Android开发之Sqlite的使用

在Android中存储数据可以用文件、数据库、网络，其中文件和数据库是最常用的，数据库我们常用的就是Sqlite，它是一种经量级的、嵌入式的关系型数据库；在android中当需要操作SQLite数据库的时候需要得到一个SQLiteOpenHelper对象，而SQLiteOpenHelper是一个抽象类，用户需要继承这个类

package com.example.sqlite.db;
 
import android.content.Context;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
 
/**
 * DatabaseHelper作为一个访问SQLite的助手类，提供两个方面的功能，
 * 第一，getReadableDatabase(),getWritableDatabase()可以获得SQLiteDatabse对象，通过该对象可以对数据库进行操作
 * 第二，提供了onCreate()和onUpgrade()两个回调函数，允许我们在创建和升级数据库时，进行自己的操作
 * @author Administrator
 *
 */
public class DatabaseHelper extends SQLiteOpenHelper{
 
	public static final int VERSION = 1;
	public DatabaseHelper(Context context, String name, CursorFactory factory,
			int version) {
		super(context, name, factory, version);
		// TODO Auto-generated constructor stub
	}
	public DatabaseHelper(Context context, String name){
		this(context, name, VERSION);
		Log.i("debug", "DatabaseHelper");
	}
	public DatabaseHelper(Context context, String name, int version){
		this(context, name, null, version);
	}
 
	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		Log.i("debug", "create a database");
		//执行SQL语句
		db.execSQL("create table user (id int, name varchar(20))");
	}
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		Log.i("debug", "Upgrade a database");
	}
}

下面是对数据库的进行增、删、改、查操作

布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
 
    <Button
        android:id="@+id/create_db"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/create_db"/>
    <Button
        android:id="@+id/update_db"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/update_db"/>
    <Button
        android:id="@+id/insert"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/insert"/>
    <Button
        android:id="@+id/update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/update"/>
    <Button
        android:id="@+id/query"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/query"/>
    <Button
        android:id="@+id/delete"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/delete"/>
 
</LinearLayout>

在Activity处理代码

package com.example.sqlite;
 
import com.example.sqlite.db.DatabaseHelper;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
 
/**
 * SQLite的创建、更新、修改、插入、查询、删除操作
 * @author Administrator
 *
 */
public class SqliteActivity extends Activity {
 
	private Button create_db;
	private Button update_db;   //更新数据库的版本号
	private Button insert;
	private Button update;
	private Button query;
	private Button delete;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_sqlite);
		create_db = (Button)findViewById(R.id.create_db);
		update_db = (Button)findViewById(R.id.update_db);
		insert = (Button)findViewById(R.id.insert);
		update = (Button)findViewById(R.id.update);
		query = (Button)findViewById(R.id.query);
		delete = (Button)findViewById(R.id.delete);
		create_db.setOnClickListener(new CreateListener());
		update_db.setOnClickListener(new UpdateDBListener());
		insert.setOnClickListener(new InsertListener());
		update.setOnClickListener(new UpdateListener());
		query.setOnClickListener(new QueryListener());
		delete.setOnClickListener(new Deletelistener());
	}
 
	class CreateListener implements OnClickListener{
 
		@Override
		public void onClick(View arg0) {
			// TODO Auto-generated method stub
			Log.i("debug", "on create db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			//只有调用了DatabaseHelper的getReadableDatabase()或getWritableDatabase()才会创建数据库
			SQLiteDatabase db = dbHelper.getWritableDatabase();
		}
 
	}
	/**
	 * 更新数据库的版本号
	 * @author Administrator
	 *
	 */
	class UpdateDBListener implements OnClickListener{
 
		@Override
		public void onClick(View arg0) {
			// TODO Auto-generated method stub
			Log.i("debug", "on update db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db", 2);
			SQLiteDatabase db = dbHelper.getReadableDatabase();
		}
 
	}
 
	class InsertListener implements OnClickListener{
 
		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "insert db");
			ContentValues values = new ContentValues();
			//向该对象插入键值对，其中键是列名，值是希望插入这一列的值，值的数据类型必须一致
			values.put("id", 1);
			values.put("name", "zhang");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			//调用insert方法插入数据
			db.insert("user", null, values);
		}
 
	}
	class UpdateListener implements OnClickListener{
 
		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "update db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			ContentValues values = new ContentValues();
			values.put("name", "zhangsanfeng");
			//第一个参数是要更新的表名
			//第二个参数是一个ContentValeus对象
			//第三个参数是where子句
			db.update("user", values, "id=?", new String[]{"1"});
		}
 
	}
	class QueryListener implements OnClickListener{
 
		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "query db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getReadableDatabase();
			Cursor cursor = db.query("user", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);
			int count = cursor.getCount();
			System.out.println("query---count = >" + count);
			while(cursor.moveToNext()){
				String name = cursor.getString(cursor.getColumnIndex("name"));
				System.out.println("query--->" + name);
			}
		}
 
	}
	class Deletelistener implements OnClickListener{
 
		@Override
		public void onClick(View v) {
			// TODO Auto-generated method stub
			Log.i("debug", "delete db");
			DatabaseHelper dbHelper = new DatabaseHelper(SqliteActivity.this, "text_mars_db");
			SQLiteDatabase db = dbHelper.getWritableDatabase();
			db.delete("user", "id=?", new String[]{"1"});
		}
 
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_sqlite, menu);
		return true;
	}
 
}

运行效果

样例代码

点击打开链接