从sqlite删除项目后，RecyclerView不会更新吗? [英] RecyclerView does not update after deleting an item from sqlite?

问题描述

我已经从sqlite填充了recyclerview.单击每行时，行将从sqlite删除，但是recyclerview在删除后不显示更新的列表.回收者视图仅在再次启动活动后才显示更新的列表.我的问题是如何从recylcerview中删除项目后立即更新回收者视图，而无需刷新.

I have populated recyclerview from sqlite .when clicking each row ,row will delete from sqlite but recyclerview not showing updated list after delete. Recycler view show updated list only after launching activity once again. My question is how to update the recycler view soon after deleting an item from the recylcerview without refresh.

以下是我的代码

SecondActivity.java

SecondActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;

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

public class SecondActivity extends AppCompatActivity {
    DatabaseHelpher helpher;
    List<DatabaseModel> dbList;
RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);


        helpher = new DatabaseHelpher(this);
        dbList= new ArrayList<DatabaseModel>();
        dbList = helpher.getDataFromDB();


        mRecyclerView = (RecyclerView)findViewById(R.id.recycleview);

        mRecyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);

        // specify an adapter (see also next example)
        mAdapter = new RecyclerAdapter(this,dbList);
        mRecyclerView.setAdapter(mAdapter);
mAdapter.notifyDataSetChanged ();
    }

    @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_second, menu);
        return true;
    }



    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

DatabaseHelpher.java

DatabaseHelpher.java

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;

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

public class DatabaseHelpher extends SQLiteOpenHelper {
    private static final String DATABASE_NAME="student";
    private static final int DATABASE_VERSION = 1;
    private static final String STUDENT_TABLE = "stureg";
    private static final String STU_TABLE = "create table "+STUDENT_TABLE +"(name TEXT,email TEXT primary key,roll TEXT,address TEXT,branch TEXT)";

Context context;

    public DatabaseHelpher(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(STU_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        db.execSQL("DROP TABLE IF EXISTS " + STUDENT_TABLE);

        // Create tables again
        onCreate(db);
    }
/* Insert into database*/
    public void insertIntoDB(String name,String email,String roll,String address,String branch){
        Log.d("insert", "before insert");

        // 1. get reference to writable DB
        SQLiteDatabase db = this.getWritableDatabase();

        // 2. create ContentValues to add key "column"/value
        ContentValues values = new ContentValues();
        values.put("name", name);
        values.put("email", email);
        values.put("roll", roll);
         values.put("address", address);
        values.put("branch", branch);

        // 3. insert
        db.insert(STUDENT_TABLE, null, values);
        // 4. close
        db.close();
        Toast.makeText(context, "insert value", Toast.LENGTH_LONG);
        Log.i("insert into DB", "After insert");
    }
/* Retrive  data from database */
    public List<DatabaseModel> getDataFromDB(){
        List<DatabaseModel> modelList = new ArrayList<DatabaseModel>();
        String query = "select * from "+STUDENT_TABLE;

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

        if (cursor.moveToFirst()){
            do {
                DatabaseModel model = new DatabaseModel();
                model.setName(cursor.getString(0));
                model.setEmail(cursor.getString(1));
                model.setRoll(cursor.getString(2));
                model.setAddress(cursor.getString(3));
                model.setBranch(cursor.getString(4));

                modelList.add(model);
            }while (cursor.moveToNext());
        }


        Log.d("student data", modelList.toString());


        return modelList;
    }


    /*delete a row from database*/

    public void deleteARow(String email){
        SQLiteDatabase db= this.getWritableDatabase();
        db.delete(STUDENT_TABLE, "email" + " = ?", new String[] { email });
        db.close();
    }

}

DatabaseModel.java

DatabaseModel.java

public class DatabaseModel {
    private String name;
    private String roll;
    private String address;
    private String branch;
    private String email;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRoll() {
        return roll;
    }

    public void setRoll(String roll) {
        this.roll = roll;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getBranch() {
        return branch;
    }

    public void setBranch(String branch) {
        this.branch = branch;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

RecyclerAdapter.java

RecyclerAdapter.java

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

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


public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {

  static   List<DatabaseModel> dbList;
    static  Context context;

    static DatabaseHelper dh;
    RecyclerAdapter(Context context, List<DatabaseModel> dbList ){
        this.dbList = new ArrayList<DatabaseModel>();
        this.context = context;
        this.dbList = dbList;
dh=new DatabaseHelper(context);
    }

    @Override
    public RecyclerAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View itemLayoutView = LayoutInflater.from(parent.getContext()).inflate(
                R.layout.item_row, null);

        // create ViewHolder

        ViewHolder viewHolder = new ViewHolder(itemLayoutView);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerAdapter.ViewHolder holder, int position) {

        holder.name.setText(dbList.get(position).getName());
        holder.email.setText(dbList.get(position).getEmail());

    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        public TextView name,email;

        public ViewHolder(View itemLayoutView) {
            super(itemLayoutView);
            name = (TextView) itemLayoutView
                    .findViewById(R.id.rvname);
            email = (TextView)itemLayoutView.findViewById(R.id.rvemail);
            itemLayoutView.setOnClickListener(this);

        }

        @Override
        public void onClick(View v) {
           dh.delete(dbList.get(getAdapterPosition()).getEmail);


            Toast.makeText(RecyclerAdapter.context, "you have clicked Row " + getAdapterPosition(), Toast.LENGTH_LONG).show();
        }
    }
}

我曾尝试使用mAdapter.notifyDataSetChanged ();更新recyclerview，但它对我不起作用.请推荐给我.谢谢

i have tried to update recyclerview using mAdapter.notifyDataSetChanged (); but it doesn't working for me.please sugget me.Thank you

推荐答案

从您的arraylist和数据库中删除数据，然后通知您的列表将更新.

Remove data from both from your arraylist and from database and than notify your list will update.

或

从数据库中删除数据，删除后从数据库中获取数据，并用新数据重新加载您的数组列表将完成您的工作

Delete data from database and after delete get data from database and reload your arraylist with new data will do your work

dbList.remove(getAdapterPosition());
notifyDataSetChanged();
//or use this for better perfomance.
notifyItemRemoved(getAdapterPosition());

删除方法中的通过位置

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