我的活动中有一些碎片
[1], [2], [3], [4], [5], [6]
如果当前活动片段是[2],那么在返回按钮上按下我必须从[2]返回到[1],否则什么也不做。
最好的做法是什么?
编辑:应用程序不能从[3]…[6]返回[2]
我的活动中有一些碎片
[1], [2], [3], [4], [5], [6]
如果当前活动片段是[2],那么在返回按钮上按下我必须从[2]返回到[1],否则什么也不做。
最好的做法是什么?
编辑:应用程序不能从[3]…[6]返回[2]
当前回答
我认为最简单的方法是创建一个接口,并在Activity中检查片段是否属于接口类型,如果是,则调用它的方法来处理弹出。下面是要在片段中实现的接口。
public interface BackPressedFragment {
// Note for this to work, name AND tag must be set anytime the fragment is added to back stack, e.g.
// getActivity().getSupportFragmentManager().beginTransaction()
// .replace(R.id.fragment_container, MyFragment.newInstance(), "MY_FRAG_TAG")
// .addToBackStack("MY_FRAG_TAG")
// .commit();
// This is really an override. Should call popBackStack itself.
void onPopBackStack();
}
下面是如何实现它。
public class MyFragment extends Fragment implements BackPressedFragment
@Override
public void onPopBackStack() {
/* Your code goes here, do anything you want. */
getActivity().getSupportFragmentManager().popBackStack();
}
在你的Activity中,当你处理弹出时(可能在onBackPressed和onOptionsItemSelected中),使用这个方法弹出backstack:
public void popBackStack() {
FragmentManager fm = getSupportFragmentManager();
// Call current fragment's onPopBackStack if it has one.
String fragmentTag = fm.getBackStackEntryAt(fm.getBackStackEntryCount() - 1).getName();
Fragment currentFragment = getSupportFragmentManager().findFragmentByTag(fragmentTag);
if (currentFragment instanceof BackPressedFragment)
((BackPressedFragment)currentFragment).onPopBackStack();
else
fm.popBackStack();
}
其他回答
检查后台工作完美
@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK)
{
if (getFragmentManager().getBackStackEntryCount() == 1)
{
// DO something here since there is only one fragment left
// Popping a dialog asking to quit the application
return false;
}
}
return super.onKeyDown(keyCode, event);
}
创建接口:
后退按钮处理程序接口
public interface BackButtonHandlerInterface {
void addBackClickListener (OnBackClickListener onBackClickListener);
void removeBackClickListener (OnBackClickListener onBackClickListener);
}
OnBackClickListener
public interface OnBackClickListener {
boolean onBackClick();
}
在活动:
public class MainActivity extends AppCompatActivity implements BackButtonHandlerInterface {
private ArrayList<WeakReference<OnBackClickListener>> backClickListenersList = new ArrayList<>();
@Override
public void addBackClickListener(OnBackClickListener onBackClickListener) {
backClickListenersList.add(new WeakReference<>(onBackClickListener));
}
@Override
public void removeBackClickListener(OnBackClickListener onBackClickListener) {
for (Iterator<WeakReference<OnBackClickListener>> iterator = backClickListenersList.iterator();
iterator.hasNext();){
WeakReference<OnBackClickListener> weakRef = iterator.next();
if (weakRef.get() == onBackClickListener){
iterator.remove();
}
}
}
@Override
public void onBackPressed() {
if(!fragmentsBackKeyIntercept()){
super.onBackPressed();
}
}
private boolean fragmentsBackKeyIntercept() {
boolean isIntercept = false;
for (WeakReference<OnBackClickListener> weakRef : backClickListenersList) {
OnBackClickListener onBackClickListener = weakRef.get();
if (onBackClickListener != null) {
boolean isFragmIntercept = onBackClickListener.onBackClick();
if (!isIntercept) isIntercept = isFragmIntercept;
}
}
return isIntercept;
}
}
在片段:
public class MyFragment extends Fragment implements OnBackClickListener{
private BackButtonHandlerInterface backButtonHandler;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
backButtonHandler = (BackButtonHandlerInterface) activity;
backButtonHandler.addBackClickListener(this);
}
@Override
public void onDetach() {
super.onDetach();
backButtonHandler.removeBackClickListener(this);
backButtonHandler = null;
}
@Override
public boolean onBackClick() {
//This method handle onBackPressed()! return true or false
return false;
}
}
更新
提供自定义向后导航
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
}
}
这是一个非常好的和可靠的解决方案:http://vinsol.com/blog/2014/10/01/handling-back-button-press-inside-fragments/
这家伙已经制作了一个抽象片段,处理backPress行为,并使用策略模式在活动片段之间切换。
对于你们中的一些人来说,抽象课程可能会有一些缺陷。
简单地说,链接中的解决方案是这样的:
// Abstract Fragment handling the back presses
public abstract class BackHandledFragment extends Fragment {
protected BackHandlerInterface backHandlerInterface;
public abstract String getTagText();
public abstract boolean onBackPressed();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(!(getActivity() instanceof BackHandlerInterface)) {
throw new ClassCastException("Hosting activity must implement BackHandlerInterface");
} else {
backHandlerInterface = (BackHandlerInterface) getActivity();
}
}
@Override
public void onStart() {
super.onStart();
// Mark this fragment as the selected Fragment.
backHandlerInterface.setSelectedFragment(this);
}
public interface BackHandlerInterface {
public void setSelectedFragment(BackHandledFragment backHandledFragment);
}
}
和在活动中的用法:
// BASIC ACTIVITY CODE THAT LETS ITS FRAGMENT UTILIZE onBackPress EVENTS
// IN AN ADAPTIVE AND ORGANIZED PATTERN USING BackHandledFragment
public class TheActivity extends FragmentActivity implements BackHandlerInterface {
private BackHandledFragment selectedFragment;
@Override
public void onBackPressed() {
if(selectedFragment == null || !selectedFragment.onBackPressed()) {
// Selected fragment did not consume the back press event.
super.onBackPressed();
}
}
@Override
public void setSelectedFragment(BackHandledFragment selectedFragment) {
this.selectedFragment = selectedFragment;
}
}
我认为最简单的方法是创建一个接口,并在Activity中检查片段是否属于接口类型,如果是,则调用它的方法来处理弹出。下面是要在片段中实现的接口。
public interface BackPressedFragment {
// Note for this to work, name AND tag must be set anytime the fragment is added to back stack, e.g.
// getActivity().getSupportFragmentManager().beginTransaction()
// .replace(R.id.fragment_container, MyFragment.newInstance(), "MY_FRAG_TAG")
// .addToBackStack("MY_FRAG_TAG")
// .commit();
// This is really an override. Should call popBackStack itself.
void onPopBackStack();
}
下面是如何实现它。
public class MyFragment extends Fragment implements BackPressedFragment
@Override
public void onPopBackStack() {
/* Your code goes here, do anything you want. */
getActivity().getSupportFragmentManager().popBackStack();
}
在你的Activity中,当你处理弹出时(可能在onBackPressed和onOptionsItemSelected中),使用这个方法弹出backstack:
public void popBackStack() {
FragmentManager fm = getSupportFragmentManager();
// Call current fragment's onPopBackStack if it has one.
String fragmentTag = fm.getBackStackEntryAt(fm.getBackStackEntryCount() - 1).getName();
Fragment currentFragment = getSupportFragmentManager().findFragmentByTag(fragmentTag);
if (currentFragment instanceof BackPressedFragment)
((BackPressedFragment)currentFragment).onPopBackStack();
else
fm.popBackStack();
}
最理想的方法如下: 片段:当按下后退按钮并自定义时调用的回调
public class MyActivity extends Activity
{
//...
//Defined in Activity class, so override
@Override
public void onBackPressed()
{
super.onBackPressed();
myFragment.onBackPressed();
}
}
public class MyFragment extends Fragment
{
//Your created method
public static void onBackPressed()
{
//Pop Fragments off backstack and do your other checks
}
}