单击后退按钮时MainActivity未更新

so I'm trying to make note or a todo app and when I insert the data the data is getting inserted in database but when I go back it is not updated on the main menu SO here's the MainActivity

所以我正在尝试做笔记或todo应用程序,当我插入数据时数据被插入数据库但是当我回去时它没有在主菜单上更新SO这里是MainActivity

   package com.frolicfreak.bhushan.memo;
   import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.ContextMenu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

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

import static com.frolicfreak.bhushan.memo.DatabaseHelper.Table_Name;
import static com.frolicfreak.bhushan.memo.DatabaseHelper.col1;
import static com.frolicfreak.bhushan.memo.DatabaseHelper.col2;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

FloatingActionButton fab;
DatabaseHelper mydb;

ListView listView;
ArrayAdapter<String> mAdapter;

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

    mydb =new DatabaseHelper(this);

    fab= (FloatingActionButton)findViewById(R.id.fab);
    fab.setOnClickListener(this);

    ListView listView = (ListView)findViewById(R.id.list);
    registerForContextMenu(listView);

    ArrayList<String> theList =new ArrayList<>();
    Cursor data= mydb.getAllData();

    if (data.getCount()==0){
        Toast.makeText(MainActivity.this,"data not inserted",Toast.LENGTH_LONG).show();
    }
    else
    {
        while(data.moveToNext()){
            theList.add(data.getString(1));
            ListAdapter listAdapter=new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,theList);
            listView.setAdapter(listAdapter);
        }
    }
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    if (v.getId()==R.id.list) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
    }
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
    switch(item.getItemId()) {
        case R.id.edit:
            // edit stuff here
            return true;
        case R.id.delete:
            int count = mydb.deleterow(Table_Name, col1);
            return true;
        default:
            return super.onContextItemSelected(item);
    }
}


@Override
public void onClick(View v) {

    Intent intent= new Intent(this,Main2Activity.class);
    startActivity(intent);

}
}

and My DatabaaseHelper java file

和我的DatabaaseHelper java文件

 package com.frolicfreak.bhushan.memo;

 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;

 import java.util.ArrayList;

/**
  * Created by BHUSHAN on 24-08-2017.
 */

public class DatabaseHelper extends SQLiteOpenHelper {

public static final String Database_Name = "Memo.db";
public static final String Table_Name = "Memo";
public static final String col1 = "ID";
public static final String col2 = "data";


public DatabaseHelper(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, data 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 data, String Data) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(col2, Data);
    long result = db.insert(Table_Name, null, contentValues);
    if (result==-1)
        return false;
    else
        return true;
}

public ArrayList<String> getList(){
    ArrayList<String> taskList = new ArrayList<>();
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor= db.query(Table_Name,new String[]{col1},new String(col2),null,null,null,null);
    while (cursor.moveToNext()){
        int index= cursor.getColumnIndex(col1);
        taskList.add(cursor.getString(index));
    }
    cursor.close();
    db.close();
    return taskList;
}

public Cursor getAllData() {

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


public int deleterow(String table_Name, String col1) {
    SQLiteDatabase db = this.getReadableDatabase();
    int count = db.delete(Table_Name, DatabaseHelper.col1, null);
    return count;
}
}

my Main2Activity class

我的Main2Activity类

 package com.frolicfreak.bhushan.memo;

 import android.support.design.widget.FloatingActionButton;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.EditText;
 import android.widget.Toast;

public class Main2Activity extends AppCompatActivity {
DatabaseHelper db;

EditText Data;
FloatingActionButton add;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    db = new DatabaseHelper(this);

    Data = (EditText)findViewById(R.id.edit);
    add =(FloatingActionButton)findViewById(R.id.add);

    AddData();
}

public void AddData(){
    add.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    boolean isInserted = db.insertData(Data.getText().toString(),
                            Data.getText().toString() );
                    if (isInserted==true)
                        Toast.makeText(Main2Activity.this,"data inserted",Toast.LENGTH_LONG).show();
                    else
                        Toast.makeText(Main2Activity.this,"data not inserted",Toast.LENGTH_LONG).show();
                }
            }
    );
}

}

Now one more thing I actually want to edit and update the data (option) also so If anyone can help me with that? and when I delete any data from the list all the data gets delete when I reopen the app so please help with that too thankyou in advance

现在还有一件事我真的想编辑和更新数据(选项)也是如此,如果有人可以帮助我吗?当我从列表中删除任何数据时,当我重新打开应用程序时,所有数据都会被删除,所以请提前帮助。

1 个解决方案

#1

you should get your data from database in onResume function, not in the oncreate.

你应该在onResume函数中从数据库中获取数据,而不是在oncreate中。

add this code into your mainactivity

将此代码添加到您的mainactivity中

@Override
public void onResume() {
    super.onResume(); 
    ArrayList<String> theList =new ArrayList<>();
    Cursor data= mydb.getAllData();
    listView.setAdapter(null);

    if (data.getCount()==0){
        Toast.makeText(MainActivity.this,"data not inserted",Toast.LENGTH_LONG).show();
    }
    else
    {
        while(data.moveToNext()){
            theList.add(data.getString(1));
            ListAdapter listAdapter=new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,theList);
            listView.setAdapter(listAdapter);
        }
    }
}

#1