android - 保存我的 recyclerview 和 cardview 的状态

Question

我想在以下情况下保存我的 recyclerview 的状态(当用户按下 fab 按钮时，它会动态地包含 cardviews)

a) 用户关闭应用程序然后重新打开它和b) 当用户从 Activity 转到主屏幕，然后返回 Activity 时

我想要它，以便用户在微调器中输入的卡片 View 和值保存在这些实例上。

我怎样才能做到这一点？ Intent ？共享首选项？

create.java 这是带有卡片 View 的 Activity 。我的 mainactivity 代码是主屏幕有 3 个按钮的地方，其中一个按钮转到这个 create.java 屏幕

public class create extends AppCompatActivity {



    //a list to store all the products
    List<Product> productList;

    //the recyclerview
    RecyclerView recyclerView;


    Product mProduct;
    private Map<String, String> numberItemValues = new HashMap<>();
    private Map<Integer, Integer> mSpinnerSelectedItem = new HashMap<Integer, Integer>();


   // RelativeLayout relativeLayout;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.create);
        findViewById(R.id.relativeLayout).requestFocus();



        findViewById(R.id.relativeLayout).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                InputMethodManager imm = (InputMethodManager) view.getContext()
                        .getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
            }
        });


        //opens csv
        InputStream inputStream = getResources().openRawResource(R.raw.shopitems);
         CSVFile csvFile = new CSVFile(inputStream);

       final List<String>  mSpinnerItems = csvFile.read();


        //getting the recyclerview from xml
        recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        //initializing the productlist
        productList = new ArrayList<>();
        productList.add(new Product(mSpinnerItems, "Test Edit Text",false, "Text String 2"));




        final ProductAdapter  adapter = new ProductAdapter(this, productList, numberItemValues);


        //TODO FAB BUTTON
        FloatingActionButton floatingActionButton =
             findViewById(R.id.fab);


        floatingActionButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                productList.add(mProduct);
                if(adapter != null)
                    adapter.notifyDataSetChanged();


                //Handle the empty adapter here

            }
        });









        //setting adapter to recyclerview
        recyclerView.setAdapter(adapter);









    }



    private class CSVFile {
        InputStream inputStream;

        public CSVFile(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        public List<String> read() {
            List<String> resultList = new ArrayList<String>();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            try {
                String line;
                while ((line = reader.readLine()) != null) {
                    String[] row = line.split(",");
                    //TODO I edited this part so that you'd add the values in our new hash map variable

                    numberItemValues.put(row[1], row[0]);

                    resultList.add(row[1]);
                }
            } catch (IOException e) {
                Log.e("Main", e.getMessage());
            } finally {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    Log.e("Main", e.getMessage());
                }
            }
            return resultList;
        }
    }



}

产品适配器

public class ProductAdapter extends RecyclerView.Adapter<ProductAdapter.ProductViewHolder> {

    private Map<Integer, Integer> mSpinnerSelectedItem = new HashMap<Integer, Integer>();

    private Map<String, String> numberItemValues = new HashMap<>();





   // private SearchableSpinner spinner;

    //we are storing all the products in a list
    private List<Product> productList;

    private Activity create;


    //TODO CODE FOR CSV FILE


    /*InputStream inputStream = getResources().openRawResource(R.raw.shopitems);
    CSVFile csvFile = new CSVFile(inputStream);
    final List<String>  mSpinnerItems = csvFile.read();*/


    InputStream inputStream = null;
    List<String>  mSpinnerItems = null;
    CSVFile csvFile = null;


    //TODO END OF CODE FOR CSV FILE

    public ProductAdapter(Activity activity) {
        create = activity;

    }


    //getting the context and product list with constructor
    /*public ProductAdapter(Activity activity, List<Product> productList) {
        // this.mCtx = mCtx;

       *//* inputStream = create.getResources().openRawResource(R.raw.shopitems);
        csvFile = new CSVFile(inputStream);
        mSpinnerItems = csvFile.read();*//*

        create = activity;
        this.productList = productList;
    }*/


    public ProductAdapter(Activity activity, List<Product> productList, Map<String, String> numberList) {
        numberItemValues = numberList;
        create = activity;
        this.productList = productList;
    }

    @Override
    public ProductViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //inflating and returning our view holder
        LayoutInflater inflater = LayoutInflater.from(create);
        View view = inflater.inflate(R.layout.layout_products, null);
        return new ProductViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ProductViewHolder holder, final int position) {


        // //getting the product of the specified position




        ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(create, R.layout.item_spinner_layout,
                Product.getSpinnerItemsList());
        spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        holder.spinner.setAdapter(spinnerArrayAdapter);

        holder.spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int mPosition, long id) {
                mSpinnerSelectedItem.put(position, mPosition);


                TextView mTextView = view.findViewById(R.id.mSpinnerText);


                //TODO CODE FOR GETTING AISLE NUMBER AND PUTTING IT IN THE TEXTVIEW
                /*String currentItem = mSpinnerItems.get(position);
                String aisleNumber = numberItemValues.get(currentItem);
                holder.textView5.setText(aisleNumber);

*/




                //String currentItem = holder.spinner.getSelectedItem().toString();
                String currentItem = holder.spinner.getItemAtPosition(mPosition).toString();

                Set<String> set = numberItemValues.keySet(); for(String key : set) {String value = numberItemValues.get(key); Log.e("DATA ", "key = " + key + " value = " + value); }





                //String currentItem = holder.spinner.getItemAtPosition(mPosition).toString();
                String aisleNumber = numberItemValues.get(currentItem);
                holder.textView5.setText(aisleNumber);

                Log.e("SELECTION TEST", " Selected map item = " + aisleNumber );


            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });


        //binding the data with the viewholder views
        if (mSpinnerSelectedItem.containsKey(position)) {
            holder.spinner.setSelection(mSpinnerSelectedItem.get(position));
        }


        holder.getView().setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(create);


                // set title
                alertDialogBuilder.setTitle("Delete Item");

                // set dialog message
                alertDialogBuilder
                        .setMessage("Are you sure you want to delete this item?")
                        .setCancelable(false)
                        .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                // if this button is clicked, close
                                // current activity


                                holder.checkBox.setChecked(false);
                                holder.spinner.setSelection(0);



                                productList.remove(holder.getAdapterPosition());
                                notifyItemRemoved(holder.getAdapterPosition());

                                Toast.makeText(create, "Item removed.", Toast.LENGTH_LONG).show();


                            }
                        })
                        .setNegativeButton("No", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                // if this button is clicked, just close
                                // the dialog box and do nothing
                                dialog.cancel();
                            }
                        });

                // create alert dialog
                AlertDialog alertDialog = alertDialogBuilder.create();

                // show it
                alertDialog.show();

            }
        });





    }


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


    class ProductViewHolder extends RecyclerView.ViewHolder {

        SearchableSpinner spinner;
        EditText editText;
        TextView textView5;
        CheckBox checkBox;
        LinearLayout linearLayout;
        View rootView;


        public ProductViewHolder(View itemView) {
            super(itemView);

            spinner = itemView.findViewById(R.id.spinner);
            editText = itemView.findViewById(R.id.editText);
            textView5 = itemView.findViewById(R.id.textView5);
            checkBox = itemView.findViewById(R.id.checkBox);
            rootView = itemView.findViewById(R.id.linearLayout);


            checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    // makes the set disappear when checkbox is ticked.
                    if(isChecked){

                        checkBox.setChecked(false);
                        spinner.setSelection(0);

                        productList.remove(getAdapterPosition());
                        notifyItemRemoved(getAdapterPosition());



                        Toast.makeText(create, "Done!", Toast.LENGTH_LONG).show();
                    }

                }
            });



        }

        public View getView() {
            return rootView;
        }

    }

    //TODO CODE FOR CSV FILE
    private class CSVFile {
        InputStream inputStream;

        public CSVFile(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        public List<String> read() {
            List<String> resultList = new ArrayList<String>();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            try {
                String line;
                while ((line = reader.readLine()) != null) {
                    String[] row = line.split(",");

                    numberItemValues.put(row[1], row[0]);

                    resultList.add(row[1]);
                }
            } catch (IOException e) {
                Log.e("Main", e.getMessage());
            } finally {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    Log.e("Main", e.getMessage());
                }
            }
            return resultList;
        }
    }


}

Product.Java

public class Product {

    private static String editText;
    private static Boolean checkBox;
    private static String textView5;

    public static List<String> spinnerItemsList = new ArrayList<String>();

    public Product(List spinner, String editText, Boolean checkBox, String textView5) {

        this.editText = editText;
        this.spinnerItemsList = spinner;
        this.checkBox = checkBox;
        this.textView5 = textView5;
    }
    public static String getEdittext () {
        return editText;
    }

    public static boolean getCheckbox () {
        return checkBox;
    }

    public static String getTextview () {
        return textView5;
    }
    public static List<String> getSpinnerItemsList () {
        return spinnerItemsList;
    }
}

Spinner 的 MyListAdapter 代码

public class MyListAdapter extends ArrayAdapter<String> {
    int groupid;
    List<String> items;
    Context context;
    String path;





    public MyListAdapter(Context context, int vg, int id, List<String> items) {
        super(context, vg, id, items);
        this.context = context;
        groupid = vg;
        this.items = items;

    }

    static class ViewHolder {
        public TextView textid;
        public TextView textname;

    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        {

            View rowView = convertView;
            if (rowView == null) {
                LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                rowView = inflater.inflate(groupid, parent, false);
                ViewHolder viewHolder = new ViewHolder();
                viewHolder.textid = (TextView) rowView.findViewById(R.id.txtid);
                viewHolder.textname = (TextView) rowView.findViewById(R.id.txtname);
                rowView.setTag(viewHolder);
            }
            // Fill data in the drop down.
            ViewHolder holder = (ViewHolder) rowView.getTag();
            String row = items.get(position);
            //holder.textid.setText(row[0]); //prints aisle number, dont need

            holder.textname.setText(row);



            return rowView;
        }

    }

}

Answer 1

您应该将数据保存在sharedPreferences 或database 中，并且每次您打开 Activity 时都从存储的列表中读取数据。

要存储在数据库中，你需要一个像这样的数据库助手类

public class DataBase_CITY extends SQLiteOpenHelper {
// The Android's default system path of your application database.
private static String DB_PATH = "";
public static String TABLE;
private static String DB_NAME;
private static String[] FIELD_NAMES;
private static String[] FIELD_TYPES;

private SQLiteDatabase myDataBase;

private final Context myContext;

/**
 * Constructor Takes and keeps a reference of the passed context in order to
 * access to the application assets and resources.
 *
 * @param context
 */
public DataBase_CITY(Context context, String dataBaseName, String tableName, 
   String[] fieldNames, String[] fieldTypes) {

    super(context, dataBaseName, null, 1);
    DB_NAME = dataBaseName;
    TABLE = tableName;
    FIELD_NAMES = fieldNames;
    FIELD_TYPES = fieldTypes;

    this.myContext = context;

    System.err.println(context.getApplicationInfo().dataDir);

    DB_PATH = context.getApplicationInfo().dataDir + File.separator
            + "databases" + File.separator;

    System.out.println(DB_PATH);
}

/**
 * Creates a empty database on the system and rewrites it with your own
 * database.
 */
public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();

    if (dbExist) {
        // do nothing - database already exist
        // Toast.makeText(myContext, "already exist",
        // Toast.LENGTH_LONG).show();
    } else {

        // By calling this method and empty database will be created into
        // the default system path
        // of your application so we are gonna be able to overwrite that
        // database with our database.
        this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            // throw new Error("Error copying database");

        }
    }

}

/**
 * Check if the database already exist to avoid re-copying the file each
 * time you open the application.
 *
 * @return true if it exists, false if it doesn't
 */
private boolean checkDataBase() {

    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
        // Toast.makeText(myContext, "already exist",
        // Toast.LENGTH_LONG).show();
    } catch (SQLiteException e) {

        // database does't exist yet.
        // Toast.makeText(myContext, "not already exist",
        // Toast.LENGTH_LONG).show();
    }

    if (checkDB != null) {

        checkDB.close();

    }

    return checkDB != null ? true : false;
}

/**
 * Copies your database from your local assets-folder to the just created
 * empty database in the system folder, from where it can be accessed and
 * handled. This is done by transfering bytestream.
 */
private void copyDataBase() throws IOException {

    // Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

    // Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);

    // transfer bytes from the Input file to the output file
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }

    // Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();

}

public void openDataBase() throws SQLException {

    // Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null,
            SQLiteDatabase.OPEN_READONLY);

}

@Override
public synchronized void close() {

    if (myDataBase != null)
        myDataBase.close();

    super.close();

}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("Create table " + TABLE + " (UserID INTEGER PRIMARY KEY AUTOINCREMENT, "
            + FIELD_NAMES[0] + " " + FIELD_TYPES[0] + ", "
            + FIELD_NAMES[1] + " " + FIELD_TYPES[1] + ", "
            + FIELD_NAMES[2] + " " + FIELD_TYPES[2] + ")");
}

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

public void updateDB(String[] arguments) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(FIELD_NAMES[0], Integer.parseInt(arguments[0]));
    values.put(FIELD_NAMES[1], arguments[1]);
    values.put(FIELD_NAMES[2], Integer.parseInt(arguments[2]));

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

}

要在其中存储数据，您需要以下方法

private static void updateCityTable(String TableName, int id, String name, int 
province_id) {
    DataBase_CITY helper = new DataBase_CITY(G.CONTEXT,
            "CITY_DATABASE", TableName, G.CityTableFields, G.CityTableFieldTypes);
    try {
        helper.updateDB(new String[]{
                String.valueOf(id),
                name,
                String.valueOf(province_id)});

    } catch (Exception e) {
        e.printStackTrace();
    }

}

你可以像这样从数据库中读取

private String cityDataBaseChecker(String TableName, String column, String columnName, String amount) {
    DataBase_PROVINCE helper = new DataBase_PROVINCE(G.CONTEXT,
            "CITY_DATABASE", TableName, G.CityTableFields, G.CityTableFieldTypes);
    try {
        helper.createDataBase();
    } catch (IOException ioe) {
        throw new Error("Unable to create database");
    }

    SQLiteDatabase sqld = helper.getWritableDatabase();

    Cursor cursor = sqld.rawQuery("select * from " + TableName + " where " + columnName + "=\"" + amount + "\" order by " + column, null);
    String title = null;
    if (cursor.moveToFirst()) {
        do {
            title = cursor.getString(cursor.getColumnIndex(column));
            System.out.println("city =" + title);
        } while (cursor.moveToNext());
    }
    sqld.close();
    return title;
}

您可以像这样定义字段名称和类型

public static String[] CityTableFields = new String[]{"id", "name", "province_id"};
public static String[] CityTableFieldTypes = new String[]{"INT", "TEXT", "INT"};