android - RecyclerView 的第一项丢失

Question

我有一个 Activity 。我正在创建一个文件，该文件在创建 Activity 时包含一些数据。正确创建所有文件并正确写入数据。以下是我的代码

public class MyRecordingsActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private RecordingsAdapter recordingsAdapter;
    private ArrayList<Recording>  recordingArrayList;
    private File userRecordingFile;
    private static final String USER_MIX_DIR = "UserMix";
    private String lines[]=new String[]{};

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


        for(int i=0;i<5;i++){
            try{
                userRecordingFile = new File(createRecordingFiles(), "Recording"+i+".txt");
                FileWriter writer = new FileWriter(userRecordingFile);
                writer.append("DEF"+i+"\nHIJ "+i);
                writer.flush();
                writer.close();
            }
            catch (Exception e){
                e.printStackTrace();
            }

        }

        getSupportActionBar().hide();

        recordingArrayList=new ArrayList<>();
        recyclerView=findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        recyclerView.setHasFixedSize(true);

        readFiles();


        Toast.makeText(getApplicationContext(),lines[0],Toast.LENGTH_SHORT).show();
        Toast.makeText(getApplicationContext(),lines[1],Toast.LENGTH_SHORT).show();
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[0],lines[1]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[2],lines[3]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[4],lines[5]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[6],lines[7]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[8],lines[9]));

        recordingsAdapter=new RecordingsAdapter(recordingArrayList);
        recyclerView.setAdapter(recordingsAdapter);
    }


    public  File createRecordingFiles() {

        File dirRoot = getExternalCacheDir();

        File workDir = new File(dirRoot, USER_MIX_DIR);
        //Toast.makeText(getApplicationContext(), "HI", Toast.LENGTH_SHORT).show();
        if (!workDir.exists()) {
            workDir.mkdirs();

            File recordingFile = new File(workDir, "Recording File ");
            try {
                recordingFile.createNewFile();
            } catch (IOException e) {

            }
        }
        return workDir;
    }


    public void readFiles(){
        StringBuilder text = new StringBuilder();
        BufferedReader br=null;
        try {
            File dirRoot = getExternalCacheDir();
            File workDir = new File(dirRoot, USER_MIX_DIR);

            for(int i=0;i<5;i++){
                File file = new File(workDir,"Recording"+i+".txt");

                br = new BufferedReader(new FileReader(file));
                String line;
                while ((line = br.readLine()) != null) {
                    text.append(line);
                    text.append('\n');
                    lines=text.toString().split("\n");

                }
            }


            br.close() ;
        }catch (IOException e) {
            e.printStackTrace();
        }


    }

}

我写的 Toast 正确显示了 DEF0 和 HIJ 0，但它们没有显示在 recyclerview 中。以下是屏幕截图

以下是我的适配器类

public class RecordingsAdapter extends RecyclerView.Adapter<RecordingsAdapter.RecyclerViewHolder> {
    public static final int TYPE_HEAD=0;
    public static final int TYPE_LIST=1;
    private ArrayList<Recording> recordingArrayList;

    public RecordingsAdapter(ArrayList<Recording> recordingArrayList) {
        this.recordingArrayList = recordingArrayList;
    }

    @Override
    public RecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view;
        RecyclerViewHolder recyclerViewHolder;

        if(viewType == TYPE_LIST){
            view= LayoutInflater.from(parent.getContext()).inflate(R.layout.cell_my_recordings,parent,
                    false);
            recyclerViewHolder=new RecyclerViewHolder(view,viewType);
            return recyclerViewHolder;

        }else if(viewType == TYPE_HEAD){
            view= LayoutInflater.from(parent.getContext()).inflate(R.layout.head_layout,parent,
                    false);
            recyclerViewHolder=new RecyclerViewHolder(view,viewType);
            return recyclerViewHolder;
        }
        return null;
    }

    @Override
    public void onBindViewHolder(RecyclerViewHolder holder, int position) {
        Recording recording;
        if(holder.view_type==TYPE_LIST){
            recording=recordingArrayList.get(position);
            holder.imageView.setImageResource(recording.getImage_id());
            holder.typeTextView.setText(recording.getTitle());
            holder.dateTimeTextView.setText(recording.getDatetime());

        }else if (holder.view_type == TYPE_HEAD){
            holder.typeHeaderTextView.setText("TYPE");
            holder.titleHeaderTextView.setText("TITLE");
            holder.dateTimeHeaderTextView.setText("DATE/TIME");
        }
    }

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

    @Override
    public int getItemViewType(int position) {
        if(position==0){
            return TYPE_HEAD;
        }
        return TYPE_LIST;
    }

    public static class RecyclerViewHolder extends RecyclerView.ViewHolder{
        int view_type;
        ImageView imageView;
        TextView typeTextView,dateTimeTextView;
        TextView typeHeaderTextView,titleHeaderTextView,dateTimeHeaderTextView;

        public RecyclerViewHolder(View itemView, int viewType) {
            super(itemView);
            if(viewType==TYPE_LIST){
                typeTextView=itemView.findViewById(R.id.tv_cell_recording_recording_name);
                imageView=itemView.findViewById(R.id.iv_cell_recordings);
                dateTimeTextView=itemView.findViewById(R.id.tv_cell_recording_date_time);
                view_type=1;
            }else if(viewType==TYPE_HEAD){
                typeHeaderTextView=itemView.findViewById(R.id.tv_type_head_layout);
                titleHeaderTextView=itemView.findViewById(R.id.tv_title_head_layout);
                dateTimeHeaderTextView=itemView.findViewById(R.id.tv_date_time_head_layout);
                view_type=0;
            }

        }
    }
} 

DEf0 和 HIJ 0 没有显示在 recyclerview 中。我不明白为什么它们没有显示在我的回收站 View 中。我的日志中没有错误。任何帮助将不胜感激

Answer 1

你做错了....

您要在 recyclerview 中添加五个项目，但首先要考虑的是标题。

所以这会将您的第一个项目作为标题，您会看到其他四个项目。

您需要做的是，将虚拟项目作为第一个项目传递，然后添加您的 5 个项目。

这样你就可以解决你的问题。

你可以这样试试:

recordingArrayList.add(new Recording(R.drawable.ic_launcher,"", ""));
recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[0],lines[1]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[2],lines[3]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[4],lines[5]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[6],lines[7]));
        recordingArrayList.add(new Recording(R.drawable.ic_launcher,lines[8],lines[9]));

或者你也可以按照下面的方式进行:

更改适配器代码

@Override
    public int getItemCount() {
        return recordingArrayList.size() + 1;
    }

@Override
    public void onBindViewHolder(RecyclerViewHolder holder, int position) {
        Recording recording;
        if(holder.view_type==TYPE_LIST){
            recording=recordingArrayList.get(position - 1);
            ...

        }else if (holder.view_type == TYPE_HEAD){
            holder.typeHeaderTextView.setText("TYPE");
            holder.titleHeaderTextView.setText("TITLE");
            holder.dateTimeHeaderTextView.setText("DATE/TIME");
        }
    }

但是你需要用这种方式验证空列表