4.SQLite的使用

SQLite

核心代码:

组件:

public class DatabaseHelper extends SQLiteOpenHelper {private static final int VERSION = 1;//在SQLiteOepnHelper的子类当中，必须有该构造函数public DatabaseHelper(Context context, String name, CursorFactory factory,int version) {//必须通过super调用父类当中的构造函数super(context, name, factory, version);}//该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候，才会调用这个方法@Overridepublic void onCreate(SQLiteDatabase db) {//execSQL函数用于执行SQL语句db.execSQL("create table user(id int,name varchar(20))");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {System.out.println("update a Database");}}

调用组件:

public class SQLiteActivity extends Activity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db");SQLiteDatabase db = dbHelper.getReadableDatabase();ContentValues values = new ContentValues();values.put("字段名", "数据");db.insert();db.update();db.query();    }}

控件图例:

具体应用:

组件:

package mars.sqlite3.db;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.database.sqlite.SQLiteDatabase.CursorFactory;//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public class DatabaseHelper extends SQLiteOpenHelper {private static final int VERSION = 1;//在SQLiteOepnHelper的子类当中，必须有该构造函数public DatabaseHelper(Context context, String name, CursorFactory factory,int version) {//必须通过super调用父类当中的构造函数super(context, name, factory, version);// TODO Auto-generated constructor stub}public DatabaseHelper(Context context,String name){this(context,name,VERSION);}public DatabaseHelper(Context context,String name,int version){this(context, name,null,version);}//该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候，才会调用这个方法@Overridepublic void onCreate(SQLiteDatabase db) {// TODO Auto-generated method stubSystem.out.println("create a Database");//execSQL函数用于执行SQL语句db.execSQL("create table user(id int,name varchar(20))");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stubSystem.out.println("update a Database");}}

组件调用:

package mars.sqlite3;import mars.sqlite3.db.DatabaseHelper;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class SQLiteActivity extends Activity {    /** Called when the activity is first created. */private Button createButton;private Button insertButton;private Button updateButton;private Button updateRecordButton;private Button queryButton;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        createButton = (Button)findViewById(R.id.createDatabase);        updateButton = (Button)findViewById(R.id.updateDatabase);        insertButton = (Button)findViewById(R.id.insert);        updateRecordButton = (Button)findViewById(R.id.update);        queryButton = (Button)findViewById(R.id.query);        createButton.setOnClickListener(new CreateListener());        updateButton.setOnClickListener(new UpdateListener());        insertButton.setOnClickListener(new InsertListener());        updateRecordButton.setOnClickListener(new UpdateRecordListener());        queryButton.setOnClickListener(new QueryListener());    }    class CreateListener implements OnClickListener{@Overridepublic void onClick(View v) {//创建一个DatabaseHelper对象DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db");//只有调用了DatabaseHelper对象的getReadableDatabase()方法，或者是getWritableDatabase()方法之后，才会创建，或打开一个数据库SQLiteDatabase db = dbHelper.getReadableDatabase();}    }    class UpdateListener implements OnClickListener{@Overridepublic void onClick(View v) {DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);SQLiteDatabase db = dbHelper.getReadableDatabase();}        }    class InsertListener implements OnClickListener{@Overridepublic void onClick(View v) {//生成ContentValues对象ContentValues values = new ContentValues();//想该对象当中插入键值对，其中键是列名，值是希望插入到这一列的值，值必须和数据库当中的数据类型一致values.put("id", 1);values.put("name","zhangsan");DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);SQLiteDatabase db = dbHelper.getWritableDatabase();//调用insert方法，就可以将数据插入到数据库当中db.insert("user", null, values);}    }    //更新操作就相当于执行SQL语句当中的update语句    //UPDATE table_name SET XXCOL=XXX WHERE XXCOL=XX...    class UpdateRecordListener implements OnClickListener{public void onClick(View arg0) {// TODO Auto-generated method stub//得到一个可写的SQLiteDatabase对象DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_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{@Overridepublic void onClick(View v) {System.out.println("aaa------------------");Log.d("myDebug", "myFirstDebugMsg");DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db");SQLiteDatabase db = dbHelper.getReadableDatabase();Cursor cursor = db.query("user", new String[]{"id","name"}, "id=?", new String[]{"1"}, null, null, null);while(cursor.moveToNext()){String name = cursor.getString(cursor.getColumnIndex("name"));System.out.println("query--->" + name);}}    }    }

项目文件地址: