setter getter on android

Question

maybe its really stupid question. but i stuck 5 hours because this setter getter.

i have class Home_Fragment, there is value id_product in there.. this my Home_Fragment class

public class Home_Fragment extends ListFragment {

private Detail_Produk dp;

@Override
public void onActivityCreated(Bundle savedInstanceState) {
     dp = new Detail_Produk("1");
     //** After this i call another activity but not Detail_Produk
}

and in my Detail_Produk class

String test;

View v;

public Detail_Produk() {
    super();
}

public Detail_Produk(String test) {
    super();
    this.test = test;
}

public String getIDProduk() {
    return test;
}

public void setIDProduk(String test) {
    this.test = test;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    v = inflater.inflate(R.layout.detail_produk, container, false);
    Toast.makeText(getActivity(), "ID : " + getIDProduk().toString(), Toast.LENGTH_SHORT).show();
    return v;
}

when i call activity Detail_Produk from another activity (not Home_Fragment). on line Toast its giving me error Java.Lang.NullPointerException.

my code error or i can't because i call Detail_Product Activity not from Home_Fragment?

or should i use Shared Preferences?

Thanks before :)

Answer 1

The problem here is that the Detail_Produk instance that you're creating explicitly in your Home_Fragment (and passing the test value to) is lost as soon as the onActivityCreated() completes.

The instance on which the onCreateView() is actually getting called is instantiated by the Android framework when your other activity requests to start the Detail_Produk activity. That instance does not have its test value set and hence you get the NPE.

You should pass this value through an Intent extra. Take a look at this Android developer tutorial on how an Activity can retrieve data from an Intent that started it.

http://developer.android.com/training/basics/firstapp/starting-activity.html#ReceiveIntent

Answer 2

dp = new Detail_Produk(1);

1 is not a string. And Detail_Produk does not have a constructor that accepts an integer argument. Not sure what's going on here. Your code should not compile, let alone barf out a NPE, which I assume is here getIDProduk().toString()

Answer 3

我认为您应该使用共享首选项，因此该值将保持不变。您可以在Home_Fragment中创建静态变量，然后在其中保存值并在Detail_Produk类中访问它