11. When does onResume() method called?
onResume() method is an activity lifecycle method. This is called
when the activity come to foreground. You can override this method in
your activity to execute code when activity is started, restarted or
comes to foreground.
12. How to launch an activity in your
application?
For launching an activity, we need to create an explicit intent
that defines the activity that we wish to start. In the below code
snippet, the first parameter to Intent constructor is the current
activity context and the second parameter is your new activity
class.startActivity() method can be
called on Activity context.
Intent intent = new Intent(this,
SecondActivity.class);
startActivity(intent);
If you want to start an activity from fragment
Intent intent = new Intent(getActivity(),
SecondActivity.class);
getActivity().startActivity(intent);
13. How to define an Activity as launcher
activity in application Manifest file?
All the activities used in the application should be defined in
application manifest file. For launcher activity you need to define
intent filter as shown in the below code snippets.
<activity android:name=".MyActivity"
android:label="@string/app_name">
<intent-filter>
<action
android:name="android.intent.action.MAIN" />
<category
android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
14. What is a ANR ?
ANR is short for Application Not Responding. Android systems shows
this dialog, if application is performing too much of task on main
thread and been unresponsive for a long period of time.
15. What are the measures to avoid application
ANR?
ANR in application is annoying to user. It can be caused due to
various reasons. Below are some of the tips to avoid ANR
Perform all you long running
network or database operation in separate thread
If you have too much of background
tasks, then take it off the UI thread. You may use IntentService
Server not responding for longer
period can be guilt for ANR. To avoid always define HTTP time out
for your all your webs service calls.
- Be watchful of infinite loops during your complex
calculations
16. What is the difference between a regular .png
and a nine-patch image?
The nine patch images are extension with
.9.png.
Nine-patch image allows resizing that can be used as background or
other image size requirements for the target device. The Nine-patch
refers to the way you can resize the image: 4 corners that are
unscaled, 4 edges that are scaled in 1 axis, and the middle one that
can be scaled into both axes.
17. How to share text using android share Intent
?
Share intent is an easy and convenient way of sharing content of
your application with other apps.
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, "This
is my text to send.");
sendIntent.setType("text/plain");
startActivity(sendIntent);
18. What is the use of WebView in android?
A WebView is an android UI component that displays webpages. It
can either display a remote webpage or can also load static HTML
data. This encompasses the functionality of a browser that can be
integrated to application. WebView uses the WebKit rendering engine
to display web pages and includes methods to navigate forward and
backward through a history, zoom in and out, etc.
19. Define different kind of context in android
Context defines the current state of application or object.
Context provides access to things such as creating new activity
instance, access databases, start a service, etc. You can get
the context by invoking
getApplicationContext(),
getContext(),
getBaseContext()
or
this when in the activity class.
//Creating ui instance
ImageButton button = new
ImageButton(getContext());
//creating adapter
ListAdapter adapter = new
SimpleCursorAdapter(getApplicationContext(), ...);
//querying content provider
getApplicationContext().getContentResolver().query(uri,
...);
//start activity. Here this means activity
context
Intent intent = new
Intent(this, SecondActivity.class);
20. What are the different storage methods in
android
Android offers several different options for data persistence.
Shared Preferences
– Store private primitive data in key-value pairs. This sometimes
gets limited as it offers only key value pairs. You cannot save your
own java types.
Internal Storage
– Store private data on the device memory
External Storage
– Store public data on the shared external storage
- SQLite Databases – Store structured data
in a private database. You can define many number of tables and can
store data like other RDBMS.
