Android数据库编程SQLite详解
参考: http://www.ataaw.com/?p=322
程序开发离不开数据库，数据库作为一种不可或缺的存储技术，同样的，在Android中也为我们提供了数据库支持，使用的是SQLite数据库系统。
SQLite是一种轻型数据库系统，并以嵌入式为设计目标，占用资源低，因此作为手机操作系统优秀的数据库系统选择平台。
SQLite的使用涉及两个重要的类，一个是SQLiteOpenHelper和SQLiteDatabase，SQLiteOpenHelper是SQLite的数据库辅助类，而SQLiteDatabase作为SQLite的数据库实体类，用于管理数据库增删改查等操作，下面我们详细解析SQLite的具体使用方法。
让DatabaseHelper继承SQLiteOpenHelper，分别覆盖onCreate、onUpgrade和onOpen方法，这样在数据库的具体操作的时候，我们可以轻易获取数据库实例对象，具体应用我们继续分析以下代码，我们先来创建数据库。
创建数据表：
插入数据信息：
删除数据：
更新数据信息：
删除数据表：
有以上实例可以完成Android平台下数据库SQLite的基本数据库操作方法，我们可以看出与其他数据库操作的方法基本一样，通过SQL命令语句即可完成SQLite的各种操作，实现起来非常方便。
我的例子源代码:
string.xml
main.xml
java代码:
程序开发离不开数据库，数据库作为一种不可或缺的存储技术，同样的，在Android中也为我们提供了数据库支持，使用的是SQLite数据库系统。
SQLite是一种轻型数据库系统，并以嵌入式为设计目标，占用资源低，因此作为手机操作系统优秀的数据库系统选择平台。
SQLite的使用涉及两个重要的类，一个是SQLiteOpenHelper和SQLiteDatabase，SQLiteOpenHelper是SQLite的数据库辅助类，而SQLiteDatabase作为SQLite的数据库实体类，用于管理数据库增删改查等操作，下面我们详细解析SQLite的具体使用方法。
public class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context, String name, CursorFactory cursorFactory, int version) {
super(context, name, cursorFactory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 创建数据库后，对数据库的操作
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// 更改数据库版本的操作
}
@Override
public void onOpen(SQLiteDatabase db) {
super.onOpen(db);
// 打开数据库后首先被执行
}
}
让DatabaseHelper继承SQLiteOpenHelper，分别覆盖onCreate、onUpgrade和onOpen方法，这样在数据库的具体操作的时候，我们可以轻易获取数据库实例对象，具体应用我们继续分析以下代码，我们先来创建数据库。
private static final String DATABASE_NAME = "ataawcom.db"; //定义数据库名称
private static final int DATABASE_VERSION = 1;//定义数据库版本
private static final String TABLE_NAME = "ataaw";//定义数据表名称
DatabaseHelper dbHelper = new DatabaseHelper(this, DATABASE_NAME, null,
DATABASE_VERSION);//通过DatabaseHelper定义数据库
创建数据表：
void CreateTable() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME
+ " (ID INTEGER PRIMARY KEY, Name VARCHAR, Password VARCHAR);";
try {
db.execSQL(sql);
} catch (SQLException ex) {//异常处理
}
}
插入数据信息：
private void insert() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
String sql = "insert into " + TABLE_NAME
+ " (name, age) values (‘ATAAW’,'ATAAW.COM’)";
db.execSQL(sql);//执行指定的 sql
} catch (SQLException ex) {
txtMsg.setText("插入数据失败\n" + ex.toString() + "\n");
}
}
删除数据：
private void delete() {
try {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete(TABLE_NAME, " id=1", null);
} catch (SQLException e) {//异常处理
}
}
更新数据信息：
private void update() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
ContentValues values = new ContentValues();
values.put("name", "ataaw.com");
db.update(TABLE_NAME, values, "id<=?", new String[] { "3" });
} catch (SQLException e) {//异常处理
}
}
删除数据表：
private void dropTable() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;
try {
db.execSQL(sql);
} catch (SQLException ex) {//异常处理
}
}
有以上实例可以完成Android平台下数据库SQLite的基本数据库操作方法，我们可以看出与其他数据库操作的方法基本一样，通过SQL命令语句即可完成SQLite的各种操作，实现起来非常方便。
我的例子源代码:
string.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">我的数据库操作例子</string>
<string name="app_name">操作数据库</string>
<string name="createDb_success">创建数据库成功</string>
<string name="deleteDb_success">删除数据库成功</string>
<string name="createTable_success">创建表成功</string>
<string name="deleteTable_success">删除表成功</string>
<string name="insert_success">插入数据成功</string>
<string name="update_success">修改数据成功</string>
<string name="delete_success">删除数据成功</string>
<string name="select_success">查询成功</string>
<string name="createDb_failure">创建数据库失败</string>
<string name="deleteDb_failure">删除数据库失败</string>
<string name="createTable_failure">创建表失败</string>
<string name="deleteTable_failure">删除表失败</string>
<string name="insert_failure">插入数据失败</string>
<string name="update_failure">修改数据失败</string>
<string name="delete_failure">删除数据失败</string>
<string name="select_failure">查询失败</string>
</resources>
main.xml
<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout
android:id="@+id/widget36"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
>
<TextView
android:id="@+id/widget32"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
android:layout_x="0px"
android:layout_y="0px"
>
</TextView>
<Button
android:id="@+id/bt_createDB"
android:layout_width="142dp"
android:layout_height="wrap_content"
android:layout_x="8dp"
android:layout_y="23dp"
android:text="创建数据库" />
<Button
android:id="@+id/bt_deleteDB"
android:layout_width="142dp"
android:layout_height="wrap_content"
android:layout_x="166dp"
android:layout_y="22dp"
android:text="删除数据库" />
<Button
android:id="@+id/bt_createTable"
android:layout_width="142dp"
android:layout_height="wrap_content"
android:layout_x="8dp"
android:layout_y="78dp"
android:text="创建表" />
<Button
android:id="@+id/bt_deleteTable"
android:layout_width="142dp"
android:layout_height="wrap_content"
android:layout_x="166dp"
android:layout_y="78dp"
android:text="删除表" />
<Button
android:id="@+id/bt_insert"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_x="2dp"
android:layout_y="153dp"
android:text="新增" />
<Button
android:id="@+id/bt_update"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_x="80dp"
android:layout_y="151dp"
android:text="修改" />
<Button
android:id="@+id/bt_delete"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_x="159dp"
android:layout_y="152dp"
android:text="删除" />
<Button
android:id="@+id/bt_select"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_x="237dp"
android:layout_y="152dp"
android:text="查询" />
<TextView
android:id="@+id/vt_info"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_x="6dp"
android:layout_y="325dp"
android:text="Inf......" />
<TextView
android:id="@+id/widget41"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_x="10dp"
android:layout_y="249dp"
android:text="ID:" />
<EditText
android:id="@+id/et_id"
android:layout_width="82dp"
android:layout_height="42px"
android:layout_x="30dp"
android:layout_y="236dp"
android:textSize="12sp" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/et_name"
android:layout_width="130dp"
android:layout_height="42px"
android:layout_x="185dp"
android:layout_y="235dp"
android:textSize="12sp" />
<TextView
android:id="@+id/widget43"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_x="157dp"
android:layout_y="246dp"
android:text="名字:" />
</AbsoluteLayout>
java代码:
package com.db;
import java.util.Date;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteCursorDriver;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteQuery;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class DatabaseActivity extends Activity {
private Button bt_createDB;
private Button bt_deleteDB;
private Button bt_createTable;
private Button bt_deleteTable;
private Button bt_insert;
private Button bt_update;
private Button bt_delete;
private Button bt_select;
private TextView vt_info;
private EditText et_id;
private EditText et_name;
private String databaseNama="DatabaseText.db";
private String tableNama="TestTable";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bt_createDB = (Button)findViewById(R.id.bt_createDB);
bt_deleteDB = (Button)findViewById(R.id.bt_deleteDB);
bt_insert = (Button)findViewById(R.id.bt_insert);
bt_update = (Button)findViewById(R.id.bt_update);
bt_delete = (Button)findViewById(R.id.bt_delete);
bt_select = (Button)findViewById(R.id.bt_select);
bt_createTable = (Button)findViewById(R.id.bt_createTable);
bt_deleteTable = (Button)findViewById(R.id.bt_deleteTable);
bt_createDB.setOnClickListener(new CreateDbOnClickListener());
bt_deleteDB.setOnClickListener(new DeleteDbOnClickListener());
bt_createTable.setOnClickListener(new CreateTableOnClickListener());
bt_deleteTable.setOnClickListener(new DeleteTableOnClickListener());
bt_insert.setOnClickListener(new InsertRecordOnClickListener());
bt_update.setOnClickListener(new UpdateRecordOnClickListener());
bt_delete.setOnClickListener(new DeleteRecordOnClickListener());
bt_select.setOnClickListener(new SelectRecordOnClickListener());
vt_info = (TextView)findViewById(R.id.vt_info);
et_id = (EditText)findViewById(R.id.et_id);
et_name = (EditText)findViewById(R.id.et_name);
}
class CreateDbOnClickListener implements View.OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db = null;
try {
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, DatabaseActivity.MODE_PRIVATE, new CursorFactory(){
@Override
public Cursor newCursor(SQLiteDatabase db,
SQLiteCursorDriver masterQuery, String editTable,
SQLiteQuery query) {
// TODO Auto-generated method stub
return null;
}
});
vt_info.setText(getString(R.string.createDb_success));
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(e.getMessage());
}finally{
if(db!=null) db.close();
}
}
}
class DatabaseUtils {
public SQLiteDatabase getDatabase() {
SQLiteDatabase db = null;
try {
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama,
DatabaseActivity.MODE_PRIVATE, new CursorFactory() {
@Override
public Cursor newCursor(SQLiteDatabase db,
SQLiteCursorDriver masterQuery,
String editTable, SQLiteQuery query) {
return null;
}
});
return db;
} catch (Exception e) {
return null;
} finally {
if (db != null)
db.close();
}
}
}
class DeleteDbOnClickListener implements View.OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
if(DatabaseActivity.this.deleteDatabase(databaseNama)){
vt_info.setText(getString(R.string.deleteDb_success));
}else{
vt_info.setText(getString(R.string.deleteDb_failure));
}
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(e.getMessage());
}
}
}
class CreateTableOnClickListener implements View.OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db = null;
try {
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
if(db!=null){
db.execSQL("create table "+tableNama+"(id integer primary key,name varchar2(100));");
vt_info.setText(getString(R.string.createTable_success));
}
} catch (Exception e) {
vt_info.setText(getString(R.string.createTable_failure)+"\n"+e.getMessage());
}finally{
if(db!=null) db.close();
}
}
}
class DeleteTableOnClickListener implements View.OnClickListener{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db = null;
try {
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
if(db!=null){
db.execSQL("drop table "+tableNama+";");
vt_info.setText(getString(R.string.deleteTable_success));
}
} catch (Exception e) {
vt_info.setText(getString(R.string.deleteTable_failure)+"\n"+e.getMessage());
}finally{
if(db!=null) db.close();
}
}
}
class InsertRecordOnClickListener implements View.OnClickListener{
String id = null;
String name = null;
String sql = null;
SQLiteDatabase db = null;
Cursor cursor = null;
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
id = et_id.getText().toString();
name = et_name.getText().toString();
if(id==null||id.trim().length()==0){
vt_info.setText("ID is null.");
return ;
}
if(name==null||name.trim().length()==0){
vt_info.setText("Name is null.");
return ;
}
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
sql = "select count(*) from "+tableNama+" where upper(id)='"+id.toUpperCase()+"'";
cursor = db.rawQuery(sql, null);
if(cursor.moveToFirst()){
do{
int num = cursor.getInt(0);
if(num>0){
vt_info.setText("The same record of id is exist.");
return;
}
}while(cursor.moveToNext());
}
sql = "insert into "+tableNama+"(id,name) values('"+id+"','"+name+"')";
db.execSQL(sql);
vt_info.setText(getString(R.string.insert_success));
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(getString(R.string.insert_failure)+"\n"+e.getMessage());
}finally{
if(cursor!=null) cursor.close();
if(db!=null) db.close();
}
}
}
class UpdateRecordOnClickListener implements View.OnClickListener{
String id = null;
String name = null;
String sql = null;
SQLiteDatabase db = null;
Cursor cursor = null;
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
id = et_id.getText().toString();
name = et_name.getText().toString();
if(id==null||id.trim().length()==0){
vt_info.setText("ID is null.");
return ;
}
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
sql = "update "+tableNama+" set name='"+name+"' where upper(id)=upper("+id+")";
db.execSQL(sql);
vt_info.setText(getString(R.string.update_success));
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(getString(R.string.update_failure)+"\n"+e.getMessage());
}finally{
if(cursor!=null) cursor.close();
if(db!=null) db.close();
}
}
}
class DeleteRecordOnClickListener implements View.OnClickListener{
String id = null;
String name = null;
String sql = null;
SQLiteDatabase db = null;
Cursor cursor = null;
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
id = et_id.getText().toString();
name = et_name.getText().toString();
if(id==null||id.trim().length()==0){
vt_info.setText("ID is null.");
return ;
}
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
sql = "delete from "+tableNama+" where upper(id)=upper("+id+")";
db.execSQL(sql);
vt_info.setText(getString(R.string.delete_success));
et_id.setText("");
et_name.setText("");
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(getString(R.string.delete_failure)+"\n"+e.getMessage());
}finally{
if(cursor!=null) cursor.close();
if(db!=null) db.close();
}
}
}
class SelectRecordOnClickListener implements View.OnClickListener{
String id = null;
String name = null;
String sql = null;
SQLiteDatabase db = null;
Cursor cursor = null;
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
db = DatabaseActivity.this.openOrCreateDatabase(databaseNama, MODE_PRIVATE, null);
id = et_id.getText().toString();
sql = "select id,name from " + tableNama + " where 1=1";
if (id != null && id.trim().length() > 0)
sql = sql + " and id=" + id + "";
if (name != null && name.trim().length() > 0)
sql = sql + " and upper(name) like %upper('" + name + "')%";
cursor = db.rawQuery(sql, null);
if (cursor.moveToFirst()) {
et_id.setText(cursor.getString(0));
et_name.setText(cursor.getString(1));
}
vt_info.setText(getString(R.string.select_success));
} catch (Exception e) {
// TODO: handle exception
vt_info.setText(getString(R.string.select_failure)+"\n"+e.getMessage());
}finally{
if(cursor!=null) cursor.close();
if(db!=null) db.close();
}
}
}
}