android raw讀取超過1M文件的方法

轉載自：http://www.cnblogs.com/yaoshi641/archive/2010/12/26/1917443.html

android raw讀取超過1M文件的方法

近日在琢磨android系統,程序中用到了sqlite數據庫,一切代碼妥當,在發佈時遇到點問題,就是raw單個文件不能超過1M,否則會報錯"Data exceeds UNCOMPRESS_DATA_MAX ",而我的數據庫的初始容量就是5M啦,網上尋找多時,大致分成兩種方法:
1>是將文件移動到sdcard中.這樣倒是不受文件大小限制,不過對於apk的發佈....不用我多說了吧.
2>將單個文件分割成多個1M以下的小文件....這個倒是個方法.只是用上去總是有點彆扭.需要找文件分割工具...或者自己寫一個.

     於是,自然想到用壓縮的方法.android的sdk完全採用了java的zip壓縮類.這就爲我實現壓縮提供了極大方便.經過測試,本人的sqlite庫,原始大小爲5M,用zip壓縮後700K,哈哈,完全滿足系統限制.然後在讀取時,解壓縮到apk的數據庫默認目錄下即可. 不在廢話,以下是本人的代碼:



import java.io.BufferedInputStream;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.zip.ZipEntry;

import java.util.zip.ZipInputStream;


import android.app.ProgressDialog;

import android.content.Context;

import android.database.Cursor;

import android.database.SQLException;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

import android.os.AsyncTask;


public class DBSourse {

    private static final String DATABASE_NAME = "Test.db";

    private static final int DATABASE_VERSION = 1;

    private DatabaseHelper mDbHelper;

    private SQLiteDatabase mDb;

    private final Context mCtx;

    private static int mDBRawResource = 0;

    public DBSourse(Context ctx,int DBRawResource) {

        this.mCtx = ctx;

        mDBRawResource = DBRawResource;

    }

    public DBSourse(Context ctx) {

        this.mCtx = ctx;

        if (mDBRawResource == 0)

            new Exception("必須指定以zip壓縮的數據庫Raw文件");

    }


    public static class DatabaseHelper extends SQLiteOpenHelper {

        DatabaseHelper(Context context) {

            super(context, DATABASE_NAME, null, DATABASE_VERSION);

        }


        @Override

        public void onCreate(SQLiteDatabase db) {   


        }


        @Override

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        }

    }

   

   

    class DBDialogTask extends AsyncTask<String, Integer, Integer> {

        ProgressDialog m_pDialog;

        int StreamLen;

        @Override

        protected Integer doInBackground(String... params) { // 後臺進程執行的具體計算在這裏實現

            String dbPathString = params[0];

            int len = 1024;//

            int readCount = 0, readSum = 0;

            byte[] buffer = new byte[len];       

            InputStream inputStream;

            OutputStream output;

            try {

                inputStream = mCtx.getResources().openRawResource(mDBRawResource); //這裏就是Raw文件引用位置

                output = new FileOutputStream(dbPathString);

               

                ZipInputStream zipInputStream = new ZipInputStream(

                        new BufferedInputStream(inputStream));

                ZipEntry zipEntry = zipInputStream.getNextEntry();

                BufferedInputStream b = new BufferedInputStream(

                        zipInputStream);

                StreamLen = (int) zipEntry.getSize();

                while ((readCount = b.read(buffer)) != -1) {

                //    readCount = b.read(buffer);

                    output.write(buffer,0,readCount);

                    readSum = readSum + readCount;

                    publishProgress(readSum);

                }

                output.flush();

                output.close();

            } catch (IOException e) {

                e.printStackTrace();

            }

            return StreamLen;

        }


        @Override

        // 運行於UI線程。如果在doInBackground(Params...)

        // 中使用了publishProgress(Progress...)，就會觸發這個方法。在這裏可以對進度條控件根據進度值做出具體的響應。

        protected void onProgressUpdate(Integer... values) {

            super.onProgressUpdate(values);

            if (m_pDialog.getMax() != StreamLen)

                m_pDialog.setMax(StreamLen);

            m_pDialog.setProgress(values[0]);


        }


        @Override

        // 執行預處理，它運行於UI線程，可以爲後臺任務做一些準備工作，比如繪製一個進度條控件。

        protected void onPreExecute() {

            super.onPreExecute();


            m_pDialog = new ProgressDialog(mCtx);

            m_pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

            m_pDialog.setTitle("提示");

            m_pDialog.setMessage("正在升級數據庫,請勿關閉應用程序");

            m_pDialog.show();


        }


        @Override

        // 運行於UI線程，可以對後臺任務的結果做出處理，結果就是doInBackground(Params...)的返回值

        protected void onPostExecute(Integer result) {

            super.onPostExecute(result);

            m_pDialog.setProgress(result);

            m_pDialog.cancel();

            if (onDBInstalledListener != null)

                onDBInstalledListener.OnDBInstalled();

        }


    }   

   

    protected OnDBInstalledListener onDBInstalledListener;


   

    public void setOnDBInstalledListener(OnDBInstalledListener onDBInstalledListener) {

        this.onDBInstalledListener = onDBInstalledListener;

    }

   

    public void InstallDatabase() {

        mDbHelper = new DatabaseHelper(mCtx);

        SQLiteDatabase sdbreader = mDbHelper.getReadableDatabase();

        File dbfile = new File(sdbreader.getPath());

        if (dbfile.length()<4096){//依據數據庫大小判斷,是否需要執行安裝.暫時沒仔細想別的辦法

            DBDialogTask dialogTask = new DBDialogTask();

            dialogTask.execute(sdbreader.getPath());

        }else{

            if (onDBInstalledListener != null)

                onDBInstalledListener.OnDBInstalled(); //這裏可以委託一個方法,用以安裝完數據庫後的初始化工作

        }

    }


    public DBSourse open() throws SQLException {

        if( mDbHelper == null)

            mDbHelper = new DatabaseHelper(mCtx);

        if (mDb == null)

            mDb = mDbHelper.getWritableDatabase();

        if (!mDb.isOpen())

            mDb = mDbHelper.getWritableDatabase();

        return this;

    }


    public void close() {

        mDbHelper.close();

    }

   

    public Cursor GetSomeData() {

        return mDb.query("table",

                new String[] { "_id", "a1", "a2" }, "a1 = 1",

                null, null, null, "a2");

    }

   

    public interface OnDBInstalledListener{

        void OnDBInstalled();

    }

}




然後在需要調用數據庫的地方,創建此類,調用InstallDatabase方法.由線程從raw中解壓數據庫資源...爲了在數據庫安裝完成後執行某些操作還可以綁定方法OnDBInstalledListener

對了,忘記說了,將sqlite數據庫從ddms中導出後,用zip壓縮,然後存入raw文件夾即可.(別問我怎麼將文件壓縮成zip.還有別壓縮成rar格式.).至於當壓縮後的文件依然超過1M怎麼辦呢?我倒是沒琢磨,不過初步考慮有兩種方法:
1>分割壓縮後的文件(這個方法純屬於雜交...).
2>分卷壓縮.我傾向於這個辦法,不過沒有考慮如何實現.哪位大牛實現了,煩勞通告一下.呵呵