Android中如何对数据库进行操作

本篇内容介绍了"Android中如何对数据库进行操作"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

一个好的习惯是创建一个辅助类来简化你的Android数据库交互。考虑创建一个数据库适配器，来添加一个与数据库交互的包装层。它应该提供直观的、强类型的方法，如添加、删除和更新项目。数据库适配器还应该处理查询和对创建、打开和关闭数据库的包装。

它还常用静态的Android数据库常量来定义表的名字、列的名字和列的索引。下面的代码片段显示了一个标准数据库适配器类的框架。它包括一个SQLiteOpenHelper类的扩展类，用于简化打开、创建和更新数据库。

import android.content.Context;   import android.database.*;   import android.database.sqlite.*;   import android.database.sqlite.SQLiteDatabase.CursorFactory;   import android.util.Log;   public class MyDBAdapter    {  // The name and column index of each column in your database.   public static final String KEY_NAME="name";   public static final int NAME_COLUMN = 1;       // TODO: Create public field for each column in your table.   // SQL Statement to create a new database.   private static final String DATABASE_CREATE = "create table " +   DATABASE_TABLE + " (" + KEY_ID + " integer primary key autoincrement, " +   KEY_NAME + " text not null);";       // Variable to hold the database instance   private SQLiteDatabase db;       // Context of the application using the database.   private final Context context;       // Database open/upgrade helper   private myDbHelper dbHelper;       public MyDBAdapter(Context _context) {   context = _context;   dbHelper = new myDbHelper(context, DATABASE_NAME, null, DATABASE_VERSION);   }       public MyDBAdapter open() throws SQLException {   db = dbHelper.getWritableDatabase();   return this;   }       public void close() {   db.close();   }       public long insertEntry(MyObject _myObject) {   ContentValues contentValues = new ContentValues();   // TODO fill in ContentValues to represent the new row   return db.insert(DATABASE_TABLE, null, contentValues);   }       public boolean removeEntry(long _rowIndex) {   return db.delete(DATABASE_TABLE, KEY_ID + "=" + _rowIndex, null) > 0;   }   public Cursor getAllEntries () {   return db.query(DATABASE_TABLE, new String[] {KEY_ID, KEY_NAME},   null, null, null, null, null);   }   public MyObject getEntry(long _rowIndex) {   MyObject objectInstance = new MyObject();   // TODO Return a cursor to a row from the database and   // use the values to populate an instance of MyObject   return objectInstance;   }   public int updateEntry(long _rowIndex, MyObject _myObject) {   String where = KEY_ID + "=" + _rowIndex;   ContentValues contentValues = new ContentValues();   // TODO fill in the ContentValue based on the new object   return db.update(DATABASE_TABLE, contentValues, where, null);   }       private static class myDbHelper extends SQLiteOpenHelper    {   public myDbHelper(Context context, String name, CursorFactory factory, int version) {   super(context, name, factory, version);   }       // Called when no database exists in   // disk and the helper class needs   // to create a new one.   @Override   public void onCreate(SQLiteDatabase _db) {   _db.execSQL(DATABASE_CREATE);   }

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