转自http://www.android-study.com/jichuzhishi/493.html
Android内置了常用于嵌入式系统的sqlite,免去了开发者自己安装的功夫。sqlite 支持多数 sql92 标准,很多常用的sql命令都能在sqlite上面使用,除此之外Android还提供了一系列自定义的方法去简化对SQLite数据库的操作。不过有跨平台需求的程序就建议使用标准的sql语句,毕竟这样容易在多个平台之间移植。
先贴出本文程序运行的结果:
本文主要讲解了sqlite的基本用法,如:创建数据库,使用sql命令查询数据表、插入数据,关闭数据库,以及使用GridView实现了一个分页栏(关于GridView的用法),用于把数据分页显示。
分页栏的pagebuttons.xml的源码:
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<? xml version = "1.0" encoding = "utf-8" ?>
< RelativeLayout xmlns:android = "http://schemas.android.com/apk/res/android"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
android:paddingBottom = "4dip" >
< TextView
android:id = "@+id/ItemText"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content"
android:layout_below = "@+id/ItemImage"
android:layout_centerHorizontal = "true"
android:text = "TextView01"
/>
</ RelativeLayout >
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main.xml源码:
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@H_316_403@
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<? xml version = "1.0" encoding = "utf-8" ?>
< LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
android:orientation = "vertical"
android:layout_width = "fill_parent"
android:layout_height = "fill_parent" >
< Button
android:id = "@+id/btnCreateDB"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
android:text = "创建数据库"
/>
< Button
android:id = "@+id/btnInsertRec"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
android:text = "插入一串实验数据"
/>
< Button
android:id = "@+id/btnClose"
android:layout_width = "fill_parent"
android:layout_height = "wrap_content"
/>
< EditText
android:id = "@+id/EditText01"
android:layout_width = "fill_parent"
android:layout_height = "256dip"
android:text = "@+id/EditText01"
/>
< GridView
android:id = "@+id/gridview"
android:layout_width = "fill_parent"
android:layout_height = "32dip"
android:numColumns = "auto_fit"
android:columnWidth = "40dip"
/>
</ LinearLayout >
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本文程序源码:
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package com.testsqlite;
import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlException;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.GridView;
import android.widget.SimpleAdapter;
public class testsqlite extends Activity {
/** Called when the activity is first created. */
Button btnCreateDB,btnInsert,btnClose;
sqliteDatabase db;
static final int PageSize = 10 ; // 分页时,每页的数据总数
private static final String TABLE_NAME = "stu" ;
private static final String ID = "id" ;
private static final String NAME = "name" ;
SimpleAdapter saPageID; // 分页栏适配器
ArrayList<HashMap<String,String>> lstPageID; // 分页栏的数据源,与PageSize和数据总数相关
@Override
public void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
setContentView(R.layout.main);
btnCreateDB = (Button) this .findViewById(R.id.btnCreateDB);
btnCreateDB.setOnClickListener( new ClickEvent());
btnInsert = (Button) this .findViewById(R.id.btnInsertRec);
btnInsert.setOnClickListener( new ClickEvent());
btnClose = (Button) this .findViewById(R.id.btnClose);
btnClose.setOnClickListener( new ClickEvent());
edtsql = (EditText) this .findViewById(R.id.EditText01);
GridView gridview = (GridView) findViewById(R.id.gridview); // 分页栏控件
// 生成动态数组,并且转入数据
lstPageID = new ArrayList<HashMap<String,String>>();
// 生成适配器的ImageItem <====> 动态数组的元素,两者一一对应
saPageID = new SimpleAdapter(testsqlite. this , // 没什么解释
lstPageID, // 数据来源
R.layout.pagebuttons, // XML实现
new String[] { "ItemText" }, new int [] { R.id.ItemText });
gridview.setAdapter(saPageID);
// 添加消息处理
gridview.setOnItemClickListener( new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0,View arg1, int arg2,
long arg3) {
LoadPage(arg2); // 根据所选分页读取对应的数据
}
});
}
class ClickEvent implements View.OnClickListener {
@Override
public void onClick(View v) {
if (v == btnCreateDB) {
CreateDB();
} else if (v == btnInsert) {
InsertRecord( 16 ); // 插入16条记录
RefreshPage();
} else if (v == btnClose) {
db.close();
}
}
}
/**
* 表示从TABLE_NAME表获取数据,跳过10行,取9行
*/
void LoadPage( int pageID) {
String sql = "select * from " + TABLE_NAME + " Limit "
+ String.valueOf(PageSize) + " Offset "
+ String.valueOf(pageID * PageSize);
Cursor rec = db.rawQuery(sql, null );
setTitle( "当前分页的数据总数:" + String.valueOf(rec.getCount()));
// 取得字段名称
String title = "" ;
int colCount = rec.getColumnCount();
for ( int i = 0 ; i < colCount; i++)
title = title + rec.getColumnName(i) + " " ;
// 列举出所有数据
String content = "" ;
int recCount = rec.getCount();
for ( int i = 0 ; i < recCount; i++) { // 定位到一条数据
rec.moveToPosition(i);
for ( int ii = 0 ; ii < colCount; ii++) // 定位到一条数据中的每个字段
{
content = content + rec.getString(ii) + " " ;
}
content = content + "/r/n" ;
}
rec.close();
}
/**
* 在内存创建数据库和数据表
*/
void CreateDB() {
// 在内存创建数据库
db = sqliteDatabase.create( null );
Log.e( "DB Path" ,db.getPath());
String amount = String.valueOf(databaseList().length);
Log.e( "DB amount" ,amount);
// 创建数据表
String sql = "CREATE TABLE " + TABLE_NAME + " (" + ID
+ " text not null," + NAME + " text not null " + ");" ;
try {
db.execsql( "DROP TABLE IF EXISTS " + TABLE_NAME);
} catch (sqlException e) {
}
}
/**
* 插入N条数据
*/
void InsertRecord( int n) {
int total = id + n;
for (; id < total; id++) {
String sql = "insert into " + TABLE_NAME + " (" + ID + "," + NAME
+ ") values('" + String.valueOf(id) + "','test');" ;
try {
} catch (sqlException e) {
}
}
}
/**
* 插入之后刷新分页
*/
void RefreshPage() {
String sql = "select count(*) from " + TABLE_NAME;
Cursor rec = db.rawQuery(sql, null );
rec.moveToLast();
long recSize = rec.getLong( 0 ); // 取得总数
rec.close();
int pageNum = ( int ) (recSize / PageSize) + 1 ; // 取得分页数
lstPageID.clear();
for ( int i = 0 ; i < pageNum; i++) {
HashMap<String,String> map = new HashMap<String,String>();
map.put( "ItemText" , "No." + String.valueOf(i));
lstPageID.add(map);
}
saPageID.notifyDataSetChanged();
}
}
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