如何在recyclerview中获取物品的ID [英] how to get ID of the items in recyclerview

问题描述

我正在使用幻灯片从recyclerview中删除，但是当getAdapterPosition()与sql表的row_id不匹配时，就会出现问题.添加数据后如何从适配器获取ID以及如何更新recyclerview(直到我重新打开应用程序或更改方向后，它才显示新数据)?

i'm using slide to delete from recyclerview but the problem comes when getAdapterPosition() doesn't match with the row_id of sql table. how can i get id from the adapter and how to update recyclerview when the data is added(it doesn't display new data until i reopen the app or change orientation) ?

公共类MainActivity扩展了AppCompatActivity {

public class MainActivity extends AppCompatActivity {

RecyclerView mRecyclerView;
MyAdapter myAdapter;
ImageButton floatButton;

DbHelper dbHelper;

ArrayList<Information> data;


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


    floatButton = (ImageButton) findViewById(R.id.imageButton);
    floatButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, AddDetailPage.class);
            MainActivity.this.startActivity(intent);
        }
    });


    dbHelper = new DbHelper(this);

    data = new ArrayList<>();

    mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    myAdapter = new MyAdapter(this, showData());


    mRecyclerView.setAdapter(myAdapter);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));


    ItemTouchHelper helper = new ItemTouchHelper(createHelperCallback());
    helper.attachToRecyclerView(mRecyclerView);
}

private ItemTouchHelper.Callback createHelperCallback() {
    ItemTouchHelper.SimpleCallback simpleItemCallback = new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN, 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) {
            deleteItem(viewHolder.getAdapterPosition());
        }
    };
    return simpleItemCallback;
}


public ArrayList<Information> showData() {
    Cursor res = dbHelper.showData();
    while (res.moveToNext()) {
        Information information = new Information();
        information.ID = res.getString(0);
        information.first = res.getString(0);
        information.second = res.getString(2);
        information.detail = res.getString(3);
        data.add(information);
    }
    return data;
}

public void deleteItem(int position){
    DbHelper dbHelper = new DbHelper(this);
    dbHelper.delete(position);


    myAdapter.notifyItemRemoved(position);

    myAdapter.delete(position);
}

}

公共类MyAdapter扩展了RecyclerView.Adapter {

public class MyAdapter extends RecyclerView.Adapter {

private MainActivity mainactivity;
private ArrayList<Information> data;
private LayoutInflater layoutInflater;

public MyAdapter(MainActivity mainActivity, ArrayList<Information> information) {
    this.mainactivity = mainActivity;
    this.data = information;
    layoutInflater = LayoutInflater.from(mainActivity);
    notifyDataSetChanged();
}


@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = layoutInflater.inflate(R.layout.list_item, parent, false);
    return new ViewHolder(view, data);
}


@Override
public void onBindViewHolder(MyAdapter.ViewHolder holder, int position) {
    holder.first.setText(data.get(position).first);
    holder.second.setText(data.get(position).second);
    holder.detail.setText(data.get(position).detail);

}

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

public class ViewHolder extends RecyclerView.ViewHolder{

    TextView first, second, detail;
    ArrayList<Information> info;


    public ViewHolder(View itemView, ArrayList<Information> data) {
        super(itemView);

        this.info = data;

        first = (TextView) itemView.findViewById(R.id.firstText);
        second = (TextView) itemView.findViewById(R.id.secondText);
        detail = (TextView) itemView.findViewById(R.id.detail);
    }

}

public void delete(int x){
    data.remove(x);
    notifyDataSetChanged();
}

}

公共类DbHelper扩展了SQLiteOpenHelper {

public class DbHelper extends SQLiteOpenHelper {

public static final String DATABASE_NAME = "students.db";
public static final String TABLE_NAME = "student_table";
public static final String ID = "_id";
public static final String FIRST_NAME = "first_name";
public static final String SECOND_NAME = "second_name";
public static final String DETAIL = "detail";

public DbHelper(Context context) {
    super(context, DATABASE_NAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + TABLE_NAME + "( " + ID + " INTEGER PRIMARY KEY AUTOINCREMENT ," + FIRST_NAME + " TEXT ," + SECOND_NAME + " TEXT ," + DETAIL + " TEXT );");
}

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

public boolean insertData(String first, String second, String detail) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues contentValues = new ContentValues();
    contentValues.put(FIRST_NAME, first);
    contentValues.put(SECOND_NAME, second);
    contentValues.put(DETAIL, detail);
    long x = db.insert(TABLE_NAME, null, contentValues);

    if (x == -1) {
        return false;
    } else {
        return true;
    }


}

public Cursor showData() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
    return res;
}

public void delete(int x) {
    int y = x + 1;
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(TABLE_NAME, ID + "=" + y, null);
}

}

推荐答案

在适配器中为此特定对象的获取ID创建此方法，并将该ID传递给删除DbHelper类的功能.

Create this method in your adapter to the get id of that specific object and pass the id to the delete the fuction of DbHelper class.

int getId(int position){
    return data.get(position).ID;
}

并避免直接访问类的成员.取而代之的是，您可以使用getter和setter方法.

And avoid accessing the members of a class directly. Instead of that you can use getter and setter methods.

要在添加新数据后更新recyclerview，可以在适配器的相应插入方法中调用notifyDataSetChanged().

And for updating the recyclerview after adding new data you can call notifyDataSetChanged() in the respective insert method in your adapter.

要将新元素添加到回收器视图中，请在适配器中添加此方法

To add a new element into your recycler view add this method in your adapter

void addItem(Informationn infoObj){
     data.add(infoObj);
     notifyDataSetChanged();
}

使用您的适配器对象调用此方法，并将新项目作为参数传递，您的recyclerview将使用新项目进行更新

Call this method using your adapter object and pass the new item as parameter and your recyclerview will be updated with the new items

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