保存切换按钮状态

Question

因此，这里的目标是在活动中按“后退”按钮时，在recyclerview中保留切换按钮的状态。

目前这是一个简单的设置：

MainActivity（包含recyclerview）>购物车

这是我尝试过的：

在MainActivity文件中（不是适配器）：

[...]
@Override
    protected void onSaveInstanceState(Bundle state)
    {
        super.onSaveInstanceState(state);
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        // save RecyclerView state
        mBundleRecyclerViewState = new Bundle();
        Parcelable listState = recyclerView.getLayoutManager().onSaveInstanceState();
        mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, listState);
    }



    @Override
    protected void onResume()
    {
        super.onResume();
        Toast toast = Toast.makeText(this,
                "OnResume Triggered",
                Toast.LENGTH_SHORT);
        toast.show();
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        // restore RecyclerView state
        if (mBundleRecyclerViewState != null) {
            Parcelable listState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);
            recyclerView.getLayoutManager().onRestoreInstanceState(listState);
        }
    }

我注意到的奇怪的事情是： -在应用启动时触发onResume -按下时会触发onCreate和onResume。我忽略这是否是正常行为。 -切换按钮的状态从不保存。

整个mainactivity文件：

package com.example.notes;

import android.content.Intent;
import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.firebase.ui.firestore.FirestoreRecyclerOptions;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.firebase.firestore.CollectionReference;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.Query;

import android.os.Parcelable;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

import static android.content.Intent.EXTRA_TEXT;

public class MainActivity extends AppCompatActivity {

    public static final String ITEM_EXTRA = "com.example.application.example.EXTRA_TEXT";
    private FirebaseFirestore db = FirebaseFirestore.getInstance();
    private CollectionReference notebookRef = db.collection("Notebook");
    private final String KEY_RECYCLER_STATE = "recycler_state";
    private static Bundle mBundleRecyclerViewState;

    private NoteAdapter adapter;

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

        SQLiteOpenHelper DatabaseHelper = new DBHelper(this);
        try {
            SQLiteDatabase db = DatabaseHelper.getReadableDatabase();
            Toast toast = Toast.makeText(this,
                    "Database Exists !",
                    Toast.LENGTH_SHORT);
            toast.show();
            db.close();
        } catch(SQLiteException e) {
            Toast toast = Toast.makeText(this,
                    "Database unavailable",
                    Toast.LENGTH_SHORT);
            toast.show();
        }

        setUpRecyclerView();

        FloatingActionButton button = (FloatingActionButton) findViewById(R.id.button_add_note);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openCart();
            }
        });
    }

    private void setUpRecyclerView() {
        Query query = notebookRef.orderBy("id", Query.Direction.DESCENDING);

        FirestoreRecyclerOptions<Note> options = new FirestoreRecyclerOptions.Builder<Note>()
                .setQuery(query, Note.class)
                .build();

        adapter = new NoteAdapter(options);

        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new GridLayoutManager(this, 2));
        recyclerView.setAdapter(adapter);
    }

    public void openCart() {
        Intent intent = new Intent(this, Cart.class);
        intent.putExtra(ITEM_EXTRA, NoteAdapter.getTrolly().toString());
        startActivity(intent);
    }

    @Override
    protected void onStart() {
        super.onStart();
        adapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        adapter.stopListening();
    }

    @Override
    protected void onSaveInstanceState(Bundle state)
    {
        super.onSaveInstanceState(state);
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        // save RecyclerView state
        mBundleRecyclerViewState = new Bundle();
        Parcelable listState = recyclerView.getLayoutManager().onSaveInstanceState();
        mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, listState);
    }



    @Override
    protected void onResume()
    {
        super.onResume();
        Toast toast = Toast.makeText(this,
                "OnResume Triggered",
                Toast.LENGTH_SHORT);
        toast.show();
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        // restore RecyclerView state
        if (mBundleRecyclerViewState != null) {
            Parcelable listState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);
            recyclerView.getLayoutManager().onRestoreInstanceState(listState);
        }
    }

}

请告知我是否需要其他代码，谢谢