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POUpdating global variables in listview (Android)
 

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    <p>I have an issue that I am trying to resolve. I have created a list with three items in it that also allows you to add images to the list by following this tutorial... </p> <p>Here, in order, is what I did. 1. I began by creating a class called 'Item' to serve as a model for the list items.</p> <pre><code>public class Item { public int Id; public String IconFile; public String Name; public Item(int id, String iconFile, String name { Id = id; IconFile = iconFile; Name = name; } } </code></pre> <p>.2. I then created a class called 'Model' to provide an ArrayList for my items. However, instead of simply putting text in the list names I included global variables.</p> <p><a href="http://www.debugrelease.com/2013/06/24/android-listview-tutorial-with-images-and-text/" rel="nofollow">http://www.debugrelease.com/2013/06/24/android-listview-tutorial-with-images-and-text/</a></p> <pre><code>public class Model extends Globals { public static ArrayList&lt;Item&gt; Items; public static void LoadModel() { Items = new ArrayList&lt;Item&gt;(); Items.add(new Item(1, "temperature_icon.png", "Temperature/Humidity" + temperature + "°C / " + humidity + "%")); Items.add(new Item(2, "gas_icon.png", "LPG" + lpg +" ppm")); Items.add(new Item(3, "alcohol_icon.png", "Alcohol" + alcohol + " ppm")); } public static Item GetbyId(int id) { for(Item item : Items) { if (item.Id == id) { return item; } } return null; } } </code></pre> <p>.3. (Extra step) I added a global class to have access to the global variables.</p> <pre><code>public abstract class Globals extends Activity { static int temperature; static int humidity; static int lpg; static int alcohol; } </code></pre> <p>.4. Add listview widget to main activity layout.</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"&gt; &lt;ListView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/listView" /&gt; &lt;/LinearLayout&gt; </code></pre> <p>.5. Add custom layout since I am displaying more than text.</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center_vertical" android:minHeight="64dp"&gt; &lt;ImageView android:id="@+id/imageView" android:layout_width="32dp" android:layout_height="32dp" android:layout_alignParentLeft="true" android:layout_marginLeft="9dp" android:layout_alignParentTop="true"/&gt; &lt;TextView android:layout_alignBottom="@+id/imageView" android:layout_width="97dp" android:layout_height="32dp" android:id="@+id/textView" android:layout_alignParentLeft="true" android:layout_marginLeft="66dp" android:layout_alignParentRight="true" android:gravity="center_vertical"/&gt; &lt;/RelativeLayout&gt; </code></pre> <p>.6. Create custom adapter to display data</p> <pre><code>public class ItemAdapter extends ArrayAdapter&lt;String&gt; { private final Context context; private final String[] Ids; private final int rowResourceId; public ItemAdapter(Context context, int textViewResourceId, String[] objects) { super(context, textViewResourceId, objects); this.context = context; this.Ids = objects; this.rowResourceId = textViewResourceId; } @Override public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); View rowView = inflater.inflate(rowResourceId, parent, false); ImageView imageView = (ImageView) rowView.findViewById(R.id.imageView); TextView textView = (TextView) rowView.findViewById(R.id.textView); int id = Integer.parseInt(Ids[position]); String imageFile = Model.GetbyId(id).IconFile; textView.setText(Model.GetbyId(id).Name); // get input stream InputStream ims = null; try { ims = context.getAssets().open(imageFile); } catch (IOException e) { e.printStackTrace(); } // load image as Drawable Drawable d = Drawable.createFromStream(ims, null); // set image to ImageView imageView.setImageDrawable(d); return rowView; } } </code></pre> <p>.7. Load model, find listview and assign adapter in the main activity.</p> <pre><code>public class MainActivity extends Globals { ListView listView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Model.LoadModel(); listView = (ListView) findViewById(R.id.listView); String[] ids = new String[Model.Items.size()]; for (int i= 0; i &lt; ids.length; i++) { ids[i] = Integer.toString(i+1); } ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids); listView.setAdapter(adapter); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } } </code></pre> <p>.Okay, so now that you hopefully understand what I have done, I can explain the problem. I would like to update the global variables in the listview based on data that I will be receiving over USB. However, I cannot seem to figure out how to do this. I tried the following code within the main activity but it did not update the data...</p> <pre><code>temperature = 5; adapter.notifyDataSetChanged(); </code></pre> <p>Any help would be greatly appreciated. Thank you for your time.</p> <h2>Update</h2> <p>So I have created a new ArrayList with the new data that I want to display in the ListView. I then populate the ListView, set the ListView to the adapter and then call notifyDataSetChanged. However, my code still does not seem to update. Any advice is greatly welcomed!</p> <pre><code>public class MainActivity extends Activity { public static int temperature; public static int humidity; public static int lpg; public static int alcohol; ListView listView; ListView listView1; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Model.LoadModel(); listView = (ListView) findViewById(R.id.listView); String[] ids = new String[Model.Items.size()]; for (int i= 0; i &lt; ids.length; i++) { ids[i] = Integer.toString(i+1); } ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids); listView.setAdapter(adapter); //Simulate updated data that will come from USB temperature = 1; humidity = 60; lpg = 5000; alcohol = 500; //Create new ArrayList with updated data ArrayList&lt;Item&gt; Items1; Items1 = new ArrayList&lt;Item&gt;(); Items1.add(new Item(1, "temperature_icon.png", "Temperature/Humidity" + temperature + "°C / " + humidity + "%")); Items1.add(new Item(2, "gas_icon.png", "LPG" + lpg +" ppm")); Items1.add(new Item(3, "alcohol_icon.png", "Alcohol" + alcohol + " ppm")); //Populate ListView listView1 = (ListView) findViewById(R.id.listView); String[] ids1 = new String[Items1.size()]; for (int i= 0; i &lt; ids1.length; i++) { ids1[i] = Integer.toString(i+1); } //Bind new ListView to Adapter listView1.setAdapter(adapter); adapter.notifyDataSetChanged(); listView1.invalidateViews(); } </code></pre> <h2>Update # 2</h2> <p>I have now both created a new listview to display the updated data, as well as created a new adapter to which I can attach the listview. However, when I call notifyDataSetChanged(); the new data is not displayed; I still see the original data.</p> <pre><code>public class MainActivity extends Activity { public static int temperature; public static int humidity; public static int lpg; public static int alcohol; ListView listView; ListView listView_new; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Model.LoadModel(); listView = (ListView) findViewById(R.id.listView); String[] ids = new String[Model.Items.size()]; for (int i= 0; i &lt; ids.length; i++) { ids[i] = Integer.toString(i+1); } ItemAdapter adapter = new ItemAdapter(this,R.layout.row, ids); listView.setAdapter(adapter); //--Simulate new data--// temperature = 1; humidity = 60; lpg = 5000; alcohol = 500; //Create new ArrayList with updated data ArrayList&lt;Item&gt; Items_new; Items_new = new ArrayList&lt;Item&gt;(); Items_new.add(new Item(1, "temperature_icon.png", "Temperature/Humidity " + temperature + "°C / " + humidity + "%")); Items_new.add(new Item(2, "gas_icon.png", "LPG " + lpg +" ppm")); Items_new.add(new Item(3, "alcohol_icon.png", "Alcohol " + alcohol + " ppm")); //Populate ListView listView_new = (ListView) findViewById(R.id.listView); String[] ids_new = new String[Items_new.size()]; for (int j= 0; j &lt; ids_new.length; j++) { ids_new[j] = Integer.toString(j+1); } //Create new adapter ItemAdapter adapter_new = new ItemAdapter (this,R.layout.row, ids_new); //Bind new ListView to Adapter listView_new.setAdapter(adapter_new); //listView_new.invalidateViews(); adapter_new.notifyDataSetChanged(); } </code></pre>
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