How to create our own Listener interface in android

Question

Could someone help me to create user defined listener interface with some code snippets

User · Answer

In Android you can create an interface such as Listener and your Activity implements it but i don t think it is a good idea  if we have many components to listen the changes of their state we can create a BaseListener implements interface Listener and use type code to handle them  we can bind the method when we create XML file for example    lt Button           android id    id button4            android layout width  match parent            android layout height  wrap content            android text  Button4            android onClick  Btn4OnClick    gt    and the source code    public void Btn4OnClick View view              String strTmp      Button04             tv setText strTmp               but i don t think it is a good idea

User · Answer

Create listener interface   public interface YourCustomListener       public void onCustomClick View view                  pass view as argument or whatever you want      And create method setOnCustomClick in another activity or fragment    where you want to apply your custom listener          public void setCustomClickListener YourCustomListener yourCustomListener        this yourCustomListener  yourCustomListener      Call this method from your First activity  and pass the listener interface

User · Answer

Simple method to do this approach  Firstly implements the OnClickListeners in your Activity class   Code   class MainActivity extends Activity implements OnClickListeners   protected void OnCreate Bundle bundle            super onCreate bundle           setContentView R layout activity main xml           Button b1  Button findViewById R id sipsi           Button b2  Button findViewById R id pipsi           b1 SetOnClickListener this           b2 SetOnClickListener this          public void OnClick View V                int i v getId            switch i                        case R id sipsi                          you can do anything from this button             break                    case R id pipsi                              you can do anything from this button                    break

User · Answer

I have done it something like below for sending my model class from the Second Activity to First Activity  I used LiveData to achieve this  with the help of answers from Rupesh and TheCodeFather   Second Activity  public static MutableLiveData lt AudioListModel gt  getLiveSong             MutableLiveData lt AudioListModel gt  result   new MutableLiveData lt  gt             result setValue liveSong           return result           liveSong  is AudioListModel declared globally  Call this method in the First Activity  PlayerActivity getLiveSong   observe this  new Observer lt AudioListModel gt                   Override             public void onChanged AudioListModel audioListModel                    if  PlayerActivity mediaPlayer    null  amp  amp  PlayerActivity mediaPlayer isPlaying                          Log d  LiveSong--- gt Changes-- gt    audioListModel getSongName                                                   May this help for new explorers like me

User · Answer

Create a new file   MyListener java   public interface MyListener          you can define any parameter as per your requirement     public void callback View view  String result       In your activity  implement the interface   MyActivity java   public class MyActivity extends Activity implements MyListener       override            public void onCreate            MyButton m   new MyButton this                method is invoked when MyButton is clicked      override     public void callback View view  String result                  do your stuff here           In your custom class  invoke the interface when needed   MyButton java   public class MyButton       MyListener ml          constructor     MyButton MyListener ml              Setting the listener         this ml   ml             public void MyLogicToIntimateOthers               Invoke the interface         ml callback this   success

User · Answer

please do read observer pattern  listener interface  public interface OnEventListener       void onEvent EventResult er          or void onEvent    as per your need     then in your class say Event class  public class Event       private OnEventListener mOnEventListener       public void setOnEventListener OnEventListener listener            mOnEventListener   listener             public void doEvent                           code code code                          and in the end           if  mOnEventListener    null               mOnEventListener onEvent eventResult      event result object              in your driver class MyTestDriver  public class MyTestDriver       public static void main String   args            Event e   new Event            e setOnEventListener new OnEventListener                  public void onEvent EventResult er                        do your work                                      e doEvent

User · Answer

I have created a Generic AsyncTask Listener which get result from AsycTask seperate class and give it to  CallingActivity using Interface Callback    new GenericAsyncTask context new AsyncTaskCompleteListener                          public void onTaskComplete String response                                      do your work                             execute      Interface  interface AsyncTaskCompleteListener lt T gt       public void onTaskComplete T result       GenericAsyncTask  class GenericAsyncTask extends AsyncTask lt String  Void  String gt         private AsyncTaskCompleteListener lt String gt  callback       public A Context context  AsyncTaskCompleteListener lt String gt  cb            this context   context          this callback   cb             protected void onPostExecute String result           finalResult   result         callback onTaskComplete result              Have a look at this   this question for more details

User · Answer

There are 4 steps   1 create interface class  listener   2 use interface in view 1  define variable    3 implements interface to view 2  view 1 used in view 2   4 pass interface in view 1 to view 2  Example   Step 1  you need create interface and definde function  public interface onAddTextViewCustomListener       void onAddText String text       Step 2  use this interface in view   public class CTextView extends TextView         onAddTextViewCustomListener onAddTextViewCustomListener    listener custom      public CTextView Context context  onAddTextViewCustomListener onAddTextViewCustomListener            super context           this onAddTextViewCustomListener   onAddTextViewCustomListener          init context  null              public CTextView Context context   Nullable AttributeSet attrs            super context  attrs           init context  attrs              public CTextView Context context   Nullable AttributeSet attrs  int defStyleAttr            super context  attrs  defStyleAttr           init context  attrs               RequiresApi api   Build VERSION CODES LOLLIPOP      public CTextView Context context   Nullable AttributeSet attrs  int defStyleAttr  int defStyleRes            super context  attrs  defStyleAttr  defStyleRes           init context  attrs              public void init Context context   Nullable AttributeSet attrs             if  isInEditMode                return             call listener         onAddTextViewCustomListener onAddText  this TextView added              Step 3 4  implements to activity   public class MainActivity extends AppCompatActivity implements onAddTextViewCustomListener          Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main              get main view from layout         RelativeLayout mainView    RelativeLayout findViewById R id mainView              create new CTextView and set listener         CTextView cTextView   new CTextView getApplicationContext    this              add cTextView to mainView         mainView addView cTextView               Override     public void onAddText String text            Log i  Message    text

User · Answer

In the year of 2018  there s no need for listeners interfaces  You ve got Android LiveData to take care of passing the desired result back to the UI components   If I ll take Rupesh s answer and adjust it to use LiveData  it will like so   public class Event        public LiveData lt EventResult gt  doEvent                             code code code                           and in the end           LiveData lt EventResult gt  result   new MutableLiveData lt  gt              result setValue eventResult            return result            and now in your driver class MyTestDriver   public class MyTestDriver       public static void main String   args            Event e   new Event            e doEvent   observe this  new  Observer lt EventResult gt                   Override             public void onChanged final EventResult er                       do your work                                      For more information along with code samples you can read my post about it  as well as the offical docs   When and why to use LiveData  Official docs

[android] How to create our own Listener interface in android?

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