当 RecyclerView 为空时如何使 SwipeRefreshLayout 工作

Question

I noticed the SwipeRefreshLayout works when my RecyclerView is filled with data but not when the RecyclerView is empty. Is there a way to override this behavior?

My app fetches some data from the server and populates the RecyclerView . So for example, if the user has forgotten to turn on their internet but started my app, I want them to be able to turn it on and swipe up to refresh instead of going back and starting the activity again.

Here's is my activity's xml. I have removed some code to make this less verbose. I had one more button outside of the SwipeRefreshLayout and I have also removed my constraints.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BreakfastActivity"
    android:orientation="vertical">

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/b_swipe_refresh_layout"
        android:layout_width="match_parent"
        android:layout_height="0dp">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/rv_breakfast"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </android.support.v4.widget.SwipeRefreshLayout>

</android.support.constraint.ConstraintLayout>

And this is the .java file:

public class BreakfastActivity extends AppCompatActivity implements SwipeRefreshLayout.OnRefreshListener {

    // to display the menu
    RecyclerView rv_breakfast;
    RecyclerView.Adapter my_adapter;

    // the actual menu
    ArrayList<Menu> menu;

    private SwipeRefreshLayout swipeRefreshLayout;

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

        rv_breakfast = findViewById(R.id.rv_breakfast);
        swipeRefreshLayout = findViewById(R.id.b_swipe_refresh_layout);

        swipeRefreshLayout.setRefreshing(true);
        swipeRefreshLayout.setOnRefreshListener(this);

        rv_breakfast.setLayoutManager(new LinearLayoutManager(this));

        new GetMenu(this).execute();
    }

    @Override
    public void onRefresh() {
        new GetMenu(this).execute();
    }

    static class GetMenu extends GetMenuBase {

        WeakReference<BreakfastActivity> context;

        GetMenu(BreakfastActivity b) {
            context = new WeakReference<>(b);
            meal_type = "breakfast";
            b.swipeRefreshLayout.setRefreshing(true);
        }

        @Override
        protected void onPostExecute(JSONObject parent) {
            // process the output of the server side script script
            b.swipeRefreshLayout.setRefreshing(false);
        }
    }

The java file is again devoid of some code not concerning the question. GetMenuBase extends an AsyncTask and implements doInBackground() and makes a call to the server and returns the JSON output.

Answer 1

The problem is that when your RecyclerView is empty then your height will be 0dp because you've set the height to wrap_content and 0dp to your SwipeRefreshLayout .

Change the height of your SwipeRefreshLayout or your RecyclerView to match_parent .