活动到活动回调侦听器 [英] activity to activity callback listener

问题描述

我们假设有2个活动Activity1和Activity2.我需要从methodAct2(在Activity2内部)调用方法methodAct1()(在Activity1内部).我认为应该使用回调侦听器工作-我不想使用EventBus库！

Let's suppose 2 activities Activity1 and Activity2. I need to call method methodAct1() (inside Activity1) from methodAct2 (inside Activity2). I think it should work using callback listener - I don't want to use EventBus libs!

我使用以下代码得到java.lang.NullPointerException:

界面:

public interface MyListener {
    public void listen();
}

创建事件的活动:

public class Activity2 extends Activity {

    private MyListener  myListener;

    public void setUpListener(MyListener myListener) {
        this.myListener = myListener;
    }

    private void doWork(){
        //do stuff 
        myListener.listen();
    }
}

完成工作后我想在该事件中获得的活动:

Activity where I'd like to get that event when work is done:

public class Activity1 extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Activity2 activity2 = new Activity2();
        activity2.setUpListener(new setUpListener() {
            @Override
            public void listen() {
                // get the event here

            }
        });
    }
}

推荐答案

这绝对不可能.您永远不会自己实例化一个新的活动.您不会同时运行两个活动.

This is absolutely not possible. You never instanciate a new Activity yourself. You will not have two Activities running at the same time.

如果您希望另一个Activity根据您先前的Activity想要做什么，则需要将其添加到Intent中.

If you want another Activity to do something, based on what your previous Activity wants, then you need to add that to your Intent.

Intent intent = new Intent(this, Activity2.class);
intent.putExtra("data field", "data value");
startActivity(intent);

如果您希望通过回调实现特定功能，那么您可能会想到片段.这样，您可以运行相同的Activity，并且可以告诉各个Fragment他们需要做什么.

If you want specific functionality through a callback then you might be thinking of Fragments. In this way, you can have the same Activity running and it can tell individual Fragments what they need to do.

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