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:
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import java.io.BufferedInputStream;
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import java.io.File;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.OutputStream;
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import java.util.zip.ZipEntry;
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import java.util.zip.ZipInputStream;
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import android.app.ProgressDialog;
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import android.content.Context;
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import android.database.Cursor;
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import android.database.SQLException;
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import android.database.sqlite.SQLiteDatabase;
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import android.database.sqlite.SQLiteOpenHelper;
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import android.os.AsyncTask;
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public class DBSourse {
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private static final String DATABASE_NAME = "Test.db";
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private static final int DATABASE_VERSION = 1;
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private DatabaseHelper mDbHelper;
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private SQLiteDatabase mDb;
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private final Context mCtx;
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private static int mDBRawResource = 0;
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public DBSourse(Context ctx,int DBRawResource) {
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this.mCtx = ctx;
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mDBRawResource = DBRawResource;
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}
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public DBSourse(Context ctx) {
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this.mCtx = ctx;
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if (mDBRawResource == 0)
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new Exception("必須指定以zip壓縮的數據庫Raw文件");
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}
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public static class DatabaseHelper extends SQLiteOpenHelper {
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DatabaseHelper(Context context) {
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super(context, DATABASE_NAME, null, DATABASE_VERSION);
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}
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@Override
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public void onCreate(SQLiteDatabase db) {
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}
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@Override
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public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
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}
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}
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class DBDialogTask extends AsyncTask<String, Integer, Integer> {
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ProgressDialog m_pDialog;
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int StreamLen;
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@Override
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protected Integer doInBackground(String... params) { // 後臺進程執行的具體計算在這裏實現
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String dbPathString = params[0];
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int len = 1024;//
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int readCount = 0, readSum = 0;
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byte[] buffer = new byte[len];
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InputStream inputStream;
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OutputStream output;
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try {
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inputStream = mCtx.getResources().openRawResource(mDBRawResource); //這裏就是Raw文件引用位置
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output = new FileOutputStream(dbPathString);
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ZipInputStream zipInputStream = new ZipInputStream(
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new BufferedInputStream(inputStream));
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ZipEntry zipEntry = zipInputStream.getNextEntry();
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BufferedInputStream b = new BufferedInputStream(
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zipInputStream);
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StreamLen = (int) zipEntry.getSize();
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while ((readCount = b.read(buffer)) != -1) {
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// readCount = b.read(buffer);
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output.write(buffer,0,readCount);
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readSum = readSum + readCount;
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publishProgress(readSum);
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}
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output.flush();
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output.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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return StreamLen;
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}
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@Override
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// 運行於UI線程。如果在doInBackground(Params...)
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// 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。
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protected void onProgressUpdate(Integer... values) {
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super.onProgressUpdate(values);
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if (m_pDialog.getMax() != StreamLen)
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m_pDialog.setMax(StreamLen);
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m_pDialog.setProgress(values[0]);
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}
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@Override
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// 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。
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protected void onPreExecute() {
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super.onPreExecute();
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m_pDialog = new ProgressDialog(mCtx);
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m_pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
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m_pDialog.setTitle("提示");
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m_pDialog.setMessage("正在升級數據庫,請勿關閉應用程序");
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m_pDialog.show();
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}
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@Override
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// 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
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protected void onPostExecute(Integer result) {
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super.onPostExecute(result);
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m_pDialog.setProgress(result);
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m_pDialog.cancel();
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if (onDBInstalledListener != null)
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onDBInstalledListener.OnDBInstalled();
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}
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}
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protected OnDBInstalledListener onDBInstalledListener;
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public void setOnDBInstalledListener(OnDBInstalledListener onDBInstalledListener) {
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this.onDBInstalledListener = onDBInstalledListener;
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}
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public void InstallDatabase() {
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mDbHelper = new DatabaseHelper(mCtx);
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SQLiteDatabase sdbreader = mDbHelper.getReadableDatabase();
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File dbfile = new File(sdbreader.getPath());
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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
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DBDialogTask dialogTask = new DBDialogTask();
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dialogTask.execute(sdbreader.getPath());
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}else{
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if (onDBInstalledListener != null)
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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
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}
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}
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public DBSourse open() throws SQLException {
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if( mDbHelper == null)
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mDbHelper = new DatabaseHelper(mCtx);
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if (mDb == null)
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mDb = mDbHelper.getWritableDatabase();
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if (!mDb.isOpen())
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mDb = mDbHelper.getWritableDatabase();
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return this;
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}
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public void close() {
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mDbHelper.close();
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}
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public Cursor GetSomeData() {
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return mDb.query("table",
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new String[] { "_id", "a1", "a2" }, "a1 = 1",
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null, null, null, "a2");
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}
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public interface OnDBInstalledListener{
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void OnDBInstalled();
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}
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}
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
有事兒聯繫.完事.