问题
I am calling some fragments from HomeScreen.java. Now whenever i press back button in any fragment, its closes the application. But i want previous fragment which was loaded.Following is HomeScreen.java code.
public class HomeScreen extends AppCompatActivity implements JobListFragment.OnJobSelectedListener {
Timer timer;
TimerTask timerTask;
final android.os.Handler handler = new android.os.Handler();
FragmentTransaction transaction;
android.app.FragmentManager fragmentManager;
ProfileFragment profileFragment;
HomeFragment homeFragment;
LocationFragment locationFragment;
JobListFragment jobListFragment;
JobDetailsFragment jobDetailsFragment;
ActionBar actionBar;
Toolbar toolbar;
Fragment fragment;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.homescreen);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
actionBar = getSupportActionBar();
KitLocate.initKitLocate(HomeScreen.this, "f08fb7d8-bc35-46c6-aaad-07657eb4a59c");
KitLocate.setUniqueUserID(HomeScreen.this, Utils.getUniqueId(HomeScreen.this));
String onlineStatus = Utils.getStringPref(HomeScreen.this, Constants.onlineStatus);
profileFragment =new ProfileFragment();
homeFragment = new HomeFragment();
locationFragment=new LocationFragment();
jobListFragment = new JobListFragment();
jobDetailsFragment = new JobDetailsFragment();
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
transaction.add(R.id.fragmentContainer, homeFragment);
transaction.commit();
}
public void startTimer() {
//set a new Timer
timer = new Timer();
//initialize the TimerTask's job
initializeTimerTask();
//schedule the timer, after the first 5000ms the TimerTask will run every 10000ms
timer.schedule(timerTask, 1000, 10000); //
}
public void stoptimertask(View v) {
//stop the timer, if it's not already null
if (timer != null) {
timer.cancel();
timer = null;
}
}
public void initializeTimerTask() {
timerTask = new TimerTask() {
public void run() {
//use a handler to run a toast that shows the current timestamp
handler.post(new Runnable() {
public void run() {
String locality = PeriodicHandler.getInstance().getLocality();
String subLocality = PeriodicHandler.getInstance().getSubLocality();
LocationFragment locationFrag = (LocationFragment)
getFragmentManager().findFragmentById(R.id.fragmentContainer);
/*if(locationFrag != null){
System.out.println();
locationFrag.updateLocationText();
}*/
}
});
}
};
}
@Override
public void onJObSelected(int position, String jobId) {
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
jobDetailsFragment = new JobDetailsFragment();
if(jobDetailsFragment.isAdded() || jobDetailsFragment.isHidden()){
System.out.println("44444444444444444444");
Bundle bundle = new Bundle();
bundle.putString(Constants.jobID, jobId);
jobDetailsFragment.setArguments(bundle);
transaction.replace(R.id.fragmentContainer, jobDetailsFragment);
transaction.addToBackStack(null);
}else{
Bundle bundle = new Bundle();
bundle.putString(Constants.jobID, jobId);
jobDetailsFragment.setArguments(bundle);
transaction.add(R.id.fragmentContainer, jobDetailsFragment);//transaction.show(profileFragment);
}
transaction.commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.home_menu, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.action_account:
actionBar.setDisplayShowHomeEnabled(false);
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
System.out.println("isadded"+profileFragment.isAdded()+"isHidden"+profileFragment.isHidden());
if(profileFragment.isAdded() || profileFragment.isHidden()) {
/*transaction.show(profileFragment);
transaction.hide(locationFragment);*/
profileFragment = new ProfileFragment();
transaction.replace(R.id.fragmentContainer, profileFragment, LocationFragment.TAG);
transaction.addToBackStack("account");
}else{
transaction.add(R.id.fragmentContainer, profileFragment);//transaction.show(profileFragment);
}
transaction.commit();
break;
case R.id.action_profile_location:
actionBar.setDisplayShowHomeEnabled(false);
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
System.out.println("isadded"+locationFragment.isAdded()+"isHidden"+locationFragment.isHidden());
if(locationFragment.isAdded() || locationFragment.isHidden()) {
/*transaction.show(locationFragment);
transaction.hide(profileFragment);*/
locationFragment = new LocationFragment();
transaction.replace(R.id.fragmentContainer, locationFragment);
transaction.addToBackStack(null);
}
else{
transaction.add(R.id.fragmentContainer, locationFragment);//transaction.show(profileFragment);
}
transaction.commit();
break;
case R.id.action_profile_time:
actionBar.setDisplayShowHomeEnabled(false);
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
System.out.println("isadded" + jobListFragment.isAdded() + "isHidden" + jobListFragment.isHidden());
if(jobListFragment.isAdded() || jobListFragment.isHidden()){
System.out.println("111111111111111111");
// transaction.show(jobListFragment);
jobListFragment = new JobListFragment();
transaction.replace(R.id.fragmentContainer, jobListFragment);
transaction.addToBackStack("profile");
}else{
transaction.add(R.id.fragmentContainer, jobListFragment);//transaction.show(profileFragment);
}
transaction.commit();
break;
case android.R.id.home:
actionBar.setDisplayShowHomeEnabled(false);
actionBar.setDisplayHomeAsUpEnabled(false);
actionBar.setHomeButtonEnabled(false);
fragmentManager = getFragmentManager();
transaction = fragmentManager.beginTransaction();
System.out.println("isadded"+homeFragment.isAdded()+"isHidden"+homeFragment.isHidden());
if(homeFragment.isAdded() || homeFragment.isHidden()){
System.out.println("55555555555555555");
//transaction.remove(homeFragment);
//transaction.add(R.id.fragmentContainer, homeFragment);
//transaction.show(homeFragment);
homeFragment = new HomeFragment();
transaction.replace(R.id.fragmentContainer, homeFragment);
transaction.addToBackStack("home");
}else{
transaction.add(R.id.fragmentContainer, homeFragment);//transaction.show(profileFragment);
}
transaction.commit();
break;
}
return true;
}
/*@Override
public void onBackPressed() {
if (getFragmentManager().popBackStackImmediate()) return;
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
finish();
else
finishAfterTransition();
}*/
}
So i have three menu icons, i am loading fragments from menu clicks.So please let me know something i did wrong.
回答1:
Suppose you have 3 fragments
(1) Fragment A
(2) Fragment B
(3) Fragment C
You are going A to B then B to C then Backpress will return to B then again Backpress will return to A then Backpress will close app.
Method for replace Fragment by adding Tag:
Pass your fragment and tag as arguments in below method.
private void replaceFragment(Fragment frag, String tag) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.replace(R.id.realtabcontent, frag);
transaction.addToBackStack(tag);
transaction.commitAllowingStateLoss();
}
No need to write onBackPress() or fragmentManager.popBackStack(), it will automatically handle.
Done
回答2:
Add this
@Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
}
else
{
super.onBackPressed;
}
}
来源：https://stackoverflow.com/questions/30779054/fragments-addtobackstack-closing-the-application