use in code  Reference your android id s int value in code using  R id somename   effectively a constant   this int can change from build to build so never copy an id from gen package name R java  just use  R id somename    Also  an id assigned to a Preference in XML is not used when the Preference generates its View     Assign id via code  programmatically    Manually set ids using someView setId int   The int must be positive  but is otherwise arbitrary- it can be whatever you want  keep reading if this is frightful   For example  if creating and numbering several views representing items  you could use their item number    Uniqueness of ids   XML-assigned ids will be unique  Code-assigned ids do not have to be unique Code-assigned ids can  theoretically  conflict with XML-assigned ids  These conflicting ids won t matter if queried correctly  keep reading     When  and why  conflicting ids don t matter   findViewById int  will iterate depth-first recursively through the view hierarchy from the View you specify and return the first View it finds with a matching id  As long as there are no code-assigned ids assigned before an XML-defined id in the hierarchy  findViewById R id somename  will always return the XML-defined View so id d    Dynamically Creating Views and Assigning IDs   In layout XML  define an empty ViewGroup with id  Such as a LinearLayout with android id    id placeholder   Use code to populate the placeholder ViewGroup with Views  If you need or want  assign any ids that are convenient to each view  Query these child views using placeholder findViewById convenientInt   API 17 introduced View generateViewId   which allows you to generate a unique ID     If you choose to keep references to your views around  be sure to instantiate them with getApplicationContext   and be sure to set each reference to null in onDestroy  Apparently leaking the Activity  hanging onto it after is is destroyed  is wasteful       Reserve an XML android id for use in code  API 17 introduced View generateViewId   which generates a unique ID   Thanks to take-chances-make-changes for pointing this out     If your ViewGroup cannot be defined via XML  or you don t want it to be  you can reserve the id via XML to ensure it remains unique   Here  values ids xml defines a custom id    lt  xml version  1 0  encoding  utf-8   gt   lt resources gt       lt item name  reservedNamedId  type  id   gt   lt  resources gt    Then once the ViewGroup or View has been created  you can attach the custom id  myViewGroup setId R id reservedNamedId     Conflicting id example  For clarity by way of obfuscating example  lets examine what happens when there is an id conflict behind the scenes   layout mylayout xml   lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout     xmlns android  http   schemas android com apk res android      android layout width  match parent      android layout height  match parent      android orientation  vertical   gt       lt LinearLayout         android id    id placeholder          android layout width  fill parent          android layout height  wrap content          android orientation  horizontal   gt   lt  LinearLayout gt    To simulate a conflict  lets say our latest build assigned R id placeholder   id placeholder  an int value of 12    Next  MyActivity java defines some adds views programmatically  via code    int placeholderId   R id placeholder     placeholderId  12    returns  placeholder  which has id  12  ViewGroup placeholder    ViewGroup this findViewById placeholderId   for  int i 0  i lt 20  i         TextView tv   new TextView this getApplicationContext            One new TextView will also be assigned an id  12      tv setId i       placeholder addView tv       So placeholder and one of our new TextViews both have an id of 12  But this isn t really a problem if we query placeholder s child views      Will return a generated TextView   placeholder findViewById 12       Whereas this will return the ViewGroup  placeholder      as long as its R id remains 12   Activity this findViewById 12      Not so bad

User · Answer

You can just use the View setId integer  for this  In the XML  even though you re setting a String id  this gets converted into an integer  Due to this  you can use any  positive  Integer for the Views  you add programmatically      According to View documentation           The identifier does not have to be unique in this view s hierarchy      The identifier should be a positive number          So you can use any positive integer you like  but in this case there   can be some views with equivalent id s  If you want to search for some   view in hierarchy calling to setTag with some key objects may be   handy    Credits to this answer

[android] How can I assign an ID to a view programmatically?

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