如何在不使用notifyDataSetChanged()的情况下更新Listview中的某些数据？

Question

我正在尝试ListView使用下载任务列表创建一个.

下载任务在Service(DownloadService)中管理.每次接收到一大块数据时,任务通过a发送进度Broadcast,由Fragment包含ListView(SavedShowListFragment)的接收.收到Broadcast消息后,SavedShowListFragment将更新适配器和触发器中下载任务的进度notifyDataSetChanged().

列表中的每一行都包含a ProgressBar,a TextView表示正在下载的文件的标题,1表示进度的数值,a Button表示下载完成时暂停/恢复下载或播放保存的节目.

问题是暂停/恢复/播放Button通常没有响应(onClick()没有被调用),我认为这是因为整个列表都经常更新notifyDataSetChanged()(每次都有一大块数据,即收到1024字节,这可能是每秒多次,特别是当有多个下载任务正在运行时).

我想我可以在下载任务中增加数据块的大小,但我真的认为我的方法根本不是最优的!

可以经常打电话notifyDataSetChanged()让ListViewUI无响应吗？

有什么办法只更新一些Views的ListView行,即在我的情况ProgressBar和TextView与进步的数值,而不调用notifyDataSetChanged(),这将更新整个清单吗？

要更新下载任务的进度ListView,有没有比"getChunk/sendBroadcast/updateData/notifyDataSetChanged"更好的选项？

以下是我的代码的相关部分.

下载服务中的下载任务

public class DownloadService extends Service {

    //...

    private class DownloadTask extends AsyncTask<SavedShow, Void, Map<String, Object>> {

        //...

        @Override
        protected Map<String, Object> doInBackground(SavedShow... params) { 

            //...

            BufferedInputStream in = new BufferedInputStream(connection.getInputStream());

            byte[] data = new byte[1024];
            int x = 0;

            while ((x = in.read(data, 0, 1024)) >= 0) {

                if(!this.isCancelled()){
                    outputStream.write(data, 0, x);
                    downloaded += x;

                    MyApplication.dbHelper.updateSavedShowProgress(savedShow.getId(), downloaded);

                    Intent intent_progress = new Intent(ACTION_UPDATE_PROGRESS);
                    intent_progress.putExtra(KEY_SAVEDSHOW_ID, savedShow.getId());
                    intent_progress.putExtra(KEY_PROGRESS, downloaded );
                    LocalBroadcastManager.getInstance(DownloadService.this).sendBroadcast(intent_progress);         
                }
                else{
                    break;
                }
            }

            //...
        }

        //...
    }
}

SavedShowListFragment

public class SavedShowListFragment extends Fragment {   

    //...

    @Override
    public void onResume() {         
        super.onResume();

        mAdapter = new SavedShowAdapter(getActivity(), MyApplication.dbHelper.getSavedShowList());

        mListView.setAdapter(mAdapter);

        //...
    }


    private ServiceConnection mDownloadServiceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {

            // Get service instance

            DownloadServiceBinder binder = (DownloadServiceBinder) service;
            mDownloadService = binder.getService();

            // Set service to adapter, to 'bind' adapter to the service

            mAdapter.setDownloadService(mDownloadService);

            //...
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {

            // Remove service from adapter, to 'unbind' adapter to the service

            mAdapter.setDownloadService(null);
        }
    };


    private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {

            String action = intent.getAction();

            if(action.equals(DownloadService.ACTION_UPDATE_PROGRESS)){  
                mAdapter.updateItemProgress(intent.getLongExtra(DownloadService.KEY_SAVEDSHOW_ID, -1),
                        intent.getLongExtra(DownloadService.KEY_PROGRESS, -1));
            }

            //...
        }
    };

    //...

}

SavedShowAdapter

public class SavedShowAdapter extends ArrayAdapter<SavedShow> { 

    private LayoutInflater mLayoutInflater;

    private List<Long> mSavedShowIdList; // list to find faster the position of the item in updateProgress

    private DownloadService mDownloadService;

    private Context mContext;

    static class ViewHolder {
        TextView title;
        TextView status;
        ProgressBar progressBar;
        DownloadStateButton downloadStateBtn;
    }

    public static enum CancelReason{ PAUSE, DELETE };

    public SavedShowAdapter(Context context, List<SavedShow> savedShowList) {
        super(context, 0, savedShowList);       
        mLayoutInflater = (LayoutInflater) context.getSystemService( Context.LAYOUT_INFLATER_SERVICE ); 

        mContext = context;

        mSavedShowIdList = new ArrayList<Long>();

        for(SavedShow savedShow : savedShowList){
            mSavedShowIdList.add(savedShow.getId());
        }
    }

    public void updateItemProgress(long savedShowId, long progress){
        getItem(mSavedShowIdList.indexOf(savedShowId)).setProgress(progress);
        notifyDataSetChanged();
    }

    public void updateItemFileSize(long savedShowId, int fileSize){
        getItem(mSavedShowIdList.indexOf(savedShowId)).setFileSize(fileSize);
        notifyDataSetChanged();
    }


    public void updateItemState(long savedShowId, int state_ind, String msg){

        SavedShow.State state = SavedShow.State.values()[state_ind];

        getItem(mSavedShowIdList.indexOf(savedShowId)).setState(state);

        if(state==State.ERROR){
            getItem(mSavedShowIdList.indexOf(savedShowId)).setError(msg);
        }

        notifyDataSetChanged();
    }

    public void deleteItem(long savedShowId){
        remove(getItem((mSavedShowIdList.indexOf(savedShowId))));       
        notifyDataSetChanged();
    }

    public void setDownloadService(DownloadService downloadService){
        mDownloadService = downloadService;
        notifyDataSetChanged();
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {

        ViewHolder holder;
        View v = convertView;

        if (v == null) {

            v = mLayoutInflater.inflate(R.layout.saved_show_list_item, parent, false);

            holder = new ViewHolder();

            holder.title = (TextView)v.findViewById(R.id.title);
            holder.status = (TextView)v.findViewById(R.id.status);
            holder.progressBar = (ProgressBar)v.findViewById(R.id.progress_bar);
            holder.downloadStateBtn = (DownloadStateButton)v.findViewById(R.id.btn_download_state);

            v.setTag(holder);
        } else {
            holder = (ViewHolder) v.getTag();
        }

        holder.title.setText(getItem(position).getTitle());

        Integer fileSize = getItem(position).getFileSize();
        Long progress = getItem(position).getProgress();
        if(progress != null && fileSize != null){
            holder.progressBar.setMax(fileSize);

            holder.progressBar.setProgress(progress.intValue());

            holder.status.setText(Utils.humanReadableByteCount(progress) + " / " +
                    Utils.humanReadableByteCount(fileSize));
        }

        holder.downloadStateBtn.setTag(position);

        SavedShow.State state = getItem(position).getState();

        /* set the button state */

        //...

        /* set buton onclicklistener */

        holder.downloadStateBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                int position = (Integer) v.getTag();

                SavedShow.State state = getItem(position).getState();

                if(state==SavedShow.State.DOWNLOADING){

                    getItem(position).setState(SavedShow.State.WAIT_PAUSE);
                    notifyDataSetChanged();

                    mDownloadService.cancelDownLoad(getItem(position).getId(), CancelReason.PAUSE);

                }
                else if(state==SavedShow.State.PAUSED || state==SavedShow.State.ERROR){                 

                    getItem(position).setState(SavedShow.State.WAIT_DOWNLOAD);
                    notifyDataSetChanged();

                    mDownloadService.downLoadFile(getItem(position).getId());

                }
                if(state==SavedShow.State.DOWNLOADED){

                    /* play file */
                }

            }
        });

        return v;
    }
} 

Answer 1

当然,正如pjco所说,不要以那种速度更新.我建议每隔一段时间发送一次广播.更好的是,拥有一个容器来处理数据,例如进度,并通过轮询更新每个间隔.

但是,我认为有时更新listview是一件好事notifyDataSetChanged.实际上,当应用程序具有更高的更新频率时,这是最有用的.请记住:我并不是说您的更新触发机制是正确的.

解

基本上,您将需要更新特定位置notifyDataSetChanged.在以下示例中,我假设了以下内容:

1. 您的列表视图称为mListView.
2. 您只想更新进度
3. 您的convertView中的进度条具有ID R.id.progress

public boolean updateListView(int position, int newProgress) {
    int first = mListView.getFirstVisiblePosition();
    int last = mListView.getLastVisiblePosition();
    if(position < first || position > last) {
        //just update your DataSet
        //the next time getView is called
        //the ui is updated automatically
        return false;
    }
    else {
        View convertView = mListView.getChildAt(position - first);
        //this is the convertView that you previously returned in getView
        //just fix it (for example:)
        ProgressBar bar = (ProgressBar) convertView.findViewById(R.id.progress);
        bar.setProgress(newProgress);
        return true;
    }
}

笔记

这个例子当然不完整.您可以使用以下顺序:

1. 更新您的数据(当您收到新进度时)
2. 调用updateListView(int position)应使用相同的代码,但使用您的数据集并且不使用参数进行更新.

另外,我刚注意到你发布了一些代码.由于您使用的是Holder,您可以简单地将持有者放入功能中.我不会更新代码(我认为这是不言自明的).

最后,只是为了强调,更改整个代码以触发进度更新.一种快速的方法是改变你的服务:用if语句包裹发送广播的代码,该语句检查上次更新是否超过一秒或半秒以及下载是否已完成(无需检查完成但是确保完成后发送更新):

在您的下载服务中

private static final long INTERVAL_BROADCAST = 800;
private long lastUpdate = 0;

现在在doInBackground中,使用if语句包装发送的intent

if(System.currentTimeMillis() - lastUpdate > INTERVAL_BROADCAST) {
    lastUpdate = System.currentTimeMillis();
    Intent intent_progress = new Intent(ACTION_UPDATE_PROGRESS);
    intent_progress.putExtra(KEY_SAVEDSHOW_ID, savedShow.getId());
    intent_progress.putExtra(KEY_PROGRESS, downloaded );
    LocalBroadcastManager.getInstance(DownloadService.this).sendBroadcast(intent_progress);
}

Answer 2

简短的回答:不要根据数据速度更新UI

除非您正在编写速度测试样式应用程序,否则以这种方式更新没有用户利益.

ListView是非常优化的(因为你似乎已经知道因为你正在使用ViewHolder模式).

你试过notifyDataSetChanged()每1秒钟一次吗？

每1024个字节的速度非常快.如果某人以8Mbps的速度下载,可能每秒更新超过1000次,这肯定会导致ANR.

您应该以不会导致UI阻止的间隔轮询金额,而不是根据下载的金额更新进度.

无论如何,为了帮助避免阻止UI线程,您可以将更新发布到Handler.

玩弄价值,sleep以确保您不会经常更新.你可以尝试低至200 毫秒,但我不会低于500毫秒,以确保.确切的值取决于您要定位的设备和需要布局传递的项目数.

注意:这只是一种方法,有很多方法可以完成这样的循环.

private static final int UPDATE_DOWNLOAD_PROGRESS = 666;

Handler myHandler = new Handler()
{
    @Override
    handleMessage(Message msg)
    {
        switch (msg.what)
        {
            case UPDATE_DOWNLOAD_PROGRESS:
                myAdapter.notifyDataSetChanged();
                break;
            default:
                break;
        }
    }
}



private void runUpdateThread() { 
    new Thread(
     new Runnable() {
         @Override
         public void run() {
             while ( MyFragment.this.getIsDownloading() )
             {
                  try 
                  {    
                      Thread.sleep(1000); // Sleep for 1 second

                      MyFragment.this.myHandler
                          .obtainMessage(UPDATE_DOWNLOAD_PROGRESS)
                          .sendToTarget();
                  } 
                  catch (InterruptedException e) 
                  {
                      Log.d(TAG, "sleep failure");
                  }
             }

         }
     } ).start(); 
}