java - 输入流在循环中崩溃

Question

出于某种原因，每当我尝试将数据库从 Assets 文件夹复制到模拟器或某些手机上的数据库(适用于大多数手机)时，我都会崩溃。我已将范围缩小到这段代码。

        //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open(DB_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();

这是辅助类的完整代码

public class NewDbHelper extends SQLiteOpenHelper {
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.bv.studyguide/databases/";
private static String DB_NAME = "studyguide.db";
private SQLiteDatabase myDataBase; 
private final Context myContext;
private static int DB_VERSION = 2;
private SQLiteDatabase db;
private Cursor cursor;

/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 */
public NewDbHelper(Context context) {

    super(context, DB_NAME, null, DB_VERSION);
    this.myContext = context;
}   

/**
 * Creates a empty database on the system and rewrites it with your own database.
 * */
public void createDataBase() throws IOException{

    boolean dbExist = checkDataBase();

    if (dbExist) { 
        Log.v("DB Exists", "db exists"); 
        // By calling this method here onUpgrade will be called on a 
        // writeable database, but only if the version number has been 
        // bumped 
        this.getWritableDatabase(); 
        } 

    dbExist = checkDataBase(); 

    if (!dbExist) { 
        // By calling this method and empty database will be created into 
        // the default system path of your application so we are gonna be 
        // able to overwrite that database with our database. 
        this.getReadableDatabase(); 
        try { 
            copyDataBase(); 
        } catch (IOException e) { 
            throw new Error("Error copying database"); 
        } 
    } 


}

/**
 * Check if the database already exist to avoid re-copying the file each time you open the application.
 * @return true if it exists, false if it doesn't
 */
private boolean checkDataBase(){

    SQLiteDatabase checkDB = null;

    try{
        String myPath = DB_PATH + DB_NAME;
        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(DB_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();

}

public void openDataBase() throws SQLException{

    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

}

@Override
public synchronized void close() {

        if(myDataBase != null)
            myDataBase.close();

        super.close();

}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE android_metadata (locale TEXT)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (newVersion > oldVersion) 
        Log.v("Database Upgrade","Database version higher than old.");
        myContext.deleteDatabase(DB_NAME);
}

代码运行良好，直到到达实际的 while 循环。根本不进入循环，只是在 while 行上崩溃并出现 IO 异常。我不知道这意味着什么，而且我不太熟悉 InputStream 和 OutputStream，所以我不知道问题可能是什么。在我的 Droid X 和 Droid 2 上运行良好，但在 Droid 1 或 LG670 上运行不佳。大家有什么想法吗？

这是堆栈跟踪:

java.lang.Error: Error copying database
at com.bv.studyguide.NewDbHelper.createDataBase(NewDbHelper.java:63)
at com.bv.studyguide.ArmyStudyGuide.onCreate(ArmyStudyGuide.java:39)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
at android.app.ActivityThread.access$2300(ActivityThread.java:125)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:893)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:651)
at dalvik.system.NativeStart.main(Native Method)

更新:我还遇到了另一个具有相同代码的应用程序的问题(实际上)。除了复制数据库时没有给出异常(exception)。它复制整个数据库，但随后决定不在数据库中放入任何内容。因此它读取了 3072 字节，但其中唯一的表是 android_metadata 表。我真的很困惑。这个字节数组是否导致了问题？

Answer 1

我找到了问题所在。在 Gingerbread 之前，Android 不允许您从资源文件夹访问大于 1GB 的文件。因此，我只是将文件分段，并创建了一个循环遍历它们并在运行时将文件重新组合在一起的方法。