与Firestore异步 [英] Async with Firestore

问题描述

我正在尝试使 ProgressBar 旋转，同时将 Firestore 中的数据加载到 ListView 中.然后，加载后- ProgressBar 应该消失.

I'm trying to make ProgressBar rotate, while data from Firestore is loading into the ListView. And then, after loading - the ProgressBar should disappear.

这就是我尝试的方法，但是在多线程中，我仍然是一个完整的零.

That's how I tried to do it, but in multithreading I'm still a complete zero.

这是内部类，我尝试在其中使用异步:

It's inner class, where I try to use async:

ProgressBar prog;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_result);
    prog = findViewById(R.id.progressCircle);
    prog.setVisibility(View.INVISIBLE);
    class MyProgress extends AsyncTask<Void, Integer, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            prog.setVisibility(View.VISIBLE);
        }
        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            prog.setVisibility(View.INVISIBLE);
        }
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
        }
        @Override
        protected Void doInBackground(Void... voids) {
            query.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                @Override
                public void onComplete(Task<QuerySnapshot> task) {
                    if (task.isSuccessful()) {
                        List<Places> placesList = new ArrayList<>();
                        for (DocumentSnapshot document : task.getResult()) {
                            Places places = document.toObject(Places.class);
                            System.out.println(places);
                            placesList.add(places);
                        }
                        if (placesList.size() > 0) {
                            System.out.println(placesList);
                            int placeCount = placesList.size();
                            Random randomGenerator = new Random();
                            ArrayList<Places> randomPlaceList = new ArrayList<>();
                            for (int i = 0; i < 3; i++) {
                                int randomIndex = randomGenerator.nextInt(placeCount);;
                                Places item = placesList.get(randomIndex);
                                randomPlaceList.add(item);
                            }
                            ListView mListView = findViewById(R.id.place_list);
                            mAdapter = new PlaceAdapter(randomPlaceList, getBaseContext());
                            mListView.setAdapter(mAdapter);
                        }
                    } else {
                        error.setVisibility(View.VISIBLE);
                    }
                }
            });
        return null;
    }
}

活动布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:background="@drawable/card_new_bg">

    <ProgressBar
        android:id="@+id/progressCircle"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true" />

    <ListView
        android:id="@+id/name_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_centerInParent="true" >
    </ListView>
</RelativeLayout>

推荐答案

将异步任务与按设计是异步的Firebase调用一起使用是相当多余的.

It's rather redundant to use async task with firebase calls which are async by design.

您可以简单地创建两个方法:

What you can simply do is to create two methods:

public void showLoading(){
  prog.setVisibility(View.VISIBLE);
}

public void hideLoading(){
    prog.setVisibility(View.GONE);
}

在调用异步调用Firebase之前，请先调用这些方法.

And right before calling your async call to firebase call these methods.

收到结果后，调用隐藏方法:

When you receive the result call the hiding method:

public void queryFirebase() {
    showLoading();
    query.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
                List<Places> placesList = new ArrayList<>();
                for (DocumentSnapshot document : task.getResult()) {
                    Places places = document.toObject(Places.class);
                    System.out.println(places);
                    placesList.add(places);
                }
                if (placesList.size() > 0) {
                    int placeCount = placesList.size();
                    Random randomGenerator = new Random();
                    ArrayList<Places> randomPlaceList = new ArrayList<>();
                    for (int i = 0; i < 3; i++) {
                        int randomIndex = randomGenerator.nextInt(placeCount);;
                        Places item = placesList.get(randomIndex);
                        randomPlaceList.add(item);
                    }
                    ListView mListView = findViewById(R.id.place_list);
                    mAdapter = new PlaceAdapter(randomPlaceList, getBaseContext());
                    mListView.setAdapter(mAdapter);
                }
            } else {
                error.setVisibility(View.VISIBLE);
            }
            hideLoading();
        }
    });
}

那你就做:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_result);
    prog = findViewById(R.id.progressCircle);
    prog.setVisibility(View.INVISIBLE);
    queryFirebase();
}

这篇关于与Firestore异步的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！