Essential Android Interfaces edit forum

Basic Listener

The “listener” or “observer” pattern is the most common strategy for creating asynchronous callbacks in Android development.

public class MyCustomObject {       
  
  //1 - Define the interface 
  public interface MyCustomObjectListener {
      public void onAction(String action);
  }

  //2 - Declare your listener object
  private MyCustomObjectListener listener;

  // and initialize it in the costructor
  public MyCustomObject() {        
    this.listener = null; 
 }

 //3 - Create your listener setter
 public void setCustomObjectListener(MyCustomObjectListener listener) {
    this.listener = listener;
 }

 // 4 - Trigger listener event
 public void makeSomething(){
    if (this.listener != null){
       listener.onAction("hello!");
 }        
}

Now on your Activity:

public class MyActivity extends Activity {
   public final String TAG = "MyActivity";

  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main_activity);
        

      MyCustomObject mObj = new MyCustomObject();
    
      //5 - Implement listener callback
      mObj.setCustomObjectListener(new MyCustomObjectListener() {
        @Override
          public void onAction(String action) {
              Log.d(TAG, "Value: "+action);
          }
      });
   }
}

Table Of Contents
39 ACRA
55 Interfaces
64 Menu
112 Loader
119 Xposed
132 Colors
135 Fresco
140 AdMob
147 Button
156 Vk SDK
170 XMPP
176 OpenCV
200 FileIO
203 Moshi
217 Paint
231 AIDL
241 JCodec
243 Okio
255 Looper
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