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() ?
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
在kotlin的情况下使用这个onAttach回调
override fun onAttach(context: Context) {
super.onAttach(context)
val callback: OnBackPressedCallback = object :
OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
// your onbackpressed code
}
}
requireActivity().onBackPressedDispatcher.addCallback(this, callback)
}
其他回答
在片段的onCreate方法中添加以下内容:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
OnBackPressedCallback callback = new OnBackPressedCallback(true) {
@Override
public void handleOnBackPressed() {
//Handle the back pressed
}
};
requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
}
使用导航组件,你可以这样做:
Java
public class MyFragment extends Fragment {
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// This callback will only be called when MyFragment is at least Started.
OnBackPressedCallback callback = new OnBackPressedCallback(true /* enabled by default */) {
@Override
public void handleOnBackPressed() {
// Handle the back button event
}
});
requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
// The callback can be enabled or disabled here or in handleOnBackPressed()
}
...
}
科特林
class MyFragment : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// This callback will only be called when MyFragment is at least Started.
val callback = requireActivity().onBackPressedDispatcher.addCallback(this) {
// Handle the back button event
}
// The callback can be enabled or disabled here or in the lambda
}
...
}
在mainActivity实现回调接口中
protected mainActivity.OnBackPressedListener onBackPressedListener;
public interface OnBackPressedListener {
void doBack();
}
public void setOnBackPressedListener(mainActivity.OnBackPressedListener onBackPressedListener) {
this.onBackPressedListener = onBackPressedListener;
}
@Override
public void onBackPressed() {
if (onBackPressedListener != null) {
onBackPressedListener.doBack();
} else {
super.onBackPressed();
}
}
在片段实现接口OnBackPressedListener,我们写在mainActivity
implements mainActivity.OnBackPressedListener
mainActivity是我的基本活动,在你的片段onCreateView方法中编写以下代码
((mainActivity) getActivity()).setOnBackPressedListener(this);
并实现OnBackPressedListener接口方法doBack
@Override
public void doBack() {
//call base fragment
}
现在使用doBack()方法调用你想要调用的fragment
非常简短而甜蜜的回答:
getActivity().onBackPressed();
我案例的整个场景说明:
我在MainActivity中有FragmentA, 我从FragmentA打开FragmentB (FragmentB是FragmentA的子或嵌套片段)
Fragment duedateFrag = new FragmentB();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.container_body, duedateFrag);
ft.addToBackStack(null);
ft.commit();
现在如果你想从FragmentB访问FragmentA你可以简单地输入getActivity().onBackPressed();在FragmentB。
如果你使用EventBus,它可能是一个更简单的解决方案:
在你的片段中:
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
EventBus.getDefault().register(this);
}
@Override
public void onDetach() {
super.onDetach();
EventBus.getDefault().unregister(this);
}
// This method will be called when a MessageEvent is posted
public void onEvent(BackPressedMessage type){
getSupportFragmentManager().popBackStack();
}
在你的Activity类中你可以定义:
@Override
public void onStart() {
super.onStart();
EventBus.getDefault().register(this);
}
@Override
public void onStop() {
EventBus.getDefault().unregister(this);
super.onStop();
}
// This method will be called when a MessageEvent is posted
public void onEvent(BackPressedMessage type){
super.onBackPressed();
}
@Override
public void onBackPressed() {
EventBus.getDefault().post(new BackPressedMessage(true));
}
java只是一个POJO对象
这是超级干净的,没有接口/实现的麻烦。