Develop Reference

How to open the side navigation drawer when click on bottom menu?

This is what i'm trying to achieve
I want settings menu click will appear side nav drawer
HomeActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
mMainFrame = (FrameLayout) findViewById(R.id.main_frame);
mMainNav = (BottomNavigationView) findViewById(R.id.main_nav);
homeFragment = new HomeFragment();
analyticsFragment = new AnalyticsFragment();
paymentFragment = new PaymentFragment();
settingsFragment = new SettingsFragment();
drawerLayout = findViewById(R.id.drawerlayout);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.main_frame,new HomeFragment()).commit();
mMainNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.navigation_home:
setFragment(homeFragment);
return true;
case R.id.navigation_analytics:
setFragment(analyticsFragment);
return true;
case R.id.navigation_payment:
setFragment(paymentFragment);
return true;
case R.id.navigation_settings:
drawerLayout.openDrawer(GravityCompat.END);
return true;
default:
return false;
}
}
});
BottomNavigationView navView = findViewById(R.id.main_nav);
navView.setItemIconTintList(null);
And this is the error i get
Unable to start activity ComponentInfo{com.example.ewallet/com.example.ewallet.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.app.Activity.findViewById(int)' on a null object reference
EDIT : I tried to paste some of my code here but StackOverflow error too many code to post

You didn't bind your object correctly and caused a NullPointerException.
Please paste your code and we can help you.
I saw a weird part, but maybe this error will still appear, you may need to paste your layout.xml
mMainNav = (BottomNavigationView) findViewById(R.id.main_nav);
BottomNavigationView navView = findViewById(R.id.main_nav);
navView.setItemIconTintList(null);
Should be modify to
mMainNav.setItemIconTintList(null);
You can check if it is null with
getActivity().findViewById(R.id.XXX)
UPDATE
drawerLayout = (DrawerLayout)getView().findViewById(R.id.drawerlayout);
case R.id.navigation_settings:
drawerLayout.openDrawer(drawerLayout);
return true;

Took me 4 days to figure this out. Turned out you need to have drawerlayout in your activity layout. My problem was drawerlayout from different xml that's why returned null. Thx for those who tried for helping me
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/drawer_layout"
android:fitsSystemWindows="true"
tools:openDrawer="end">
<include
layout="#layout/app_bar_settings"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="#+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="end"
android:fitsSystemWindows="true"
app:headerLayout="#layout/nav_header_settings"
app:menu="#menu/activity_settings_drawer" />
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/container"
tools:context=".HomeActivity">
<FrameLayout
android:id="#+id/main_frame"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginBottom="56dp">
</FrameLayout>
<android.support.design.widget.BottomNavigationView
android:id="#+id/main_nav"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="?android:attr/windowBackground"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:labelVisibilityMode="labeled"
app:itemTextColor="#color/colorPrimaryDark"
app:menu="#menu/bottom_nav_menu" />
</android.support.constraint.ConstraintLayout>
</android.support.v4.widget.DrawerLayout>

Android Fragment not showing up after inflation

I have a fragment that I would like to display on top of an activity. This is the code that I'm trying right now...
MainActivity.class
FragmentManager fragmentManager = getSupportFragmentManager();
DirectionsFragment directionsFragment = new DirectionsFragment();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
fragmentTransaction.add(R.id.directions_fragment_framelayout, directionsFragment);
fragmentTransaction.commit();
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
<!-- irrelevant parameters -->
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<FrameLayout
android:id="#+id/directions_fragment_framelayout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
<com.mapbox.mapboxsdk.maps.MapView>
<!-- A BUNCH OF CHILDREN -->
</com.mapbox.mapboxsdk.maps.MapView>
</RelativeLayout>
DirectionsFragment.class
public class DirectionsFragment extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
ViewGroup viewGroup = (ViewGroup) inflater.inflate(R.layout.fragment_directions, container, false);
return viewGroup;
}
}
fragment_directions.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
<!-- irrelevant params -->
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="#+id/directions_listview"
android:layout_width="match_parent"
android:layout_height="match_parent"
<!-- irrelevant params -->
/>
</android.support.constraint.ConstraintLayout>
The activity itself runs fine; when I trigger the fragment to show, it runs through the FragmentTransaction and fragment view inflation fine (confirmed using logs and breakpoints). Since the fragment is being added to a FrameLayout, why isn't the fragment showing up? Thanks in advance!

I think it will be helpfull
Try to swap your FrameLayout and MapView in activity_main.xml
Your code is working fine but its behind the map view thats why its not showing.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
<!-- irrelevant parameters -->
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.mapbox.mapboxsdk.maps.MapView>
<!-- A BUNCH OF CHILDREN -->
</com.mapbox.mapboxsdk.maps.MapView>
<FrameLayout
android:id="#+id/directions_fragment_framelayout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
</RelativeLayout>
Add background color in your fragment layout because fragment loaded but transparent layout.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:background="#android:color/white"
android:layout_height="match_parent">
<ListView
android:id="#+id/directions_listview"
android:layout_width="match_parent"
android:layout_height="match_parent"
<!-- irrelevant params -->
/>
</android.support.constraint.ConstraintLayout>

Reason for a fragment to not show up

so I know there are a few topics around here that ask about this but none seemed to be the cause of my issue. I have an ActionBarActivity that is going to be switching between a few different fragments, but I'm having a problem getting one of the fragments to show up. The activity does show a fragment when it is first loaded and does that fine. Here is the code that is setting up the initial fragment with the method to switch between fragments that I'm using.
#Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_container);
final ActionBar actionBar = getSupportActionBar();
actionBar.setTitle("");
if (savedInstanceState == null) navigateTo(START_SCREEN);
}
public void navigateTo(int sectionNumber, Serializable objectParam) {
Fragment fragment = null;
switch (sectionNumber) {
case START_SCREEN:
fragment = createStartScreenFragment(); //returns an instance of the class for this fragment
break;
case SCREEN_TWO:
fragment = createSecondScreenFragment(); //returns an instance of the class for this fragment
break;
}
if (fragment == null) return;
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction trans = fm.beginTransaction();
trans.add(R.id.activity_container, fragment, fragment.getTag());
trans.commit();
trans.show(fragment);
}
activity_containers.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:id="#+id/activity_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
The first fragment that loads successfuly
<GridLayout
android:id="#+id/fragment_start_screen"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.android.Activity">
<TextView
android:id="#+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clickable="true"
/>
...
</GridLayout>
And here is the fragment xml that isn't showing up
<TextView android:id="#+id/section_label" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fadingEdge="vertical"
android:cacheColorHint="#00000000"
android:fastScrollEnabled="true"
android:padding="2dp">
</ListView>
And here is the misbehaving fragments relevant code:
public class SecondFragment extends Fragment {
public final static int SECTION_NUMBER = 1;
private String mTag = "TAG";
private ParentActivity parentActivity;
public SecondFragment() {
}
public static fragment newInstance() {
SecondFragment fragment = new SecondFragment();
Bundle args = new Bundle();
fragment.setArguments(args);
return fragment;
}
#Override
public void onAttach(final Activity activity) {
super.onAttach(activity);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
parentActivity = (ParentActivity) getActivity();
View rootView = inflater.inflate(R.layout.fragment_second_fragment, container, false);
ListView list = (ListView) rootView.findViewById(R.id.list);
return super.onCreateView(inflater, container, savedInstanceState);
}
}
The biggest problem I'm having here is that there is no error message shown. The text view in the first fragment is supposed to trigger the second fragment to show up on the screen. This used to work when I had that fragment as a DialogFragment and just called .show() on an instance of it. I need it to be a regular fragment now and it doesn't show up. There's no error message that I can see, though debugging it does show it running through all of my code successfully and it looks like its properly inflating the view.
So what could I be missing here that is preventing the fragment from displaying?

Your layout
<TextView android:id="#+id/section_label" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fadingEdge="vertical"
android:cacheColorHint="#00000000"
android:fastScrollEnabled="true"
android:padding="2dp">
</ListView>
Should be within a ViewGroup
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView android:id="#+id/section_label" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:scrollbars="vertical"
android:fadingEdge="vertical"
android:cacheColorHint="#00000000"
android:fastScrollEnabled="true"
android:padding="2dp">
</ListView>
</LinearLayout>
And you should return rootView in onCreateView().
Also, you might need to use replace method of Fragment Manager to replace one fragment with another, instead of add.

Get fragment in Tabhost is null

I have made a tab container with TabHost, the layout xml file is like below:
<TabHost
android:id="#android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TabWidget
android:id="#android:id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</TabWidget>
<FrameLayout
android:id="#android:id/tabcontent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="60dip" >
<fragment
android:id="#+id/tab1"
android:name="com.test.Tab1Fragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<fragment
android:id="#+id/tab5"
android:name="com.test.Tab5Fragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
</TabHost>
In MainActivity, I init and add tab into activity in onCreate callback like this,
tabHost = (TabHost) findViewById(android.R.id.tabhost);
tabHost.setup();
tabHost.addTab(tabHost.newTabSpec("tab1").setIndicator(mRes.getString(R.string.tab1)).setContent(R.id.tab1));
tabHost.addTab(tabHost.newTabSpec("tab5").setIndicator(mRes.getString(R.string.tab5)).setContent(R.id.tab5));
On the tab changed, I want to find the current fragment, and do some init while current fragment is showing.
private OnTabChangeListener tabChangedListener = new OnTabChangeListener() {
public void onTabChanged(String tabid) {
Log.d(TAG, "tab changed " + tabid);
currentTab = tabid;
TabChangeCallback currentFragment = (TabChangeCallback) getFragmentManager().findFragmentByTag(currentTab);
if(currentFragment != null) {
currentFragment.onTabChanged(currentTabIndex);
} else {
Log.d(TAG, "get fragment null ");
}
}
};
Question is why getFragmentManager().findFragmentByTag(currentTab) is return null, and I couldn't call the fragment init code. thanks for your help.

I think if you are dealing with only fragment in the Tabhost then you better use FragmentTabHost. It will be more optimized and easy.
Example
And getting child fragment by Tag - link

This issue is because the fragemnt has not created at the time OnTabChnaged gets called.
Please check my answer here

Android ListView setOnItemClickListener not working

I am trying to make a ListView with TextViews, I want each textview to be able to be clicked and based on it's position a Fragment is pulled up. However, the itemOnClickListener seems to not even be called.
mDrawerList = (ListView) findViewById(R.id.devices_drawer);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, drawerInfo));
mDrawerList.setItemsCanFocus(false);
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
final int pos, long id) {
Log.d(TAG, "CLICKED " + pos);
selectDevice(pos);
}
});
here's the xml for the list item:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/deviceText"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="center"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
List view xml file:
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="#+id/devices_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="left"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="#android:color/transparent"
android:dividerHeight="0dp" />
<FrameLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.v4.widget.DrawerLayout>

It's your whole xml drawer (I presume you try to do a navigation drawer) ? If you have a parent layout check the android:descendantFocusability="blocksDescendants" otherwise you have to wrap your textview in a layout (LinearLayout is sufficient if you don't have a complex UI for the item).
The new OnItemClickListener is an AdapterView.OnItemClickListerner?
(An excellent how-to http://www.vogella.com/articles/AndroidActionBar/article.html#actionbar_navigation_drawer )

Is there a reason you are using mDrawerList.setItemsCanFocus(false);? You don't have any focusable items in your item layout, so it's safe to remove that call. Should work ok after that.

Also check if you are using Button in list row item, it'll over-ride you list item click event

For list items inside your list.. you have to set the attributes below
android:focusable="false"
android:focusableInTouchMode="false"