java如何将getBooks()中生成的值(ArrayList<Book>Books变量)放入onCreate方法?
我正在使用函数getBooks在MainActivity中生成Book对象的ArrayList。但我无法将ArrayList放入onCreate,因为每次在onCreate中访问它时,我都会收到一个outofBounds异常,指示我的列表大小为0
另外,如何通过bundle发送此对象列表。我实际上尝试了parcelable,但是在片段的onCreate中,savedinstancestate始终为空,应用程序停止
public class MainActivity extends AppCompatActivity implements FragmentA.Communicator{
FragmentA f1;
FragmentB f2;
static ArrayList<Book> b = new ArrayList<Book>();
FragmentManager manager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getBooks();
Log.d("Main-Title",b.get(3).getTitle());
manager = getSupportFragmentManager();
f1 = (FragmentA) manager.findFragmentById(R.id.fragment);
f1.setCommunicator(this);
}
@Override
public void respond(int index) {
f2 = (FragmentB) manager.findFragmentById(R.id.fragment2);
if(f2!=null && f2.isVisible())
{
f2.changeData(index);
}
else
{
Bundle bundle = new Bundle();
bundle.putInt("index", index);
Fragment newFragment = new FragmentC();
newFragment.setArguments(bundle);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment, newFragment);
transaction.addToBackStack(null);
transaction.commit();
}
}
private void getBooks(){
String url = Book.API.BASE_URL;
//ArrayList<Book> boo;
Retrofit retrofit = new Retrofit.Builder().baseUrl(Book.API.BASE_URL).addConverterFactory(GsonConverterFactory.create()).build();
Book.API api = retrofit.create(Book.API.class);
Call<ArrayList<Book>> call = api.getBooks();
call.enqueue(new Callback<ArrayList<Book>>() {
@Override
public void onResponse(Call<ArrayList<Book>> call, Response<ArrayList<Book>> response) {
ArrayList<Book> Books = response.body();
for(Book h: Books){
Log.d("Title",h.getTitle());
b.add(h);
}
}
@Override
public void onFailure(Call<ArrayList<Book>> call, Throwable t) {
Toast.makeText(getApplicationContext(),t.getMessage(),Toast.LENGTH_SHORT).show();
}
});
}
}
# 1 楼答案
如果您试图异步获取数据,则getBooks()方法在检索数据之前不会停止。所以你的名单是空的