公交查询APP

package com.seventh.busquery.db; 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 busSQLiteOpenHelper 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/com.seventh.busquery/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 = "bus.db"; private static String ASSETS_NAME = "bus.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 busSQLiteOpenHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, null, version); this.myContext = context; } public busSQLiteOpenHelper(Context context, String name, int version){ this(context,name,null,version); } public busSQLiteOpenHelper(Context context, String name){ this(context,name,DB_VERSION); } public busSQLiteOpenHelper (Context context) { this(context, DB_PATH + DB_NAME); } public void createDataBase() throws IOException{ boolean dbExist = checkDataBase(); if(dbExist){ }else{ 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(); } } //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; } public void copyDataBase(){ InputStream myInput; String outFileName; OutputStream myOutput; byte[] buffer = new byte[1024]; int length; try { myInput = myContext.getAssets().open(ASSETS_NAME); outFileName = DB_PATH + DB_NAME; myOutput = new FileOutputStream(outFileName); while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } myOutput.flush(); myOutput.close(); myInput.close(); } catch (IOException e) { e.printStackTrace(); } } //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) { } }