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Android适配器未更新

android-adapter android-recyclerview class android java

puk789 · 技术社区 · 7 年前

我想在适配器的帮助下,在回收器视图中显示匹配对象的列表(匹配=两个彼此喜欢的用户)。

这是我的活动,旨在显示这些匹配项:

public class MatchesActivity extends AppCompatActivity {

// variables:
private RecyclerView mMatchesRecyclerView;
private RecyclerView.Adapter mMatchItemAdapter;
private RecyclerView.LayoutManager mMatchesLayoutManager;

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

    mMatchesRecyclerView = findViewById(R.id.matches_recyclerView);
    mMatchesRecyclerView.setNestedScrollingEnabled(false);
    mMatchesRecyclerView.setHasFixedSize(true);

    // set layout manager & pass it to the recycler view:
    mMatchesLayoutManager = new LinearLayoutManager(MatchesActivity.this);
    mMatchesRecyclerView.setLayoutManager(mMatchesLayoutManager);

    // set match adapter & pass it to the recycler view:
    mMatchItemAdapter = new MatchItemAdapter(getMatchesList(), MatchesActivity.this);
    mMatchesRecyclerView.setAdapter(mMatchItemAdapter);

    // add test items to the recycler view:
    Match testMatch = new Match("abcdefgh");
    matchesList.add(testMatch);
    mMatchItemAdapter.notifyDataSetChanged();
    Log.d("MatchesActivity", "TEST LIST: " + matchesList.toString());
}

private ArrayList<Match> matchesList = new ArrayList<Match>();
private List<Match> getMatchesList() {
    Log.d("MatchesActivity", "getMatchesList function: " + matchesList.toString());
    return matchesList;
}
}

这是我的适配器,用于为相关布局充气;用相关对象数据填充它:

public class MatchItemAdapter extends RecyclerView.Adapter<MatchViewholder> {

private List<Match> mMatchesList;
private Context mViewContext;

public MatchItemAdapter(List<Match> matchesList, Context context) {
    this.mMatchesList = matchesList;
    this.mViewContext = context;
    Log.d("MatchItemAdapter", "Constructor: " + mMatchesList.toString());
}

// inflate the layout:
@Override
public MatchViewholder onCreateViewHolder(ViewGroup parent, int viewType) {
    View layoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_matches, null, false);
    RecyclerView.LayoutParams lp = new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    layoutView.setLayoutParams(lp);
    MatchViewholder matchViewholder = new MatchViewholder(layoutView);
    Log.d("MatchItemAdapter", "onCreateViewHolder: " + mMatchesList.toString());
    return matchViewholder;
}

// populate each row within the layout:
@Override
public void onBindViewHolder(MatchViewholder holder, int position) {
    Log.d("MatchItemAdapter", "onBindViewHolder: " + mMatchesList.toString());
    holder.mMatchID.setText(mMatchesList.get(position).getMatchID());
}

@Override
public int getItemCount() {
    return 0;
}

}

Match类当前仅接受matchID参数,该参数为字符串。将使用默认图像和此匹配ID字符串创建对象。目前,我还没有准备好数据库中的真正匹配对象,所以我想在稍后继续之前检查回收器视图和适配器是否按预期工作。

然而,当我去Matches活动时,它是空的,没有显示任何内容。正如您从MatchesActivity onCreate方法中所看到的,我创建了一个带有matchID=“abcdefgh”的测试Match对象,然后将其添加到matchesList中。因此,我希望将“abcdefgh”文本传递给适配器,并显示在MatchesActivity中。

我的日志语句表明Match对象已成功创建并添加到列表中,但是,getMatchesList()函数返回一个空列表,然后在适配器构造函数中也使用该列表,(我认为这是)导致活动不显示任何内容。

我对Android和Java开发相对较新,尤其是回收器视图和适配器,但从我收集的信息来看

mMatchItemAdapter.notifyDataSetChanged();

因为在那之前一切似乎都很好,所以不能正常工作。任何帮助都将不胜感激!

1 回复 | 直到 7 年前

ADM 7 年前

您正在返回0。您应该做的是返回 mMatchesList 列表

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