Android SQLite使用

一、Cursor的使用

使用Cursor实现增删改查功能

使用Cursor增加和修改：

ContentValues values = new ContentValues();
values.put(RadioDbConst.RadioStation.BAND, station.getBand());
values.put(RadioDbConst.RadioStation.FREQUENCY, station.getFrequencyStr());
values.put(RadioDbConst.RadioStation.IS_STERO, station.isStereoInt());
values.put(RadioDbConst.RadioStation.TYPE, station.getType());

ContentResolver resolver = mContext.getContentResolver();
StationInfo mInfo = getCollectStation(station.getBand(), station.getFrequencyStr());
if (null != mInfo) {
Log.i(TAG, "collect -- has");
if (mInfo.getType() != 2 || mInfo.isStereoInt() != station.isStereoInt()) {
Log.i(TAG, "collect -- update");
String selection = RadioDbConst.RadioStation.TYPE + " = ?" + " and " + RadioDbConst.RadioStation.IS_STERO + " ?";
String[] selectionArgs = { String.valueOf(2), String.valueOf(station.isStereoInt()) };
resolver.update(RadioProvider.CONTENT_URI_COLLECT, values, selection, selectionArgs);
}
} else {
Log.i(TAG, "collect -- insert value:" + values.getAsString(RadioDbConst.SavedStation.FREQUENCY));
resolver.insert(RadioProvider.CONTENT_URI_COLLECT, values);
}

使用Cursor删除：

int id = mContext.getContentResolver().delete(RadioProvider.CONTENT_URI_RADIO_STATION, selection, selectionArgs);

使用Cursor查询：

String selection = RadioDbConst.RadioStation.BAND + " = ? " + "and" + RadioDbConst.RadioStation.FREQUENCY + " = ?";
String[] selectionArgs = { fre };
StationInfo si = null;
Cursor cursor = mContext.getContentResolver().query(RadioProvider.CONTENT_URI_COLLECT, null, selection, selectionArgs, null);
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
int b = cursor.getInt(cursor.getColumnIndex(RadioDbConst.RadioStation.IS_STERO));
int type = cursor.getInt(cursor.getColumnIndex(RadioDbConst.RadioStation.TYPE));
si = new StationInfo(band, fre, b, type);
Log.e("si", si.toString());
}
cursor.close();

二、DBHelper

1.构造函数

private Context mContext;

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, null, version);
mContext = context;

try {
createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}

public DatabaseHelper(Context context, String name, int version) {
this(context, name, null, version);
}

public DatabaseHelper(Context context, String name) {
this(context, name, StaticCode.DATABASE_VERSION);
}

public DatabaseHelper(Context context) {
this(context, StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME);
}

2.检查数据库是否有效

/**
* 检查数据库是否有效
*
* @return
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
boolean isCecked = false;
String myPath = StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME;
try {
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
if (checkDB != null) {
checkDB.close();
isCecked = true;
}
} catch (Exception e) {

}

return isCecked;
}

3.创建数据库

public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// 数据库已存在，do nothing.
} else {
// 创建数据库
File dir = new File(StaticCode.DATABASE_FILEPATH);
if (!dir.exists()) {
dir.mkdirs();
}
File dbf = new File(StaticCode.DATABASE_FILEPATH + StaticCode.DATABASE_NAME);
if (dbf.exists()) {
dbf.delete();
}
SQLiteDatabase.openOrCreateDatabase(dbf, null);
}
}

4.将本地资源文件夹中的数据库复制到刚刚创建的空数据库

/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(ASSETS_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}

//复制assets下的大数据库文件时用这个
private void copyBigDataBase() throws IOException{
InputStream myInput;
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
for (int i = ASSETS_SUFFIX_BEGIN; i < ASSETS_SUFFIX_END+1; i++) {
myInput = myContext.getAssets().open(ASSETS_NAME + "." + i);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myInput.close();
}
myOutput.close();
}

注意：

execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了很久才明白，见execSQL的源码注释 (Multiple statements separated by ;s are not supported.)

将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M以下， 如果有超过1M的大文件，则需要先分割为N个小文件，然后使用copyBigDatabase()替换copyDatabase()

5.创建表

db.execSQL("CREATE TABLE IF NOT EXISTS "
+ RadioDbConst.RadioStation.TABLE_NAME + " ("
+ RadioDbConst.RadioStation._ID
+ " integer primary key autoincrement,"
+ RadioDbConst.RadioStation.FREQUENCY + " text,"
+ RadioDbConst.RadioStation.TITLE + " text,"
+ RadioDbConst.RadioStation.BAND + " integer,"
+ RadioDbConst.RadioStation.IS_STERO + " integer,"
+ RadioDbConst.RadioStation.TYPE + " integer);");

6.Android 将数据库文件保存至sdcard中

三、Android SQLite数据库(dictionary.db文件)与apk文件一起发布

四、数据库处理

package cn.arthur.common;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

/**
* @author Joshua
* 用法：
* DBHelper dbHelper = new DBHelper(this);
* dbHelper.createDataBase();
* SQLiteDatabase db = dbHelper.getWritableDatabase();
* Cursor cursor = db.query()
* db.execSQL(sqlString);
* 注意：execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了很久才明白
* 见execSQL的源码注释 (Multiple statements separated by ;s are not supported.)
* 将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M以下
* 如果有超过1M的大文件，则需要先分割为N个小文件，然后使用copyBigDatabase()替换copyDatabase()
*/
public class DBHelper extends SQLiteOpenHelper {
//用户数据库文件的版本
private static final int DB_VERSION    = 1;
//数据库文件目标存放路径为系统默认位置，cn.arthur.examples 是你的包名
private static String DB_PATH        = "/data/data/cn.arthur.examples/databases/";
/*
//如果你想把数据库文件存放在SD卡的话
private static String DB_PATH        = android.os.Environment.getExternalStorageDirectory().getAbsolutePath()
+ "/arthurcn/drivertest/packfiles/";
*/
private static String DB_NAME         = "hello.db";
private static String ASSETS_NAME     = "hello.db";

private SQLiteDatabase myDataBase    = null;
private final Context myContext;

/**
* 如果数据库文件较大，使用FileSplit分割为小于1M的小文件
* 此例中分割为 hello.db.101    hello.db.102    hello.db.103
*/
//第一个文件名后缀
private static final int ASSETS_SUFFIX_BEGIN    = 101;
//最后一个文件名后缀
private static final int ASSETS_SUFFIX_END        = 103;

/**
* 在SQLiteOpenHelper的子类当中，必须有该构造函数
* @param context    上下文对象
* @param name        数据库名称
* @param factory    一般都是null
* @param version    当前数据库的版本，值必须是整数并且是递增的状态
*/
public DBHelper(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, null, version);
this.myContext = context;
}

public DBHelper(Context context, String name, int version){
this(context,name,null,version);
}

public DBHelper(Context context, String name){
this(context,name,DB_VERSION);
}

public DBHelper (Context context) {
this(context, DB_PATH + DB_NAME);
}

public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//数据库已存在，do nothing.
}else{
//创建数据库
try {
File dir = new File(DB_PATH);
if(!dir.exists()){
dir.mkdirs();
}
File dbf = new File(DB_PATH + DB_NAME);
if(dbf.exists()){
dbf.delete();
}
SQLiteDatabase.openOrCreateDatabase(dbf, null);
// 复制asseets中的db文件到DB_PATH下
copyDataBase();
} catch (IOException e) {
throw new Error("数据库创建失败");
}
}
}

//检查数据库是否有效
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
String myPath = DB_PATH + DB_NAME;
try{
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}

/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(ASSETS_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}

//复制assets下的大数据库文件时用这个
private void copyBigDataBase() throws IOException{
InputStream myInput;
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
for (int i = ASSETS_SUFFIX_BEGIN; i < ASSETS_SUFFIX_END+1; i++) {
myInput = myContext.getAssets().open(ASSETS_NAME + "." + i);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myInput.close();
}
myOutput.close();
}

@Override
public synchronized void close() {
if(myDataBase != null){
myDataBase.close();
}
super.close();
}

/**
* 该函数是在第一次创建的时候执行，
* 实际上是第一次得到SQLiteDatabase对象的时候才会调用这个方法
*/
@Override
public void onCreate(SQLiteDatabase db) {
}

/**
* 数据库表结构有变化时采用
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}

}