无法从OnClickListener类访问Application变量

Question

I have an OnCLick listener class in my Android app defined as below. I need to access an application-level variable, but the last line in this code generates this compile error: "The method getApplication() is undefined for the type OnClickListenerSelectPresetItem"

How can I access Application variables from this class?

public class OnClickListenerSelectPresetItem implements OnClickListener {
    private long glbMealId = ((MyApplication) this.getApplication()).getMealId();

Answer 1

The error is pretty explicit. this is the listener object, not the Context executing the listener.

You should use ActivityExecutingListener.this.getApplication() .

EDIT : If your listener is not an anonymous/inner class, you need to store the Context in the listener instance :

public class OnClickListenerSelectPresetItem implements OnClickListener {
  private long glbMealId;
  private Activity activity;

  public OnClickListenerSelectPresetItem(Activity activity) {
    this.activity = activity; // facultative, but you may need it in onClick() ...
    this.glbMealId = ((MyApplication) activity.getApplication()).getMealId();
  }

  ...
}

Answer 2

The this operator in your case references OnClickListenerSelectPresetItem .

Here is an example of what you're trying to do, cut-pasted from one of my projects:

public class PageFragment extends Fragment {

    private boolean isVisible( View view )
    {
        return true; // fake 
    }

    private class OnLikeClickListener implements OnClickListener
    {
        private boolean isVisible = PageFragment.this.isVisible(); // <------
        @Override
        public void onClick(View v) 
        {
            // Do whatever

        }

    }
}

Answer 3

OK. Finally understood what your question is all about.

You wanna reference your implementation of the Application class. So either:

1. Pass an Activity to the constructor of OnClickListenerSelectPresetItem as @pdegand59 suggested.

2. Make MyApplication a singleton, for convenience (this is what I do because I don't like passing Activities): Android Application as Singleton