Android中数据库常见操作实例分析
本文实例讲述了Android中数据库常见操作。分享给大家供大家参考,具体如下:
android中数据库操作是非常常见了,我们会经常用到,操作的方法也有很多种形式,这里我就把最常见的两种形式记录下来了,以备以后用到方便查看。我就不写注释和解释了,因为android数据库的操作和其它数据库操作本质上都是一样的,大同小异。需要的一些基本解释都在代码中,直接上代码了。
简单的代码文件目录:
首先这个类是数据库帮助类,DBHelper.java,代码如下:
package net.loonggg.db; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; /** * 数据库帮助类,继承android自带的SQLiteOpenHelper 主要用于数据库的创建与更新 * * @author loonggg * */ public class DBHelper extends SQLiteOpenHelper { public DBHelper(Context context) { super(context, DBInfo.DB.DB_NAME, null, DBInfo.DB.DB_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DBInfo.Table.USER_INFO_CREATE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL(DBInfo.Table.USER_INFO_DROP); onCreate(db); } }
其次是数据库信息类,DBInfo.java,代码如下:
package net.loonggg.db; /** * 数据库信息类,主要是保存一些数据库的版本,名字,及数据库表的创建语句和表的信息等,通过这个类记录,方便操作 * * @author loonggg * */ public class DBInfo { /** * 数据库信息 * * @author loonggg * */ public static class DB { // 数据库名称 public static final String DB_NAME = "test.db"; // 数据库的版本号 public static final int DB_VERSION = 1; } /** * 数据库表的信息 * * @author loonggg * */ public static class Table { public static final String USER_INFO_TB_NAME = "user_table"; public static final String USER_INFO_CREATE = "CREATE TABLE IF NOT EXISTS " + USER_INFO_TB_NAME + " ( _id INTEGER PRIMARY KEY,userId text,userName text)"; public static final String USER_INFO_DROP = "DROP TABLE" + USER_INFO_TB_NAME; } }
再次是数据库操作类,DBService.java,代码如下:
package net.loonggg.service; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import net.loonggg.db.DBHelper; import net.loonggg.db.DBInfo.Table; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; /** * 数据库操作类,这个类主要的功能是:存放数据库操作的一些方法 这里有一些例子:包含数据库的增删改查,分别有两种方法的操作,各有优缺点,都在解释中 * * @author loonggg * */ public class DBService { private DBHelper dbHelper = null; public DBService(Context context) { dbHelper = new DBHelper(context); } /** * 添加一条记录到数据库 * * @param id * @param name */ public void add(String id, String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); // 不好之处:无返回值,无法判断是否插入成功 db.execSQL("insert into user_table (userId,userName) values (?,?)", new Object[] { id, name }); db.close(); } public long addAndroid(String id, String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("userId", id); values.put("userName", name); // 好处:有返回值 long result = db.insert(Table.USER_INFO_TB_NAME, null, values);// 返回值是插入的是第几行,大于0代表添加成功 db.close(); return result; } /** * 查询某条记录是否存在 * * @param name * @return */ public boolean find(String name) { SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.rawQuery( "select * from user_table where userName = ?", new String[] { name }); boolean result = cursor.moveToNext(); db.close(); return result; } public boolean findAndroid(String name) { SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.query(Table.USER_INFO_TB_NAME, null, "userName = ?", new String[] { name }, null, null, null); boolean result = cursor.moveToNext();// true代表查找到了 db.close(); return result; } /** * 修改一条记录 * * @param id * @param name */ public void update(String id, String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); // 缺点无返回值 db.execSQL("update user_table set userName = ? where userId = ?", new Object[] { name, id }); db.close(); } public int updateAndroid(String id, String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("userName", name); // 返回值大于0代表修改更新成功 int result = db.update(Table.USER_INFO_TB_NAME, values, "userId = ?", new String[] { id }); db.close(); return result; } /** * 删除一条记录 * * @param name */ public void delete(String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); db.execSQL("delete from user_table where userName = ?", new String[] { name }); db.close(); } public int deleteAndroid(String name) { SQLiteDatabase db = dbHelper.getWritableDatabase(); int result = db.delete(Table.USER_INFO_TB_NAME, "userName = ?", new String[] { name });// 返回值为受影响的行数,大于0代表成功 db.close(); return result; } /** * 返回所有的数据库信息 * * @return */ public List<HashMap<String, String>> findAll() { List<HashMap<String, String>> list = null; SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select * from user_table", null); if (cursor.getCount() > 0) { list = new ArrayList<HashMap<String, String>>(); while (cursor.moveToNext()) { String id = cursor.getString(cursor.getColumnIndex("userId")); String name = cursor.getString(cursor .getColumnIndex("userName")); HashMap<String, String> map = new HashMap<String, String>(); map.put("id", id); map.put("name", name); list.add(map); } } cursor.close(); db.close(); return list; } public List<HashMap<String, String>> findAllAndroid() { List<HashMap<String, String>> list = null; SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = db.query(Table.USER_INFO_TB_NAME, new String[] { "userId", "userName" }, null, null, null, null, null); if (cursor.getCount() > 0) { list = new ArrayList<HashMap<String, String>>(); while (cursor.moveToNext()) { String id = cursor.getString(cursor.getColumnIndex("userId")); String name = cursor.getString(cursor .getColumnIndex("userName")); HashMap<String, String> map = new HashMap<String, String>(); map.put("id", id); map.put("name", name); list.add(map); } } cursor.close(); db.close(); return list; } }
最后是MainActivity,简单的调用了一下,这些操作,代码如下:
package net.loonggg.test; import net.loonggg.service.DBService; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.Button; public class MainActivity extends Activity { private Button queryOne; private Button insert; private Button update; private Button delete; private Button findAll; private DBService service; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); queryOne = (Button) findViewById(R.id.queryOne); insert = (Button) findViewById(R.id.insert); update = (Button) findViewById(R.id.update); delete = (Button) findViewById(R.id.delete); findAll = (Button) findViewById(R.id.findAll); queryOne.setOnClickListener(new ButtonListener()); insert.setOnClickListener(new ButtonListener()); update.setOnClickListener(new ButtonListener()); delete.setOnClickListener(new ButtonListener()); findAll.setOnClickListener(new ButtonListener()); service = new DBService(this); } class ButtonListener implements View.OnClickListener { @Override public void onClick(View v) { switch (v.getId()) { case R.id.queryOne: // service.find("loonggg"); service.findAndroid("loonggg"); break; case R.id.insert: // service.add("1", "loonggg"); service.addAndroid("2", "heihei"); break; case R.id.update: // service.update("1", "timmy"); service.updateAndroid("1", "haha"); break; case R.id.delete: // service.delete("timmy"); service.deleteAndroid("heihei"); break; case R.id.findAll: // service.findAll(); service.findAllAndroid(); break; default: break; } } } }
还有MainActivity对应的布局文件,activity_main.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <Button android:id="@+id/queryOne" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="查询一条记录" /> <Button android:id="@+id/insert" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="添加" /> <Button android:id="@+id/update" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="修改" /> <Button android:id="@+id/delete" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="删除" /> <Button android:id="@+id/findAll" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="查询全部" /> </LinearLayout>
到这里就介绍完了,这些代码并不高深,之所以记录下来,是留着以后用到的时候方便查看,当然这个代码对于初学者,还是非常有帮助的。
希望本文所述对大家Android程序设计有所帮助。
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