Question

我已经在这里尝试了类似问题的一些建议，正如您在一些注释掉的代码中看到的那样。我是新人，所以你能帮帮我吗？如果您需要编码以尝试解决问题，请告诉我。提前谢谢。

我甚至试图做错误所说的但我真的不知道把GenericTypeIndicator放到哪里。

我收到此错误：

com.google.firebase.database.DatabaseException：类java.util.List 有泛型类型参数，请改用GenericTypeIndicator 在com.google.android.gms.internal.zzelw.zzb（未知来源）在com.google.android.gms.internal.zzelw.zza（未知来源）在com.google.android.gms.internal.zzelw.zzb（未知来源）在com.google.android.gms.internal.zzelx.zze（未知来源）在com.google.android.gms.internal.zzelw.zzb（未知来源）在com.google.android.gms.internal.zzelw.zza（未知来源）在com.google.firebase.database.DataSnapshot.getValue（未知来源）在 com.firebase.ui.database.ClassSnapshotParser.parseSnapshot（ClassSnapshotParser.java:29） ...

这是我的代码：

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.homeRecyclerView)
    RecyclerView mHomeRecyclerView;

    @BindView(R.id.emptyTextView)
    TextView mEmptyTextView;

    protected static final Query sInspirationQuery =
            FirebaseDatabase.getInstance().getReference().child("Inspirations");

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);


        ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayShowTitleEnabled(false);
        actionBar.setDisplayShowHomeEnabled(true);
        actionBar.setIcon(R.mipmap.ic_launcher);

        //mHomeRecyclerView.setHasFixedSize(true);
        mHomeRecyclerView.setLayoutManager(new LinearLayoutManager(this));


    }

    @Override
    protected void onStart() {
        super.onStart();


        attachRvAdapter();
    }

    @Override
    protected void onStop() {
        super.onStop();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.options_menu, menu);
        Drawable addInspirationDrawable = menu.findItem(R.id.addInspiration).getIcon();
        Drawable userAccountDrawable = menu.findItem(R.id.userAccount).getIcon();
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if(id == R.id.addInspiration) {
            String className = "com.example.jessie.inspirationexchange.CreateActivity";
            nextActivity(className);
        } else if(id == R.id.userAccount) {
            String className = "com.example.jessie.inspirationexchange.UserActivity";
            nextActivity(className);
        }
        return super.onOptionsItemSelected(item);
    }

    private void nextActivity(String className) {
        Intent intent = null;
        try {
            intent = new Intent(this, Class.forName(className));
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        startActivity(intent);
    }

    public void attachRvAdapter() {
        RecyclerView.Adapter adapter = newAdapter();
        mHomeRecyclerView.setAdapter(adapter);
    }



    protected RecyclerView.Adapter newAdapter() {
        FirebaseRecyclerOptions<Inspiration> options =
                new FirebaseRecyclerOptions.Builder<Inspiration>()
                        .setQuery(sInspirationQuery, Inspiration.class)
                        .setLifecycleOwner(this)
                        .build();

        return new FirebaseRecyclerAdapter<Inspiration, CardViewHolder>(options) {
            @Override
            public CardViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                return new CardViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.inspiration_card, parent, false));
            }

            @Override
            protected void onBindViewHolder(@NonNull CardViewHolder holder, int position, @NonNull Inspiration model) {
                holder.bind(model);
            }

//            SnapshotParser<Inspiration> mSnapshotParser = new SnapshotParser<Inspiration>() {
//                @NonNull
//                @Override
//                public Inspiration parseSnapshot(@NonNull DataSnapshot snapshot) {
//                    GenericTypeIndicator<List<Inspiration>> t = new GenericTypeIndicator<List<Inspiration>>();
//
//                    return (Inspiration) snapshot.child("Inspirations").getValue(t);
//                }
//            };

            @Override
            public void onDataChanged() {
                super.onDataChanged();

                //GenericTypeIndicator<List<Inspiration>> t = new GenericTypeIndicator<List<Inspiration>>();
                mEmptyTextView.setVisibility(getItemCount() == 0 ? View.VISIBLE : View.GONE);
            }


        };

    }

}

我的模特：

public class Inspiration {

    private String mTitle;
    private String mBody;
    private List<String> mCategoriesChose;
    private String mAuthor;

    public Inspiration() {
    }

    public Inspiration(String title, String body, List categories) {
        mTitle = title;
        mBody = body;
        mCategoriesChose = categories;
    }

    public String getAuthor() {
        return mAuthor;
    }

    public void setAuthor(String author) {
        mAuthor = author;
    }

    public String getTitle() {
        return mTitle;
    }

    public void setTitle(String title) {
        mTitle = title;
    }

    public String getBody() {
        return mBody;
    }

    public void setBody(String body) {
        mBody = body;
    }

    public List<String> getCategoriesChose() {
        return mCategoriesChose;
    }

    public void setCategoriesChose(List categoriesChose) {
        mCategoriesChose = categoriesChose;
    }

    @Override
    public String toString() {
        return "Inspiration{" +
                "mTitle='" + mTitle + '\'' +
                ", mBody='" + mBody + '\'' +
                ", mCategoriesChose=" + mCategoriesChose.toString() +
                '}';
    }

}

这是JSON的样子（只有1个对象）

{
  "Inspirations" : {
    "-L5un07HfHu0XT-XfLX2" : {
      "author" : "User1",
      "body" : "test 1",
      "categoriesChose" : [ "Character", "Courage", "Determination" ],
      "title" : "gov"
    }
  }
}

Answer 1

您不能在主要对象中包含您尝试反序列化的列表和地图类型对象。这是因为Java类型擦除系统的工作方式。在运行时，通过反射无法知道列表或映射声明的泛型类型，这意味着它不知道哪些类型的对象可以放在那里。

当您尝试反序列化的顶级对象是一个通用列表时，

getValue()与<VirtualHost *:*> ProxyPreserveHost On ProxyPass "/" "http://123.123.123.12" ProxyPassReverse "/" "http://123.123.123.12" ServerName mydomain.com </VirtualHost>一起使用，但这是关于它的。如果它嵌入在任何地方，它就无法工作。错误消息在这一点上有点误导。您必须从快照中提取项目并自行创建对象。

Answer 2

我通过删除数据库中的嵌套数组解决了这个问题。删除后，它就像一个魅力。如果有人想回答如何解决嵌套数组内部数据库的问题，请随时发帖。

将Firebase数据库中的对象检索到我的RecyclerView中

2 个答案: