How to execute the click event on an image that is in the activity fragment?

Question

How to execute the click event on an image that is in the activity fragment?

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#1 by (1 votes)
#2 by (0 votes)

0

I want to execute the function that is fragment - remove task () - on an image that is in the fragment being added in the activity at runtime, and I am not getting it, help me !!!

Activity code

public class MainActivity extends AppCompatActivity {

private ImageView botao_deletar;
public static SQLiteDatabase banco_dados;

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
}

Fragment code

public class ListaNotificacoes extends Fragment {

View minha_view;


private ListView lista_notify;
private ArrayAdapter<String> itens_adaptador;
private ArrayList<String> itens;
private ArrayList<Integer> ids;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    minha_view = inflater.inflate(R.layout.lista_notificacoes, container, false);
    return minha_view;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
}

private void remover_tarefa(Integer id){
    try {
        banco_dados.execSQL("DELETE FROM lista_notificacoes WHERE id="+id);
        recupera_tarefa();
    }catch (Exception e){
        e.printStackTrace();
    }
}

What I tried to do ...

public class ListaNotificacoes extends Fragment {

View minha_view;


private ListView lista_notify;
private ImageView botao_deletar;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    minha_view = inflater.inflate(R.layout.lista_notificacoes, container, false);
    return minha_view;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    recupera_tarefa();

    botao_deletar = (ImageView) getActivity().findViewById(R.id.botao_deletar);

    botao_deletar.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            remover_tarefa(lista_notify.getId());
        }
    });
}

private void remover_tarefa(Integer id){
    try {
        banco_dados.execSQL("DELETE FROM lista_notificacoes WHERE id="+id);
        recupera_tarefa();
    }catch (Exception e){
        e.printStackTrace();
    }
}

The error that shows in the console ...

Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

android

asked by anonymous 21.05.2017 / 17:01

2 answers

Call to a member function fetch_object () on a non-object php error at the time of hosting

score 1 · Answer 1

I'll assume you can not reference your ImageView in your code, okay?

If I'm wrong, let me know. Anyway, what you do to get the widget reference is to use my_view as the identifier.

The findViewById () method can be called in two ways:

View.findViewById()
Activity.findViewById() || Context.findViewById() ~ Context as Activity.

In fragments , we need to pass identificador so that the method can find its view , if we do not pass, it will not work, since you are not in an activity.

Your final code looks like this:

Button deleteTask;
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    minha_view = inflater.inflate(R.layout.lista_notificacoes, container, false);

    deleteTask = (Button) minha_view.findViewById(R.id.action_delete_task) // mude para o Id do seu componente
    deleteTask.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            remover_tarefa(taskId);
        }
    });

    return minha_view;
}

If you're using Java 8 , you can use Lambda Expressions to write less and avoid boilerplate code . Your code would look like this:

deleteTask = (Button) minha_view.findViewById(R.id.action_delete_task)
deleteTask.setOnClickListener(v -> remover_tarefa(taskId))

In order to use Lambda Expressions , you need to enable compatibility with Java 8 . To do this, you need to modify the build.gradle at the application level, that is, in the app module.

android {
    ...
    defaultConfig {
    ...
        jackOptions {
           enabled true
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
 }

score 0 · Answer 2

You are getting this error because in the onActivityCreated method of your fragment, you are looking for a view in your activity, but it belongs to your fragment.

If you analyze the life cycle of a fragment, the onActivityCreated method executes after onCreateView , which means that you already have the view inflated and you can already use it.

Just change your code, and change getActivity() to getView() , in the onActivityCreated method of your snippet:

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    recupera_tarefa();

    botao_deletar = (ImageView) getView().findViewById(R.id.botao_deletar);

    botao_deletar.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            remover_tarefa(lista_notify.getId());
        }
    });
}

Note : There should actually be a view with the R.id.botao_deletar id in the layout ( R.layout.lista_notificacoes ) that is inflated by its snippet so that a NullPointerException .