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POWhy main thread can't update UI elements inside a horizontallistview?
 

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  1. POWhy main thread can't update UI elements inside a horizontallistview?
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    <p>Last few days I'm trying to update some UI Views inside a custom <a href="https://github.com/TomIsYourName/Android-HorizontalListView" rel="nofollow noreferrer">HorizontalListView</a>. I've been trying countless way like using Async Task, posting message via handler etc. I didn't figure out to update them. As a result, I tried to build a queue system to update them one by one. Here is my code and it's still not updating them.</p> <pre><code>import java.lang.ref.WeakReference; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import roboguice.RoboGuice; import CustomChannel; import EGPInfo; import android.content.Context; import android.os.Handler; import android.util.Log; import android.widget.TextView; public class EPGLoader { static private EPGLoader _instance; public static EPGLoader getInstance(Context context) { if (_instance == null) { _instance = new EPGLoader(); } mContext = context; return _instance; } private HashMap&lt;String, WeakReference&lt;EPGChannel&gt;&gt; _cachedChannels; private Queue&lt;EPGChannel&gt; _queue; private EPGThread _thread; private static Context mContext; private boolean _isBusy; public EPGLoader() { _cachedChannels = new HashMap&lt;String, WeakReference&lt;EPGChannel&gt;&gt;(); _queue = new LinkedList&lt;EPGChannel&gt;(); _isBusy = false; } public void load(ArrayList&lt;TextView&gt; textViews, CustomChannel channel) { Iterator&lt;EPGChannel&gt; it = _queue.iterator(); EPGChannel epgChannel = new EPGChannel(); epgChannel.setChannel(channel); epgChannel.setTextViews(textViews); while (it.hasNext()) { if (it.next().equals(epgChannel)) { it.remove(); break; } } _queue.add(epgChannel); loadNext(); } private void loadNext() { Iterator&lt;EPGChannel&gt; it = _queue.iterator(); if (!_isBusy &amp;&amp; it.hasNext()) { _isBusy = true; EPGChannel epgChannel = it.next(); it.remove(); EPGChannel epgCache = get(epgChannel.getChannel().getChannelId()); if (epgCache != null) { Log.i("A", "Cache"); epgChannel.textViews.get(0).setText("1"); epgChannel.textViews.get(1).setText("2"); epgChannel.textViews.get(2).setText("3"); epgChannel.textViews.get(3).setText("4"); _isBusy = false; loadNext(); } else { _thread = new EPGThread(epgChannel); _thread.start(); Log.i("A", "Live"); } } } private EPGChannel get(String channelId) { if (_cachedChannels.containsKey(channelId)) { return _cachedChannels.get(channelId).get(); } else { return null; } } private class EPGThread extends Thread { private EPGChannel EPGChannel; final Handler threadHandler = new Handler(); final Runnable threadCallBack = new Runnable() { @Override public void run() { onLoad(); } }; public EPGThread(EPGChannel epgChannel) { this.EPGChannel = epgChannel; } private void onLoad() { if (_thread != null) { EPGChannel epgChannel = _thread.EPGChannel; // epgChannel.getTextViews().get(1).setText(epgChannel.getChannel().getName()); epgChannel.getTextViews().get(0).setText("1"); epgChannel.getTextViews().get(1).setText("2"); epgChannel.getTextViews().get(2).setText("3"); epgChannel.getTextViews().get(3).setText("4"); } _thread = null; _isBusy = false; loadNext(); } @Override public void run() { try { _isBusy = true; ChannelManager channelManager = RoboGuice.getInjector(mContext).getInstance(ChannelManager.class); ArrayList&lt;EGPInfo&gt; epgInfo = channelManager.getChannelEPG(EPGChannel.getChannel().getChannelId()); if (epgInfo.size() == 2) { EPGChannel.getChannel().updateEPGInformations(epgInfo.get(0), epgInfo.get(1)); } if (!_cachedChannels.containsKey(EPGChannel.getChannel().getChannelId())) _cachedChannels.put(EPGChannel.getChannel().getChannelId(), new WeakReference&lt;EPGLoader.EPGChannel&gt;(EPGChannel)); } catch (Exception e) { e.printStackTrace(); } finally { threadHandler.post(threadCallBack); } } } private class EPGChannel { private ArrayList&lt;TextView&gt; textViews; private CustomChannel channel; public ArrayList&lt;TextView&gt; getTextViews() { return textViews; } public void setTextViews(ArrayList&lt;TextView&gt; textViews) { this.textViews = textViews; } public CustomChannel getChannel() { return channel; } public void setChannel(CustomChannel channel) { this.channel = channel; } } } </code></pre> <p>I call it from main thread when getView event of ArrayAdapter fires. </p> <pre><code>@Override public View getView(int position, View retval, ViewGroup parent) { if (retval == null) { retval = LayoutInflater.from(parent.getContext()).inflate(R.layout.channel_item, null); } final CustomChannel currentChannel = getItem(position); final TextView nowTitle = (TextView) retval.findViewById(R.id.channel_item_current_show_title); final TextView nowPlayTime = (TextView) retval.findViewById(R.id.channel_item_current_show_play_time); final TextView nextTitle = (TextView) retval.findViewById(R.id.channel_item_next_show_title); final TextView nextPlayTime = (TextView) retval.findViewById(R.id.channel_item_next_show_play_time); ArrayList&lt;TextView&gt; textViews = new ArrayList&lt;TextView&gt;(); textViews.add(nowTitle); textViews.add(nowPlayTime); textViews.add(nextTitle); textViews.add(nextPlayTime); EPGLoader.getInstance(mContext).load(textViews, currentChannel); return retval; } </code></pre> <p>So, what is wrong with my codes? Thanks in advance.</p> <p>Edit: I replace the HorizontalListView with normal Android's ListView and it works but I have to use HorizontalListView in the project. Any suggesstions? </p> <p>Edit 2: I reward to back (HorizontalListView) and tried to set Background color of some UI controllers, guess what? It updated. It doesn't update text property!!! Why????<img src="https://i.stack.imgur.com/lKSda.png" alt="enter image description here"></p>
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    1. USnesimtunc
    1. USnesimtunc
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    1. COSome advice: you should use ViewHolder when you work with ListView in your getView() method. Also where is the return statement in your getView method?
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      1. POWhy main thread can't update UI elements inside a horizontallistview?
      1. USMarek
    2. COretval variable is the return value @Marek ;)
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      1. POWhy main thread can't update UI elements inside a horizontallistview?
      1. USnesimtunc
    3. COYou have to use "return" statement to return the value. In my getView method I am returning the created View by "return view;" retval is not return Value, it is just the old view to reuse. There was a tutorial on how to use getView() method properly. It was from google I/O presentation but I can't find it now... UPDATE - http://www.youtube.com/watch?v=N6YdwzAvwOA P.S I am having hard time to understand how this code is working on your machine without return statement...
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      1. POWhy main thread can't update UI elements inside a horizontallistview?
      1. USMarek
 

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