All About ANDROID

Singleton classes comes under "Creational design pattern", Singleton pattern restricts from creating multiple instances of the class,and ensure that only one object should be available in the JVM, there are different ways to implement singleton classes as below :- Ways to define Singleton classes :- 1. By defining the singleton class object as static final variable, this is known as early initialization of singleton object. public class SingletoneClassExample{ Private static final instance = new SingletoneClassExample(); // Define private constructor to avoid other classes from creating instance private SingletoneClassExample(){ } public static SingletoneClassExample getInstance(){         return instance;   } } By creating singleton class using above method the class object will be created at class loading itself, so if application is not using this class still the object will be created. 2. Define singleton class object on method call public clas...

          Shared preferences allows android application to save data in the form of "Key-Value" pair, shared preferences will be an , XML file which will be stored in applications internal storage space under " shared_prefs " folder under data/data/(package name of the application) . Shared Preferences won't clear data after "force close" of an application, it will get cleared only in case of user clears the application data (under settings -> apps -> clear Data) or uninstall an application. Shared preferences can be edited using SharedPreferences.Editor class. APIs to access shared preference below, getDefaultSharedPreferences()  :- Return default shared preference file which is used by PrefrenceManager in the given context. getSharedPreferences(String my_prf_name, int mode) :- Returns shared preference file of the given name. Below are  sample code snippets, 1. Saving data in to the shared preferences, //Retrieve shared prefere...

While adding call logs we can set number in CallLog.Calls.NUMBER field , same for date  and duration. CallLog.Calls.CACHED_NAME will be filled with the cached name in case if the number is already saved in Contacts database. ContentValues values = new ContentValues(); values.put(CallLog.Calls.NUMBER, number); values.put(CallLog.Calls.DATE, System.currentTimeMillis()); values.put(CallLog.Calls.DURATION, 0); values.put(CallLog.Calls.TYPE, CallLog.Calls.OUTGOING_TYPE); //Type of call Outgoing/Incoming/Missed etc values.put(CallLog.Calls.NEW, 1); values.put(CallLog.Calls.CACHED_NAME, ""); values.put(CACHED_NUMBER_TYPE, 0); values.put(CACHED_NUMBER_LABEL, ""); this.getContentResolver().insert(CallLog.Calls.CONTENT_URI, values); Below Permissions are required to add call logs , add it in Manifest file, <uses-permission android:name="android.permission.WRITE_CALL_LOG"></uses-permission> <uses-permission android:name="android.perm...

I'm working on Android hybrid apps from last 5 years, its very tough to stay in touch with Native android UI, Now I started learning through sample applications, so thought of sharing my learning here.           RecyclerView has came with Material design in Android Lollipop, RecyclerView is advanced, flexible version of Listview, RecyclerView uses the view holder pattern  and improve the performance by reusing off screen views and rebinds them to the data which is scrolling on the screen, now lets see the difference between list view and recyclerview. Difference between RecyclerView and Listview :- 1. RecyclerView forces to use RecyclerView.ViewHolder (Inbuilt view Holder) to hold the elements, to reuse the cells while scrolling, which was optional in Listview which we used to create in adapters getView() method. 2. Animation while adding list items or removing list items are already added in the recyclerview. 3. List views were only of vertical...

If you want to start an android application on device restarts, you need to listen for BOOT_COMPLETED broadcast in the manifest file and launch the Launcher activity in onreceive of BOOT_COMPLETED broadcast receiver. Follow below steps to launch activity on device boot up :- 1. Register for Boot completed receiver in Android Manifest file. Add below Permission to receive BOOT_COMPLETED broadcast, <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" /> Register for Boot completed broadcast receiver , <receiver android:name="AppAutostartReceiver" android:enabled="true" > <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> </intent-filter> </receiver> 2. Add custom Broadcast receiver in the application, public class AppAutostartReceiver extends BroadcastReceiver { @Override public void onReceive(Context cont...

Launch modes defines how an instance of an activity is associated with the current task. You can define different launch modes as below, 1. Standard 2. Single Top 3. Single Task 4. Single Instance 1. Standard :- Default activity mode will be Standard.Activity instance will be created every time for each new intent. 2. Single Top :-  Single top activity will be created if the activity is not on the top of the stack , if activity is on the top of the stack OnNewIntent() of activity gets called otherwise new instance will be created and pushed in to the stack. 3. Single Task :- Instance of the activity will be created only if it doesn't exist in the system otherwise it will be moved to front and onNewIntent() will be called. 4. Single Instance :- Same as single task, any activity launched from this activity will start the new task always so single instance activity will not share the same stack with other activities, so OnNewIntent() will be called for every inte...