java - 在应用程序启动时创建 SQLite 数据库

Question

我有这个帮助文件，如何调用函数从另一个 Activity (主 Activity )创建数据库和表。

package com.example.addressbook;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;

public class DBHelper extends SQLiteOpenHelper {

   public static final String DATABASE_NAME = "MyDBName.db";
   public static final String CONTACTS_TABLE_NAME = "contacts";
   public static final String CONTACTS_COLUMN_ID = "id";
   public static final String CONTACTS_COLUMN_NAME = "name";
   public static final String CONTACTS_COLUMN_EMAIL = "email";
   public static final String CONTACTS_COLUMN_STREET = "street";
   public static final String CONTACTS_COLUMN_CITY = "place";
   public static final String CONTACTS_COLUMN_PHONE = "phone";
   private HashMap hp;

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

   @Override
   public void onCreate(SQLiteDatabase db) {
      // TODO Auto-generated method stub
      db.execSQL(
      "create table contacts " +
      "(id integer primary key, name text,phone text,email text, street text,place text)"
      );
   }

   @Override
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      // TODO Auto-generated method stub
      db.execSQL("DROP TABLE IF EXISTS contacts");
      onCreate(db);
   }

   public boolean insertContact  (String name, String phone, String email, String street,String place)
   {
      SQLiteDatabase db = this.getWritableDatabase();
      ContentValues contentValues = new ContentValues();
      contentValues.put("name", name);
      contentValues.put("phone", phone);
      contentValues.put("email", email);    
      contentValues.put("street", street);
      contentValues.put("place", place);
      db.insert("contacts", null, contentValues);
      return true;
   }

   public Cursor getData(int id){
      SQLiteDatabase db = this.getReadableDatabase();
      Cursor res =  db.rawQuery( "select * from contacts where id="+id+"", null );
      return res;
   }

   public int numberOfRows(){
      SQLiteDatabase db = this.getReadableDatabase();
      int numRows = (int) DatabaseUtils.queryNumEntries(db, CONTACTS_TABLE_NAME);
      return numRows;
   }

   public boolean updateContact (Integer id, String name, String phone, String email, String street,String place)
   {
      SQLiteDatabase db = this.getWritableDatabase();
      ContentValues contentValues = new ContentValues();
      contentValues.put("name", name);
      contentValues.put("phone", phone);
      contentValues.put("email", email);
      contentValues.put("street", street);
      contentValues.put("place", place);
      db.update("contacts", contentValues, "id = ? ", new String[] { Integer.toString(id) } );
      return true;
   }

   public Integer deleteContact (Integer id)
   {
      SQLiteDatabase db = this.getWritableDatabase();
      return db.delete("contacts", 
      "id = ? ", 
      new String[] { Integer.toString(id) });
   }

   public ArrayList<String> getAllCotacts()
   {
      ArrayList<String> array_list = new ArrayList<String>();

      //hp = new HashMap();
      SQLiteDatabase db = this.getReadableDatabase();
      Cursor res =  db.rawQuery( "select * from contacts", null );
      res.moveToFirst();

      while(res.isAfterLast() == false){
           array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_NAME)));
         res.moveToNext();
      }
    return array_list;
    } 
    }

Answer 1

只需从您的 Activity 中这样调用您的助手即可

DBHelper helper = new DBHelper(this);

并使用其方法，例如

helper.getAllCotacts();