我的 Listview 太慢了。并在向上滚动时崩溃

Question

我有一个应用程序，其 ListView 有 15 行。如果有新的查询要搜索，我将 adapter 设置为 null 并清除 Allvideos 变量并使用

创建一个新查询

`new ArrayList();

当用户点击最后一行“更多结果”时，我将项目添加到Allvideos。但是在我的应用程序中进行一些搜索并将该项目添加到列表后，我的应用程序运行缓慢，当我尝试向上滚动时它崩溃了。这是我的Adapter

public class VideosAdapter extends BaseAdapter {

// The list of videos to display
public static List<Video> videos;
// An inflator to use when creating rows
private LayoutInflater mInflater;
private Context context;

/**
 * @param context this is the context that the list will be shown in - used to create new list rows
 * @param videos this is a list of videos to display
 */
public VideosAdapter(Context context, List<Video> videos) {
    VideosAdapter.videos = videos;
    this.mInflater = LayoutInflater.from(context);
    this.context = context;
}

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

@Override
public Object getItem(int position) {
    return videos.get(position);
}

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

public Object getItem(int position) {
    return videos.get(position);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    final Video video = videos.get(position);
    ViewHolder viewHolder;
    if(video.getTitle()==null && video.getDuration()==-1)
    {
        convertView = mInflater.inflate(R.layout.more_results, null);
        View thumbnail = convertView.findViewById(R.id.thumbnail);
        thumbnail.setVisibility(View.INVISIBLE);
        return convertView;
    }
        //animation = AnimationUtils.loadAnimation(context, R.anim.push_up_in);
            // If convertView wasn't null it means we have already set it to our list_item_user_video so no need to do it again
    else if(convertView == null){
        convertView = mInflater.inflate(R.layout.list_item_user_video, null);
        viewHolder = new ViewHolder();
        viewHolder.thumb = (UrlImageView) convertView.findViewById(R.id.list_image);
        viewHolder.duration=(TextView) convertView.findViewById(R.id.duration);
        viewHolder.title = (TextView) convertView.findViewById(R.id.userVideoTitleTextView);

        convertView.setTag(viewHolder);
    }
    else{
        // we've just avoided calling findViewById() on resource everytime
        // just use the viewHolder
        viewHolder = (ViewHolder) convertView.getTag();
        }
    // We are using a custom imageview so that we can load images using urls
    // For further explanation see: http://blog.blundell-apps.com/imageview-with-loading-spinner/

    //TextView size=(TextView) convertView.findViewById(R.id.size);




    int durationmin=video.getDuration()/60;
    int durationsec=video.getDuration()%60;

    if(durationsec<10) viewHolder.duration.setText(durationmin+":0"+durationsec);
    else{
        viewHolder.duration.setText(durationmin+":"+durationsec);
    }
     // thumb image

    // Get a single video from our list
    // Set the image for the list item
    viewHolder.thumb.setImageDrawable(video.getThumbUrl());
    // Set the title for the list item

    //ytapi.com düzelene kadar böyle kalacak.

    //size.setText(df.format(MainActivity.getSizeOf(MainActivity.getDownloadUrl(videoid)))+" MMB");

    viewHolder.title.setText(video.getTitle());

    /*animation.setDuration(1000);
    convertView.startAnimation(animation);
    animation = null;*/

    return convertView;
}

我将项目添加到列表并使用此代码设置适配器。

    if(Allvideos.isEmpty())
    {
        Allvideos=videos;
    }
    else
    {
        //Remove extra more results row 
        Allvideos.remove(Allvideos.size()-1);
        for(int i=0;i<videos.size();i++)
        {
            Allvideos.add(videos.get(i));

        }
    }   

    VideosAdapter adapter = new VideosAdapter(getContext(), Allvideos);
    //adapter.notifyDataSetChanged();
    setAdapter(adapter);

我的logcat是这样的。

08-22 15:53:40.557: E/InputEventReceiver(619): Exception dispatching input event.
08-22 15:53:40.657: E/AndroidRuntime(619): FATAL EXCEPTION: main
08-22 15:53:40.657: E/AndroidRuntime(619): java.lang.NullPointerException
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.skymaster.tut.ui.adapter.VideosAdapter.getView(VideosAdapter.java:108)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.AbsListView.obtainView(AbsListView.java:2255)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.ListView.makeAndAddView(ListView.java:1769)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.ListView.fillUp(ListView.java:706)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.ListView.fillGap(ListView.java:645)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5040)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3197)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.widget.AbsListView.onTouchEvent(AbsListView.java:3471)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.View.dispatchTouchEvent(View.java:7127)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2170)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1905)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919)
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1925)
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1379)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.app.Activity.dispatchTouchEvent(Activity.java:2396)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.support.v7.app.ActionBarActivityDelegateICS$WindowCallbackWrapper.dispatchTouchEvent(ActionBarActivityDelegateICS.java:268)
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1873)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.View.dispatchPointerEvent(View.java:7307)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3174)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3119)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4155)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4134)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4226)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:171)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:163)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4205)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4245)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.Choreographer.doCallbacks(Choreographer.java:555)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.Choreographer.doFrame(Choreographer.java:523)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.os.Handler.handleCallback(Handler.java:615)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.os.Handler.dispatchMessage(Handler.java:92)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.os.Looper.loop(Looper.java:137)
08-22 15:53:40.657: E/AndroidRuntime(619):  at android.app.ActivityThread.main(ActivityThread.java:4745)
08-22 15:53:40.657: E/AndroidRuntime(619):  at java.lang.reflect.Method.invokeNative(Native Method)
08-22 15:53:40.657: E/AndroidRuntime(619):  at java.lang.reflect.Method.invoke(Method.java:511)
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-22 15:53:40.657: E/AndroidRuntime(619):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-22 15:53:40.657: E/AndroidRuntime(619):  at dalvik.system.NativeStart.main(Native Method)

并且在这一行出现错误 java:108 我从 site(video.getDuration()) 获取持续时间，它的第二种类型是 360 秒而不是 6 分钟。

duration.setText(durationmin+":"+durationsec);  

为了平滑滚动，我使用了ViewHolder，但它并没有解决我的问题。正如您在我的代码中看到的那样，我的每一行布局中都有URLIMAGEVIEW。使用此项目，我从 url 为每一行加载不同的图像。并且在加载图像时，微调器会出现，直到加载完成。 URLIMAGEVIEW 也在另一个 Thread 中，而不是 ui Thread。 URLIMAGEVIEW 会是我的应用出错或拖慢的原因吗？

Answer 1

为什么要将视频作为静态字段；没有必要，这是一种不好的做法。

此外，在显示列表中的项目时，考虑扩展ArrayAdapter 而不是BaseAdapter；这样你只需要覆盖getView；而不是 getPosition、getCount 等。

if(Allvideos.isEmpty())
{
    Allvideos=videos;
}
else
{
    //Remove extra more results row 
    Allvideos.remove(Allvideos.size()-1);

考虑在此处使用页脚，而不是每次都添加和删除最后一项。作为奖励，它使您的 getView 方法更简单。

    for(int i=0;i<videos.size();i++)
    {
        Allvideos.add(videos.get(i));

您可能想查看 addAll 方法。

    }
}   

VideosAdapter adapter = new VideosAdapter(getContext(), Allvideos);

您不需要每次都重新创建适配器。相反，请执行以下操作：

//fields
private ArrayList<Video> videos;
private ArrayAdapter mAdapter;
private View footer;

protected void onCreate(Bundle savedInstanceState) {
    ListView list = findViewById(R.id.list);
    footer = getLayoutInflater().inflate(R.layout.more_results, null);
    list.addFooterView(footer);
    videos = new ArrayList<Video>
    mAdapter = new VideosAdapter(this, videos);
    list.setAdapter(mAdapter);
}

public addItemsToList(List<Video> items){
    videos.addAll(items);
    mAdapter.notifyDataSetChanged();
}

作为奖励，页脚始终位于列表的末尾。如果你想删除它，你可以切换页脚的可见性，这也很好。

关于您的错误；添加页脚时，问题将得到解决。当前问题是由您的 moreResults 布局引起的。

convertView = mInflater.inflate(R.layout.more_results, null);
View thumbnail = convertView.findViewById(R.id.thumbnail);
thumbnail.setVisibility(View.INVISIBLE);
return convertView;

请注意，如果您的适配器下次尝试回收此视图，则 convertView 不会为空；但是，这里没有设置标签。因此，会发生 nullPointerException。

Answer 2

我认为你在某些 if 块中错过了 convertView.setTag(viewHolder)。因为这个 viewHolder 为空。

Answer 3

我在两个文本行上的列表视图和每行的图像上遇到了同样的问题。我发现问题在于图像的尺寸。尽管文件大小非常小，但尺寸却很高（大约 1600x1600）。我只是在 Photoshop 中减小了尺寸（大约 512x512），现在它可以毫无延迟地滚动。