recyclerview+fab

recyclerview+fab 是指在 Android 应用中使用 RecyclerView 和 FloatingActionButton（简称 FAB）的组合。RecyclerView 是一个强大的列表控件，可以高效地显示大量数据，而 FAB 则是一个浮动操作按钮，通常用于触发应用中的主要操作。

相关问题

Android sqlite recyclerview 完整示例

以下是一个简单的 Android SQLite RecyclerView 完整示例：

1. 创建一个名为 "Note" 的 Java 类表示笔记：

public class Note {
    private int id;
    private String title;
    private String content;

    public Note() {}

    public Note(int id, String title, String content) {
        this.id = id;
        this.title = title;
        this.content = content;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

2. 创建一个名为 "NoteDatabaseHelper" 的类用于创建和管理 SQLite 数据库：

public class NoteDatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "notes_db";
    private static final int DATABASE_VERSION = 1;

    private static final String TABLE_NAME = "notes";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_TITLE = "title";
    private static final String COLUMN_CONTENT = "content";

    public NoteDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "("
                + COLUMN_ID + " INTEGER PRIMARY KEY,"
                + COLUMN_TITLE + " TEXT,"
                + COLUMN_CONTENT + " TEXT" + ")";
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public void addNote(Note note) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(COLUMN_TITLE, note.getTitle());
        values.put(COLUMN_CONTENT, note.getContent());

        db.insert(TABLE_NAME, null, values);
        db.close();
    }

    public List<Note> getAllNotes() {
        List<Note> notesList = new ArrayList<>();

        String selectQuery = "SELECT  * FROM " + TABLE_NAME;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        if (cursor.moveToFirst()) {
            do {
                Note note = new Note();
                note.setId(cursor.getInt(0));
                note.setTitle(cursor.getString(1));
                note.setContent(cursor.getString(2));
                notesList.add(note);
            } while (cursor.moveToNext());
        }

        cursor.close();
        db.close();

        return notesList;
    }

    public void updateNote(Note note) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(COLUMN_TITLE, note.getTitle());
        values.put(COLUMN_CONTENT, note.getContent());

        db.update(TABLE_NAME, values, COLUMN_ID + " = ?",
                new String[] { String.valueOf(note.getId()) });
        db.close();
    }

    public void deleteNote(Note note) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_NAME, COLUMN_ID + " = ?",
                new String[] { String.valueOf(note.getId()) });
        db.close();
    }
}

3. 创建一个名为 "NoteAdapter" 的类来显示笔记列表：

public class NoteAdapter extends RecyclerView.Adapter<NoteAdapter.MyViewHolder> {
    private List<Note> notesList;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView title, content;

        public MyViewHolder(View view) {
            super(view);
            title = view.findViewById(R.id.title);
            content = view.findViewById(R.id.content);
        }
    }

    public NoteAdapter(List<Note> notesList) {
        this.notesList = notesList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.note_list_row, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Note note = notesList.get(position);
        holder.title.setText(note.getTitle());
        holder.content.setText(note.getContent());
    }

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

4. 创建一个名为 "MainActivity" 的 Activity，显示 RecyclerView：

public class MainActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private NoteAdapter noteAdapter;
    private List<Note> notesList = new ArrayList<>();
    private NoteDatabaseHelper databaseHelper;

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

        recyclerView = findViewById(R.id.recycler_view);
        databaseHelper = new NoteDatabaseHelper(this);

        notesList.addAll(databaseHelper.getAllNotes());

        noteAdapter = new NoteAdapter(notesList);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setAdapter(noteAdapter);
    }

    @Override
    protected void onResume() {
        super.onResume();
        notesList.clear();
        notesList.addAll(databaseHelper.getAllNotes());
        noteAdapter.notifyDataSetChanged();
    }

    public void addNewNote() {
        Note note = new Note();
        note.setTitle("Title");
        note.setContent("Content");

        databaseHelper.addNote(note);
        notesList.add(note);
        noteAdapter.notifyItemInserted(notesList.size() - 1);
    }
}

5. 创建一个名为 "activity_main.xml" 的布局文件来显示 RecyclerView：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="16dp"
        android:clipToPadding="false" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_marginBottom="16dp"
        android:layout_marginEnd="16dp"
        android:clickable="true"
        android:src="@drawable/ic_add_white_24dp" />

</RelativeLayout>

6. 创建一个名为 "note_list_row.xml" 的布局文件来显示每个笔记：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="8dp">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/title"
        android:textSize="14sp"
        android:textColor="@android:color/darker_gray" />

</RelativeLayout>

7. 在 MainActivity 中添加一个 FloatingActionButton 来添加新笔记：

FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        addNewNote();
    }
});

这是一个简单的 Android SQLite RecyclerView 完整示例，它可以让你了解如何在 Android 应用中使用 SQLite 和 RecyclerView。

用java写一个recyclerView类似相册支持多选删除的例子

好的，以下是一个用 Java 编写的 RecyclerView 类似相册支持多选删除的例子：

1. 创建 RecyclerView 布局文件 `activity_main.xml`，包含一个 RecyclerView 和一个 FloatingActionButton：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="56dp" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab_delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@android:drawable/ic_menu_delete"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_margin="16dp"
        android:visibility="gone" />

</RelativeLayout>

2. 创建 RecyclerView 的 Item 布局文件 `item_photo.xml`，包含一个 ImageView 和一个 CheckBox：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/image_view"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:scaleType="centerCrop" />

    <CheckBox
        android:id="@+id/check_box"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"
        android:layout_margin="8dp" />

</RelativeLayout>

3. 创建 RecyclerView 的 ViewHolder 类 `PhotoViewHolder.java`：

public class PhotoViewHolder extends RecyclerView.ViewHolder {

    public ImageView imageView;
    public CheckBox checkBox;

    public PhotoViewHolder(View itemView) {
        super(itemView);
        imageView = itemView.findViewById(R.id.image_view);
        checkBox = itemView.findViewById(R.id.check_box);
    }

}

4. 创建 RecyclerView 的 Adapter 类 `PhotoAdapter.java`：

public class PhotoAdapter extends RecyclerView.Adapter<PhotoViewHolder> {

    private List<Photo> photoList;
    private List<Photo> selectedPhotoList;
    private Context context;

    public PhotoAdapter(List<Photo> photoList, Context context) {
        this.photoList = photoList;
        this.context = context;
        selectedPhotoList = new ArrayList<>();
    }

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

    @Override
    public void onBindViewHolder(PhotoViewHolder holder, int position) {
        Photo photo = photoList.get(position);
        Glide.with(context).load(photo.getUrl()).into(holder.imageView);
        holder.checkBox.setChecked(selectedPhotoList.contains(photo));
        holder.itemView.setOnClickListener(v -> {
            if (selectedPhotoList.contains(photo)) {
                selectedPhotoList.remove(photo);
            } else {
                selectedPhotoList.add(photo);
            }
            notifyDataSetChanged();
        });
    }

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

    public void deleteSelectedPhotos() {
        for (Photo photo : selectedPhotoList) {
            photoList.remove(photo);
        }
        notifyDataSetChanged();
    }

    public void showDeleteButton(boolean show) {
        ((MainActivity) context).runOnUiThread(() -> {
            FloatingActionButton fabDelete = ((MainActivity) context).findViewById(R.id.fab_delete);
            if (show) {
                fabDelete.setVisibility(View.VISIBLE);
                fabDelete.setOnClickListener(v -> {
                    deleteSelectedPhotos();
                    selectedPhotoList.clear();
                    fabDelete.setVisibility(View.GONE);
                });
            } else {
                fabDelete.setVisibility(View.GONE);
            }
        });
    }
}

5. 在 Activity 中初始化 RecyclerView 和 Adapter：

public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private PhotoAdapter photoAdapter;

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

        recyclerView = findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new GridLayoutManager(this, 3));
        List<Photo> photoList = new ArrayList<>();
        photoList.add(new Photo("https://picsum.photos/id/0/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/1/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/2/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/3/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/4/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/5/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/6/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/7/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/8/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/9/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/10/200/300"));
        photoList.add(new Photo("https://picsum.photos/id/11/200/300"));
        photoAdapter = new PhotoAdapter(photoList, this);
        recyclerView.setAdapter(photoAdapter);

        recyclerView.addOnItemTouchListener(new RecyclerView.OnItemTouchListener() {
            GestureDetector gestureDetector = new GestureDetector(MainActivity.this, new GestureDetector.SimpleOnGestureListener() {
                @Override
                public boolean onSingleTapConfirmed(MotionEvent e) {
                    return true;
                }

                @Override
                public void onLongPress(MotionEvent e) {
                    View child = recyclerView.findChildViewUnder(e.getX(), e.getY());
                    if (child != null) {
                        int position = recyclerView.getChildAdapterPosition(child);
                        photoAdapter.showDeleteButton(true);
                        super.onLongPress(e);
                    }
                }
            });

            @Override
            public boolean onInterceptTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {
                View child = rv.findChildViewUnder(e.getX(), e.getY());
                if (child != null && gestureDetector.onTouchEvent(e)) {
                    int position = rv.getChildAdapterPosition(child);
                    return true;
                }
                return false;
            }

            @Override
            public void onTouchEvent(@NonNull RecyclerView rv, @NonNull MotionEvent e) {

            }

            @Override
            public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

            }
        });
    }
}

其中，`Photo` 类是一个简单的 Java 类，表示一张照片，包含一个 `url` 属性。在 `PhotoAdapter` 中，通过 Glide 加载图片，点击 Item 时选中或取消选中，长按 Item 时显示删除按钮，点击删除按钮时删除选中的照片。在 Activity 中，通过 `GestureDetector` 监听 RecyclerView 的长按事件，当长按 Item 时显示删除按钮。