Android View setID int id programmatically - how to avoid ID conflicts

Question

I m adding TextViews programmatically in a for-loop and add them to an ArrayList   How do I use TextView setId int id   What Integer ID do I come up with so it doesn t conflict with other IDs

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This works for me   static int id   1      Returns a valid id that isn t in use public int findId          View v   findViewById id         while  v    null             v   findViewById   id                 return id

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This was a comment to dilettante s answer but it got too long   hehe   Of course a static is not needed here   You could use SharedPreferences to save  instead of static  Either way  the reason is to save the current progress so that its not too slow for complicated layouts  Because  in fact  after its used once  it will be rather fast later  However  I dont feel this is a good way to do it because if you have to rebuild your screen again  say onCreate gets called again   then you probably want to start over from the beginning anyhow  eliminating the need for static  Therefore  just make it an instance variable instead of static   Here is a smaller version that runs a bit faster and might be easier to read   int fID   0   public int findUnusedId         while  findViewById   fID     null        return fID      This above function should be sufficient  Because  as far as I can tell  android-generated IDs are in the billions  so this will probably return 1 the first time and always be quite fast  Because  it wont actually be looping past the used IDs to find an unused one  However  the loop is there should it actually find a used ID   However  if you still want the progress saved between subsequent recreations of your app  and want to avoid using static  Here is the SharedPreferences version   SharedPreferences sp   getSharedPreferences  your pref name   MODE PRIVATE    public int findUnusedId         int fID   sp getInt  find unused id   0       while  findViewById   fID     null        SharedPreferences Editor spe   sp edit        spe putInt  find unused id   fID       spe commit        return fID      This answer to a similar question should tell you everything you need to know about IDs with android  https   stackoverflow com a 13241629 693927  EDIT FIX  Just realized I totally goofed up the save  I must have been drunk

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From API level 17 and above  you can call  View generateViewId    Then use View setId int    If your app is targeted lower than API level 17  use ViewCompat generateViewId

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The  Compat  library now also supports the generateViewId   method for API levels prior 17    Just make sure to use a version of the Compat library that is 27 1 0   For example  in your build gradle file  put     implementation  com android support appcompat-v7 27 1 1  Then you can simply use the generateViewId   from the ViewCompat class instead of the View class as follow      Will assign a unique ID myView id   ViewCompat generateViewId     Happy coding

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In order to dynamically generate View Id  form API 17 use  generateViewId    Which will generate a value suitable for use in setId int   This value will not collide with ID values generated at build time by aapt for R id

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public String TAG         return this getClass   getSimpleName       private AtomicInteger lastFldId   null   public int generateViewId         if lastFldId    null            int maxFld   0          String fldName               Field   flds   R id class getDeclaredFields            R id inst   new R id             for  int i   0  i  lt  flds length  i                  Field fld   flds i                try                   int value   fld getInt inst                    if  value  gt  maxFld                        maxFld   value                      fldName   fld getName                                    catch  IllegalAccessException e                    Log e TAG     error getting value for      fld getName             e toString                                     Log d TAG     maxId   maxFld     name   fldName           lastFldId   new AtomicInteger maxFld              return lastFldId addAndGet 1

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You can set ID s you ll use later in R id class using an xml resource file  and let Android SDK give them unique values during compile time    res values ids xml       lt item name  my edit text 1  type  id   gt   lt item name  my button 1  type  id   gt   lt item name  my time picker 1  type  id   gt      To use it in the code   myEditTextView setId R id my edit text 1

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inspired by  dilettante answer  here s my solution as an extension function in kotlin     sets a valid id that isn t in use    fun View findAndSetFirstValidId         var i  Int     do           i   Random nextInt         while  findViewById lt View gt  i     null      id   i

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Since API 17  the View class has a static method generateViewId   that will      generate a value suitable for use in setId int

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int fID  do       fID   Tools generateViewId      while  findViewById fID     null   view setId fID          public class Tools       private static final AtomicInteger sNextGeneratedId   new AtomicInteger 1       public static int generateViewId             if  Build VERSION SDK INT  lt  17                for                        final int result   sNextGeneratedId get                    int newValue   result   1                  if  newValue  gt  0x00FFFFFF                      newValue   1     Roll over to 1  not 0                  if  sNextGeneratedId compareAndSet result  newValue                         return result                                            else               return View generateViewId

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Just an addition to the answer of  phantomlimb    while View generateViewId   require API Level    17  this tool is compatibe with all API   according to current API Level  it decide weather using system API or not   so you can use ViewIdGenerator generateViewId   and View generateViewId   in the same time and don t worry about getting same id  import java util concurrent atomic AtomicInteger   import android annotation SuppressLint  import android os Build  import android view View            link View generateViewId     API Level  gt   17           API Level     lt p gt           API Level        link View generateViewId             link View generateViewId                 Id       lt p gt                       lt p gt     while   link View generateViewId    require API Level  gt   17  this tool is compatibe with all API      lt p gt     according to current API Level  it decide weather using system API or not  lt br gt     so you can use   link ViewIdGenerator generateViewId    and   link View generateViewId    in the    same time and don t worry about getting same id         author fantouchx gmail com     public class ViewIdGenerator       private static final AtomicInteger sNextGeneratedId   new AtomicInteger 1         SuppressLint  NewApi       public static int generateViewId              if  Build VERSION SDK INT  lt  17                for                        final int result   sNextGeneratedId get                       aapt-generated IDs have the high byte nonzero  clamp to the range under that                  int newValue   result   1                  if  newValue  gt  0x00FFFFFF                      newValue   1     Roll over to 1  not 0                  if  sNextGeneratedId compareAndSet result  newValue                         return result                                            else               return View generateViewId

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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

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My Choice      Method that could us an unique id      int getUniqueId            return  int                      SystemClock currentThreadTimeMillis

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I use   public synchronized int generateViewId         Random rand   new Random        int id      while  findViewById id   rand nextInt Integer MAX VALUE    1     null       return id      By using a random number I always have a huge chance of getting the unique id in first attempt

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Also you can define ids xml in res values  You can see an exact example in android s sample code   samples ApiDemos src com example android apis RadioGroup1 java samples ApiDemp res values ids xml

[android] Android: View.setID(int id) programmatically - how to avoid ID conflicts?

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