无法弄清楚为什么RecyclerView没有显示我的观点

Question

我一遍又一遍地检查了代码。我没有收到任何错误，但我的recylcerview没有显示我的数据。任何帮助，将不胜感激。

这是我的layout / Activity，它包含了recyclerview对象：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    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:layout_margin="16dp"
    tools:context="com.checkinsystems.ez_score.MatchActivity">

    <Button
        android:id="@+id/create_match_button"
        android:layout_width="0dp"
        android:layout_height="65dp"
        android:onClick="goToNewMatchFormActivity"
        android:text="@string/create_match_button"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>


    <Button
        android:id="@+id/edit_match_button"
        android:layout_width="0dp"
        android:layout_height="65dp"
        android:layout_marginTop="15dp"
        android:onClick="goToNewMatchToEdit"
        android:text="@string/edit_match_button"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/create_match_button"/>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/match_list_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/edit_match_button"
        android:layout_marginTop="8dp"
        app:layoutManager="LinearLayoutManager"/>


</android.support.constraint.ConstraintLayout>

以下是我创建的列表行布局（我希望在recylcerview中显示的内容）：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    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="wrap_content"
    android:orientation="vertical"
    android:padding="8dp">

    <TextView
        android:id="@+id/match_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="0dp"
        android:text="Match Name"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/imageView"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintHorizontal_bias="0.502"/>

    <TextView
        android:id="@+id/match_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Match Date"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@+id/imageView"
        app:layout_constraintTop_toBottomOf="@+id/match_name"/>


    <ImageView
        android:id="@+id/imageView"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="0dp"
        android:layout_weight="1"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/ic_more_vert_black_24dp"/>


</android.support.constraint.ConstraintLayout>

这是我的Adapter类：

package com.checkinsystems.ez_score;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.checkinsystems.ez_score.model.Match;

import java.util.List;


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

    private List<Match> mMatches;
    private Context mContext;

    public MatchItemAdapter(Context context, List<Match> items){
        this.mContext = context;
        this.mMatches = items;
    }

    @Override
    public MatchItemAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        LayoutInflater inflater = LayoutInflater.from(mContext);
        View itemView = inflater.inflate(R.layout.list_item_match, parent, false);
        ViewHolder viewHolder = new ViewHolder(itemView);

        return viewHolder;
    }

    @Override
    public void onBindViewHolder(MatchItemAdapter.ViewHolder holder, int position) {
        Match match = mMatches.get(position);

        try {
            holder.tvName.setText(match.getMatchName());
            holder.tvDate.setText(match.getMatchDate());
            holder.imageView.findViewById(R.id.imageView);
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

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


    public static class ViewHolder extends RecyclerView.ViewHolder{

        public TextView tvName;
        public TextView tvDate;
        public ImageView imageView;

        public ViewHolder(View itemView){
            super(itemView);

            tvName = (TextView)itemView.findViewById(R.id.match_name);
            tvDate = (TextView)itemView.findViewById(R.id.match_date);
            imageView = (ImageView)itemView.findViewById(R.id.imageView);
        }
    }
}

这是我的活动（控制器）：

package com.checkinsystems.ez_score;

import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;

import com.checkinsystems.ez_score.Sample.SampleDataProvider;
import com.checkinsystems.ez_score.model.Match;

import java.io.File;
import java.util.List;

import static com.checkinsystems.ez_score.MainActivity.CURRENT_MATCH_NAME;
import static com.checkinsystems.ez_score.MainActivity.MY_GLOBAL_PREFS;

public class MatchActivity extends AppCompatActivity {

    private static final String TAG = "MatchActivity";
    private static RecyclerView mRecyclerView;
    List<Match> mMatchList = SampleDataProvider.sMatchList;


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

        // place the current match name in the action bar
        SharedPreferences sharedPreferences = getSharedPreferences(MY_GLOBAL_PREFS, MODE_PRIVATE);
        String currentMatchName = sharedPreferences.getString(CURRENT_MATCH_NAME, "current_match_name");

        if (!(currentMatchName.equals(""))) {
            ActionBar actionBar =  getSupportActionBar();
            if (actionBar != null) {
                actionBar.setTitle(currentMatchName);
            }
        }

        MatchItemAdapter adapter = new MatchItemAdapter(this, mMatchList);
        mRecyclerView = (RecyclerView)findViewById(R.id.match_list_view);
        mRecyclerView.setAdapter(adapter);

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

        SharedPreferences sharedPreferences = getSharedPreferences(MY_GLOBAL_PREFS, MODE_PRIVATE);
        String currentMatchName = sharedPreferences.getString(CURRENT_MATCH_NAME, "current_match_name");

        if (!(currentMatchName.equals(""))) {
            ActionBar actionBar =  getSupportActionBar();
            Log.d(TAG, "action bar value: " + actionBar);
            if (actionBar != null) {
                actionBar.setTitle(currentMatchName);
            }
        }
    }


    // onClick handler to go to NewMatchFormActivity
    public void goToNewMatchFormActivity(View view) {

        Intent intent = new Intent(this, NewMatchFormActivity.class);
        startActivity(intent);
    }

    public void goToNewMatchToEdit(View view) {

        Intent intent = new Intent(this, EditMatchActivity.class);
        startActivity(intent);
    }
}

这是Match对象（Data Model）类：

package com.checkinsystems.ez_score.model;

导入android.os.Parcel; import android.os.Parcelable;

import com.checkinsystems.ez_score.utils.MatchHelper;

import java.util.ArrayList;

public class Match {

    private String mMatchId;
    private String mClubId;
    private String mMatchName;
    private String mMatchDate;
    private String mMatchLevel;
    private ArrayList<MatchStage> mStages;
    private ArrayList<Competitors> mCompetitors;

    public Match() {

    }

    public Match(String matchId, String clubID, String time, String matchName, String matchDate,
                 String matchLevel, ArrayList<MatchStage> stages, ArrayList<Competitors> competitors) {

        if(matchId == null){
            mMatchId = MatchHelper.createID(matchDate, clubID, time);
        }

        mClubId = clubID;
        mMatchName = matchName;
        mMatchDate = matchDate;
        mMatchLevel = matchLevel;
        mStages = stages;
        mCompetitors = competitors;
    }

    public String getMatchId() {
        return mMatchId;
    }

    public void setMatchId(String matchId) {
        mMatchId = matchId;
    }

    public String getClubId() {
        return mClubId;
    }

    public void setClubId(String clubId) {
        mClubId = clubId;
    }

    public String getMatchName() {
        return mMatchName;
    }

    public void setMatchName(String matchName) {
        mMatchName = matchName;
    }

    public String getMatchDate() {
        return mMatchDate;
    }

    public void setMatchDate(String matchDate) {
        mMatchDate = matchDate;
    }

    public String getMatchLevel() {
        return mMatchLevel;
    }

    public void setMatchLevel(String matchLevel) {
        mMatchLevel = matchLevel;
    }

    public ArrayList<MatchStage> getStages() {
        return mStages;
    }

    public void setStages(ArrayList<MatchStage> stages) {
        mStages = stages;
    }

    public ArrayList<Competitors> getCompetitors() {
        return mCompetitors;
    }

    public void setCompetitors(ArrayList<Competitors> competitors) {
        mCompetitors = competitors;
    }

    @Override
    public String toString() {
        return "Match{" +
                "mMatchId='" + mMatchId + '\'' +
                ", mMatchName='" + mMatchName + '\'' +
                ", mMatchDate='" + mMatchDate + '\'' +
                ", mMatchLevel='" + mMatchLevel + '\'' +
                ", mStages=" + mStages +
                ", mCompetitors=" + mCompetitors +
                '}';
    }

}

以下是我的样本数据提供者：

package com.checkinsystems.ez_score.Sample;


import com.checkinsystems.ez_score.model.Match;
import com.checkinsystems.ez_score.model.MatchStage;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class SampleDataProvider {

    public static List<Match> sMatchList;
    public static Map<String, Match> sMatchMap;

    public static List<MatchStage> sMatchStages;
    public static Map<String, MatchStage> sMatchStageMap;

    static {
        sMatchList = new ArrayList<>();
        sMatchMap = new HashMap<>();

        sMatchStages = new ArrayList<>();
        sMatchStageMap = new HashMap<>();

        addStage(new MatchStage(null, 1, "Zombie Apocalypse", 2, 4, 3, 1, 10, 45, "comstock"));
        addStage(new MatchStage(null, 2, "Police Training", 2, 3, 3, 1, 11, 55, "comstock"));
        addStage(new MatchStage(null, 3, "Get Those Guys", 2, 4, 3, 1, 13, 65, "comstock"));
        addStage(new MatchStage(null, 4, "Self Defense", 2, 2, 3, 1, 10, 62, "comstock"));
        addStage(new MatchStage(null, 5, "Stand Your Ground", 2, 5, 3, 1, 9, 35, "comstock"));


//
//        addMatch(new Match(null, "Dog Fight", "May 31, 2016", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Kick Some Ass", "April 16, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Sharp Shooter", "October 10, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Destroy", "January 1, 2016", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Marksman", "May 14, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Training Day", "November 15, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Last Stand", "December 31, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
    }

    private static void addMatch(Match match){
        sMatchList.add(match);
        sMatchMap.put(match.getMatchId(), match);
    }

    private static void addStage(MatchStage stage){
        sMatchStages.add(stage);
        sMatchStageMap.put(stage.getStageId(), stage);
    }
}

我使用静态初始化程序块来创建Match对象列表以进行测试。这是我尝试用来填充recyclerview的内容。您会在我的MatchActivity顶部看到这一点。

Answer 1

您的sMatchList对象为空，bcz您已注释了下一行代码：

 //        addMatch(new Match(null, "Dog Fight", "May 31, 2016", "17:00:00", "2", (ArrayList)sMatchStages));
 //        addMatch(new Match(null, "Kick Some Ass", "April 16, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Sharp Shooter", "October 10, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Destroy", "January 1, 2016", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Marksman", "May 14, 2017", "17:00:00", "2", (ArrayList)sMatchStages));
//        addMatch(new Match(null, "Training Day", "November 15, 2017", "17:00:00", "2", (ArrayList)sMatchStages)); }

取消对它们的注释，我想这一切都会好起来的。

Answer 2

您已在xml布局中将宽度和高度属性指定为0dp，并且您没有使用权重，因此不会使用wrap_content或match_parent。

Answer 3

sMatchList永远不会更新，因为代码已被注释掉。

Answer 4

似乎您没有为LayoutManager

设置RecyclerView

在设置适配器之前添加此行：

mRecyclerView.setLayoutManager(new LinearLayoutManager(this));