Viewpager, Cursor and Fragment

Question

I am new to the viewpager and was wondering if anyone could point me to a tutorial or source code of a project that uses a viewpager with fragments and a database. I\'ve see

Answer 1

You need to create abstract class adapter to use both cursor and pager adapter and extend to your own adapter and bind the view.

public abstract class CursorPagerAdapter extends PagerAdapter {

public static final String TAG = CursorPagerAdapter.class.getSimpleName();

protected WeakReference ctxRef;

protected boolean mDataValid;
protected boolean mAutoRequery;
protected Cursor mCursor;
protected int mRowIDColumn;

protected ChangeObserver mChangeObserver;
protected DataSetObserver mDataSetObserver;

/**
 * If set the adapter will call requery() on the cursor whenever a content change notification is
 * delivered. Implies {@link #FLAG_REGISTER_CONTENT_OBSERVER}.
 *
 * @deprecated This option is discouraged, as it results in Cursor queries being performed on the
 *             application's UI thread and thus can cause poor responsiveness or even Application
 *             Not Responding errors. As an alternative, use {@link android.app.LoaderManager} with
 *             a {@link android.content.CursorLoader}.
 */
@Deprecated
public static final int FLAG_AUTO_REQUERY = 0x01;

/**
 * If set the adapter will register a content observer on the cursor and will call {@link
 * # onContentChanged()} when a notification comes in. Be careful when using this flag: you will
 * need to unset the current Cursor from the adapter to avoid leaks due to its registered
 * observers. This flag is not needed when using a CursorAdapter with a {@link
 * android.content.CursorLoader}.
 */
public static final int FLAG_REGISTER_CONTENT_OBSERVER = 0x02;

public CursorPagerAdapter(Context context, Cursor c, int flags) {
    init(context, c, flags);
}

void init(Context context, Cursor c, int flags) {
    if ((flags & FLAG_AUTO_REQUERY) == FLAG_AUTO_REQUERY) {
        flags |= FLAG_REGISTER_CONTENT_OBSERVER;
        mAutoRequery = true;
    } else {
        mAutoRequery = false;
    }

    boolean cursorPresent = c != null;
    mCursor = c;
    mDataValid = cursorPresent;
    ctxRef = new WeakReference<>(context);
    mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;

    if ((flags & FLAG_REGISTER_CONTENT_OBSERVER) == FLAG_REGISTER_CONTENT_OBSERVER) {
        mChangeObserver = new ChangeObserver();
        mDataSetObserver = new MyDataSetObserver();
    } else {
        mChangeObserver = null;
        mDataSetObserver = null;
    }

    if (cursorPresent) {
        if (mChangeObserver != null) {
            c.registerContentObserver(mChangeObserver);
        }

        if (mDataSetObserver != null) {
            c.registerDataSetObserver(mDataSetObserver);
        }
    }
}

public Cursor getCursor() {
    return mCursor;
}

@Override
public int getCount() {
    if (mDataValid && mCursor != null)
        return mCursor.getCount();
    else
        return 0;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    if (!mDataValid) {
        throw new IllegalStateException("this should only be called when the cursor is valid");
    }

    if (!mCursor.moveToPosition(position)) {
        throw new IllegalStateException("couldn't move cursor to position " + position);
    }

    Context context = ctxRef.get();
    if (context != null) {
        View v = newView(context, mCursor, (ViewGroup) container);
        bindView(v, context, mCursor);

        ((ViewPager) container).addView(v);

        return v;
    } else {
        throw new IllegalStateException("context is null");
    }
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    ((ViewPager) container).removeView((View) object);
}

@Override
public int getItemPosition(Object object) {
    return POSITION_NONE;
}

@Override
public boolean isViewFromObject(View view, Object o) {
    return view == o;
}

public abstract View newView(Context context, Cursor cursor, ViewGroup parent);

public abstract void bindView(View view, Context context, Cursor cursor);

public void changeCursor(Cursor cursor) {
    Cursor old = swapCursor(cursor);
    if (old != null) {
        old.close();
    }
}

public Cursor swapCursor(Cursor newCursor) {
    if (newCursor == mCursor) return null;

    Cursor oldCursor = mCursor;
    if (oldCursor != null) {
        if (mChangeObserver != null) {
            oldCursor.unregisterContentObserver(mChangeObserver);
        }
        if (mDataSetObserver != null) {
            oldCursor.unregisterDataSetObserver(mDataSetObserver);
        }
    }

    mCursor = newCursor;
    if (newCursor != null) {
        if (mChangeObserver != null) {
            newCursor.registerContentObserver(mChangeObserver);
        }

        if (mDataSetObserver != null) {
            newCursor.registerDataSetObserver(mDataSetObserver);
        }

        mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
        mDataValid = true;
        // notify the observers about the new cursor
        notifyDataSetChanged();
    } else {
        mRowIDColumn = -1;
        mDataValid = false;
        notifyDataSetChanged();
    }

    return oldCursor;
}

private void onContentChange() {
    if (mAutoRequery && mCursor != null && !mCursor.isClosed()) {
        mDataValid = mCursor.requery();
    }
}

private class ChangeObserver extends ContentObserver {

    public ChangeObserver() {
        super(new Handler());
    }

    /**
     *
     * @return True if self-change notifications should be delivered to the observer.
     */
    @Override
    public boolean deliverSelfNotifications() {
        return true;
    }

    /**
     * This method is called when a content change occurs.
     * @param selfChange
     */
    @Override
    public void onChange(boolean selfChange) {
        onContentChange();
    }
}

private class MyDataSetObserver extends DataSetObserver {

    @Override
    public void onChanged() {
        mDataValid = true;
        notifyDataSetChanged();
    }

    @Override
    public void onInvalidated() {
        mDataValid = false;
        notifyDataSetChanged();
    }
}

}

Sample Adapter (in kotlin):

class SampleAdapter(context: Context, cursor: Cursor?, autoQuery: Int): CursorPagerAdapter(context, cursor, autoQuery) {

internal var mContext: Context
internal var mLayoutInflater: LayoutInflater
internal var aQuery: AQuery
val imageWidth = Helper.getDisplayWidth(context)
init {
    mContext = context
    mLayoutInflater = mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
    aQuery = AQuery(context)
}

override fun newView(context: Context?, cursor: Cursor?, parent: ViewGroup?): View {
    return mLayoutInflater.inflate(R.layout.your_item_row, parent, false)
}

override fun bindView(view: View?, context: Context?, cursor: Cursor?) {
    val sampleVo = SampleVo.getValueFromCursor(cursor)
    val tvTitle = view?.findViewById(R.id.tvTitle)
    tvTitle?.text = sampleVo.title
}

Original Source: link