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RecyclerView不显示任何数据

android-recyclerview android

Diana Vrabie · 技术社区 · 8 年前

我为这个问题挣扎了一段时间。我有个活动( SerieActivity )其中,我允许用户选择各种项目并给它们赋值。项目存储在 ArrayList<Variable> 哪里 Variable 是我定义的一个类。项目显示在 RecyclerView .这个很好用。单击该活动中的按钮后,用户将被发送到另一个活动( Result )显示与 ArrayList 在里面 连续性 ,以及用户输入的相应值。

在我的 后果 活动我已创建 连续性 类,然后 阵列列表 存储原始值的步骤 阵列列表 从…起 连续性 .然而,我的 后果 类未填充数据。可能会出什么问题?

这是我的代码:

变量 班

public class Variable {

    boolean known;
    String unit, name;
    double value;
}

RVAdapterSerie -中使用的RecyclerView适配器 连续性 班

public class RVAdapterSerie extends RecyclerView.Adapter<RVAdapterSerie.ViewHolder> {

    private Context context;
    private ArrayList<Variable> variableList;

    public RVAdapterSerie(Context context, ArrayList<Variable> variableList) {
        this.context = context;
        this.variableList = variableList;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.recycler_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(RVAdapterSerie.ViewHolder holder, int position) {
        Variable v = variableList.get(position);
        holder.setItems(v);
    }

    @Override
    public int getItemCount() {
        return variableList.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        private CheckBox checkBox;
        private EditText editText;
        private TextView textView;

        public ViewHolder(View itemView) {
            super(itemView);
            checkBox = itemView.findViewById(R.id.value_cb);
            editText = itemView.findViewById(R.id.value_et);
            textView = itemView.findViewById(R.id.value_tv);
        }

        public void setItems (Variable variable) {
            checkBox.setText(variable.getName());
            editText.setText(String.format("%.3f", variable.getValue()));
            textView.setText(variable.getUnit());
        }
    }
}

连续性 班

public class SerieActivity extends AppCompatActivity {

    public ArrayList<Variable> mList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_serie);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        RecyclerView recyclerView = findViewById(R.id.serie_rv);
        RVAdapterSerie rvAdapterSerie = new RVAdapterSerie(this, mList);
        recyclerView.setAdapter(rvAdapterSerie);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));


        populateList();
        rvAdapterSerie.notifyDataSetChanged();

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.serie_fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(SerieActivity.this, Result.class);
                intent.putExtra("tag", "serie");
                startActivity(intent);
            }
        });
    }

    public void populateList() {
        mList.add(new Variable(false, "dummyunit", "dummyname", 0));
        mList.add(new Variable(false, "diofishafuio", "ghfuef", 0));
        mList.add(new Variable(false, "diofishdfesffafuio", "ghfuef", 0));
        //add dummy items
    }
}

RVResultAdapter -RecyclerView-in适配器 后果 班

public class RVResultAdapter extends RecyclerView.Adapter<RVResultAdapter.ViewHolder> {

    private Context context;
    private ArrayList<Variable> variableList;

    public RVResultAdapter(Context context, ArrayList<Variable> variableList) {
        this.context = context;
        this.variableList = variableList;
    }

    @Override
    public RVResultAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.result_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(RVResultAdapter.ViewHolder holder, int position) {
        Variable v = variableList.get(position);
        holder.setItems(v);
    }

    @Override
    public int getItemCount() {
        return variableList.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        TextView textView1;
        TextView textView2;
        TextView textView3;

        public ViewHolder(View itemView) {
            super(itemView);
            textView1 = itemView.findViewById(R.id.result_name_tv);
            textView2 = itemView.findViewById(R.id.result_value_tv);
            textView3 = itemView.findViewById(R.id.result_unit_tv);
        }

        public void setItems (Variable variable) {
            textView1.setText(variable.getName());
            textView2.setText(String.format("%.3f", variable.getValue()));
            textView3.setText(variable.getUnit());
        }
    }
}

后果 班

public class Result extends AppCompatActivity {

    public ArrayList<Variable> rList = new ArrayList<>();

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

        Intent intent = getIntent();
        String tag = intent.getExtras().getString("tag");

        if (tag.equals("serie")) {
            SerieActivity serieActivity = new SerieActivity();
            rList = serieActivity.mList;
        }

        RecyclerView recyclerView = findViewById(R.id.result_rv);
        RVResultAdapter rvResultAdapter = new RVResultAdapter(this, rList);
        recyclerView.setAdapter(rvResultAdapter);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        rvResultAdapter.notifyDataSetChanged();
    }
}

我的问题是在 后果 。当我上下滚动时,它会显示蓝色的“内容结束”内容,所以我猜是RecyclerView 是那里,但没有任何数据。非常感谢您的帮助。我对Android和Java编程非常陌生,所以我想这一定是一件我看不到的蠢事。

3 回复 | 直到 8 年前

Khemraj Sharma 8 年前

你在干什么伙计。如何从的新对象获取列表 SerieActivity.class ?

    if (tag.equals("serie")) {
        SerieActivity serieActivity = new SerieActivity();
        rList = serieActivity.mList;
    }

这是完全错误的方式。如果要在活动之间传递列表。可以使用可包裹的方法 putExtra 和 getExtra 。

假设您的列表是字符串列表,则使数据 ArrayList<String> 和使用 intent.putStringArrayListExtra("data", data)

以下是您需要的代码框架:

首先需要创建一个Parcelable对象类,请参见示例

public class Student implements Parcelable {

        int id;
        String name;

        public Student(int id, String name) {
            this.id = id;
            this.name = name;

        }

        public int getId() {
            return id;
        }

        public String getName() {
            return name;
        }


        @Override
        public int describeContents() {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public void writeToParcel(Parcel dest, int arg1) {
            // TODO Auto-generated method stub
            dest.writeInt(id);
            dest.writeString(name);
        }

        public Student(Parcel in) {
            id = in.readInt();
            name = in.readString();
        }

        public static final Parcelable.Creator<Student> CREATOR = new Parcelable.Creator<Student>() {
            public Student createFromParcel(Parcel in) {
                return new Student(in);
            }

            public Student[] newArray(int size) {
                return new Student[size];
            }
        };
    }

和列表

ArrayList<Student> arraylist = new ArrayList<Student>();

调用活动的代码

Intent intent = new Intent(this, SecondActivity.class);
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("mylist", arraylist);
intent.putExtras(bundle);       
this.startActivity(intent);

调用活动的代码

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second);   

    Bundle bundle = getIntent().getExtras();
    ArrayList<Student> arraylist = bundle.getParcelableArrayList("mylist");
}

rubin94 8 年前

所以你打电话来 SerieActivity 中的构造函数 Results 活动和执行 populateList() 在…内 onCreate() 。您不应该以这种方式创建活动,因为 onCreate() 将永远不会被调用。相反,您应该使用 putExtra 和使用 Parcelable 界面

M Ali Khattak 8 年前

只需像这样设置recyclerview代码,首先初始化适配器,然后设置布局管理器,然后设置为adapter to recyclerview。

recyclerView=(recyclerView)findViewById(R.id.recycler\u视图);

    mAdapter = new MoviesAdapter(movieList);
    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());
    recyclerView.setAdapter(mAdapter);

    prepareMovieData();