带有 FirebaseRecyclerAdapter 的 RecyclerView 仍然是空的

Question

我目前正在尝试使用 Firebase 实时数据库构建应用程序，我那里已经有一些数据，它们的结构如下（导出的摘录JSON）

{
"userdata" : {
    "593QfAvxxxxxxxxxxxHqCMA3" : {
      "calcentries" : {
        "-LJy_hvvm3ySUqM6sQcf" : {
          "candyCount" : 0,
          "evolutionLine" : {
            "candyNeeded" : 25,
            "evolvedSpecies" : 2,
            "precondition" : {
              "buddyKm" : 0,
              "preconditionType" : "NONE"
            }
          },
          "evolvedSpeciesTransferCount" : 0,
          "newPokedexEntry" : false,
          "pokemonCount" : 0,
          "possibleEvoCountWithPreconditionsMet" : 0,
          "possibleEvolutionCount" : 0,
          "preconditionsMet" : false,
          "sourceSpecies" : 1,
          "sourceSpeciesCountAfterEvolutions" : 0,
          "sourceSpeciesTransferCount" : 0
        },
        "-LJy_hwMVTM20f0c5JOJ" : { ...

}

我尝试使用 FirebaseRecyclerAdapter (Firebase UI 4.1.0) 在 RecyclerView 中显示它们。这就是我在 activity

的 onCreate 中初始化 RecyclerView 和适配器的方式

mRecyclerView = findViewById(R.id.rv_calculation_input);

RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this,1, LinearLayoutManager.VERTICAL,false);

mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);

FirebaseRecyclerOptions<CalculationInputEntry> opt
     = new FirebaseRecyclerOptions.Builder<CalculationInputEntry>()
         .setLifecycleOwner(this)
         .setQuery(AppUtil.getCurrentUserRef().child("calcentries"), CalculationInputEntry.class)
         .build();

mAdapter = new FirebaseRecyclerAdapter<CalculationInputEntry, CalculationInputEntryViewHolder>(opt) {        
     @NonNull
     @Override
     public CalculationInputEntryViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
          View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_main, parent, false);
          return new CalculationInputEntryViewHolder(v);
     }

     @Override
     protected void onBindViewHolder(@NonNull CalculationInputEntryViewHolder holder, int position, @NonNull CalculationInputEntry model) {
           holder.bindEntry(model);
     }
 };

mRecyclerView.setAdapter(mAdapter);

视图仍然是空的... 通过设置生命周期所有者，应该不需要在适配器上手动调用 startListening 和 stopListening，对吧？

我将 Firebase 日志级别设置为调试，发现相当多的条目引发了 "CHILD_ADDED" 事件，甚至显示了预期的数据...

D/EventRaiser: Raising /userdata/593QxxxxxxxxxCMA3/calcentries: CHILD_ADDED: { -LJy_tNakAl19tH5H_tb: {preconditionsMet=false, sourceSpeciesCountAfterEvolutions=0, newPokedexEntry=false, possibleEvoCountWithPreconditionsMet=0, possibleEvolutionCount=0, candyCount=0, sourceSpeciesTransferCount=0, evolutionLine={candyNeeded=25, precondition={buddyKm=0, preconditionType=NONE}, evolvedSpecies=375}, pokemonCount=0, sourceSpecies=374, evolvedSpeciesTransferCount=0} }

但他们似乎永远无法接通 UI。

这里是涉及的模型类，我正在使用Lombok 来生成getter、setter 和所需的构造函数（至少我希望我包含了所有需要的东西）。我已经将一些字段从枚举更改为字符串，以防万一这可能是个问题...注意：前面有很多代码...

计算输入项

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class CalculationInputEntry implements Comparable, Parcelable {

    //Pokédex number for less data redundancy when serializing
    private int sourceSpecies;
    private SpeciesEvolution evolutionLine;

    //input variables
    private int candyCount;
    private int pokemonCount;
    private boolean newPokedexEntry;
    private boolean preconditionsMet;

    //calculation and result variables
    private int possibleEvolutionCount; // 0 when preconditionsMet false
    private int sourceSpeciesTransferCount;
    private int evolvedSpeciesTransferCount;
    private int sourceSpeciesCountAfterEvolutions;
    private int possibleEvoCountWithPreconditionsMet;

    public CalculationInputEntry(int species, SpeciesEvolution evolution, int candyCount, int pokemonCount) {
        this.sourceSpecies = species;
        this.evolutionLine = evolution;
        this.candyCount = candyCount;
        this.pokemonCount = pokemonCount;
        this.preconditionsMet = false;
        this.newPokedexEntry = false;
    }

   //some other methods, including compareTo and the Parcelable stuff
}

物种进化

@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
public class SpeciesEvolution implements Parcelable {
    private int candyNeeded;
    private EvolutionPrecondition precondition;
    private int evolvedSpecies;

    //Parcelable stuff here
}

进化前提条件

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public class EvolutionPrecondition implements Parcelable {

    private String preconditionType;
    private int buddyKm;
    private String evoItem;

   //Parcelable stuff
}

我的模型有什么问题还是我太盲目看不到真正的问题？任何提示将不胜感激...

Answer 1

By setting the lifecycle owner, manually calling startListening and stopListening on the adapter should not be necessary, right?

不，两者都是必需的。为了能够显示来自 Firebase 数据库的数据，您需要开始监听更改，为此您应该在 onStart() 方法中添加以下代码行：

@Override
protected void onStart() {
    super.onStart();
    mAdapter.startListening();
}

要停止侦听更改，您需要在 onStop() 方法中添加以下代码行：

@Override
protected void onStop() {
    super.onStop();
    if(mAdapter != null) {
        mAdapter.stopListening();
    }
}

请参阅我在中的回答，我已经解释了为什么您应该删除侦听器。

Answer 2

我解决了。不需要 start/stopListening，我的 getters/setters 或 DatabaseReference 也不是错误的...

就是这条线

mRecyclerView.setHasFixedSize(true);

在我删除它之后，我可以将所有内容恢复到问题中显示的状态。我从这个 GitHub 问题 https://github.com/firebase/FirebaseUI-Android/issues/204 中得到了灵感无论如何都要感谢 Alex Mamo :)

带有 FirebaseRecyclerAdapter 的 RecyclerView 仍然是空的

RecyclerView with FirebaseRecyclerAdapter remains empty

android

android-recyclerview

firebase-realtime-database

firebaseui