Smooth Scrolling List/TableView for Titanium Android

For those who have been using the Titanium TableView UI to render lists, you may have noticed that there is a significant lag on the scroll animation when the number of list items are increased. Most of the time, if there are images on the row, the list becomes choppy and sometimes the application crashes (especially on android).  Since most of the solutions I found only adds minimal improvement on the performance, I just accepted this issue as unresolvable until a titanium sdk update handles this.

However, after using different titanium views for a while, I accidentally discovered a viable alternative to the TableView. After seeing WebViews render lists containing a lot of items with ease, I realized that I can use it as a substitute for my TableViews.

To create a "ListView" type of UI on the WebView, I used the html Table on the code like below: (Please note that I have used Mustache for rendering the data on the html template)

1:  <table border="0" style="width:100%;">  
2:                 {{#table_rows}}  
3:                 <tr onclick="Ti.App.fireEvent('app:handleRowSelect', { index : '{{row_index}}' })">  
4:                      <td>  
5:                           <img src="{{{image_url}}}" style="width:320px; height:240px; position:relative; left:10px; top:5px;"/>  
6:                      </td>  
7:                 </tr>  
8:                 {{/table_rows}}  
9:  </table>   

As you can seen on the code, I just used styles to make the rows look like a list on a TableView.  You can also see that I am firing an event whenever a row is clicked. I'll explain later how it is used.. Here is what the views look like when running on Android tablet:

You can make them look almost exactly the same so the user wouldn't notice that you are indeed using only a WebView instead of a ListView on android.

To simulate the TableView "click" event handler, you must declare an event handler on your application to capture the event fired from your html:

1:  function handleRowSelect(e) {  
2:   alert('You have selected the row with index ' + e.index);  
3:  }  
4:    
5:  Ti.App.addEventListener('app:handleRowSelect', handleRowSelect);  

Whenever the app:handleRowSelect is fired from the HTML, the handleRowSelect function will be called and the event data will be passed as parameters to this function. From the HTML code above, the   Event is fired with an object that contains the index of the row: Ti.App.fireEvent('app:handleRowSelect', { index : '{{row_index}}' }) and from this, you will be able to perform any operation on the data corresponding to the row selected.

You can try and see for yourself the huge performance improvement from using the WebView for large lists on android from here

Gap Appears on HTML div When Using Titanium Webview on Android

I encountered this irritating bug when using a WebView on my application and I was trying to make a div that has a fixed position on the page. At first I thought I set the styles wrong but a further investigation confirms that a gap is really being generated when displaying the div on the WebView.

After looking a bit on my code I found out that Hardware Acceleration affects the WebView and causes this bug to appear. On my application, the setting (for hardware acceleration) can be found on the /platform/android/AndroidManifest.xml file.

Here is the part where the property is set:

1:  <application android:icon="@drawable/appicon"  
2:            android:hardwareAccelerated="true"   
3:            android:label="AndroidWebViewElemGaps" android:name="AndroidwebviewelemgapsApplication"  
4:            android:debuggable="false">  

Removing this setting fixes the WebView but if you really need hardware acceleration for your app, you are out of luck for the mean time. It's worth noting though that not all devices are affected by this bug. Here is the app running on smartphone without any problems:

Source code for my test project can be found in here.