How To Create A Launcher Android

Repository

https://github.com/enyason/AndroidLauncherApplication

What Will I Learn?

How to create a custom launcher from scratch
Enable launcher Mode for our Application
Implement Home Screen
Implement App drawer fragment to show all applicationss

Resources

KISS Launcher source - https://github.com/alexander255/kiss-launcher

Difficulty

Intermediate

Tutorial Duration - 35 - 40Mins

Tutorial Content

Today I begin a new tutorial series on how to create a custom android launcher from scratch using android studio.

Launcher is the name given to the part of the Android user interface that lets users customize the home screen (e.g. the phone's desktop), launch mobile apps, make phone calls, and perform other tasks on Android devices (devices that use the Android mobile operating system). source. With this in mind , we will move right away into building a launcher application with the behaviours stated above.

In today's tutorial, we will implement the following features

Enable launcher Mode for our Application
Implement Home Screen with a Home Button
Implement App drawer fragment to show all applications

STEP 1 : Create a New Project

Create a new project and select empty activity to get started

STEP 2 : Enable Launcher Mode

To make our app act and behave like an android launcher, we will add some attributes to the main activity in our manifest file.

          <activity                                      android:name=".MainActivity"                          android:launchMode="singleTask"                          android:theme="@style/AppTheme"                          android:clearTaskOnLaunch="true"                          android:stateNotNeeded="true"            >
            <intent-filter>         <action android:name="android.intent.action.MAIN"            />
            <category android:name="android.intent.category.LAUNCHER"            />
            <category android:name="android.intent.category.HOME"            />
            <category android:name="android.intent.category.DEFAULT"            />
            </intent-filter>
            </activity>

code explanation

The categories android.intent.category.HOME and android.intent.category.DEFAULT will cause our application to behave like a launcher. So whenever we click on the home button, it is listed out as one of the launchers available .
The launch mode is set to single task to make sure that only one instance of this Activity is held by the system at any time

With the above steps implemented, our app should behave like shown in the image below

Implement Home Screen And Apps Drawer Screen With Fragment

To implement the Home and apps drawer screen, we will create two fragments which will be contained in our MainActivity.

STEP 3 : Create A fragment Container in MainActivity Layout

                      <?            xml version="1.0" encoding="utf-8"            ?>            
            <RelativeLayout            
               xmlns:android="http://schemas.android.com/apk/res/android"              
   xmlns:app="http://schemas.android.com/apk/res-auto"              
   xmlns:tools="http://schemas.android.com/tools"              
   android:layout_width="match_parent"            
               android:layout_height="match_parent"                          tools:context="com.nexdev.enyason.androidlauncherapplication.MainActivity">    <FrameLayout            
                          android:layout_width="match_parent"                          android:id="@+id/container"                          android:layout_height="match_parent"></FrameLayout>
            </RelativeLayout>

code explanation

The FrameLayout in the code block above will serve as a container for any fragment being loaded into the MainActivity

STEP 3 : Create Fragment for Home Screen

XML Layout code

                      <?            xml version="1.0" encoding="utf-8"            ?>            
            <RelativeLayout            
                          xmlns:android="http://schemas.android.com/apk/res/android"            
                          xmlns:app="http://schemas.android.com/apk/res-auto"            
                          xmlns:tools="http://schemas.android.com/tools"            
                          android:layout_width="match_parent"            
                          android:layout_height="match_parent"            
               tools:context="com.nexdev.enyason.androidlauncherapplication.MainActivity">
            <ImageView            
                          android:id="@+id/icon_drawer"            
                          android:layout_marginBottom="20dp"            
                          android:layout_centerInParent="true"            
                          android:layout_alignParentBottom="true"            
                          android:src="@drawable/ic_apps"            
                          android:layout_width="wrap_content"            
                          android:layout_height="wrap_content"            />
            </RelativeLayout>

The image view displays the home button icon that provides access to the Apps Drawer Screen

Java code

                      public class            HomeScreenFragment            extends            Fragment {
public            HomeScreenFragment() {}
            @Nullable     @Overridepublic            View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View view = inflater.inflate(R.layout.              fragment_home_screen            ,container,false);return            view;     } }

complete source code

The Home Screen XML layout created at the beginning of STEP 3 is inflated and returned as a view in the onCreateView method of the HomeScreenFragment

STEP 4 : Create Fragment for Apps Drawer

XML Layout code

                      <?            xml version="1.0" encoding="utf-8"            ?>            
            <RelativeLayout            
                          xmlns:android="http://schemas.android.com/apk/res/android"            
                          xmlns:app="http://schemas.android.com/apk/res-auto"            
                          xmlns:tools="http://schemas.android.com/tools"            
                          android:layout_width="match_parent"            
                          android:layout_height="match_parent"            
               tools:context="com.nexdev.enyason.androidlauncherapplication.MainActivity">
            <android.support.v7.widget.CardView            
                   app:cardBackgroundColor="#FFF"            
                          android:layout_width="match_parent"            
                          android:layout_height="match_parent">                       <RelativeLayout              
                              android:layout_width="match_parent"              
                              android:layout_height="match_parent">
              <TextView              
                              android:textColor="#000"              
                              android:textStyle="bold"              
                              android:layout_centerInParent="true"              
                              android:text="Apps Drawer"              
                              android:layout_width="wrap_content"              
                              android:layout_height="wrap_content"              />
              </RelativeLayout>
              </android.support.v7.widget.CardView>
                           </RelativeLayout>

Java code

                      public class            AppsDrawerFragment            extends            Fragment {
public            AppsDrawerFragment() {}
            @Nullable     @Override            public            View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View view = inflater.inflate(R.layout.              fragment_apps_drawer            ,container,false);return            view;     }
            }

STEP 5 : Attach Fragment to MainActivity

In the onCreate menu of the MainActivity, load the HomeScreenFragment

                      public class            MainActivity            extends            AppCompatActivity {
            @Override            protected void            onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);         setContentView(R.layout.              activity_main            );         loadFragment(new            HomeScreenFragment());
            }
private boolean            loadFragment(Fragment fragment) {
                        if            (fragment !=            null) {
            getSupportFragmentManager()                     .beginTransaction()                     .replace(R.id.              container            , fragment)                     .commit();return true;
            }
return false;
            }
            }

code explanation

The loadFragment method takes an instance of the HomeScreenFragment and attach it to the MainActivity, with it's FrameLayout serving as a containing view for the fragment's layout.

With Steps 3,4 & 5 done, our app should look like this :

Implement show all applications Feature in The Drawer Screen

STEP 6 : Create A Java Class with Application Info Attributes

                      public class            AppInfo  {
            CharSequence            label;     CharSequence            packageName;     Drawable            icon; }

STEP 6 : Create a custom Adapter Class that extends the RecyclerView Adapter Class

In the constructor of our custom adapter, we are going to fetch the app list from the phone with all its attribute

                      public class            AppsDrawerAdapter            extends            RecyclerView.Adapter<AppsDrawerAdapter.ViewHolder> {
private static            Context            context;private static            List<AppInfo>            appsList;public            AppsDrawerAdapter(Context c ) {                          context            = c;            setUpApps();     }            public static void            setUpApps(){        PackageManager pManager =            context.getPackageManager();
            appsList            =            new            ArrayList<AppInfo>();         Intent i =            new            Intent(Intent.              ACTION_MAIN            ,            null);         i.addCategory(Intent.              CATEGORY_LAUNCHER            );         List<ResolveInfo> allApps = pManager.queryIntentActivities(i, 0);
for            (ResolveInfo ri : allApps) {             AppInfo app =            new            AppInfo();             app.label            = ri.loadLabel(pManager);             app.packageName            = ri.activityInfo.packageName;
            Log.i(" Log package ",app.packageName.toString());             app.icon            = ri.activityInfo.loadIcon(pManager);appsList.add(app);
            }
            }
            }

complete source code

code explanation

The AppsDrawerAdapter constructor requires a context from the application, which will be used to get the Package Manager.
In the setUpApps method of the AppsDrawerAdapter class, we use the queryIntentActivities method of the PackageManager class to fetch all theIntents that have a category of Intent.CATEGORY_LAUNCHER. The query returns a list of the applications that can be launched by a launcher.
We use a For loop to Loop through the results of the query and add each item to a list named appsList.

STEP 6 : Display The List of Applications in the Apps Drawer Screen

With our List of installed apps available, we can now display it in our Apps Drawer Screen using a recyclerView. Include the following code to the AppDrawer Fragment Class

          @Override
            public void            onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {super.onViewCreated(view, savedInstanceState);
recyclerView            = view.findViewById(R.id.              appDrawer_recylerView            );adapter            =            new            AppsDrawerAdapter(getContext());            layoutManager            =            new            LinearLayoutManager(getContext());                          recyclerView.setLayoutManager(layoutManager);            recyclerView.setAdapter(adapter);
            }