I am new starter at android programming. Although I searched this problem on achieve I couldn't find any satisfying solution:
The problem is: I want to set an image to imageview - which is located in a fragment - dynamically.
And I want to do this using file name of the image.
But I am getting that NullPointerException:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference
Below my code are shown. I would be glad if anyone respond.
Activity class:
public class Oku extends AppCompatActivity {
private int hedefSayi;
private int actualNumber;
private FragmentManager fragmentManager;
private Fragment tempFragment;
private BottomNavigationView bottomNavigationView;
private FrameLayout fragmentContainer;
private ProgressBar progressBar;
private Button btn_tıkla;
private Vird comingVird;
private Fragment arabicImageFragment;
private Fragment turkishTextFragment;
private Fragment anlamFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_oku);
comingVird= (Vird) getIntent().getSerializableExtra("Vird.class");
hedefSayi=200;
actualNumber=hedefSayi;
fragmentContainer=findViewById(R.id.fragment_container);
bottomNavigationView=findViewById(R.id.bottom_navi);
arabicImageFragment=new Fragment_Arabic_Image(comingVird.getImageName());
//put the arabic image fragment on the container first
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container,arabicImageFragment).commit();
//on navigation item selected:
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
//get the selected items id number
int itemID=item.getItemId();
//if id number is related to the arabic image fragment, set the temp fragment as arabic image fragment
if(itemID==R.id.action_oku_arapca){
tempFragment=new Fragment_Arabic_Image(comingVird.getImageName());
}
//if id number is related to turkish text fragment, set the related fragment
else if(itemID==R.id.action_oku_turkce) { tempFragment=new Fragment_Turkce_Okunus();}
//if id number is related to the meaning set related fragment..
else if(itemID==R.id.action_oku_anlamı){ tempFragment=new Fragment_Anlam();}
//replace the fragment on the container with the temp fragment
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,tempFragment).commit();
return true;
}
});
//initiate progress bar with full progress
progressBar=findViewById(R.id.progressBar);
progressBar.setProgress(100);
btn_tıkla=findViewById(R.id.button_tıkla);
btn_tıkla.setText(""+actualNumber);
//on button click
btn_tıkla.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
progressBar.setProgress(100*actualNumber/hedefSayi);
//decrease the number and set on the text of the button
actualNumber--;
btn_tıkla.setText(""+actualNumber);
//her button tıklamada kısa titreşim ver
Vibrator vb = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
vb.vibrate(100);
}
});
}
}
Fragment Class:
public class Fragment_Arabic_Image extends Fragment {
private String imageName;
private ImageView arabicText_Image;
private int imageid;
public Fragment_Arabic_Image(String imageName) {
this.imageName = imageName;
}
@SuppressLint("ResourceType")
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_arabic_image,container,false);
imageid=getActivity().getResources().getIdentifier(imageName,"drawable",getActivity().getPackageName());
arabicText_Image=view.findViewById(R.id.img_arabic_text);
arabicText_Image.setImageResource(this.imageid);//this line causes error
return view;
}
}
Error message:
2020-08-04 14:11:18.822 12101-12101/com.codeforlite.virdlerim E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.codeforlite.virdlerim, PID: 12101java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference
at com.codeforlite.virdlerim.Fragment_Arabic_Image.onCreateView(Fragment_Arabic_Image.java:46)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2600)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:881)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2663)
at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:246)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1433)
at android.app.Activity.performStart(Activity.java:7980)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3578)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2220)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8016)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1087)
It seems like ImageView arabicText_Image is not initialized properly. check fragment_arabic_image.xml. make sure ImageView has id attribute with value "img_arabic_text"
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/img_arabic_text" />