Question

目前我收到的错误消息是无法打开该文件。我试图做的就是打开我的数据库，打开我的表并从中提取信息。以下是我到目前为止：

public class MainActivity extends Activity
{
private static final String DATABASE_NAME = "ExerciseDatabase.db";
private static final String DATABASE_TABLE = "ExerciseList";

SQLiteDatabase myDatabase;

private void openDatabase(){
    myDatabase = openOrCreateDatabase("/databaseManipulation/assets/" + DATABASE_NAME, Context.MODE_PRIVATE, null);

}

protected void onCreate(Bundle savedInstanceState) {      
openDatabase();
Cursor allData = myDatabase.rawQuery("SELECT * FROM ExerciseList", null);
Log.e("TESTLOG", allData.toString());

}
}

根据我的阅读，似乎建议创建一个新数据库并用现有数据库覆盖它，任何帮助都会很棒

Answer 1

添加此功能

public void CopyDB(InputStream inputStream, 
            OutputStream outputStream) throws IOException {
                //---copy 1K bytes at a time---
                byte[] buffer = new byte[1024];
                int length;
                while ((length = inputStream.read(buffer)) > 0) {
                    outputStream.write(buffer, 0, length);
                }
                inputStream.close();
                outputStream.close();
            }

使用此代码

try {
        String destPath = "/data/data/" + getPackageName() +
            "/databases";
        File f = new File(destPath);
        if (!f.exists()) {              
            f.mkdirs();
            f.createNewFile();

            //---copy the db from the assets folder into 
            // the databases folder---
            CopyDB(getBaseContext().getAssets().open("MyDB"),
                new FileOutputStream(destPath + "/MyDB"));
            Log.i("esfandune", "esfandune");
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 2

您可以尝试这样的事情

public class SystemHelper{

private final String DB_PATH;
private final String DB_NAME;
private final Context mContext;
private SQLiteDatabase mDataBase;

public SystemHelper(Context context) {
    super(context, "YOUR_DB_NAME_IN_ASSETS.db", null, 1);
    DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
    DB_NAME = "YOUR_DB_NAME_IN_ASSETS.db";
    mContext = context;
    createDataBase();
    openDataBase();
}

public void createDataBase() {
    try {
        boolean mDataBaseExist = checkDataBase();
        this.getReadableDatabase();
        this.close();
        if (!mDataBaseExist) {
            Files.copyFromAssets(mContext, DB_NAME, DB_PATH);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private boolean checkDataBase() {
    File dbFile = new File(DB_PATH + DB_NAME);
    return dbFile.exists();
}

@Override
public void onCreate(SQLiteDatabase db) {

}

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

}

@Override
public SQLiteDatabase getWritableDatabase() {
    return mDataBase;
}

@Override
public synchronized void close() {
    if (mDataBase != null)
        mDataBase.close();
    super.close();
}

public void openDataBase() {
    String mPath = DB_PATH + DB_NAME;
    mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.OPEN_READWRITE);
}
}

和Files.copyFromAssets（mContext，DB_NAME，DB_PATH）方法：

public static void copyFromAssets(Context context, String fileName, String path) {
    InputStream mInput = null;
    try {
        mInput = context.getAssets().open(fileName);
        File f = new File(path + fileName);
        if (!f.exists())
            f.createNewFile();
        OutputStream mOutput = new FileOutputStream(f);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer)) > 0) {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

打开使用SQLiteStudio创建的现有数据库

2 个答案: