- What is r in Android?
- What is activity life cycle?
- What is Android application life cycle?
- What is onNewIntent?
- What is the purpose of setContentView () function?
- What is the purpose of super onCreate () in android?
- What is findViewById () method used for?
- How do I use getTag on Android?
- Why @override is used in Android?
- What is the difference between onCreate and onStart Android?
- What is the use of view in Android?
- What is simple_list_item_1?
- How do I open activitymain XML?
- How do you kill an activity?
- What is R layout?
- What is onCreate method?
- What does finish () do in Android?
- What is onBackPressed in Android?
- What is toast in Android?
- Why do we need to call setContentView () in onCreate () of activity class?
- What is setContentView?
What is r in Android?
java is an auto-generated file by aapt (Android Asset Packaging Tool) that contains resource IDs for all the resources of res/ directory.
If you create any component in the activity_main.
xml file, id for the corresponding component is automatically created in this file..
What is activity life cycle?
An activity is the single screen in android. … It is like window or frame of Java. By the help of activity, you can place all your UI components or widgets in a single screen. The 7 lifecycle method of Activity describes how activity will behave at different states.
What is Android application life cycle?
Activity-lifecycle concepts To navigate transitions between stages of the activity lifecycle, the Activity class provides a core set of six callbacks: onCreate() , onStart() , onResume() , onPause() , onStop() , and onDestroy() . The system invokes each of these callbacks as an activity enters a new state.
What is onNewIntent?
Loading when this answer was accepted… This is called for activities that set launchMode to “singleTop” in their package, or if a client used the FLAG_ACTIVITY_SINGLE_TOP flag when calling startActivity(Intent).
What is the purpose of setContentView () function?
setContentView() is a very important function when it comes to programming with Android. One has to understand its use completely to work with Android UserInterface. Basically what this function does is display the Layout created thorugh XML or the Dynamically created layout view in the Screen.
What is the purpose of super onCreate () in android?
When we override a method, we have the option of completely replacing the method in our class, or of extending the existing parent class’ method. By calling super. onCreate(savedInstanceState); , you tell the Dalvik VM to run your code in addition to the existing code in the onCreate() of the parent class.
What is findViewById () method used for?
Safe code using binding objects findViewById is the source of many user-facing bugs in Android. It’s easy to pass an id that’s not in the current layout — producing null and a crash. And, since it doesn’t have any type-safety built in it’s easy to ship code that calls findViewById
How do I use getTag on Android?
Enter getTag / setTag : button1. setTag(1); button2. setTag(2);…The main reason is that code like that becomes unsupportable pretty quickly.It is non-obvious for other developers what you designed to store as tag in the view. … It just stores an Object , which requires to be cast when you want to getTag .More items…•
Why @override is used in Android?
So the reason to use the @Override annotation is to explicitly declare method overriding. Its a Java annotation (not Android-specific). You use it to mean for this method to override a method. … The compile will now give an error because the method does not override another method.
What is the difference between onCreate and onStart Android?
onCreate() is called when the when the activity is first created. onStart() is called when the activity is becoming visible to the user.
What is the use of view in Android?
View objects are used specifically for drawing content onto the screen of an Android device. While you can instantiate a View in your Java code, the easiest way to use them is through an XML layout file. An example of this can be seen when you create an simple “Hello World” application in Android Studio.
What is simple_list_item_1?
As mentioned by Klap “android.R.layout.simple_list_item_1 is a reference to an built-in XML layout document that is part of the Android OS” All the layouts are located in: sdk\platforms\android-xx\data\res\layout. To view the XML of layout : Eclipse: Simply type android.
How do I open activity
In the Project window, open app > res > layout > activity_main. xml. To make room for the Layout Editor, hide the Project window. To do so, select View > Tool Windows > Project, or just click Project on the left side of the Android Studio screen.
How do you kill an activity?
9 Answers. You can also add android:noHistory=”true” to your Activity tag in AndroidManifest. xml . Yes, all you need to do is call finish() in any Activity you would like to close.
What is R layout?
In Android R is an Java-class that is auto-generated from your resources by the build process. The R. layout member is a auto-generated class that contains all IDs for layouts.
What is onCreate method?
onCreate(Bundle savedInstanceState) Function in Android: Basically Bundle class is used to stored the data of activity whenever above condition occur in app. onCreate() is not required for apps. But the reason it is used in app is because that method is the best place to put initialization code.
What does finish () do in Android?
finish() work in android. On Clicking the back button from the New Activity, the finish() method is called and the activity destroys and returns to the home screen.
What is onBackPressed in Android?
onBackPressed() or finish() gives different behavior than backgrounding the application. … The user can have the task moved into the background, finish() the activity explicitly, or use the default behavior (which calls finish() anyway).
What is toast in Android?
A toast provides simple feedback about an operation in a small popup. It only fills the amount of space required for the message and the current activity remains visible and interactive. Toasts automatically disappear after a timeout.
Why do we need to call setContentView () in onCreate () of activity class?
As onCreate() of an Activity is called only once, this is the point where most initialization should go: calling setContentView(int) to inflate the activity’s UI, using findViewById to programmatically interact with widgets in the UI, calling managedQuery(android.
What is setContentView?
Actually setContentView() is a method part of android. app. Activity class. It helps to set our content or render our layout on the screen. Based on the value given by the user, views will be inflated and rendered after the measurement of the screen, root view, and its child views.