是否有一种方法,我们可以实现onBackPressed()在Android片段类似的方式,我们实现在Android活动?

因为Fragment的生命周期没有onBackPressed()。在android3.0片段中是否有其他替代方法来覆盖onBackPressed() ?


当前回答

根据@ hammer的回答,这里是伪代码,它应该如何工作。 假设你的主活动名为BaseActivity,它有子片段(就像SlidingMenu库的例子一样)。 以下是步骤:

首先,我们需要创建接口和类,实现它的接口具有泛型方法

Create class interface OnBackPressedListener public interface OnBackPressedListener { public void doBack(); } Create class which implements skills of OnBackPressedListener public class BaseBackPressedListener implements OnBackPressedListener { private final FragmentActivity activity; public BaseBackPressedListener(FragmentActivity activity) { this.activity = activity; } @Override public void doBack() { activity.getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE); } } Since now, we will work on our code BaseActivity and its fragments Create private listener on top of your class BaseActivity protected OnBackPressedListener onBackPressedListener; create method to set listener in BaseActivity public void setOnBackPressedListener(OnBackPressedListener onBackPressedListener) { this.onBackPressedListener = onBackPressedListener; } in override onBackPressed implement something like that @Override public void onBackPressed() { if (onBackPressedListener != null) onBackPressedListener.doBack(); else super.onBackPressed(); in your fragment in onCreateView you should add our listener @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { activity = getActivity(); ((BaseActivity)activity).setOnBackPressedListener(new BaseBackPressedListener(activity)); View view = ... ; //stuff with view return view; }

瞧,现在当你在片段中单击返回时,你应该捕获你的自定义on back方法。

其他回答

新的和更好的方法:以下片段中的代码段将帮助您捕获反按事件。

JAVA

@Override
public void onAttach(@NonNull Context context) {
    super.onAttach(context);

    OnBackPressedCallback callback = new OnBackPressedCallback(true) {
        @Override
        public void handleOnBackPressed() {
            Toast.makeText(mContext, "back pressed", Toast.LENGTH_SHORT).show();
            
            // And when you want to go back based on your condition
            if (yourCondition) {
                this.setEnabled(false);
                requireActivity().onBackPressed();
            }
        }
    };

    requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
}

科特林

activity?.onBackPressedDispatcher?.addCallback(viewLifecycleOwner, object : OnBackPressedCallback(true) {
    override fun handleOnBackPressed() {

    }
})

根据@ hammer的回答,这里是伪代码,它应该如何工作。 假设你的主活动名为BaseActivity,它有子片段(就像SlidingMenu库的例子一样)。 以下是步骤:

首先,我们需要创建接口和类,实现它的接口具有泛型方法

Create class interface OnBackPressedListener public interface OnBackPressedListener { public void doBack(); } Create class which implements skills of OnBackPressedListener public class BaseBackPressedListener implements OnBackPressedListener { private final FragmentActivity activity; public BaseBackPressedListener(FragmentActivity activity) { this.activity = activity; } @Override public void doBack() { activity.getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE); } } Since now, we will work on our code BaseActivity and its fragments Create private listener on top of your class BaseActivity protected OnBackPressedListener onBackPressedListener; create method to set listener in BaseActivity public void setOnBackPressedListener(OnBackPressedListener onBackPressedListener) { this.onBackPressedListener = onBackPressedListener; } in override onBackPressed implement something like that @Override public void onBackPressed() { if (onBackPressedListener != null) onBackPressedListener.doBack(); else super.onBackPressed(); in your fragment in onCreateView you should add our listener @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { activity = getActivity(); ((BaseActivity)activity).setOnBackPressedListener(new BaseBackPressedListener(activity)); View view = ... ; //stuff with view return view; }

瞧,现在当你在片段中单击返回时,你应该捕获你的自定义on back方法。

public class MyActivity extends Activity {

    protected OnBackPressedListener onBackPressedListener;

    public interface OnBackPressedListener {
        void doBack();
    }

    public void setOnBackPressedListener(OnBackPressedListener onBackPressedListener) {
        this.onBackPressedListener = onBackPressedListener;
    }

    @Override
    public void onBackPressed() {
        if (onBackPressedListener != null)
            onBackPressedListener.doBack();
        else
            super.onBackPressed();
    } 

    @Override
    protected void onDestroy() {
        onBackPressedListener = null;
        super.onDestroy();
    }
}

在你的片段中添加以下内容,不要忘记实现mainactivity的接口。

public class MyFragment extends Framgent implements MyActivity.OnBackPressedListener {
    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
         ((MyActivity) getActivity()).setOnBackPressedListener(this);
    }

@Override
public void doBack() {
    //BackPressed in activity will call this;
}

}

如果你想要那种功能,你需要在你的活动中覆盖它,然后给你所有的片段添加一个YourBackPressed接口,当你按下后退按钮时,你就会在相关的片段上调用这个接口。

编辑:我想补充我之前的答案。

如果我今天要这样做,我将使用广播,或者如果我希望其他面板同步更新到主/主内容面板,则可能使用有序广播。

支持库中的LocalBroadcastManager可以帮助解决这个问题,你只需要在onBackPressed中发送广播,并在你的片段中订阅。我认为Messaging是一种更加解耦的实现,可伸缩性更好,所以它是我现在的官方实现建议。只要使用Intent的动作作为你信息的过滤器。发送你新创建的ACTION_BACK_PRESSED,从你的活动发送它,并在相关片段中监听它。

if片段和使用NavController简单调用

findNavController().popBackStack()