Android, Development, Kotlin, Test

Clear all Android SharedPreferences

It may happen you would need to clear your all of your SharedPreferences without knowing in advance their keys.


This can happen when you are writing tests: you don’t want your production code to publicly expose your SharedPreferences keys neither you need a clear() method, so you didn’t implement it. You may also need to clear third party SharedPreferences to which you don’t have direct access.

Without changing your production code there is something you can do:

  • access the app SharedPreferences folder
  • get the SharedPreferences editor for each file
  • clear the SharedPreferences

You can use the following code, called in a @BeforeEach annotated method, to be sure each of your tests will run in a clean environment.

private fun clearAllSharedPreferences(context: Context) {
    val sharedPreferencesPath = File(context.filesDir.parentFile!!.absolutePath + File.separator + "shared_prefs")
    sharedPreferencesPath.listFiles()?.forEach { file ->
        context.getSharedPreferences(file.nameWithoutExtension, Context.MODE_PRIVATE).edit { clear() }


  • Be sure to include androidx.core:core-ktx in your project to have that edit() method
  • If you are running your tests using Espresso you can access the app Context using InstrumentationRegistry.getInstrumentation().targetContext

Happy coding!

Android, Development, Java, Kotlin

How to debug an Annotation Processor in Android Studio

Writing an Annotation Processor in Java/Kotlin is a very interesting task and debugging comes very handy, but unfortunately it seems not so easy to start a debug session.

rubber ducks

The following information are valid for Android Studio 3.6.3 and Kotlin 1.3.71. Gradle is the build tool used for the project.

First thing to do is setup a new Run/Debug Configuration in Android Studio:

  • Choose Run from the main menu
  • Choose Edit Configurations
  • Now click on the + symbol in the top left corner to add a new Configuration
  • Choose Remote from the list
  • Give it a friendly name (e.g. AnnotationProcessorDebugger)

Setup your breakpoints wherever you need them and then run this command from the terminal:

./gradlew --no-daemon -Dorg.gradle.debug=true :APP_MODULE_NAME:clean :APP_MODULE_NAME:compileDebugJavaWithJavac

Replace APP_MODULE_NAME with the name of the module having annotations which you want to debug. You will see the process will start and suddenly stop on > Starting Daemon waiting for you to do something.

Now, click on the Debug icon in the Toolbar (having selected the previously created AnnotationProcessorDebugger configuration) and the debugger will hit your breakpoints!

Additional info:

The clean task seems to be necessary.

Unfortunately, sometimes these steps are not enough, or simply don’t work, the debugger won’t hit your breakpoints. I see somebody else solved the issue after adding the following line to their file.


Enable the new Android Auto UI

android auto logo

In the last few weeks the new Android Auto UI is being released by Google but it’s not yet available for everyone. There are some tricks you can use to force enable it before Google releases it to everyone.

One of these tricks is explained here on Reddit.

It works on my OP6 running Android Pie, but those commands need to be executed each time I want to use the new Android Auto UI, otherwise I see the old one.

To overcome this little issue I made a Tasker profile to automatically run those commands when the smartphone is connected to a power source, so they are executed before Android Auto starts.

Here the Tasker profile! Just import it in your Tasker and enjoy the new Android Auto UI!

<TaskerData sr="" dvi="1" tv="5.8.3">
<Profile sr="prof21" ve="2">
<nme>On power change AA to new UI</nme>
<State sr="con0" ve="2">
<Int sr="arg0" val="0"/>
<Task sr="task17">
<nme>New AA UI</nme>
<Action sr="act0" ve="7">
<Str sr="arg0" ve="3">sqlite3 /data/data/ "INSERT OR REPLACE INTO Flags (packageName, version, flagType, partitionId, user, name, intVal, committed) VALUES ('',45592854,0,0,'','Boardwalk__launch_experiment_id',15592854,1);"</Str>
<Int sr="arg1" val="0"/>
<Int sr="arg2" val="1"/>
<Str sr="arg3" ve="3"/>
<Str sr="arg4" ve="3"/>
<Str sr="arg5" ve="3"/>
<Action sr="act1" ve="7">
<Str sr="arg0" ve="3">sqlite3 /data/data/ "INSERT OR REPLACE INTO Flags (packageName, version, flagType, partitionId, user, name, boolVal, committed) VALUES ('',45592854,0,0,'','Boardwalk__enabled',1,1);"</Str>
<Int sr="arg1" val="0"/>
<Int sr="arg2" val="1"/>
<Str sr="arg3" ve="3"/>
<Str sr="arg4" ve="3"/>
<Str sr="arg5" ve="3"/>
Android, Development

Android Contextual Action Bar

In this post you will learn how to implement a Contextual Action Bar (CAB) which will be useful to do actions on multiple items you have selected in a RecyclerView.

The Contextual Action Mode represents a contextual mode of the user interface and focuses user interaction toward performing contextual actions. In the case of a RecyclerView which shows a list of item, Contextual Action Mode is triggered after a long press on one of this items: this causes the Contextual Action Bar to appear at the top of the screen so then the user can interact with its actions.

Let’s follow these steps!

Initial setup

First of all, create a RecyclerView and its adapter in the usual way you do it. Here in this example I will use a RecyclerView which shows Authentication items (it is a class I made for a project, it doesn’t matter for the purpose of the example, use whatever you want, and change the names accordingly).

Theme changes

Open your styles.xml file and add the following lines:

<!--  It should be true otherwise action mode will not overlay toolbar -->
       <item name="windowActionModeOverlay">true</item>
       <!--  For Custom Action Mode Background Color/Drawable -->
       <item name="actionModeBackground">@color/colorAccent</item>

Comments should be self-explanatory.

Menu file

We need a menu file which contains the available actions for that RecyclerView. Let’s create a file into the res/menu directory like the following:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android=""

        app:showAsAction="always" />


We added a delete action that will be shown on the CAB.

Adapter changes

Our adapter we created in the first step needs to be able to keep trace of the elements we select. To do this, let’s modify our adapter and create a new field

private final SparseBooleanArray selectedItemsIds;

and initialize it in our constructor

selectedItemsIds = new SparseBooleanArray();

Now, let’s create an Interface which will be useful for all the Adapters which need the CAB, and make our Adapter implements it. Please note this is a generic interface, so adapt it to the model you are displaying in your adapter.

public interface ActionModeAdapterCallbacks<T> {

    void toggleSelection(int position);

    void clearSelections();

    int getSelectedCount();

    List<T> getSelectedItems();

This is what the implementation should look like:

public void toggleSelection(final int position) {
    if (selectedItemsIds.get(position)) {
    } else {
        selectedItemsIds.put(position, true);

public void clearSelections() {

public int getSelectedCount() {
    return selectedItemsIds.size();

public List<Authentication> getSelectedItems() {
    final List<Authentication> selectedItemList = new LinkedList<>();
    for (int i = 0; i < selectedItemsIds.size(); i++) {
    return selectedItemList;

Now, we also need the Adapter to change the view state when an item gets selected to show the user a visual feedback. To do this we can use a StateListDrawable and in the onBindViewHolder() method add this line.


Create a new xml file inside the res/drawable directory:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
    <item android:drawable="@color/colorPrimaryDark" android:state_activated="true" />
    <item android:drawable="@android:color/transparent" />

and assign it to the root view element of the layout file which represents your adapter’s row item:


Doing so, each time an item is selected or deselected, the adapter will change its color accordingly.

Fragment/Activity changes

Now, we need to make our Fragment/Activity class aware that we can trigger the Contextual Action Mode. To do so, let’s create an interface and call it ActionModeViewCallbacks.

public interface ActionModeViewCallbacks {

    void onListItemSelect(final int position);

    void onDestroyActionMode();


This interface has 2 methods:

  • onListItemSelect(final int position): to be used after a long click on an item to trigger the Action Mode (or after a single click on an item, if Action Mode was already triggered, to select this new item, too);
  • onDestroyActionMode(): reset actionMode variable to null;

Now, let’s create another interface which extends from this one:

public interface ListAuthenticationActionModeViewCallbacks extends ActionModeViewCallbacks {

    void onDeleteActionClicked();


This new interface has another method, onDeleteActionClicked(), which is where the presenter gets called (check MVP if you are not aware what MVP and a Presenter are) and asked to delete the items the user has selected (if you have more than a single action, you need to create more methods, each for any action you have).

This interface must be implemented by the Fragment/Activity which wants to use the Contextual Action Mode. The implementation looks like this:

    public void onListItemSelect(final int position) {

        final boolean hasCheckedItems = listAuthenticationAdapter.getSelectedCount() > 0;

        if (hasCheckedItems && actionMode == null) {
            // there are some selected items, start the actionMode
            actionMode = ((AppCompatActivity) getActivity()).startSupportActionMode(new ListAuthenticationToolbarActionModeCallback(this, this, listAuthenticationAdapter));
        } else if (!hasCheckedItems && actionMode != null) {
            // there no selected items, finish the actionMode

       if (actionMode != null) {
            //set action mode title on item selection
            actionMode.setTitle(getString(R.string.cab_selected, listAuthenticationAdapter.getSelectedCount()));

    public void onDestroyActionMode() 
        actionMode = null;

public void onDeleteActionClicked() {

where R.string.cab_selected is

<string name="cab_selected">%1$d selected</string>

In doing startSupportActionMode() we need to pass a ActionMode.Callback item that I haven’t explained yet. Let’s create another class which implements that interface.

public class ListAuthenticationToolbarActionModeCallback implements ActionMode.Callback {

    private final ActionModeViewCallbacks actionModeViewCallbacks;
    private final ListAuthenticationAdapter listAuthenticationAdapter;

    public ListAuthenticationToolbarActionModeCallback(final ActionModeViewCallbacks actionModeViewCallbacks, final ListAuthenticationAdapter listAuthenticationAdapter) {
        this.actionModeViewCallbacks = actionModeViewCallbacks;
        this.listAuthenticationAdapter = listAuthenticationAdapter;

    public boolean onCreateActionMode(final ActionMode mode, final Menu menu) {
        mode.getMenuInflater().inflate(, menu);
        return true;

    public boolean onPrepareActionMode(final ActionMode mode, final Menu menu) {
        return true;

    public boolean onActionItemClicked(final ActionMode mode, final MenuItem item) {
        switch (item.getItemId()) {
                return true;
        return false;

    public void onDestroyActionMode(final ActionMode mode) {

Please have a look on the official documentation here to understand how ActionMode.Callback works.


See the following screenshots:

  • first one shows the initial situation before Action Mode is triggered;
  • second one shows the situation after Action Mode was triggered by long press an item;
  • third one shows the final situation after the item “Auth 2” was deleted.

contextual action bar first contextual action bar selected contextual action bar after delete


Your Contextual Action Mode should work now! I suggest you to create different menu files, Fragment/ActivityToolbarActionModeCallback and Fragment/ActivityActionModeViewCallbacks to keep everything separated.

Please note: if you rotate the device, Contextual Action Mode is lost, you need to save its state and restore it. Another post will follow, hopefully soon!

Android, Development

Android NoteApp with Dagger and Retrofit

Today I show a simple Android project I wrote which shows the use of Dagger, Retrofit and some other stuff.

The full source code of the project is available for you here

The project’s main purposes are the following:

  • Show Dagger2 dependency injection;
  • Show MVP architecture (made through Dagger2)
  • Show the repository pattern used to cache server data
  • Show the creation and use of a CustomView

Furthermore, I have used ButterKnife to remove the boilerplate code needed to bind classes/views, and GreenDao to automatically create the SQLite repository/model classes.

This project is based on the Google Android Architecture samples which are available here


Custom Fragment Backstack in Android

Dealing with Fragments is always a pain: after some time I found a way to deal with them in a less painful way, creating a custom Fragment Backstack.

How to create your custom Fragment Backstack navigation

Put this code in your main Activity:

public class MainActivity extends AppCompatActivity {

    private Stack<Fragment> fragmentStack;

    protected void onCreate(Bundle savedInstanceState) {
        fragmentStack = new Stack<>();

    public void onBackPressed() {
        if (fragmentStack.size() == 0) {
        } else {
            showFragment(fragmentStack.lastElement(), false);

    public void showFragment(Fragment fragment, boolean addToStack) {
        if (addToStack) {
        getFragmentManager().beginTransaction().replace(, fragment).commit();


We have a fragmentStack field which is a Stack of Fragment: we use this to save the Fragments we show in our app and we initialize it in the onCreate() method of the main Activity.

In the onBackPressed() method we remove the current Fragment from the Stack and then if there is another one, we show it, otherwise we close the app because there is nothing more to be shown.

The method showFragment() is the one we use to show a Fragment on the screen; we invoke it every time we need to change the visible Fragment. If we want to save the current transaction being able to come back to the current Fragment we pass true as addToStack value, otherwise we pass false.

Have a look at the full source code on my GitHub here.


Auto hide keyboard using Android EditText

Do you want to automatically hide your keyboard whenever you touch outside it? Please continue reading and you will find out how to do it!

First, we will create our AutoHideKeyboardEditText class like the following:

public class AutoHideKeyboardEditText extends EditText {

    public AutoHideKeyboardEditText(Context context) {

    public AutoHideKeyboardEditText(Context context, AttributeSet attrs) {
        super(context, attrs);

    public AutoHideKeyboardEditText(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

    private void init() {
        setOnFocusChangeListener(new OnFocusChangeListener() {
            public void onFocusChange(View v, boolean hasFocus) {
                if (!hasFocus) {

    private void hideKeyboard(View view) {
        InputMethodManager inputMethodManager = (InputMethodManager)
        inputMethodManager.hideSoftInputFromWindow(view.getWindowToken(), 0);

Whatever Constructor is used, we set an onFocusChangeListener to hide the keyboard using the proper method if we touch outside the EditText area (if the focus is not anymore on it).

Afterwards, create a layout similar to this

<LinearLayout xmlns:android=""

being sure, whatever layout you want to use, to add clickable and focusableInTouchMode attributes with true value.

Now just add our AutoHideKeyboardTextView inside that layout. You can simply add it using XML like the following



You are done! Whenever you touch outside the EditText the keyboard will be automatically dismissed!

Please note: you should add theĀ clickable andĀ focusableInTouchMode attributes to the outermost view but if it is a ScrollView this might not work. For such case, those attributes could be added to the view directly under the ScrollView.

Full source code on my GitHub repository here.


I don’t know why this wasn’t voted as the best answer because it is indeed.


Android Studio gitignore to avoid useless files

Create a perfect Android Studio .gitignore file is sometimes tedious, so I have gathered some information on the Internet, mainly on StackOverflow, I made some experiments with my sample project over and over and finally I obtained a perfect Android Studio .gitignore file.

Usually, I create my project inside a parent folder which I initialize as my Git repository.

So, for example, this is a sample structure (folders are bolded):


  • .git
  • AndroidShowCase
    • .gradle
    • .idea
    • app
    • build
    • gradle
    • .gitignore
    • AndroidShowcase.iml
    • build.gradle
    • gradlew
    • gradlew.bat
    • settings.gradle
  • .gitignore

I use the following as content for the .gitignore file in the AndroidShowcaseRepository folder

# Built application files

# Files for the Dalvik VM

# Java class files

# Generated files

# Gradle files

# Local configuration file (sdk path, etc)

# Proguard folder generated by Eclipse

# Log Files

and the following as content for the .gitignore file in the AndroidShowcase folder


Using these two .gitignore files (and the default ones created by Android Studio inside the app folder and into other folders you could have) you will likely save only the necessary source code to your repository and not files which could be generated by Android Studio itself.

Check w3ma showcase repository for the complete source code and for more explanation!


Making TextView with clickable link in Android

I will explain how to create a TextView with inside a clickable link in Android.

Do you want to open a static link without doing other operations? So just follow the first part of this tutorial! Otherwise, if you want to have more control on the link customization and operations after the user taps on it, follow the second part of the tutorial.


Let’s create an example TextView in your layout like this one:

    android:text="@string/messageWithLink" />

Create this string in strings.xml:

<string name="messageWithLink">This is a message with a link inside!\n<a href="">Tap here to open it!</a></string>

Write this code in your activity/fragment:

TextView messageWithLinkTextView;

public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    ButterKnife.bind(this, view);

Please note: I’m using ButterKnife library to bind fields and views (I suggest you to have a look at this fantastic library!)

You are done! You should get a TextView like the one in the following screenshot and when you tap on the hyperlink the browser should open! Cool!


P.S. unfortunately I didn’t find a way of achieving this only using XML properties. If anyone knows how to do it, please let me know in the comments!


Create another TextView in your layout:

   tools:text="@string/messageWithSpannableLink" />

Create another string resource in strings.xml:

<string name="messageWithSpannableLink">This is a message with a spannable link inside!\nTap here to open it!</string>

Please note: this time there is no <a href/> tag inside the string!

Now write this code in your activity/fragment:

TextView messageWithSpannableLinkTextView;

public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    ButterKnife.bind(this, view);
    SpannableString spannableString = new SpannableString(getString(R.string.messageWithSpannableLink));
    ClickableSpan clickableSpan = new ClickableSpan() {
        public void onClick(View textView) {
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("")));
    spannableString.setSpan(clickableSpan, spannableString.length() - 20,
            spannableString.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    messageWithSpannableLinkTextView.setText(spannableString, TextView.BufferType.SPANNABLE);

You are done! You should get a TextView like the one in the following screenshot and when you tap on the hyperlink the ClickableSpan->onClick() method should be called, so you can do your operations and let the browser open the link! Cool!


Check out the complete source code on my GitHub here!