I'm new to Android Studio and I'm trying to implement a listview in a fragment with an adapter. After launching my application I have this error message
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
It seems to be something with my adapter. Here's my code:
MainActivity.java
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)
== PackageManager.PERMISSION_DENIED){
ActivityCompat.requestPermissions(MainActivity.this, new String[] {Manifest.permission.CAMERA}, 123);
} else {
}
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView bottomNav = findViewById(R.id.bottom_navigation);
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new HomeFragment()).commit();
bottomNav.setSelectedItemId(R.id.nav_home);
bottomNav.setOnItemSelectedListener(new NavigationBarView.OnItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
Fragment fragment = null;
switch (item.getItemId()){
case R.id.nav_home:
fragment = new HomeFragment();
break;
case R.id.nav_profil:
fragment = new ProfilFragment();
break;
case R.id.nav_camera:
fragment = new CameraFragment();
break;
}
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragment).commit();
return true;
}
});
}
}
activity_main.xml
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<FrameLayout
android:id="@ id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@ id/bottom_navigation"/>
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@ id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
app:menu="@menu/bttom_navigation"
app:itemIconTint="@color/white"
android:background="@android:color/holo_blue_dark"/>
</RelativeLayout>
HomeFragment.java
public class HomeFragment extends Fragment {
String mTitle[] = {"1987", "Congorama", "Bon cop bad cop 2"};
String mDescription[] = {"Lieu: Québec", "Lieu: Saint-Michel", "Lieu: Montréal"};
int images[] = {R.drawable.mille, R.drawable.congorama, R.drawable.bcb2};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home, container, false);
ListView listView = (ListView) getActivity().findViewById(R.id.Listview);
MyAdapter myadapter = new MyAdapter( getContext(), mTitle, mDescription, images);
listView.setAdapter(myadapter);
// Inflate the layout for this fragment
return view;
}
}
fragment_home.xml
<?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">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@ id/Listview"
>
</ListView>
</LinearLayout>
MyAdapter.java
public class MyAdapter extends BaseAdapter {
Context context;
String listFilm[];
String lieuFilm[];
int listImages[];
LayoutInflater inflater;
public MyAdapter(Context ctx, String[] nomFilm, String[] desFilm, int[] images ){
this.context = ctx;
this.listFilm = nomFilm;
this.lieuFilm = desFilm;
this.listImages = images;
inflater = LayoutInflater.from(ctx);
}
@Override
public int getCount() {
return listFilm.length;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
convertView = inflater.inflate(R.layout.row, null);
TextView txtview = (TextView) convertView.findViewById(R.id.textView1);
TextView txtview2 = (TextView) convertView.findViewById(R.id.textView2);
ImageView imgview = (ImageView) convertView.findViewById(R.id.image);
txtview.setText(listFilm[position]);
txtview2.setText(lieuFilm[position]);
imgview.setImageResource(listImages[position]);
return convertView;
}
}
row.xml
<?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="wrap_content"
android:orientation="horizontal"
android:padding="16dp">
<ImageView
android:layout_width="75dp"
android:layout_height="75dp"
android:src="@mipmap/ic_launcher"
android:id="@ id/image"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Main Title"
android:textColor="#000"
android:layout_margin="5dp"
android:textSize="20sp"
android:id="@ id/textView1"
/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Sub Title"
android:textColor="#a9a9a9"
android:layout_margin="5dp"
android:textSize="15sp"
android:id="@ id/textView2"
/>
</LinearLayout>
</LinearLayout>
The error points out to the line 32 of my HomeFragment, wHich is my listView.setAdapter(myadapter);
CodePudding user response：
No, there is nothing wrong with your adapter, but it is wrong with your listview.
HomeFragment.java
public class HomeFragment extends Fragment {
String mTitle[] = {"1987", "Congorama", "Bon cop bad cop 2"};
String mDescription[] = {"Lieu: Québec", "Lieu: Saint-Michel", "Lieu: Montréal"};
int images[] = {R.drawable.mille, R.drawable.congorama, R.drawable.bcb2};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home, container, false);
...
ListView listView = (ListView) view.findViewById(R.id.Listview); //use listview from inflater view instead of getActivity
...
MyAdapter myadapter = new MyAdapter( getContext(), mTitle, mDescription, images);
listView.setAdapter(myadapter);
// Inflate the layout for this fragment
return view;
}
}
CodePudding user response：
public class HomeFragment extends Fragment {
String mTitle[] = {"1987", "Congorama", "Bon cop bad cop 2"};
String mDescription[] = {"Lieu: Québec", "Lieu: Saint-Michel", "Lieu: Montréal"};
int images[] = {R.drawable.mille, R.drawable.congorama, R.drawable.bcb2};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home, container, false);
ListView listView = (ListView) getActivity().findViewById(R.id.Listview);
MyAdapter myadapter = new MyAdapter( getContext(), mTitle, mDescription, images);
listView.setAdapter(myadapter);
// Inflate the layout for this fragment
return view;
}
}
You have to use :=
ListView listView = (ListView) view.findViewById(R.id.Listview);
instead of this code :=
ListView listView = (ListView) getActivity().findViewById(R.id.Listview);