Question

出于某种原因，每当我尝试通过模拟器或某些手机（在大多数手机上工作）将我的资产文件夹中的数据库复制到数据库时，我都会崩溃。我把它缩小到这段代码。

        //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();

继承人帮助类的全部代码

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);
}

代码运行正常，直到它到达实际的while循环。根本没有进入循环，只是在具有IO异常的while行崩溃。我不知道这意味着什么，我不是很熟悉InputStream和OutputStream所以我不知道问题是什么。适用于我的Droid X和Droid 2，但不适用于Droid 1或LG670。有人有什么想法吗？

继承堆栈跟踪：

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：我也遇到了另一个具有相同代码的应用程序的问题（实际上）。复制数据库时不会出现异常。它复制整个数据库，但随后决定不在数据库中放置任何内容。所以它读取3072个字节，但其中唯一的表是android_metadata表。我真的很困惑。这个字节数组是否会导致问题？

Answer 1

我想出了问题。在Gingerbread之前，Android不允许您从assets文件夹访问大于1GB的文件。所以，我只是将这些文件分段，然后创建了一个循环遍历它们的方法，并在运行时将htem重新组合在一起。

InputStream在循环中崩溃

1 个答案: