使用 multiView RecyclerView 将两行布局彼此放置时出现问题？包括截图

Question

这里我使用了两个 viewHolder，一个用于 NoteViewHolder，另一个用于 ChecklistViewHolder，用于单个适配器。我在 recyclerView 适配器中有两个具有不同数据类型的列表。我使用 SQLite 数据库并创建了两个表，一个用于笔记，另一个用于清单，因为我为 recyclerView 中的每一行布局使用了不同的视图。我想要的是根据它们的添加方式定位注释和清单。这就是我在 RecyclerView 中得到的。

在这里，如果我添加另一个注释，它会转到黄色部分的注释部分，但我希望它转到紫色部分的清单之后。

我知道如何绑定这两个视图，绑定没有问题。我的问题是你的布局。

适配器class

    public class AdapterClass extends RecyclerView.Adapter {

    List<NoteHelper> notesList;
    List<ChecklistHelper> checklistsList;
    public static final int LAYOUT_ONE = 0;
    public static final int LAYOUT_TWO = 1;


    public AdapterClass(List<NoteHelper> notesList, List<ChecklistHelper> checklistHelperList) {
        this.notesList = notesList;
        this.checklistsList = checklistHelperList;
    }


    @Override
    public int getItemViewType(int position) {
        if (position<notesList.size())
            return LAYOUT_ONE;

       else return  LAYOUT_TWO;


    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        if(viewType==LAYOUT_ONE){
            
            View view = layoutInflater.inflate(R.layout.layout_note, parent,false);
            NoteViewHolder noteViewHolder = new NoteViewHolder(view);
            return noteViewHolder;
        }

        if(viewType==LAYOUT_TWO){
            View view = layoutInflater.inflate(R.layout.layout_checklist, parent, false);
            return new ChecklistViewHolder(view);
        }
        return null;
    }
    
    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {

    }
    
    @Override
    public int getItemCount() {
        return notesList.size() + checklistsList.size();
    }

    class NoteViewHolder extends RecyclerView.ViewHolder{
        public NoteViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }

    class ChecklistViewHolder extends RecyclerView.ViewHolder{
        public ChecklistViewHolder(@NonNull View itemView) {
            super(itemView);
        }
   }}

Activity class

public class MainActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    Button btnNote, btnChecklist;
    List<NoteHelper> listNotes;
    List<ChecklistHelper> checklistHelperList;
    DbHelper dbHelper;

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

        recyclerView = findViewById(R.id.recycler_view);
        btnNote = findViewById(R.id.btn_add_note);
        btnChecklist = findViewById(R.id.btn_add_checklist);
        recyclerView = findViewById(R.id.recycler_view);
        dbHelper = new DbHelper(this);

        listNotes = dbHelper.getNotes();
        checklistHelperList = dbHelper.getChecklists();
        
        AdapterClass adapterClass = new AdapterClass(listNotes, checklistHelperList);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(adapterClass);
        listNotes = new ArrayList<>();

        btnNote.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,activity_add_note.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);

            }
        });

        btnChecklist.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this, activity_add_checklist.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);

            }
        });
    }}

public class activity_add_note extends AppCompatActivity {
Button btnSaveNote;
EditText etNote;

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

    btnSaveNote = findViewById(R.id.btn_save_note);
    etNote = findViewById(R.id.et_note);

    btnSaveNote.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            DbHelper  dbHelper = new DbHelper(getApplicationContext());
            dbHelper.getWritableDatabase();
            String note = etNote.getText().toString();
            dbHelper.insertNote(note);

            Intent intent = new Intent(getApplicationContext(), MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(intent);
        }
    });
}}


    public class activity_add_checklist extends AppCompatActivity {
    Button btnSaveChecklist;
    EditText etChecklist;

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

        btnSaveChecklist = findViewById(R.id.btn_save_checklist);
        etChecklist = findViewById(R.id.et_checklist);
        btnSaveChecklist.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String checklist = etChecklist.getText().toString();
                DbHelper dbHelper = new DbHelper(getApplicationContext());
                dbHelper.insertChecklist(checklist);

                Intent intent = new Intent(getApplicationContext(), MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
            }
        });
    }
}

Answer 1

修改了您的代码并进行了一些改进，以便为我们提供预期的结果。让我们一步一步地看看发生了什么变化以及为什么。

物品设计

这里的目标是将两个不同的 classes 合并到一个列表中。为了使这成为可能，我们需要添加一个 BaseItem class，它将包含 NoteHelper 和 ChecklistHelper classes 的所有通用属性和函数，以便我们从 BaseItem class.Note 扩展它们，它有一个名为 getViewType 的抽象方法，以便继承的 classes 可以实现此方法并为我们提供它们的视图类型。

BaseItem.java

public abstract class BaseItem {

    int id;
    String content;
    long date;

    public BaseItem() {
        content = "";
    }

    public BaseItem(int id, String content, long date) {
        this.id = id;
        this.content = content;
        this.date = date;
    }

    public abstract int getViewType();

    public int getId() {
        return id;
    }

    public String getContent() {
        return content;
    }
}

现在如果我们看到 NoteHelper 和 ChecklistHelper classes；每个 class 都有自己的视图类型定义，并实现了 getViewType class，我们将在适配器 class.

中方便地使用它

NoteHelper.java

public class NoteHelper extends BaseItem {

    public static final int VIEW_TYPE = 0;


    public NoteHelper() {
    }

    public NoteHelper(int id, String content, long date) {
        super(id, content, date);
    }


    @Override
    public int getViewType() {
        return VIEW_TYPE;
    }
}

ChecklistHelper.java

public class ChecklistHelper extends BaseItem {

    public static final int VIEW_TYPE = 1;

    public ChecklistHelper(){

    }

    public ChecklistHelper(int id, String content, long date){
        super(id, content, date);
    }

    @Override
    public int getViewType() {
        return VIEW_TYPE;
    }

}

将两项合并到一个列表中

下一步是设计组合逻辑。例如，我根据创建日期设计了组合。但它可以基于与此类似的任何标准来完成。为了实现基于日期的组合逻辑，我们需要一个长型比较器，因为我们使用 System.currentMillis().

将创建日期保存为时间戳

ItemLongDateComparator.java

public class ItemLongDateComparator implements Comparator<BaseItem> {
    @Override
    public int compare(BaseItem baseItem, BaseItem t1) {
        return Long.compare(baseItem.date, t1.date);
    }
}

重新设计数据库助手

在主线程中进行数据库查询不是一个好的做法，因为随着数据变大，它可能会导致 UI 故障。为了防止 UI 问题，我们使用执行程序服务在后台线程中执行查询，并将结果传递给主线程。但是在我们传递结果之前，我们通过创建时间戳标准在后台线程中组合数据，然后我们使用接口将结果发送到主线程。

DbHelper.java

public class DbHelper extends SQLiteOpenHelper {

    // This background executor is only for database operations
    private final Executor dbexecutor;

    public static final String DATABASE_NAME = "NOTES.DB";
    public static final int DATABASE_VERSION = 1;

    public static final String NOTES_TABLE = "NOTES_TABLE";
    public static final String CHECKLIST_TABLE = "CHECKLIST_TABLE";

    public static final String COLUMN_ID = "ID";
    public static final String COLUMN_CONTENT = "CONTENT";
    public static final String COLUMN_DATE = "DATE";


    public DbHelper(@Nullable Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        dbexecutor = Executors.newSingleThreadExecutor();
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

        String query = " CREATE TABLE " + NOTES_TABLE + " ( " + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT ,"  +
                COLUMN_CONTENT + " TEXT, " + COLUMN_DATE + " DATE "  + " ) ";
            sqLiteDatabase.execSQL(query);

        String query2 = "CREATE TABLE " + CHECKLIST_TABLE + " ( " + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_CONTENT + " TEXT, " + COLUMN_DATE + " DATE " + " ) ";
            sqLiteDatabase.execSQL(query2);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {

        if (oldVersion>newVersion) {

            sqLiteDatabase.execSQL(" DROP TABLE IF EXISTS " + NOTES_TABLE);
            sqLiteDatabase.execSQL(" DROP TABLE IF EXISTS " + CHECKLIST_TABLE);
        }
             onCreate(sqLiteDatabase);

    }


    public void insertNote(String content, long date){
        dbexecutor.execute(()-> {
            SQLiteDatabase sqLiteDatabase;
            sqLiteDatabase = getWritableDatabase();

            ContentValues c = new ContentValues();
            c.put(COLUMN_CONTENT, content);
            c.put(COLUMN_DATE, date);
            sqLiteDatabase.insert(NOTES_TABLE, null, c);
        });
    }

    public void insertChecklist(String content, long date){
        dbexecutor.execute(()-> {
            SQLiteDatabase sqLiteDatabase;
            sqLiteDatabase = getWritableDatabase();

            ContentValues c = new ContentValues();
            c.put(COLUMN_CONTENT, content);
            c.put(COLUMN_DATE, date);
            sqLiteDatabase.insert(CHECKLIST_TABLE, null, c);
        });
    }


    private List<NoteHelper>  getNotes() {
        List<NoteHelper> notesList = new ArrayList<>();
        SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
        String query = " SELECT * FROM " + NOTES_TABLE;
        Cursor cursor = sqLiteDatabase.rawQuery(query, null);

        if (cursor.moveToFirst()) {

            do {
                int id = cursor.getInt(0);
                String content = cursor.getString(1);
                long date = cursor.getLong(2);
                NoteHelper noteHelper = new NoteHelper(id, content, date);
                notesList.add(noteHelper);
            }
            while (cursor.moveToNext());

        } else {
            sqLiteDatabase.close();
            cursor.close();
        }

        return notesList;
    }

    private List<ChecklistHelper> getChecklists(){
        List<ChecklistHelper> checklistsList = new ArrayList<>();
        SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
        String query = "SELECT * FROM " +  CHECKLIST_TABLE;
        Cursor cursor = sqLiteDatabase.rawQuery(query, null);

        if (cursor.moveToFirst()){

            do{
                int id = cursor.getInt(0);
                String content = cursor.getString(1);
                long date = cursor.getLong(2);
                ChecklistHelper checklistHelper = new ChecklistHelper(id, content, date);
                checklistsList.add(checklistHelper);

            }
            while (cursor.moveToNext());

        }

        else {
            cursor.close();
            sqLiteDatabase.close();
        }
        return checklistsList;
    }

    public void getNotesAndChecklists(OnContentReadyListener listener) {
        if(listener == null) return; // Don't proceed if the listener is null
        dbexecutor.execute(()-> {
            List<NoteHelper> notes = getNotes();
            List<ChecklistHelper> checks = getChecklists();
            // Merge lists and sort items by creation date
            List<BaseItem> items = new ArrayList<>();
            items.addAll(notes);
            items.addAll(checks);
            Collections.sort(items, new ItemLongDateComparator());
            new Handler(Looper.getMainLooper()).post(()-> listener.onContentReady(items));
        });
    }


    @MainThread
    public interface OnContentReadyListener {
        void onContentReady(List<BaseItem> combinedItems);
    }

}

将数据连接到 UI

现在我们已经完成了数据组织，我们可以轻松地使这个设计适应 UI API。在适配器 class 中，我们只使用 BaseItem 的列表 class 因为此列表将接受来自 BaseItem 的所有派生 classes。只管理一个列表而不是两个列表会更容易。

AdapterClass.java

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

    List<BaseItem> itemsList;


    public AdapterClass() {
        itemsList = new ArrayList<>();
    }


    @Override
    public int getItemViewType(int position) {
        return itemsList.get(position).getViewType();
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        if(viewType == NoteHelper.VIEW_TYPE){

            View view = layoutInflater.inflate(R.layout.layout_note, parent,false);
            return new NoteViewHolder(view);
        }

        if(viewType == ChecklistHelper.VIEW_TYPE){
            View view = layoutInflater.inflate(R.layout.layout_checklist, parent, false);
            return new ChecklistViewHolder(view);
        }
        return null;
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        int vtype = getItemViewType(position);
        BaseItem bi = itemsList.get(position);
        if(vtype == NoteHelper.VIEW_TYPE) {
            NoteViewHolder nvh = (NoteViewHolder) holder;
            TextView tv = nvh.itemView.findViewById(R.id.tv_note);
            tv.setText(bi.getContent());
        }
        else if(vtype == ChecklistHelper.VIEW_TYPE) {
            ChecklistViewHolder cvh = (ChecklistViewHolder) holder;
            TextView tv = cvh.itemView.findViewById(R.id.tv_checklist);
            tv.setText(bi.getContent());

        }
    }

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

    public void update(List<BaseItem> combinedList) {
        itemsList.clear();
        itemsList.addAll(combinedList);
        notifyItemRangeChanged(0, itemsList.size());
    }

    static class NoteViewHolder extends RecyclerView.ViewHolder{
        public NoteViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }

    static class ChecklistViewHolder extends RecyclerView.ViewHolder{
        public ChecklistViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

将数据反映到 UI

终于可以将数据反映到UI部分了。还记得我提到过完成活动而不是一次又一次地重新启动主要 activity 吗？看看添加活动现在是多么简单。

activity_add_note.java

public class activity_add_note extends AppCompatActivity {
    Button btnSaveNote;
    EditText etNote;

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

        btnSaveNote = findViewById(R.id.btn_save_note);
        etNote = findViewById(R.id.et_note);

        btnSaveNote.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String note = etNote.getText().toString();
                DbHelper  dbHelper = new DbHelper(getApplicationContext());
                dbHelper.insertNote(note, System.currentTimeMillis());

                // Finish this activity
                new Handler(Looper.getMainLooper()).postDelayed(() -> finish(), 500);

            }
        });
    }
}

activity_add_checklist.java

public class activity_add_checklist extends AppCompatActivity {
    Button btnSaveChecklist;
    EditText etChecklist;

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

        btnSaveChecklist = findViewById(R.id.btn_save_checklist);
        etChecklist = findViewById(R.id.et_checklist);
        btnSaveChecklist.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String checklist = etChecklist.getText().toString();
                DbHelper dbHelper = new DbHelper(getApplicationContext());
                dbHelper.insertChecklist(checklist, System.currentTimeMillis());

                // Finish this activity
                new Handler(Looper.getMainLooper()).postDelayed(() -> finish(), 500);
            }
        });
    }
}

主要 activity 中需要注意的一件重要事情是，我们会在每次恢复时查询这些项目。因此，当我们 return 来自其他活动时，新添加的项目将出现在列表中。

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    RecyclerView recyclerView;
    AdapterClass adapterClass;
    Button btnNote, btnChecklist;
    DbHelper dbHelper;

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

        recyclerView = findViewById(R.id.recycler_view);
        btnNote = findViewById(R.id.btn_add_note);
        btnChecklist = findViewById(R.id.btn_add_checklist);
        recyclerView = findViewById(R.id.recycler_view);
        dbHelper = new DbHelper(this);

        adapterClass = new AdapterClass();
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(adapterClass);

        btnNote.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,activity_add_note.class);
                startActivity(intent);

            }
        });

        btnChecklist.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this, activity_add_checklist.class);
                startActivity(intent);

            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "onResume: ");
        if(dbHelper == null) {
            dbHelper = new DbHelper(this);
        }
        dbHelper.getNotesAndChecklists(new DbHelper.OnContentReadyListener() {
            @Override
            public void onContentReady(List<BaseItem> combinedItems) {
                adapterClass.update(combinedItems);
            }
        });
    }
}

获取整个项目：your app

使用 multiView RecyclerView 将两行布局彼此放置时出现问题？包括截图

Problem in positioning two row layouts one below each other with multiView RecyclerView? Screenshot included

java

list

adapter

android-recyclerview

物品设计

将两项合并到一个列表中

重新设计数据库助手

将数据连接到 UI

将数据反映到 UI