如何一键选中所有的复选框?

我的Recyclerview中有一个项目列表。一开始,复选框是不可见的,当我长按任何一个项目时,每个项目上都会出现复选框,并且可以选中它。但如何提供SELECT ALL选项,并通过一次点击选中所有的复选框?

下面是我的适配器类

package adapters;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.example.mynotes.R;

import java.util.ArrayList;
import java.util.List;

import callbacks.NoteEventListener;
import model.Note;
import utils.NoteUtils;

public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.NoteHolder> {
    private Context context;
    private ArrayList<Note> notes;
    private NoteEventListener listener;
    private boolean multiCheckMode = false;


    public NotesAdapter(Context context, ArrayList<Note> notes) {
        this.context = context;
        this.notes = notes;
    }


    @NonNull
    @Override
    public NoteHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(context).inflate(R.layout.note_layout, parent, false);
        return new NoteHolder(v);
    }

    @Override
    public void onBindViewHolder(NoteHolder holder, int position) {
        final Note note = getNote(position);
        if (note != null) {
            holder.noteText.setText(note.getNoteText());
            holder.noteDate.setText(NoteUtils.dateFromLong(note.getNoteDate()));
            // init note click event
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    listener.onNoteClick(note);
                }
            });

            // init note long click
            holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View view) {
                    listener.onNoteLongClick(note);
                    return false;
                }
            });

            // check checkBox if note selected
            if (multiCheckMode) {
                holder.checkBox.setVisibility(View.VISIBLE); // show checkBox if multiMode on
                holder.checkBox.setChecked(note.isChecked());
            } else holder.checkBox.setVisibility(View.GONE); // hide checkBox if multiMode off

        }
    }

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

    private Note getNote(int position) {
        return notes.get(position);
    }


    /**
     * get All checked notes
     *
     * @return Array
     */
    public List<Note> getCheckedNotes() {
        List<Note> checkedNotes = new ArrayList<>();
        for (Note n : this.notes) {
            if (n.isChecked())
                checkedNotes.add(n);
        }

        return checkedNotes;
    }


    class NoteHolder extends RecyclerView.ViewHolder {
        TextView noteText, noteDate;
        CheckBox checkBox;

        public NoteHolder(View itemView) {
            super(itemView);
            noteDate = itemView.findViewById(R.id.note_date);
            noteText = itemView.findViewById(R.id.note_text);
            checkBox = itemView.findViewById(R.id.checkBox);
        }
    }


    public void setListener(NoteEventListener listener) {
        this.listener = listener;
    }

    public void setMultiCheckMode(boolean multiCheckMode) {
        this.multiCheckMode = multiCheckMode;
        if (!multiCheckMode)
            for (Note note : this.notes) {
                note.setChecked(false);
            }
        notifyDataSetChanged();
    }
}

主要活动

package com.example.mynotes;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import android.view.ActionMode;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

import com.google.android.material.floatingactionbutton.FloatingActionButton;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import adapters.NotesAdapter;
import callbacks.MainActionModeCallback;
import callbacks.NoteEventListener;
import db.NotesDB;
import db.NotesDao;
import model.Note;


import static com.example.mynotes.EditNoteActivity.NOTE_EXTRA_Key;

public class MainActivity extends AppCompatActivity implements NoteEventListener {
    private static final String TAG = "MainActivity";
    private RecyclerView recyclerView;
    private ArrayList<Note> notes;
    private NotesAdapter adapter;
    private NotesDao dao;
    private MainActionModeCallback actionModeCallback;
    private int chackedCount = 0;
    private FloatingActionButton fab;
    private SharedPreferences settings;
    public static final String THEME_Key = "app_theme";
    public static final String APP_PREFERENCES="notepad_settings";
    private int theme;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        settings = getSharedPreferences(APP_PREFERENCES, Context.MODE_PRIVATE);
        theme = settings.getInt(THEME_Key, R.style.AppTheme);
        setTheme(theme);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        settings = this.getSharedPreferences("My Data", MODE_PRIVATE);


        // init recyclerView
        recyclerView = findViewById(R.id.notes_list);


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

        dao = NotesDB.getInstance(this).notesDao();
    }


    private void loadNotes() {
        this.notes = new ArrayList<>();
        List<Note> list = dao.getNotes();// get All notes from DataBase
        this.notes.addAll(list);

        String mSortSettings = settings.getString("Sort", "ascending");
        if (mSortSettings.equals("ascending"))  {

                Collections.sort(notes, Note.BY_TITLE_ASCENDING);

        }

        else if (mSortSettings.equals("descending")) {

                Collections.sort(notes, Note.BY_TITLE_DESCENDING);

        }

        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        this.adapter = new NotesAdapter(this, this.notes);
        // set listener to adapter
        this.adapter.setListener(this);

        this.recyclerView.setAdapter(adapter);
        showEmptyView();

        // add swipe helper to recyclerView
        swipeToDeleteHelper.attachToRecyclerView(recyclerView);
    }

    /**
     * when no notes show msg in main_layout
     */
    private void showEmptyView() {
        if (notes.size() == 0) {
            this.recyclerView.setVisibility(View.GONE);
            findViewById(R.id.empty_notes_view).setVisibility(View.VISIBLE);

        } else {
            this.recyclerView.setVisibility(View.VISIBLE);
            findViewById(R.id.empty_notes_view).setVisibility(View.GONE);
        }
    }

    /**
     * Start EditNoteActivity.class for Create New Note
     */
    private void onAddNewNote() {
        startActivity(new Intent(this, EditNoteActivity.class));

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        int id = item.getItemId();

        if (id == R.id.action_sort) {
            showSortDialog();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }



    private void showSortDialog () {
        String[] options = {"Ascending", "Descending"};

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Sort by");

        builder.setItems(options, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                if (which == 0) {
                    SharedPreferences.Editor editor = settings.edit();
                    editor.putString("Sort", "ascending");
                    editor.apply();
                    loadNotes();

                }
                else if (which == 1) {
                    SharedPreferences.Editor editor = settings.edit();
                    editor.putString("Sort", "descending");
                    editor.apply();
                    loadNotes();

                }
            }
        });
        builder.show();
    }



    @Override
    protected void onResume() {
        super.onResume();
        loadNotes();
    }

    @Override
    public void onNoteClick(Note note) {
        // note clicked : edit note
        Intent edit = new Intent(this, EditNoteActivity.class);
        edit.putExtra(NOTE_EXTRA_Key, note.getId());
        startActivity(edit);

    }

    @Override
    public void onNoteLongClick(Note note) {
        // note long clicked : delete 

        note.setChecked(true);
        chackedCount = 1;


        adapter.setMultiCheckMode(true);

        // set new listener to adapter intend off MainActivity listener that we have implement
        adapter.setListener(new NoteEventListener() {
            @Override
            public void onNoteClick(Note note) {


                note.setChecked(!note.isChecked()); // inverse selected
                if (note.isChecked())
                    chackedCount++;
                else chackedCount--;


                if (chackedCount == 0) {
                    //  finish multi select mode wen checked count =0
                    actionModeCallback.getAction().finish();
                }

                actionModeCallback.setCount(chackedCount + "/" + notes.size());
                adapter.notifyDataSetChanged();
            }

            @Override
            public void onNoteLongClick(Note note) {

            }
        });

        actionModeCallback = new MainActionModeCallback() {
            @Override
            public boolean onActionItemClicked(ActionMode actionMode, MenuItem menuItem) {
                if (menuItem.getItemId() == R.id.action_delete_notes)
                    onDeleteMultiNotes();

                actionMode.finish();
                return false;

            }
        };

        // start action mode
        startActionMode(actionModeCallback);
        // hide fab button
        fab.setVisibility(View.GONE);
        actionModeCallback.setCount(chackedCount + "/" + notes.size());
    }

    private void onDeleteMultiNotes() {
        //delete multi notes

        List<Note> chackedNotes = adapter.getCheckedNotes();
        if (chackedNotes.size() != 0) {
            for (Note note : chackedNotes) {
                dao.deleteNote(note);
            }
            // refresh Notes
            loadNotes();
            Toast.makeText(this, chackedNotes.size() + " Note(s) Deleted successfully !", Toast.LENGTH_SHORT).show();
        } else Toast.makeText(this, "No Note(s) selected", Toast.LENGTH_SHORT).show();

        adapter.setMultiCheckMode(false);
    }

    @Override
    public void onActionModeFinished(ActionMode mode) {
        super.onActionModeFinished(mode);

        adapter.setMultiCheckMode(false); // uncheck the notes
        adapter.setListener(this); // set back the old listener
        fab.setVisibility(View.VISIBLE);
    }

    // swipe to right or to left to delete
    private ItemTouchHelper swipeToDeleteHelper = new ItemTouchHelper(
            new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
                @Override
                public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                    return false;
                }

                @Override
                public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                    //  delete note when swipe

                    if (notes != null) {
                        // get swiped note
                        Note swipedNote = notes.get(viewHolder.getAdapterPosition());
                        if (swipedNote != null) {
                            swipeToDelete(swipedNote, viewHolder);

                        }

                    }
                }
            });

    private void swipeToDelete(final Note swipedNote, final RecyclerView.ViewHolder viewHolder) {
        new AlertDialog.Builder(MainActivity.this)
                .setMessage("Delete Note?")
                .setPositiveButton("Delete", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        // delete note
                        dao.deleteNote(swipedNote);
                        notes.remove(swipedNote);
                        adapter.notifyItemRemoved(viewHolder.getAdapterPosition());
                        showEmptyView();

                        Toast.makeText(MainActivity.this, "Note deleted", Toast.LENGTH_SHORT).show();

                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        // TODO: 28/09/2018  Undo swipe and restore swipedNote
                        recyclerView.getAdapter().notifyItemChanged(viewHolder.getAdapterPosition());

                    }
                })
                .setCancelable(false)
                .create().show();

    }
}

模型类

package model;

import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.Ignore;
import androidx.room.PrimaryKey;

import java.util.Comparator;

@Entity(tableName = "notes")
public class Note {
    @PrimaryKey(autoGenerate = true)
    private int id; // default value
    @ColumnInfo(name = "text")
    private String noteText;
    @ColumnInfo(name = "date")
    private long noteDate;

    @Ignore // we don't want to store this value on database so ignore it
    private boolean checked = false;

    public Note() {
    }


    public static final Comparator<Note> BY_TITLE_ASCENDING = new Comparator<Note>() {
        @Override
        public int compare(Note o1, Note o2) {

            return o1.getNoteText().compareTo(o2.getNoteText()) ;
        }
    };

    public static final Comparator<Note> BY_TITLE_DESCENDING = new Comparator<Note>() {
        @Override
        public int compare(Note o1, Note o2) {

            return o2.getNoteText().compareTo(o1.getNoteText()) ;
        }
    };



    public Note(String noteText, long noteDate) {
        this.noteText = noteText;
        this.noteDate = noteDate;
    }

    public String getNoteText() {
        return noteText;
    }

    public void setNoteText(String noteText) {
        this.noteText = noteText;
    }

    public long getNoteDate() {
        return noteDate;
    }

    public void setNoteDate(long noteDate) {
        this.noteDate = noteDate;
    }

    public int getId() {
        return id;
    }

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

    public boolean isChecked() {
        return checked;
    }

    public void setChecked(boolean checked) {
        this.checked = checked;
    }

    @Override
    public String toString() {
        return "Note{" +
                "id=" + id +
                ", noteDate=" + noteDate +
                '}';
    }
}

请帮我解决这个问题

解决方案:

你可以在Activity工具条上添加一个选项菜单,或者在顶部添加一个按钮,这个按钮只有在以下情况下才能看到 onNoteLongClick() 在点击该按钮时,你可以迭代的是 notes 在for循环中调用ArrayList setChecked(true) 对于该数组中的所有元素

selectAllBtn.setOnClickListner(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

           //for setting every item as checked
           For(i=0;i<notes.size();i++)
           {
              notes.get(i).setChecked(true)
           }
           //notify adapter for change

           adapter.notifyDataSetChanged()

        }
    };

如果你使用工具栏上的选项菜单,也可以这样做(使用同样的逻辑)。

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