Error while trying to fill a listview

Question

I’m trying to fill my listview like this

historicos=banco.getAllH(); 
ArrayAdapter<HistoricoObjeto> itens = new ArrayAdapter<HistoricoObjeto>(this, 
            android.R.layout.simple_list_item_1, historicos); 

this.lista.setAdapter(itens);
this.lista.setClickable(true);
registerForContextMenu(lista);

More is giving null Pointer Exception error on this line

this.lista.setAdapter(itens);

I’ll put the class Histoticoobject to be clearer what and the object I use

public class HistoricoObjeto implements Serializable{

    private String id;
    public String datahora;
    public String mensagem;

    public HistoricoObjeto() {

    }

    public HistoricoObjeto(String id, String datahora, String mensagem) {
        super();
        this.setId(id);
        this.setDatahora(datahora);
        this.setMensagem(mensagem); 
    }
}

Can anyone tell me where I’m going wrong?

11-25 12:22:02.809: E/AndroidRuntime(11457): FATAL EXCEPTION: main
11-25 12:22:02.809: E/AndroidRuntime(11457): java.lang.RuntimeException: Unable to resume activity {com.ilgner.chegouahora/com.ilgner.chegouahora.Historico}: java.lang.NullPointerException
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2124)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2139)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1672)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.os.Looper.loop(Looper.java:130)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.main(ActivityThread.java:3687)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at java.lang.reflect.Method.invokeNative(Native Method)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at java.lang.reflect.Method.invoke(Method.java:507)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at dalvik.system.NativeStart.main(Native Method)
11-25 12:22:02.809: E/AndroidRuntime(11457): Caused by: java.lang.NullPointerException
11-25 12:22:02.809: E/AndroidRuntime(11457):    at com.ilgner.chegouahora.Historico.onResume(Historico.java:62)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.Activity.performResume(Activity.java:3832)
11-25 12:22:02.809: E/AndroidRuntime(11457):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2114)
11-25 12:22:02.809: E/AndroidRuntime(11457):    ... 12 more




    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_historico);
    this.lista = (ListView)findViewById(R.id.lvContatos);
    this.banco = new Banco(getApplicationContext());
    HistoricoObjeto historico = new HistoricoObjeto();
    brCollator = Collator.getInstance(new Locale("pt", "BR"));
}

@Override
protected void onResume() {
    super.onResume();
    historicos=banco.getAllH();

    historicos=ordena(brCollator, historicos);
    ArrayAdapter<HistoricoObjeto> itens = new ArrayAdapter<HistoricoObjeto>(this, 
            android.R.layout.simple_list_item_1, historicos){ 
        @Override
        public View getView (int position, View convertView, ViewGroup parent) {

                View view = super.getView(position, convertView, parent);

                // Como o simple_list_item_1 retorna um TextView, esse cast pode ser feito sem problemas
                ((TextView) view).setTextColor(Color.BLACK);

                return view;
            }}; 

    Log.e("", ""+itens.getCount());
    this.lista.setAdapter(itens);
    this.lista.setClickable(true);
    registerForContextMenu(lista);

}

Strange stopped from this mistake there , and I didn’t even do anything , but I used this code there in another list but it was with Historico was with a class Person who had name , and phone there in the list appeared the name , more now not knowing how to make appear one of the variables in the list the history class has date and time and message wanted to make appear both or one

Answer 1

historicos=banco.getAllH(); this command it returns a list or an array?

Because if it is vector, it is coherent, because the last parameter of the Arrayadapter constructor must be a vector;

Nullpointexception type errors occur when the program attempts to access a memory object that has not been instantiated (or rather initialized) until the moment of its call. What does that mean? The historical is still null or it does not have a defined value.

I suggest you use Log to see if there’s any value within historical.

I hope I’ve helped!