在使用来自 SQLite 数据库的数据的片段状态寻呼机适配器实现滑动界面期间崩溃

Question

我正在尝试实现一个滑动界面来滑动浏览包含图书列表的数据库。由于它来自数据库，因此我使用了 FragmentStatePagerAdapter。代码显示没有编译错误，但是一旦我多次滑动，应用程序就会崩溃代码：

public class swipeActivity extends AppCompatActivity {
//static int num_items;

bookAdapter mAdapter;
ViewPager mPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_swipe);

    mAdapter = new bookAdapter(getSupportFragmentManager(), this);
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setAdapter(mAdapter);


}

public static class bookAdapter extends FragmentStatePagerAdapter {
    private Context context;

    public bookAdapter(FragmentManager fm, Context c) {
        super(fm);
        context = c;
    }

    @Override
    public int getCount() {
        DBHandler db = new DBHandler(context);
        return db.getBookCount();
    }

    @Override
    public Fragment getItem(int position) {

        return ArrayListFragment.newInstance(position);
    }

}

public static class ArrayListFragment extends ListFragment {
    int mNum;
    private Cursor cursor;

    //ListView bookList;
    static ArrayListFragment newInstance(int num) {
        ArrayListFragment f = new ArrayListFragment();
        Bundle args = new Bundle();
        args.putInt("num", num);
        f.setArguments(args);

        return f;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mNum = getArguments() != null ? getArguments().getInt("num") : 1;
        DBHandler db = new DBHandler(getContext());
        cursor = db.getCursor();

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        cursor.moveToPosition(mNum);
        View v = inflater.inflate(R.layout.fragment_swipe, container, false);
        View tv = v.findViewById(R.id.textTitle);
        ((TextView) tv).setText(cursor.getString(1));
        tv = v.findViewById(R.id.textAuth);
        ((TextView) tv).setText(cursor.getString(2));
        tv = v.findViewById(R.id.textNos);
        ((TextView) tv).setText("Copies : " + cursor.getString(4));
        cursor.close();

        return v;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        /* stuff*/

    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        Log.i("FragmentList", "Item clicked: " + id);
    }
}
}

错误日志：

07-10 11:39:09.758 4081-4081/com.example.ajay_5674.library1 E/SQLiteLog: (14) cannot open file at line 32456 of [bda77dda96]

07-10 11:39:09.758 4081-4081/com.example.ajay_5674.library1 E/SQLiteLog: (14) os_unix.c:32456: (24) open(/data/user/0/com.example.ajay_5674.library1/databases/libraryInfo1-journal) - 07-10 11:39:09.758 4081-4081/com.example.ajay_5674.library1 E/SQLiteLog: (14) cannot open file at line 32456 of [bda77dda96]

07-10 11:39:09.758 4081-4081/com.example.ajay_5674.library1 E/SQLiteLog: (14) os_unix.c:32456: (24) open(/data/user/0/com.example.ajay_5674.library1/databases/libraryInfo1-journal) -

07-10 11:39:09.758 4081-4081/com.example.ajay_5674.library1 E/SQLiteLog: (14) statement aborts at 12: [SELECT * FROM library] unable to open database file 07-10 11:39:09.759 4081-4081/com.example.ajay_5674.library1 E/SQLiteQuery: exception: unable to open database file (code 14); query: SELECT * FROM library

07-10 11:39:09.759 4081-4081/com.example.ajay_5674.library1 D/AndroidRuntime: Shutting down VM

07-10 11:39:09.759 4081-4081/com.example.ajay_5674.library1 E/AndroidRuntime: FATAL EXCEPTION: main

Process: com.example.ajay_5674.library1, PID: 4081 android.database.sqlite.SQLiteCantOpenDatabaseException: unable to open database file (code 14)

编辑：发现问题。我专注于片段创建期间的查询，而在项目计数期间我没有注意到查询！固定为：

public static class bookAdapter extends FragmentStatePagerAdapter {
    private Context context;
    int num_items;
    public bookAdapter(FragmentManager fm, Context c) {
        super(fm);
        context = c;
        DBHandler db = new DBHandler(context);
        num_items = db.getBookCount();
        db.close();
    }

    @Override
    public int getCount() {

        //Log.d("Book Count :",Integer.toString(db.getBookCount()));
        return num_items;
    }

    @Override
    public Fragment getItem(int position) {

        Log.d("Book Position :",Integer.toString(position));
        return ArrayListFragment.newInstance(position);

    }

}

Answer 1

实际问题是 android.database.sqlite.SQLiteCantOpenDatabaseException: unable to open database file (code 14)，这是因为您正在创建 SQLite 数据库的多个实例。

您每次都在需要时创建一个 DBHandler。尝试减少 DBHandler 的实例。

并且您还在 onCreateView 中关闭光标并在 onCreate() 中创建它。这不好 practice.If 你在 onCreate 中打开游标，你应该在 onDestory() 中关闭它。

在使用来自 SQLite 数据库的数据的片段状态寻呼机适配器实现滑动界面期间崩溃

Crash during implementation of swipe interface using fragment state pager adapter with data from SQLite database

sqlite

android

swipe

android-fragments