Android 在Viewpager中加载图像

我在viewpager中有3个片段LeftFragment、MidFragment和Right fragment LeftFragment包含一个listview，当单击listview项时，图像将加载到MidFragment上。我遇到了一个bug，花了很多时间，但仍然没有解决。这是我的密码：

左框架网

public class LeftFragment extends Fragment{
    private  ListView listView;
    private List<ParseObject> ob;
    private ProgressDialog mProgressDialog;
    private ListViewAdapter adapter;
    private List<School> schoollist = null;
    private View v;
    MainActivity mainActivity = new MainActivity();
    MidFragment midFragment = new MidFragment();
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        v = inflater.inflate(R.layout.left_fragment, container, false);
        initComponent();
        new RemoteDataTask().execute();
        return v;
    }

    private void initComponent() {
        listView = (ListView)v.findViewById(R.id.lv_left);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                mainActivity.viewPager.setCurrentItem(1);
                School school = schoollist.get(position);
//                midFragment.index = Integer.parseInt(school.getIndex());
                midFragment.reloadData(Integer.parseInt(school.getIndex()));
            }
        });
    }

    private class RemoteDataTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mProgressDialog = new ProgressDialog(getActivity());
            // Create a progressdialog
            mProgressDialog = new ProgressDialog(getActivity());
            // Set progressdialog title
            mProgressDialog.setTitle("Please wait a moment...");
            // Set progressdialog message
            mProgressDialog.setMessage("Loading...");
            mProgressDialog.setIndeterminate(false);
            // Show progressdialog
            mProgressDialog.show();
        }

        @Override
        protected Void doInBackground(Void... params) {
            schoollist = new ArrayList<School>();
            try{
                ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("School");
                query.orderByAscending("index");
                ob = query.find();
                for (ParseObject name : ob){
                    School map = new School();
                    map.setIndex(String.valueOf(name.get("index")));
                    map.setCount(String.valueOf(name.get("count")));
                    map.setName(String.valueOf(name.get("name")));
                    schoollist.add(map);
                }
            } catch (ParseException e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            adapter = new ListViewAdapter(getActivity(), schoollist);
            listView.setAdapter(adapter);
            mProgressDialog.dismiss();
            super.onPreExecute();
        }
    }
}

中段

public class MidFragment extends Fragment {
    //    private ProgressDialog mProgressDialog;
    private ImageView mImageView;
    private VideoView mVideoView;
    private DisplayImageOptions options;
    private ImageLoader imageLoader = ImageLoader.getInstance();
    private Context mContext;
    private ImageLoadingListener animateFirstListener;
    private ArrayList<ParseObject> objectList = new ArrayList<>();
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
//          imageLoader.init(ImageLoaderConfiguration.createDefault(mContext));
//          mImageLoader = ImageLoader.getInstance();
        options = new DisplayImageOptions.Builder()
                .cacheInMemory(true)
                .cacheOnDisk(true)
                .considerExifParams(true)
                .build();
        animateFirstListener = new AnimateFirstDisplayListener();
    }
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.mid_fragment, container, false);


        initComponent(view);
        mContext = container.getContext();
        return view;

    }

    private void initComponent(View view) {
        mImageView = (ImageView) view.findViewById(R.id.image);
        mVideoView = (VideoView) view.findViewById(R.id.video);
        mImageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
        mVideoView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
//        mProgressDialog = new ProgressDialog(getActivity());
//        mProgressDialog.setTitle("Please wait a moment...");
//        mProgressDialog.setMessage("Loading...");
//        mProgressDialog.setIndeterminate(false);
    }

    public void reloadData(int index){
//        mProgressDialog.show();
        objectList.clear();
        ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Data");
        query.whereEqualTo("school",(Number)index);
        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> list, ParseException e) {
                objectList = (ArrayList<ParseObject>) list;
//                mProgressDialog.dismiss();
                if (!list.isEmpty())
                    openFirst();
            }
        });
    }


    private void openFirst(){
        ParseObject parseObject = objectList.get(0);
        ParseFile parseFile = parseObject.getParseFile("file");
        if (parseObject.getNumber("type") == (Number)1){

        }else{
//          mVideoView.setVisibility(View.GONE);
//          mImageView.setVisibility(View.VISIBLE);
            imageLoader.displayImage(parseFile.getUrl(), mImageView, options, animateFirstListener);
        }
    }
    private static class AnimateFirstDisplayListener extends SimpleImageLoadingListener {

        static final List<String> displayedImages = Collections.synchronizedList(new LinkedList<String>());

        @Override
        public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
            if (loadedImage != null) {
                ImageView imageView = (ImageView) view;
                boolean firstDisplay = !displayedImages.contains(imageUri);
                if (firstDisplay) {
                    FadeInBitmapDisplayer.animate(imageView, 500);
                    displayedImages.add(imageUri);
                }
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <VideoView
        android:id="@+id/video"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:visibility="gone" />

    <ImageView
        android:id="@+id/image"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:contentDescription="@string/app_name" />

</RelativeLayout>

布局中段

public class MidFragment extends Fragment {
    //    private ProgressDialog mProgressDialog;
    private ImageView mImageView;
    private VideoView mVideoView;
    private DisplayImageOptions options;
    private ImageLoader imageLoader = ImageLoader.getInstance();
    private Context mContext;
    private ImageLoadingListener animateFirstListener;
    private ArrayList<ParseObject> objectList = new ArrayList<>();
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
//          imageLoader.init(ImageLoaderConfiguration.createDefault(mContext));
//          mImageLoader = ImageLoader.getInstance();
        options = new DisplayImageOptions.Builder()
                .cacheInMemory(true)
                .cacheOnDisk(true)
                .considerExifParams(true)
                .build();
        animateFirstListener = new AnimateFirstDisplayListener();
    }
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.mid_fragment, container, false);


        initComponent(view);
        mContext = container.getContext();
        return view;

    }

    private void initComponent(View view) {
        mImageView = (ImageView) view.findViewById(R.id.image);
        mVideoView = (VideoView) view.findViewById(R.id.video);
        mImageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
        mVideoView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
//        mProgressDialog = new ProgressDialog(getActivity());
//        mProgressDialog.setTitle("Please wait a moment...");
//        mProgressDialog.setMessage("Loading...");
//        mProgressDialog.setIndeterminate(false);
    }

    public void reloadData(int index){
//        mProgressDialog.show();
        objectList.clear();
        ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Data");
        query.whereEqualTo("school",(Number)index);
        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> list, ParseException e) {
                objectList = (ArrayList<ParseObject>) list;
//                mProgressDialog.dismiss();
                if (!list.isEmpty())
                    openFirst();
            }
        });
    }


    private void openFirst(){
        ParseObject parseObject = objectList.get(0);
        ParseFile parseFile = parseObject.getParseFile("file");
        if (parseObject.getNumber("type") == (Number)1){

        }else{
//          mVideoView.setVisibility(View.GONE);
//          mImageView.setVisibility(View.VISIBLE);
            imageLoader.displayImage(parseFile.getUrl(), mImageView, options, animateFirstListener);
        }
    }
    private static class AnimateFirstDisplayListener extends SimpleImageLoadingListener {

        static final List<String> displayedImages = Collections.synchronizedList(new LinkedList<String>());

        @Override
        public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
            if (loadedImage != null) {
                ImageView imageView = (ImageView) view;
                boolean firstDisplay = !displayedImages.contains(imageUri);
                if (firstDisplay) {
                    FadeInBitmapDisplayer.animate(imageView, 500);
                    displayedImages.add(imageUri);
                }
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <VideoView
        android:id="@+id/video"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:visibility="gone" />

    <ImageView
        android:id="@+id/image"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:contentDescription="@string/app_name" />

</RelativeLayout>

Logcat

05-28 15:41:56.116  19297-19297/animuco.com.ckemi E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: animuco.com.ckemi, PID: 19297
    java.lang.IllegalArgumentException: view must not be null
            at com.nostra13.universalimageloader.core.imageaware.ViewAware.<init>(ViewAware.java:70)
            at com.nostra13.universalimageloader.core.imageaware.ViewAware.<init>(ViewAware.java:50)
            at com.nostra13.universalimageloader.core.imageaware.ImageViewAware.<init>(ImageViewAware.java:44)
            at com.nostra13.universalimageloader.core.ImageLoader.displayImage(ImageLoader.java:365)
            at com.nostra13.universalimageloader.core.ImageLoader.displayImage(ImageLoader.java:340)
            at animuco.com.ckemi.Fragment.MidFragment.openFirst(MidFragment.java:119)
            at animuco.com.ckemi.Fragment.MidFragment.access$200(MidFragment.java:36)
            at animuco.com.ckemi.Fragment.MidFragment$3.done(MidFragment.java:101)
            at animuco.com.ckemi.Fragment.MidFragment$3.done(MidFragment.java:95)
            at com.parse.Parse$6$1.run(Parse.java:944)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:211)
            at android.app.ActivityThread.main(ActivityThread.java:5333)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1016)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:811)

我不确定，但我认为错误是由于更新了viewpager的视图 对不起，我英语不好

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感谢大家的关注

代码有一些问题。国际海事组织

您的片段包含对其活动的引用，您已经有了一个getActivity调用。 左片段包含对中间片段的引用-糟糕的做法。 在RemoteDataTask上，您可以在 onPostExecute方法，它通常未实现，但可能导致 你将来会犯错误。

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回答你的问题。您正在初始化位于左侧片段的一个新的MidFragment实例，该实例在MidFragment未开始其生命周期且未调用CreateView之前未连接到其他任何位置。LeftFragment正在使用的中间片段与ViewPager正在使用的中间片段不同。

您可以给自己一个更具体的解决方案不是，我很模糊，这是我使用androidStart的第一个项目，然后再次阅读我的答案。如果你还有问题的话。我很乐意回答