如何将 onClick 函数传递给 Intent

Question

I want to modularize the usage of my class but I have problem in passing function. I want to be able to pass an OnClickListener from 1 activity to this CoachmarkActivity .

I tried 2 different method: 1. Passing an OnClickListener to Intent 2. Passing a class, FollowUpClass, implements Serializable, which has method onClick.

You can see the code below. It is not complete code, but you should be able to comprehend this.

public class CoachmarkActivity extends Activity {

    public static final String RES_LAYOUT = "RES-LAYOUT";
    public static final String LISTENER = "LISTENER";
    public static final String FOLLOW_UP = "FOLLOW-UP";

    @Override protected void onCreate(Bundle savedInstance) {

        setContentView(getIntent.getIntExtra(RES_LAYOUT, R.layout.activity_default))

        Button button1 = (Button) findViewById(R.id.button1);
        Button button2 = (Button) findViewById(R.id.button2);

        // 1ST ATTEMPT        
        // I want to modularize this
        OnClickListener onClickPassedFromIntent = (OnClickListener) getIntent().getSerializableExtra(LISTENER);
        button1.setOnClickListener(onClickPassedFromIntent);

        // 2ND ATTEMPT
        final FollowUpListener folllowup = (FollowUpListener) getIntent().getSerializableExtra(FOLLOW_UP);
        button2.setOnClickListener(new OnClickListener() {
            @Override void onClick() {
                // !! Here is error, exception thrown
                folllowup.onClick();
            }
        });
    }

    /**
     * Public method to be used in other activity.
     * Invocation wanna be:
     *   CoachmarkActivity.startThisActivity(getActivity(), R.layout.coachmark1, new OnClickListener() {
     *      @Override void onClick() {
     *          // Do something
     *      }
     *   });
     */
    public static void startThisActivity(Context context, int resId, OnClickListener listener) {
        Intent intent = new Intent(context, CoachmarkActivity.class);
        intent.putExtra(RES_LAYOUT, resId);
        // !! Line below is error, onClickListener is not serializable, no method can accomadate below
        intent.putExtra(LISTENER, listener);
        context.startActivity(intent);
    }

    /**
     * Public method to be used in other activity.
     * Invocation wanna be:
     *   CoachmarkActivity.startThisActivity(getActivity(), R.layout.coachmark1, new FollowUpListener() {
     *      @Override void onClick() {
     *          // Do something
     *      }
     *   });
     */
    public static void startThisActivity(Context context, int resId, FollowUpListener folllowup) {
        Intent intent = new Intent(context, CoachmarkActivity.class);
        intent.putExtra(RES_LAYOUT, resId);
        intent.putExtra(FOLLOW_UP, followup);
        context.startActivity(intent);
    }
}

The abstract class:

public abstract class FollowUpListener implements Serializable {
    public abstract void onClick();
}

The problems are stated in the comment in source code above, with tag "!!" (Just CTRL+F "!!"). What I want to do is like passing a Delegate object (function in form of variable) in C#, but in Android Java.

Any idea? Thanks.

Answer 1

You are trying to add a Serializable extra to your Intent, but OnClickListener does not implement that interface. You can achieve what you want by creating a class that implements both of the interfaces you need.

private class SerializableClickListener implements View.OnClickListener, Serializable {

    @Override public void onClick() {
        // TODO handle click
    }
}

However, just because you can doesn't mean you should. Sending a click listener to another activity is a horrible code smell, and you should really rethink how you could do this via Intents/Broadcasts.

Answer 2

I tried to pass the OnlclickListener and I couldn't. then I tried this solution.

1. I made a static click listener variable in a GlobalData class

   public static View.OnClickListener btn;

2. Then when I call the startactivity to go to another activity I did this.

    GlobalData.btn = new View.OnClickListener() { @Override public void onClick(View v) { //Listern action } }; c.startActivity(new Intent(c, DialogActivity.class));

3. Then in the second activity, I can set the static listener reference which I used to assign a listener object in the first activity.

    b1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if(GlobalData.btn!=null){ GlobalData.btn1.onClick(v); } finish(); } });

I didn't use it directly as a parameter so I can do other stuff in the second activity listener. this worked for me.

But you have to think more because you are using a static reference. this is not a 100% solution. but it's worth trying.