在应用程序还原时在片段中设置侦听器实例

问题描述

我创建了包含OnDialogClickListener参数的ErrorDialogFragment.

I have created ErrorDialogFragment which contains OnDialogClickListener parameter.

需要显示ErrorDialogFragment的所有其他Fragment或Activity都通过ErrorDialogFragment中的公共方法设置OnDialogClickListener.同时，所有这些活动和片段都实现了OnDialogClickListener.

Every other Fragment or Activity that needs to show ErrorDialogFragment sets OnDialogClickListener via public method in ErrorDialogFragment. In the same time, all those activities and fragments implements OnDialogClickListener .

如果在显示ErrorDialogFragment时用户从应用程序退出，并在一段时间后返回(从内存中删除应用程序)，则会出现问题.如果用户单击片段选项，它将被强制关闭，因为未设置OnDialogClickListener.

Problem occurs if user exits from application when ErrorDialogFragment is showed, and returns after a while (app is removed from memory). If user clicks on fragment options it will force close, because OnDialogClickListener is not set.

我对活动侦听器片段模式不满意，我该如何解决(应用程序已经在beta中.不能接受大的模式更改.

Am i wrong with with activity-listener-fragment pattern, and how do i solve this (application is in beta already.. big pattern change is not acceptable.

例如:

接口:

public interface OnDialogClickListener {
    public void OnPositiveClick(int key, Object... args);
    public void OnNegativeClick(int key, Object... args);
}

活动:

public class Home extends FragmentActivity implements TabListener, ServiceConnection, OnDialogClickListener {
    .
    .
    .
@Override
public void OnPositiveClick(int key, Object... args) {
    //some actions
}

@Override
public void OnNegativeClick(int key, Object... args) {
    //some actions
}

片段:

public class ErrorDialogFragment extends DialogFragment implements OnClickListener {

OnDialogClickListener OnDialogClickListener = null;

    .
    .
    .

public void setDialogListener(OnDialogClickListener listener)
{   
    OnDialogClickListener = listener;
}

@Override
public void onClick(DialogInterface dialog, int which) {    
    if(OnDialogClickListener != null){
        switch (which) {
            case DialogInterface.BUTTON_POSITIVE:
                this.dismiss();
                OnDialogClickListener.OnPositiveClick(KEY, args);
                break;
            default:
                this.dismiss();
                OnDialogClickListener.OnNegativeClick(KEY, args);
                break;
        }
    }
    else
        this.dismiss();
}    

推荐答案

您可以更好地在DialogFragment#onAttach(Activity)回调中进行设置，如下所示:

You're way off better setting it in DialogFragment#onAttach(Activity) callback like this:

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    try { 
        mOnDialogClickListener = (OnDialogClickListener) activity;
    } catch(ClassCastException e) {
        throw new ClassCastException(activity.toString() + "must implement" + OnDialogClickListener.class.getSimpleName());
    }
}

@Override
public void onDetach() {
    super.onDetach()
    mOnDialogClickListener = null;
}

最后，显然，使您的Activity实现OnDialogClickListener

And finally, obviously, make your Activity implements OnDialogClickListener

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