Android SQLite使用
1、Cursor的使用
使用Cursor實現增刪改查功能java
使用Cursor增長和修改：android
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刪除：sql
int id = mContext.getContentResolver().delete(RadioProvider.CONTENT_URI_RADIO_STATION, selection, selectionArgs);
使用Cursor查詢：數據庫
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();
2、DBHelper
1.構造函數ide
private Context mContext;
public DatabaseHelper(Context context, String name, CursorFactory factory, int version) {
// 必須經過super調用父類當中的構造函數
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.檢查數據庫是否有效函數
/**
* 檢查數據庫是否有效
*
* @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.建立數據庫大數據
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// 數據庫已存在，do nothing.
} else {
// 建立數據庫
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.將本地資源文件夾中的數據庫複製到剛剛建立的空數據庫this
/**
* 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();
}
//複製assets下的大數據庫文件時用這個
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：spa
execSQL不支持帶;的多條SQL語句，只能一條一條的執行，暈了好久才明白，見execSQL的源碼註釋 (Multiple statements separated by ;s are not supported.).net
將把assets下的數據庫文件直接複製到DB_PATH，但數據庫文件大小限制在1M如下， 若是有超過1M的大文件，則須要先分割爲N個小文件，而後使用copyBigDatabase()替換copyDatabase()
5.建立表
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);");
3、Android SQLite數據庫(dictionary.db文件)與apk文件一塊兒發佈
4、數據庫處理
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不支持帶;的多條SQL語句，只能一條一條的執行，暈了好久才明白
* 見execSQL的源碼註釋 (Multiple statements separated by ;s are not supported.)
* 將把assets下的數據庫文件直接複製到DB_PATH，但數據庫文件大小限制在1M如下
* 若是有超過1M的大文件，則須要先分割爲N個小文件，而後使用copyBigDatabase()替換copyDatabase()
*/
public class DBHelper extends SQLiteOpenHelper {
//用戶數據庫文件的版本
private static final int DB_VERSION = 1;
//數據庫文件目標存放路徑爲系統默認位置，cn.arthur.examples 是你的包名
private static String DB_PATH = "/data/data/cn.arthur.examples/databases/";
/*
//若是你想把數據庫文件存放在SD卡的話
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;
/**
* 若是數據庫文件較大，使用FileSplit分割爲小於1M的小文件
* 此例中分割爲 hello.db.101 hello.db.102 hello.db.103
*/
//第一個文件名後綴
private static final int ASSETS_SUFFIX_BEGIN = 101;
//最後一個文件名後綴
private static final int ASSETS_SUFFIX_END = 103;
/**
* 在SQLiteOpenHelper的子類當中，必須有該構造函數
* @param context 上下文對象
* @param name 數據庫名稱
* @param factory 通常都是null
* @param version 當前數據庫的版本，值必須是整數而且是遞增的狀態
*/
public DBHelper(Context context, String name, CursorFactory factory, int version) {
//必須經過super調用父類當中的構造函數
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){
//數據庫已存在，do nothing.
}else{
//建立數據庫
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);
// 複製asseets中的db文件到DB_PATH下
copyDataBase();
} catch (IOException e) {
throw new Error("數據庫建立失敗");
}
}
}
//檢查數據庫是否有效
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();
}
//複製assets下的大數據庫文件時用這個
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();
}
/**
* 該函數是在第一次建立的時候執行，
* 其實是第一次獲得SQLiteDatabase對象的時候纔會調用這個方法
*/
@Override
public void onCreate(SQLiteDatabase db) {
}
/**
* 數據庫表結構有變化時採用
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
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