Android Studio doesn't preview custom View

The Android Studio Layout Preview can be a powerful tool, but it still has his problems. Everything works perfectly fine while you stick to the default Android widgets, but with a custom widget you will likely incur in some kind of problem. In fact, sometimes your View is working perfectly at runtime, but it won't show in the preview.
You will get a stack trace like this one:

android.content.res.Resources$NotFoundException: Could not find attr resource matching value 0x7FFF0004 (resolved name: bar_thickness) in current configuration.

This could be caused by many factors, here are the two of them that I've found more annoying:

• Using an OvalShape in your custom View
• Using a resource in your View constructor

While the first one is currently an open bug, and not much can be done about it, the second one can be addressed with a workaround.

The Android View object provides a method to check if the View is being rendered in a preview tool, like the Android Studio one or like the eclipse plugin: isInEditMode(). This simply returns a boolean that states if the View is in a preview tool or not.

If you're using one or more resources in your View constructor you should replace them with fixed values when you're in edit mode.

For example this:

params.setMargins(getResources()
                    .getDimensionPixelSize(R.dimen.floating_label_left_margin), 0, 0, 0);

should become this:

 if (isInEditMode()) {
      params.setMargins(5, 0, 0, 0);
} else {
      params.setMargins(getResources()
              .getDimensionPixelSize(R.dimen.floating_label_left_margin), 0, 0, 0);
}

Android Menu showAsAction Ignored

While working on a menu definition in Android you have the option to specify if the menu items should be visible as icons or should be hidden in the overflow menu (the three dots at the end of the action bar). This can be achieved with the showAsAction attribute in the menu XML definition. As a default the menu items are hidden in the overflow menu.

Today this attribute was simply ignored by my Android app. This is what my menu item definition looked like:

<item
        android:title="Search"
        android:id="@+id/menu_search"
        android:icon="@drawable/ic_action_content_copy"
        custom:showAsAction="always|collapseActionView"
        android:actionViewClass="android.support.v7.widget.SearchView"/>

But the item was not shown as an icon on the action bar. As you can see I'm using a custom namespace for the showAsAction attribute. The namespace is defined as:

xmlns:custom="http://schemas.android.com/apk/res-auto"

This is required if you are working with the compat library. What I didn't know, that was causing the issue, is that when you use the showAsAction with the custom namespace your Activity must extend the support ActionBarActivity, otherwise the attribute will just be ignored.

Android Google+ Sign In Problem

Last week I was working to implement Google+ authentication in an Android app. The process is well documented on Android Developers and Google provides also a sample app on GitHub.

As stated in the quickstart, before start coding you should create a new project into the Google Developer Console, in order to register your app on the Google APIs. You have to provide your Android certificate SHA1 fingerprint and your app package name, then everything should work.

Clearly, it didn't.

While trying to login with the sample app I got back on the log an error saying:

ConnectionResult.getErrorCode() = 4

According to the documentation for ConnectionResult code 4 stands for: SIGN_IN_REQUIRED, but no other explanation is given. After many hours of searches and tests, I discovered that I was simply missing the definition of the sign-in screen in the Google Developer Console.

In the lateral menu of the Developer Console, select APIs & auth and the Consent screen fill in the required fields, save, give it a couple of minutes and you should be OK.


Hope it helps someone.

Customize AlertDialog buttons inside DialogFragment

When working with alert dialogs I was used to customize the positive and negative buttons appearance by retrieving them directly from the dialog after calling the show() method. (If you try to retrieve the buttons before the dialog is shown they will be null)
Just like this:

// Create the dialog
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setPositiveButton(R.string.btn_confirm_all, null);
builder.setNegativeButton(R.string.btn_cancel, null);
builder.setCancelable(false);
AlertDialog dialog = builder.create();
dialog.show();
// Retrieve the button
Button button = dialog.getButton(DialogInterface.BUTTON_POSITIVE);
// Customize the button
button.setTextColor(Color.WHITE);
button.setTypeface(Typeface.DEFAULT_BOLD);

Well, lately I started to use DialogFragment to embedd dialog lifecycle, the problem is that I didn't have direct access to the dialog anymore, I was just overriding the onCreateDialog() method:

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    // Create the dialog
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    builder.setPositiveButton(R.string.btn_confirm_all, null);
    builder.setNegativeButton(R.string.btn_cancel, null);
    builder.setCancelable(false);
    AlertDialog dialog = builder.create();
    return dialog;
}

The solution I found to customize the dialog button after show() was to store the just created dialog object in a global variable and then to retrieve it in the onResume() method of the DialogFragment:

@Override
public void onResume() {
     super.onResume();
     // Retrieve the button
     Button button = this.dialog.getButton(DialogInterface.BUTTON_POSITIVE);
     // Customize the button
     button.setTextColor(Color.WHITE);
     button.setTypeface(Typeface.DEFAULT_BOLD);
}

Hope it helps somebody!

Programmatically enable USB tethering on Android

Android USB tethering lets you share your phone Internet connection to your PC via an USB cable. The big advantage over the Wi-Fi tether option is in the lower battery consumption.

User can manually enable USB tethering from the phone settings, but what if your application wants to help the user enable it or force it to start?

Show the user tethering settings page

From within your application you can call activities defined by other apps, even the system ones, and the settings manager is not an exception. So, if you want the user to enable USB tethering on your device you can redirect him to the right settings page. This can be done simply by using an Intent:

 Intent intent = new Intent();  
 intent.setClassName("com.android.settings", "com.android.settings.TetherSettings");  
 startActivity(intent);  

On some phones, the ones without a mobile data capability I suppose, this settings section is "hidden" and not reachable by the user. Using this Intent will show it but the "Enable USB tethering" option could behave in strange ways.

Programmatically enable USB tethering

On ROOTED phones there's also a way to enable programmatically the USB tethering option (NOTE: This method seems to work on Android < 4.0). I haven't found a way to do it on a non rooted phone.

First of all add the following permissions to your AndroidManifest.xml:

 <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />  
 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />   

Then using Java Reflection we can call the method to enable USB tethering:

 public void switchOnTethering() {  
   Object systemService = getSystemService(Context.CONNECTIVITY_SERVICE);  
   for (Method method : systemService.getClass().getDeclaredMethods()) {  
     if (method.getName().equals("tether")) {  
       try {  
         method.invoke(systemService, "usb0");  
       } catch (IllegalArgumentException e) {  
         e.printStackTrace();  
       } catch (IllegalAccessException e) {  
         e.printStackTrace();  
       } catch (InvocationTargetException e) {  
         e.printStackTrace();  
       }  
     }  
   }  
 }  

References:

• http://stackoverflow.com/questions/14340084/enable-usb-tethering-android-programmatically-without-user-interaction
• http://stackoverflow.com/questions/9913645/android-enable-usb-tethering-programmatically-there-is-an-app-that-did-it-fo

"Collect preferences failed" eclipse ADT error

Today I updated my Android SDK in eclipse to the last version using the Android SDK Manager.

After the update was over, eclipse console was giving me this error message:

[2013-12-28 10:45:08 - Framework Resource Parser] Collect preferences failed, class java/lang/AutoCloseable not found in C:\Users\<username>\android-sdks\platforms\android-19\android.jar

Well I solved it simply by updatng the ADT eclipse plugin to the last available version.
In eclipse open: Help > Check for updates and let it work, then accept the new software to be installed.

Hope it helps somebody else!

Android Packages Organization

I like my stuff to be organized, in the same way I like my code to be organized. Here's the structure that I usually adopt for my Android projects:

• com.<company-name>.<project-name>: The main package, here I store only the Application class. All following packages will be sub-packages of this one.
• .gui: Contains all the classes related to UI management. Usually this package is empty, the content is organized in sub packages.
• .gui.activities: Contains all the Activity classes.
• .gui.fragments: Contains all the Fragment classes.
• .gui.views: Contains all the View classes.
• .gui.adapters: Contains all the Adapter classes.
• .gui.dialogs: Contains all the Dialog definition classes.
• .gui.support: Contains all the UI related classes that doesn't fit in previously described packages.
• .domain: Contains all the java beans that represents the application domain.
• .domain.enums: Contains all the enumeration files related to the application domain.
• .core: Contains all the core logic classes. These classes form a layer that services the UI classes managing local storage, web service connection, data elaboration, ...
• .db: Contains all the database management classes.
• .db.tables: Contains all the database table definition classes.
• web: Contains all the web service communication classes.
• web.messages: Contains all the message definition classes.

What do you think of it? Every comment or suggestion is welcome.

Eclipse failing during Android "export signed application package"

Sometimes eclipse fails while processing the "export signed application package" for Android. The fail can appear as a generic error message “Conversion to Dalvik format failed error 1” or as a complete crash of the  IDE.

Even restarting eclipse doesn't seem to fix the problem. A simple solution I've found that works for me is this one:

• Disable automatic project building

• Clean the project
• Export the package

• Re-enable automatic building

This seems to work on both, Mac and Windows version, of eclipse.

Let me know if this works for you also.

Samsung Galaxy Nexus problems

Screen turning on automatically

This morning my Galaxy Nexus decided he didn't want to stand by. Every time I locked the screen, it turned on again automatically. Well, after some research it turns out that this can be a software or an hardware problem. Some people resolved the (SW) problem with a  factory reset of the device, i haven't tried...

In my case it was a simple HW problem, because i solved it with some simple steps:

1. Turn off
2. Take out the battery
3. Blow with strong inside the power plug
4. Take a wooden toothpick and gently clean the plug
5. Wait a couple of minutes
6. Insert the battery
7. Turn on

In a few words it was just dirty...

While doing this, check also the orientation of the male part of the USB connector, it should be coming out straight, it shouldn't bend down or up. If it does, try carefully to bring it to a straight position using the toothpick or a small screwdriver.

If this didn't solved your problem, and you have no fear to open your phone, you could buy a replacement connector board on eBay for something like 10$.

Here you can find some more information:

• http://forum.xda-developers.com/showthread.php?t=1427539
• https://code.google.com/p/android/issues/detail?id=39625

Phone not charging

Since I'm at it, some time ago I faced another problem related to the power plug that prevented the phone from charging. The male part of the connector was bend down, making it straight (as described before) solved the problem.

GPS not fixing

Another problem I've experienced is the malfunctioning of the GPS receiver, it started all of a sudden, without apparent reason. All the location based application wasn't fixing the signal, the GPS icon would just blink forever.

What I did was simply to turn off the phone, remove the battery, wait some seconds and then turn it on again. Then it started working properly.

Hope this helps, let me know.

Samsung Galaxy Young problems

I'm an unlucky owner of a Samsung Galaxy Young (AKA Galaxy Y), a (very)low-end device. During use of this device I've faced some frustrating problems like phone that reboots automatically or network connection disappearing until you rebooted it. Adding the ridiculously short battery life it was just unusable.
I've looked for a solution to the problem, and found it in the "Use only 2G networks" option, that can be found under "Settings > Wireless and networks > Mobile networks". Now I have no more reboot or network problems, and I count stand-by battery life in days, not hours! If you haven't got a data connection, or if you are OK without a 3G one, give it a try!