Avoiding "This Handler class should be static or leaks might occur".

ExampleStaticHandler.java

  
  // This is OLD way of usnig Handler which shows an warning.
  private Handler oldHandler = new Handler() {
 
    @Override
    public void handleMessage(Message msg) {
      // Handle a message as you want.
    }
    
  }
  
  // This is NEW way to avoid the warning.
  private IStaticHandler newHandler = new IStaticHandler() {
 
    @Override
    public void handleMessage(Message msg) {
      // Handle a message as the same as old handler is doing.
    }
    
  }
    
  public void exampleOfOldHandler() {
    // No initialization
    Handler handler = oldHandler;
    handler.sendEmptyMessage(0);
  }
  
  public void exampleOfNewHandler() {
    // Initialize from factory class
    Handler handler = StaticHandlerFactory.create(newHandler);
    handler.sendEmptyMessage(0);
  }

IStaticHandler.java

import android.os.Message;
 
public interface IStaticHandler {
  void handleMessage(Message msg);
}

StaticHandlerFactory.java

import java.lang.ref.WeakReference;
 
import android.os.Handler;
import android.os.Message;
 
public class StaticHandlerFactory {
 
  public static StaticHandler create(IStaticHandler ref) {
    return new StaticHandler(ref);
  }
 
  // This has to be nested.
  static class StaticHandler extends Handler {
    WeakReference<IStaticHandler> weakRef;
 
    public StaticHandler(IStaticHandler ref) {
      this.weakRef = new WeakReference<IStaticHandler>(ref);
    }

    @Override
    public void handleMessage(Message msg) {
      if (weakRef.get() == null) {
        throw new RuntimeException("Something goes wrong.");
      } else {
        weakRef.get().handleMessage(msg);
      }
    }
  }
}