Question

片段照片：这是一个观察者内部的碎片，它本身就是一个活动视角的片段。情况是这样的：

我有一个有观察者的活动，在这个观察者里面有5个片段。在第二个片段（FRAGMENT_GALLERY）中，我有一个另一个VIEWPAGER。在这个观察者内部，我有一个片段名为FRAGMENT_PHOTOS，在这片中（FRAGMENT_PHOTOS）有一个GRIDVIEW，我只能在第一次使用IMAGEADAPTER打开应用程序（IMAGEADAPTER是扩展BASEADAPTER）。当我导航到非常接近的碎片或非常早期的碎片时，也会留下人群（显示图像）。但是，当我导航到其他一些片段（说＃4或＃5）并回到这片片段（片段照片）时，GRIDVIEW没有获得人口或没有显示图像（根据我的诊断，IMAGEADAPTER没有得到再次调用）。它只会被打开（当我们打开APP时）。请帮帮我......

当应用程序打开时，viewpager片段内的Girdview正常工作，imageadapter首次填充其中的图像。
现在，当我导航到下一个片段并返回相同的片段（FragmentPhotos）时，gridview正确显示图像..

但是当我导航到另一个片段（比如＃4或＃5）时，FragmentPhotos中的gridview不显示图像。根据我的诊断，imageadapter没有再给予回复

公共类FragmentPhotos扩展片段{

private GridView gridView;
private Bitmap[] thumbnails;
private ImageAdapter imageAdapter;
private DisplayMetrics display;
private ArrayList<String> imagesArrayList = new ArrayList<String>();
private ArrayList<String> foldersArrayList = new ArrayList<String>();
private View rootView;
private final int REQUEST_CODE=1;
private ImageView imgEnlarged;
private GetImagesFromCard imagesFromCardTask;
private Context context;

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    rootView = inflater.inflate(R.layout.fragment_photos, container, false);
    initUI(rootView);
    return rootView;
}

public void initGallery()
{
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
        requestPermissions(AppClass.INITIAL_PERMS, REQUEST_CODE);
    }
    else
    {
        if (imagesFromCardTask.getStatus().equals(AsyncTask.Status.RUNNING))
        {

        }
        else
        {
            imageAdapter = new ImageAdapter(context);
            gridView.setAdapter(imageAdapter);
            new GetImagesFromCard().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        }
    }
}

@Override
public void onStart() {
    context = this.getActivity();
    imagesFromCardTask = new GetImagesFromCard();
    super.onStart();
}

public void disableGalleryTask()
{
    if (imagesFromCardTask.getStatus()==GetImagesFromCard.Status.RUNNING)
    {
        imagesFromCardTask.cancel(true);
    }
}

private void initUI(View view) {
    display = new DisplayMetrics();
    getActivity().getWindowManager().getDefaultDisplay().getMetrics(display);
    gridView = (GridView) view.findViewById(R.id.gridGallery);
    imgEnlarged = (ImageView)view.findViewById(R.id.imgEnlarged);
    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            showImageEnlarged(position);
        }
    });
    Log.e("","Gallery initialized");
}

private class GetImagesFromCard extends AsyncTask<Void,LoadedImage,Void>
{
    Bitmap bitmap;
    ArrayList<LoadedImage> bitmapArrays=new ArrayList<LoadedImage>();

    @Override
    protected Void doInBackground(Void... params) {
        Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
        String[] projection = {MediaStore.Images.Media.DATE_TAKEN,MediaStore.Images.Media._ID,MediaStore.Images.Thumbnails._ID,MediaStore.Images.Thumbnails.DATA,MediaStore.Images.Media.DATE_TAKEN};
        String orderBy = MediaStore.Images.Media.DATE_TAKEN + " DESC";
        Cursor cursor = getActivity().getContentResolver().query(uri, projection, null, null, orderBy);
        int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);
        int size = cursor.getCount();
        if (size==0)
        {

        }
        int imageId =0;
        int i=0;
        while (i<size && !isCancelled())
        {
            cursor.moveToPosition(i);
            imageId = cursor.getInt(columnIndex);
            uri = Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + imageId);
            publishProgress(new LoadedImage(uri.toString()));
            if (i==0)
            {
                showImageEnlarged(uri);
            }
            i++;
        }
        cursor.close();
        return null;
    }

    @Override
    protected void onProgressUpdate(LoadedImage... values) {
        super.onProgressUpdate(values);
        for (LoadedImage photo: values)
        {
            imageAdapter.addPhoto(photo);
            imageAdapter.notifyDataSetChanged();
            bitmapArrays.add(photo);
        }
    }

    @Override
    protected void onCancelled() {
        Log.e("","Task Cancelled");
        super.onCancelled();
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode)
    {
        case REQUEST_CODE:
        {
            for (int i=0;i<grantResults.length;i++)
            {
                if (grantResults.length > 0 && grantResults[i] == PackageManager.PERMISSION_GRANTED)
                {
                    Log.e("Permission Granted", permissions[i]);
                }
            }
            new GetImagesFromCard().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
            break;
        }
    }
}

}

以下是我的ImageAdapter：

public class ImageAdapter extends BaseAdapter
{

    ImageLoader imageLoader;
    Context context;
    LayoutInflater inflater;
    private DisplayImageOptions options;
    ImageLoaderConfiguration config;
    ArrayList<LoadedImage> bitmapString;
    public ImageAdapter(Context context)
    {
        Log.e("","ImageAdapter called");
        DisplayImageOptions options = new DisplayImageOptions.Builder()
                .cacheInMemory(true)
                .cacheOnDisc(true)
                .considerExifParams(true)
                .build();

        this.context = context;
        inflater = LayoutInflater.from(context);
        bitmapString = new ArrayList<LoadedImage>();

        config = new ImageLoaderConfiguration.Builder(context)
                .threadPriority(Thread.MAX_PRIORITY)
                .denyCacheImageMultipleSizesInMemory()
                .defaultDisplayImageOptions(options)
                .tasksProcessingOrder(QueueProcessingType.FIFO)
                .build();

    }

    public void addPhoto(LoadedImage photo)
    {
        bitmapString.add(photo);
    }

    public void clear()
    {
        bitmapString.clear();
    }

    public void remove(int index)
    {
        bitmapString.remove(index);
    }

    @Override
    public int getCount() {
        return bitmapString.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        View view = convertView;
        final ViewHolder holder;
        if(convertView==null)
        {
            holder=new ViewHolder();
            view = inflater.inflate(R.layout.fragment_photos_grid_items,parent,false);
            holder.imageView = (ImageView)view.findViewById(R.id.imgGallery);
            holder.imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            view.setTag(holder);
        }
        else
        {
            holder = (ViewHolder)view.getTag();
        }
        imageLoader = ImageLoader.getInstance();
        imageLoader.init(config);
        imageLoader.displayImage(bitmapString.get(position).getImgString(),holder.imageView,options);
        return view;
    }

    class ViewHolder
    {
        ImageView imageView;
    }
}

以下是我的ViewPager适配器：

public class GalleryViewPagerAdapter extends FragmentStatePagerAdapter {
    private final List<Fragment> mFragments = new ArrayList<>();
    private final List<String> mFragmentTitles = new ArrayList<>();
    int numOfTabs;

    public GalleryViewPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    public void addFragment(Fragment fragment, String title)
    {
        mFragments.add(fragment);
        mFragmentTitles.add(title);
    }



    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }

    @Override
    public int getCount() {
        return mFragments.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitles.get(position);
    }
}

Answer 1

请勿在{{1}}内使用getActivity()，因为可能尚未创建活动。获取onCreateView()中的上下文。此外，由于您的onActivityCreated()方法使用了上下文，因此您必须在InitUI(view)中调用该方法。

编辑1： 致电onActivityCreated()中的initGallery()或片段中的onStart()。并在onResume()或disableGalleryTask()片段中调用onPause()。

因此，当用户可以看到视图时，只会调用onStop()。

Answer 2

在片段中的以下overriden方法中调用initGallery（）方法：

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser){
       initGallery();
    }
}

Answer 3

问题解决了!!!

实际上，当我添加这个片段（FragmentPhotos - 携带gridview）时，在viewpager中以错误的方式添加了 -

ViewPagerAdapter adapter = new ViewPagerAdapter(getFragmentManager()); //删除此

//添加此

ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager());

非常感谢大家的帮助..

在ViewPager中销毁Fragment后，不会调用ImageAdapter扩展BaseAdapter

3 个答案: