I have to include three Fragment on my main Activity on click of Three Buttons on app bar. Now, Question is I want to go back from second activity to specific fragment on mainActivity I am using Intent but at start of app intent is null and get nullpointer exception and app crash.
Here is MainActivity.java
public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;
FragmentTransaction fragmentTransaction;
HomeFragment homeFrag;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
//--------Set and Get Tool Bar-------//
setSupportActionBar(binding.appbar);
getSupportActionBar().setTitle("");
if(getIntent() !=null){
String is = getIntent().getStringExtra("check");
if(is.equals("1")){
SearchFragment searchFrag = new SearchFragment();
if(searchFrag != null){
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer, searchFrag)
.addToBackStack(null).commit();
}
}
}else{
homeFrag = new HomeFragment();
if(homeFrag!=null) {
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer, homeFrag).commit();
}
}
}
public void MoveToSearchActivity(View view){
SearchFragment searchFag = new SearchFragment();
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer,searchFag).commit();
}
public void MoveToHomeActivity(View view){
if(homeFrag!=null) {
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer, homeFrag).commit();
}
}
public void MoveToAlertFrag(View view){
AlertFragment alertFragment = new AlertFragment();
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer,alertFragment).commit();
}
And here is my FilterActivity.java from which I'm going back to fragment:
public class FilterActivity extends AppCompatActivity{
private ActivityFilterBinding binding;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_filter);
//--------------Get ToolBar-----------//
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle(" ");
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
case android.R.id.home:
Intent homeIntent = new Intent(FilterActivity.this, MainActivity.class);
homeIntent.putExtra("check",1);
startActivity(homeIntent);
break;
default:
break;
}
return true;
}
}
Thanks.
Try this in MainActivity,
// Toolbar code
...
int is = -1;
if (getIntent() != null && getIntent().hasExtra("check")) {
is = getIntent().getIntExtra("check", -1);
}
switch (is) {
case 1:
// load SearchFragment
break;
case 2:
// load MoveToAlertFrag
break;
default:
// load HomeFragment
break;
}
Related
This is my main activity where I am calling my fragments:
public class what extends AppCompatActivity {
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mToggle;
private ListView mDrawerList;
private ArrayAdapter<String> mAdapter;
private FragmentTransaction fragmentTransaction;
NavigationView navigationView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_what);
mDrawerLayout=(DrawerLayout)findViewById(R.id.drawer_layout);
mToggle=new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
fragmentTransaction= getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_content,new mainfrag());
fragmentTransaction.commit();
ActionBar actionBar= getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
navigationView=(NavigationView)findViewById(R.id.nav_view);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(0).setChecked(true);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_main:
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_main);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new mainfrag());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("SGPA and CGPA Calculator"));
item.setChecked(true);
break;
case R.id.nav_savedcal:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_savedcal);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new savedFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("Saved Calculations"));
item.setChecked(true);
break;
case R.id.nav_upldoc:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_upldoc);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new uploadedfragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("Uploaded documents"));
item.setChecked(true);
break;
case R.id.nav_site:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.setCheckedItem(R.id.nav_site);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new resultsite());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("VTU Results"));
item.setChecked(true);
break;
}
return false;
}
});
}
public boolean onOptionsItemSelected(MenuItem item ){
if(mToggle.onOptionsItemSelected(item)){
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public void onBackPressed() {
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
switch (which) {
case DialogInterface.BUTTON_POSITIVE: {
finish();
}
break;
case DialogInterface.BUTTON_NEGATIVE:
break;
}
}
};
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?").setPositiveButton("Yes", dialogClickListener)
.setNegativeButton("No", dialogClickListener).show();
return;
}
}
This is my default fragment :
public class mainfrag extends Fragment {
private View view;
private AdView adView;
private Button button10;
private Button button11;
public mainfrag() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_mainfrag, container, false);
adView = view.findViewById(R.id.adView);
button10 = (Button) view.findViewById(R.id.button10);
button10.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openmainactivity();
}
});
button11 = (Button) view.findViewById(R.id.button11);
button11.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openscheme();
}
});
return view;
}
public void openmainactivity() {
Intent intent = new Intent(getContext(), MainActivity.class);
startActivity(intent);
}
public void openscheme(){
Intent intent=new Intent(getContext(), scheme.class);
startActivity(intent);
}
}
This is one of the other fragments:
public class savedFragment extends Fragment {
RecyclerView recyclerview;
adapter_sgpa recyclerAdapter;
ArrayList<POJO> sgpaArrayList;
public savedFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentTransaction tx = getChildFragmentManager().beginTransaction();
tx.replace(R.id.container, new sgpa_frag());
tx.commit();
}
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
Fragment fragment = null;
switch (id) {
case R.id.navigation_sgpa:
sgpa_frag sf = new sgpa_frag();
FragmentManager fragmentManager = getChildFragmentManager();
fragmentManager.beginTransaction().replace(R.id.container, sf).commit();
return true;
case R.id.navigation_cgpa:
cgpa_frag cf = new cgpa_frag();
fragmentManager = getChildFragmentManager();
fragmentManager.beginTransaction().replace(R.id.container, cf).commit();
return true;
}
return false;
}
};
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View v = inflater.inflate(R.layout.fragment_saved, container, false);
BottomNavigationView nav = (BottomNavigationView) v.findViewById(R.id.bottom_navigation);
nav.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
return v;
}
}
What changes should I make in this code so that I am able to move back from the other fragments to the main fragment on pressing back button ?
Maintain one boolean variable to check current fragment is MainFragment or not.
if its not MainFragment -> replace MainFragment
Else -> super.onBackPressed()
ex:
private boolean isMainFragment=true; //make it false when move to other fragment
#Override
public void onBackPressed() {
if(!isMainFragment){
isMainFragment=true;
//replace your MainFragment
}
else{
//your logic show dialog or super.onBackPressed()
}
}
Ithink I know what you need. have a look at the last part of this documentation
"You can add a fragment transaction to the back stack. The back stack keeps track of actions in your app which can be backtracked when the user clicks Android's standard "back" button on the device. If you add a fragment transaction to the back stack then the transaction can be backtracked (reversed) with a click on the back button on the device" quotet from Jenkov
simply do fragmentTransaction.addToBackStack(null) on your main activity before you do the commit this will allow you to travel back using the back button
if you always want to travel back to the main fragment then you want to only add the main fragment to the backstack that way on pressing the back button you will always land there
in this part of your oncreate:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_what);
mDrawerLayout=(DrawerLayout)findViewById(R.id.drawer_layout);
mToggle=new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
fragmentTransaction= getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_content,new mainfrag());
//HERE YOU PUT THE CODE V
fragmentTransaction.addToBackStack(null);
//HERE YOU PUT THE CODE ^
fragmentTransaction.commit();
ActionBar actionBar= getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
// ALL THE OTHER STUFF COMMING AFTER
I am trying to retain the state of Fragment. I have MotherActivity in which I have FragmentOne,FragmentTwo,FragmentThree and inside from FragmentTwo I am calling another activity ChildActivity. Problem is that When I am pressing back button in ChildActivity it is refreshing MotherActivity and not keeping the state of my FragmentTwo instead it is showing me FragmentOne which come first time.
I only want when I am pressing BackButton from ChildActivity, on container FragmentTwo should be there:
MainAcitivity:
public class MotherActivity extends FragmentActivity {
AHBottomNavigation bottomNavigation;
Fragment selectedFragment = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bottomNavigation = (AHBottomNavigation) findViewById(R.id.navigation);
bottomNavigation.addItem(item1);
bottomNavigation.addItem(item2);
bottomNavigation.addItem(item3);
bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
#Override
public boolean onTabSelected(int position, boolean wasSelected) {
if (position == 0) {
selectedFragment = FragmentOne.newInstance(bottomNavigation);
} else if (position == 1) {
selectedFragment = FragmentTwo.newInstance(bottomNavigation);
} else if (position == 2) {
selectedFragment = FragmentThree.newInstance(bottomNavigation);
}
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout,selectedFragment);
fragmentTransaction.commit();
return true;
}
});
}
#Override
protected void onStart() {
super.onStart();
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}
public void setNotification(){
bottomNavigation.setNotification("1", 1);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
//No call for super().
}
#Override
public void onBackPressed() {
Intent intent = new Intent();
setResult(113, intent);
finish();
return;
}
}
FragmentTwo from where I am calling childActivity:
public class FragmentTwo extends Fragment {
public static AHBottomNavigation bottomNavigation1;
Card_detail_Adapter_Footer searchabledapter;
public static boolean showAddress = false;
Fragment selectedFragment;
public static FragmentTwo newInstance(AHBottomNavigation bottomNavigation) {
FragmentTwo fragment = new FragmentTwo();
bottomNavigation1 = bottomNavigation;
showNotificationCounter(3);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_cart, container, false);
if(showAddress == true){
showAddress = false;
// From here I am calling ChildActivity
Intent intent = new Intent(getActivity(), ChildActivity.class);
startActivity(intent);
}
return view;
}
}
In ChildActivity simply calling onBackPressed()
The problem is with the onStart() method of your MotherActivity.java because when you open another activity from FragmentTwo, your MotherActivity onStop() gets called. When you press back button from ChildActivity onStart() of MotherActivity called which is replacing FragmentTwo from FragmentOne by committing transaction.
Please have a look at https://developer.android.com/guide/components/activities/activity-lifecycle.html
Put code from onStart() method into onCreate() method and check if configuration been changed:
if (savedInstanceState == null) {
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}
I'm using HashMap of fragment's backstack. To save backstack and current fragment I use the code below:
public class MainActivity extends AppCompatActivity {
private HashMap<String, Stack<Fragment>> mStacks;
public static final String TAB_PROFILE = "tab_profile";
public static final String TAB_DASHBOARD = "tab_dashboard";
public static final String TAB_CHATS = "tab_chats";
public static final String TAB_SETTINGS = "tab_settings";
private String mCurrentTab;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setupViews();
if (savedInstanceState != null) {
mCurrentTab = savedInstanceState.getString("currentTab");
mStacks = (HashMap<String, Stack<Fragment>>) savedInstanceState.getSerializable("stacks");
} else
selectedTab(TAB_DASHBOARD);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable("stacks", mStacks);
outState.putString("currentTab", mCurrentTab);
}
private void setupViews() {
mStacks = new HashMap<>();
mStacks.put(TAB_PROFILE, new Stack<>());
mStacks.put(TAB_DASHBOARD, new Stack<>());
mStacks.put(TAB_CHATS, new Stack<>());
mStacks.put(TAB_SETTINGS, new Stack<>());
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
bottomNavigationView.setSelectedItemId(R.id.action_dashboard);
BottomNavigationViewHelper.removeShiftMode(bottomNavigationView);
bottomNavigationView.setOnNavigationItemSelectedListener(item -> {
switch (item.getItemId()) {
case R.id.action_profile:
selectedTab(TAB_PROFILE);
return true;
case R.id.action_dashboard:
selectedTab(TAB_DASHBOARD);
return true;
case R.id.action_chats:
selectedTab(TAB_CHATS);
return true;
case R.id.action_settings:
selectedTab(TAB_SETTINGS);
return true;
}
return true;
});
bottomNavigationView.setOnNavigationItemReselectedListener(item -> {
if (mStacks.get(mCurrentTab).size() != 1) {
mStacks.get(mCurrentTab).clear();
switch (item.getItemId()) {
case R.id.action_profile:
selectedTab(TAB_PROFILE);
break;
case R.id.action_dashboard:
selectedTab(TAB_DASHBOARD);
break;
case R.id.action_chats:
selectedTab(TAB_CHATS);
break;
case R.id.action_settings:
selectedTab(TAB_SETTINGS);
break;
}
}
});
}
private void selectedTab(String tabId) {
mCurrentTab = tabId;
if(mStacks.get(tabId).size() == 0){
if(tabId.equals(TAB_PROFILE)){
Fragment fragment = new ProfileFragment();
Bundle args = new Bundle();
args.putSerializable("user", Globals.getCurrentUser());
fragment.setArguments(args);
pushFragments(tabId, fragment,true);
} else if(tabId.equals(TAB_DASHBOARD)){
pushFragments(tabId, new DashboardFragment(),true);
}else if(tabId.equals(TAB_CHATS)){
pushFragments(tabId, new GroupsFragment(),true);
}else if(tabId.equals(TAB_SETTINGS)){
pushFragments(tabId, new SettingsFragment(),true);
}
}else {
pushFragments(tabId, mStacks.get(tabId).lastElement(),false);
}
}
public void pushFragments(String tag, Fragment fragment, boolean shouldAdd){
if(shouldAdd)
mStacks.get(tag).push(fragment);
FragmentManager manager = getFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content, fragment);
ft.commit();
}
public void popFragments(){
Fragment fragment = mStacks.get(mCurrentTab).elementAt(mStacks.get(mCurrentTab).size() - 2);
mStacks.get(mCurrentTab).pop();
FragmentManager manager = getFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.replace(R.id.content, fragment);
ft.commit();
}
#Override
public void onBackPressed() {
if(mStacks.get(mCurrentTab).size() == 1){
finish();
return;
}
popFragments();
}
}
Set new fragments using
((MainActivity)context).pushFragments(MainActivity.TAB_CHATS, fragment,true);
Layout
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:background="#color/background_material_light"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="#+id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#id/bottom_navigation"/>
<android.support.design.widget.BottomNavigationView
android:id="#+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
app:itemBackground="#color/waPrimary"
app:itemIconTint="#color/white"
app:itemTextColor="#color/white"
app:menu="#menu/menu_bottom_navigation" />
Everything works fine on screen rotation, but application crashes with exception on application hide.
java.lang.RuntimeException: Parcel: unable to marshal value %FragmentName%{c985244 #2 id=0x7f090051}
As I read, it happens when one of the objects I'm trying to pass is not Parceable, but have no idea how to fix this. Any thoughts?
UPD
After I made all of my fragments Serializable, new exception throws
java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = %FragmentName%)
...
Caused by: java.io.NotSerializableException: android.support.v7.widget.RecyclerView
UPD2
Seems like a found a solution - transient property. Now I'm trying to make all non-serializeable objects transient.
UPD3
It helped, but I don't know is it efficient enough.
Here's my suggestion:
Your activity maintains a reference to the four fragments it wants for the bottom navigation toggling.
On toggling bottom navigation, you replace the current fragment in the activity fragment manager.
While on a given fragment, as you interact with the UI, you push things on to the fragment child fragment manager.
This way, each fragment maintains its own backstack automatically, you don't have to save any state, and it all Just Works™.
Some sample code that might help.
public class MainActivity extends AppCompatActivity {
private Fragment mProfileFragment;
private Fragment mDashboardFragment;
private Fragment mChatsFragment;
private Fragment mSettingsFragment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
// Init fragments
}
else {
// Find last active fragments in fragment manager
}
setupViews();
}
private void setupViews() {
BottomNavigationView bottomNavigationView = findViewById(R.id.bottom_navigation);
bottomNavigationView.setSelectedItemId(R.id.action_dashboard);
BottomNavigationViewHelper.removeShiftMode(bottomNavigationView);
bottomNavigationView.setOnNavigationItemSelectedListener(item -> {
Fragment fragment;
switch (item.getItemId()) {
case R.id.action_profile:
fragment = mProfileFragment;
break;
case R.id.action_dashboard:
fragment = mDashboardFragment;
break;
case R.id.action_chats:
fragment = mChatsFragment;
break;
case R.id.action_settings:
fragment = mSettingsFragment;
break;
}
// Replace the currently active fragment which will be
// managing its own backstack
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.frament_container, fragment)
.commit();
});
}
}
And one of your fragments would push stuff on its own stack like this:
public class ProfileFragment extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.id.fragment_layout, container, false);
Button button = view.findViewById(R.id.some_button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Fragment someFragmentToPush = new SomeFragmentToPush();
// Use the child fragment manager to keep UI
// local to this fragment instance, adding to backstack
// for automatic popping on pressing back
getChildFragmentManager().beginTransaction()
.add(R.id.fragment_layout, someFragmentToPush)
.addToBackStack(null)
.commit();
}
});
return view;
}
}
Hope that helps!
So my problem is that the buttons that are contained within my fragments throw up an error "Unhandled Exception - Object reference not set to an instance of an object"
I thought because I had referenced the layout that contains the button that this would not cause an error. If anyone could shed some light to what I am doing wrong that would be great. I think I am either missing some vital code or have completely messed it up as I am new to using fragments and understand that they work differently from activities.
This is my MainActivity:
public class MainActivity : ActionBarActivity
{
private SupportToolbar mToolbar;
private MyActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;
private ListView mLeftDrawer;
private HomeFragment mHomeFragment;
private LogInFragment mLogInFragment;
private MatchCentreFragment mMatchCentreFragment;
private PrevCompFragment mPrevCompFragment;
private PrevFixFragment mPrevFixFragment;
private SettingsFragment mSettingsFragment;
private SocialFragment mSocialFragment;
private UpcomCompFragment mUpcomCompFragment;
private UpcomFixFragment mUpcomFixFragment;
private SupportFragment mCurrentFragment = new SupportFragment();
private Stack<SupportFragment> mStackFragments;
private ArrayAdapter mLeftAdapter;
private List<string> mLeftDataItems;
protected override void OnCreate (Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
mToolbar = FindViewById<SupportToolbar>(Resource.Id.toolbar);
mDrawerLayout = FindViewById<DrawerLayout>(Resource.Id.drawer_layout);
mLeftDrawer = FindViewById<ListView>(Resource.Id.left_drawer);
mHomeFragment = new HomeFragment();
mLogInFragment = new LogInFragment();
mMatchCentreFragment = new MatchCentreFragment();
mPrevCompFragment = new PrevCompFragment();
mPrevFixFragment = new PrevFixFragment();
mSettingsFragment = new SettingsFragment();
mSocialFragment = new SocialFragment();
mUpcomCompFragment = new UpcomCompFragment();
mUpcomFixFragment = new UpcomFixFragment();
mStackFragments = new Stack<SupportFragment>();
mLeftDrawer.Tag = 0;
SetSupportActionBar(mToolbar);
mLeftDataItems = new List<string>();
mLeftDataItems.Add("Home");
mLeftDataItems.Add("Log In");
mLeftDataItems.Add("Match Centre");
mLeftDataItems.Add("Previous Fixtures");
mLeftDataItems.Add("Upcoming Fixtures");
mLeftDataItems.Add("Previous Competitions");
mLeftDataItems.Add("Upcoming Competitions");
mLeftDataItems.Add("Settings");
mLeftDataItems.Add("Social");
mLeftAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleListItem1, mLeftDataItems);
mLeftDrawer.Adapter = mLeftAdapter;
mLeftDrawer.ItemClick += MenuListView_ItemClick;
mDrawerToggle = new MyActionBarDrawerToggle(this, mDrawerLayout, Resource.String.openDrawer, Resource.String.closeDrawer);
if (bundle != null)
{
if (bundle.GetString("DrawerState") == "Opened")
{
SupportActionBar.SetTitle(Resource.String.openDrawer);
}
else
{
SupportActionBar.SetTitle(Resource.String.closeDrawer);
}
}
else
{
SupportActionBar.SetTitle(Resource.String.closeDrawer);
}
Android.Support.V4.App.FragmentTransaction trans = SupportFragmentManager.BeginTransaction();
trans.Add(Resource.Id.fragmentContainer, mHomeFragment);
trans.Add(Resource.Id.fragmentContainer, mLogInFragment);
trans.Hide(mLogInFragment);
trans.Add(Resource.Id.fragmentContainer, mMatchCentreFragment);
trans.Hide(mMatchCentreFragment);
trans.Add(Resource.Id.fragmentContainer, mPrevFixFragment);
trans.Hide(mPrevFixFragment);
trans.Add(Resource.Id.fragmentContainer, mUpcomFixFragment);
trans.Hide(mUpcomFixFragment);
trans.Add(Resource.Id.fragmentContainer, mPrevCompFragment);
trans.Hide(mPrevCompFragment);
trans.Add(Resource.Id.fragmentContainer, mUpcomCompFragment);
trans.Hide(mUpcomCompFragment);
trans.Add(Resource.Id.fragmentContainer, mSettingsFragment);
trans.Hide(mSettingsFragment);
trans.Add(Resource.Id.fragmentContainer, mSocialFragment);
trans.Hide(mSocialFragment);
mCurrentFragment = mHomeFragment;
trans.Commit();
}
void MenuListView_ItemClick (object sender, AdapterView.ItemClickEventArgs e)
{
Android.Support.V4.App.Fragment fragment = null;
switch (e.Id)
{
case 0:
ShowFragment(mHomeFragment);
break;
case 1:
ShowFragment(mLogInFragment);
break;
case 2:
ShowFragment(mMatchCentreFragment);
break;
case 3:
ShowFragment(mPrevFixFragment);
break;
case 4:
ShowFragment(mUpcomFixFragment);
break;
case 5:
ShowFragment(mPrevCompFragment);
break;
case 6:
ShowFragment(mUpcomCompFragment);
break;
case 7:
ShowFragment(mSettingsFragment);
break;
case 8:
ShowFragment(mSocialFragment);
break;
}
mDrawerLayout.CloseDrawers();
mDrawerToggle.SyncState();
}
private void ShowFragment (SupportFragment fragment)
{
if (fragment.IsVisible)
{
return;
}
var trans = SupportFragmentManager.BeginTransaction();
fragment.View.BringToFront();
mCurrentFragment.View.BringToFront();
trans.Hide(mCurrentFragment);
trans.Show(fragment);
trans.AddToBackStack(null);
mStackFragments.Push(mCurrentFragment);
trans.Commit();
mCurrentFragment = fragment;
}
public override bool OnOptionsItemSelected(IMenuItem item)
{
switch (item.ItemId)
{
case Android.Resource.Id.Home:
//The hamburger icon was clicked which means the drawer toggle will handle the event
mDrawerToggle.OnOptionsItemSelected(item);
return true;
case Resource.Id.action_refresh:
//Refresh
return true;
case Resource.Id.action_help:
return true;
default:
return base.OnOptionsItemSelected(item);
}
}
public override bool OnCreateOptionsMenu(IMenu menu)
{
MenuInflater.Inflate(Resource.Menu.drawer_menu, menu);
return base.OnCreateOptionsMenu(menu);
}
protected override void OnSaveInstanceState(Bundle outState)
{
if(mDrawerLayout.IsDrawerOpen((int)GravityFlags.Left))
{
outState.PutString("DrawerState", "Opened");
}
else
{
outState.PutString("DrawerState", "Closed");
}
base.OnSaveInstanceState(outState);
}
protected override void OnPostCreate(Bundle savedInstanceState)
{
base.OnPostCreate(savedInstanceState);
mDrawerToggle.SyncState();
}
public override void OnConfigurationChanged(Android.Content.Res.Configuration newConfig)
{
base.OnConfigurationChanged(newConfig);
mDrawerToggle.OnConfigurationChanged(newConfig);
}
}
}
This is one of my fragments (there are several but they all contain basically the same code so far)
public class PrevFixFragment : Android.Support.V4.App.Fragment
{
Button button;
public PrevFixFragment()
{
}
public static Android.Support.V4.App.Fragment newInstance(Context context)
{
PrevFixFragment fragment = new PrevFixFragment();
return fragment;
}
public override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
}
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.Inflate(Resource.Layout.PreviousFixtures, null);
button = View.FindViewById<Button>(Resource.Id.upcombutton);
button.Click += StartNewActivity;
return view;
}
void StartNewActivity(object sender, EventArgs e)
{
Intent intent = new Intent(Activity, typeof(UpcomFixActivity));
StartActivity(intent);
}
}
}
Try moving the following lines to override void OnViewCreated or override void onActivityCreated
button = View.FindViewById<Button>(Resource.Id.upcombutton);
button.Click += StartNewActivity;
You must write View with lowercase view in statement below:
button = View.FindViewById<Button>(Resource.Id.upcombutton);
I implemented backstack navigation on Back button in MainActivity (which have many fragments) using onBackPressed(). I want to implement same backstack navigation on Up button press. Problem is I only want Up button in one fragment but the Up button appears on every fragment when I press Up button on desired fragment. Even setDisplayHomeAsEnabled(false) is not working. How to have Up button in one fragment only?
Desired Fragment:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((AppCompatActivity)getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
Main Activity
public class HomePage extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.homepage);
if (findViewById(R.id.fragment_place) != null) {
if (savedInstanceState != null) {
return;
}
HomeFrag firstFragment = new HomeFrag();
getSupportFragmentManager().beginTransaction().add(R.id.fragment_place, firstFragment).commit();
}
}
/* #Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
break;
default:
break;
}
return super.onOptionsItemSelected(item);
} */
public void selectFrag(View view) {
Fragment fr = null;
if (view == findViewById(R.id.home_btn)) {
fr = new HomeFrag();
} else if (view == findViewById(R.id.search_btn)) {
fr = new SearchFrag();
} else if (view == findViewById(R.id.log_btn)) {
fr = new LogFrag();
} else if (view == findViewById(R.id.events_btn)) {
fr = new EventFrag();
} else if (view == findViewById(R.id.profile_btn)) {
fr = new ProfileFrag();
}
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fm.beginTransaction();
fragmentTransaction.replace(R.id.fragment_place, fr).addToBackStack(null);
fragmentTransaction.commit();
}
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 0)
getFragmentManager().popBackStack();
else
super.onBackPressed();
}
}
I created a sample application on GitHub to solve such backstack problem.
Download Fragment Back Stack application