android - 使用 RxJava 从 Internet 获取数据时，ListView 无法显示项目数据

Question

我正在从互联网上获取一些工作信息，并准备使用 Listview 显示。当我使用RxJava处理多线程时，列表项无法显示。 List item cannot display getting data using RxJava而且我用了一些测试数据，可以显示Use an array as data

public class MainActivity extends AppCompatActivity {

private Toolbar mToolbar;
private ActionBar mActionbar;
private ListView mSeminarList;
private SeminarListAdapter mSeminarListAdapter;
private ArrayList<SeminarListItem> mSeminarData;


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


private void initToolbar() {
    mToolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(mToolbar);
    mActionbar = getSupportActionBar();
    mActionbar.setTitle("爱实习  爱工作");
    mToolbar.setNavigationIcon(R.mipmap.ic_menu_white_36dp);
}

private void initSlideMenu() {
    PrimaryDrawerItem priItemHome = new PrimaryDrawerItem()
            .withName("首页");
    SecondaryDrawerItem subItemSeminar = new SecondaryDrawerItem()
            .withName("宣讲信息");
    SecondaryDrawerItem subItemIntern = new SecondaryDrawerItem()
            .withName("实习信息");
    SecondaryDrawerItem subItemJob = new SecondaryDrawerItem()
            .withName("工作信息");

    Drawer result = new DrawerBuilder()
            .withActivity(this)
            .withToolbar(mToolbar)
            .addDrawerItems(
                    priItemHome, new DividerDrawerItem(),
                    subItemSeminar, subItemIntern, subItemJob
            )
            .build();
}

private void initListView() {
    mSeminarList = (ListView) findViewById(R.id.listview_seminar);
    mSeminarData = new ArrayList<SeminarListItem>();
//  getListData();
    getListDataTest();
}

private void getListData() {
    Observable.create(new Observable.OnSubscribe<Elements>() {

        public void call(Subscriber<? super Elements> subscriber) {
            try {
                String url = "http://xjh.haitou.cc/sh/uni-132";
                Connection conn = Jsoup.connect(url);
                conn.header("User-Agent", "Mozilla/5.0 (X11; Linux x86_64; rv:32.0) Gecko/20100101 Firefox/32.0");
                Document doc = conn.get();
                Elements elements = doc.select("tbody tr");
                subscriber.onNext(elements);
                subscriber.onCompleted();
            } catch (Exception e) {
                Log.d("Exception", e.toString());
            }
        }
    }).subscribeOn(Schedulers.io())
            .subscribe(new Observer<Elements>() {
        @Override
        public void onCompleted() {
            Log.d("onCompleted", "test");
            if (mSeminarListAdapter == null) {
                mSeminarListAdapter = new SeminarListAdapter(getApplicationContext(), R.layout.list_item, mSeminarData);
            }
            mSeminarList.setAdapter(mSeminarListAdapter);
            mSeminarListAdapter.notifyDataSetChanged();
        }

        @Override
        public void onError(Throwable e) {
        }

        @Override
        public synchronized void onNext(Elements elements) {
            for (Element element : elements) {
                String company = element.getElementsByClass("company").text();
                String link = element.select("a").attr("abs:href").toString();
                String time = element.getElementsByClass("hold-ymd").text();
                String address = element.getElementsByClass("text-ellipsis").text();

                SeminarListItem item = new SeminarListItem();
                item.setCompanyName(company);
                item.setTime("举办时间: " + time);
                item.setPlace("举办地点: " + address);
                item.setInfoUrl(link);
                mSeminarData.add(item);
                Log.d("test company name", company);
            }

        }
    });
}

private void getListDataTest() {
    for (int i=0; i<10; i++) {
        SeminarListItem item = new SeminarListItem();
        item.setCompanyName("company" + i);
        item.setPlace("place" + i);
        item.setTime("time" + i);
        mSeminarData.add(item);
    }
    if (mSeminarListAdapter == null) {
        mSeminarListAdapter = new SeminarListAdapter(MainActivity.this, R.layout.list_item, mSeminarData);
    }
    mSeminarList.setAdapter(mSeminarListAdapter);
    mSeminarListAdapter.notifyDataSetChanged();
}
}

以下是我的自定义适配器。

public class SeminarListAdapter extends ArrayAdapter<SeminarListItem> {

Context mContext;
int mResId;
ArrayList<SeminarListItem> mSeminarListData;

public SeminarListAdapter(Context context, int resource, ArrayList<SeminarListItem> object) {
    super(context, resource, object);
    this.mContext = context;
    this.mResId = resource;
    this.mSeminarListData = object;
}

public void setSeminarListData(ArrayList<SeminarListItem> data) {
    this.mSeminarListData = data;
    notifyDataSetChanged();
}

@Override
public int getCount() {
    if (mSeminarListData == null) {
        return 0;
    } else {
        return mSeminarListData.size();
    }
}

@Override
public SeminarListItem getItem(int position) {
    if (mSeminarListData == null) {
        return null;
    } else {
        return mSeminarListData.get(position);
    }
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder holder;

    if (convertView == null) {
        LayoutInflater inflater = ((Activity)mContext).getLayoutInflater();
        convertView = inflater.inflate(mResId, parent, false);
        holder = new ViewHolder();
        holder.companyName = (TextView) convertView.findViewById(R.id.textview_company_name);
        holder.time = (TextView) convertView.findViewById(R.id.textview_time);
        holder.place = (TextView) convertView.findViewById(R.id.textview_place);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    SeminarListItem item = mSeminarListData.get(position);
    holder.companyName.setText(item.getCompanyName());
    holder.time.setText(item.getTime());
    holder.place.setText(item.getPlace());

    return convertView;

}

class ViewHolder {
    public TextView companyName;
    public TextView time;
    public TextView place;
}
}

当我调用function getListDataTest()时，它显示成功，如果我调用function getListData()，它会失败。调试了一下，发现adapter中的getView()函数不会被调用。

我怀疑，如果我在新线程中使用 MainActivity 获取参数“context”，它会与从 UI 主线程获取的“context”不同。

Answer 1

您需要在主线程上执行 ListView 操作，即 notifyDataSetChanged。最简单的方法是使用 rxandroid 并添加

.observeOn(AndroidSchedulers.mainThread())

在订阅可观察对象之前。