Mobile Programming Lecture 5 Composite Views, Activities, Intents and Filters

Mobile ProgrammingLecture 5

Composite Views, Activities, Intents and Filters

Lecture 4 Review

• How do you get the value of a string in the strings.xml file?

• What are the steps to populate a Spinner or ListView using XML?

• How many Android application components are there? Name one.

• How do you launch an Activity B from within Activity A?

Agenda

• ViewFlipper

• SlidingDrawer

• TabLayout

• Activity LifeCycle

• Configuration Changes

• URI

• Intent Filters

ViewFlipper

A ViewFlipper allows you to switch between views that are children of the ViewFlipper

You can find it in the Transitions menu in Graphical Layout

ViewFlipper

<ViewFlipper

android:id="@+id/myViewFlipper"

android:layout_width="match_parent"

android:layout_height="match_parent" >

<RelativeLayout



</RelativeLayout>

<RelativeLayout



</RelativeLayout>

</ViewFlipper>

ViewFlipper

<ViewFlipper




<RelativeLayout



</RelativeLayout>

<RelativeLayout



</RelativeLayout>

</ViewFlipper>

Here I used RelativeLayouts, but you can place any widget you want in here.

ViewFlipper

<ViewFlipper




<TextView


android:layout_height=“wrap_content" />

<TextView


android:layout_height=“match_parent“

/ >

</ViewFlipper>

Here I also used just 2 Views. You can add more than just 2 Views if you want to.

ViewFlipper

ViewFlipper flipper;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

flipper = (ViewFlipper) findViewById(R.id.viewFlipper1);

flipper.setFlipInterval(500);

flipper.startFlipping();

}

ViewFlipper


@Override




flipper = (ViewFlipper) findViewById(R.id.viewFlipper1);

flipper.setFlipInterval(500);

flipper.startFlipping();

}

Here we set the flipper to flip every 500 milliseconds

ViewFlipper


@Override




flipper.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

flipper.showNext();

}

});

}

Here we set the flipper to flip when the flipper is clicked

• FrameLayout is designed to block out an area on the screen to display a single item.

• FrameLayout should be used to hold a single child viewo it can be difficult to organize child views in a way

that's scalable to different screen sizes without the children overlapping each other

FrameLayout

• Example:

FrameLayout

SlidingDrawer

• hides content out of the screen and allows the user to drag a handle to bring the content on screen

• can be used vertically or horizontally

• composed of two children viewso the handle, that the users drags

o the content, attached to the handle and dragged with it.

• should only be used inside of a FrameLayout or a RelativeLayout

SlidingDrawer

• Note: the android:handle and android:content attributes

• There needs to be children with id's matching these attributes

• android:handle

• android:content

• android:orientationo "vertical" or "horizontal"

• android:allowSingleTapo "true" or "false"o allow the user to open the drawer by tapping on the

handle?

SlidingDrawer - useful attributes

• open()

• close()

• setOnDrawerScrollListener(OnDrawerScrollListener)

• setOnDrawOpenListener(OnDrawerOpenListener)

• setOnDrawerCloseListener(OnDrawerCloseListener)

SlidingDrawer - useful methods

It is used to wrap multiple activities into a single window

• navigate through the activities using tabs

TabLayout

TabLayout - Anatomy

TABHOST

TABWIDGET

ACTIVITY

FRAMELAYOUT

TAB CONTENT

• TabHosto container holding TabWidget and

a FrameLayout

• TabWidgeto row of tab buttons

• FrameLayouto container holding the tab contentso each tab content is a child of

FrameLayout

TabLayout - XML<?xml version="1.0" encoding="utf-8"?>

<TabHost xmlns:android="http://schemas.android.com/apk/res/android"

android:id="@android:id/tabhost"

android:layout_width="fill_parent"

android:layout_height="fill_parent">

<LinearLayout

android:orientation="vertical"



<TabWidget

android:id="@android:id/tabs"


android:layout_height="wrap_content" />

<FrameLayout

android:id="@android:id/tabcontent"


android:layout_height="fill_parent" />

</LinearLayout>

</TabHost>

TABHOST

TABWIDGET

ACTIVITY

FRAMELAYOUT

TAB CONTENT

TabLayout - XML<?xml version="1.0" encoding="utf-8"?>

<TabHost xmlns:android="http://schemas.android.com/apk/res/android"

android:id="@android:id/tabhost"



<LinearLayout

android:orientation="vertical"



<TabWidget

android:id="@android:id/tabs"


android:layout_height="wrap_content" />

<FrameLayout

android:id="@android:id/tabcontent"


android:layout_height="fill_parent" />

</LinearLayout>

</TabHost>

TABHOST

TABWIDGET

ACTIVITY

FRAMELAYOUT

TAB CONTENT

Tabs are different Activities, we can set and specify the layout for each tab programmatically

TabLayout

• If you're going to have x number of tabs, create x number of Activities, 1 for each tab, in addition to the TabActivity (Host Activity).

• You can create x number of XML layouts for each tab, or you can reuse the same layout for each tab.

TabLayoutpublic class TabLayoutExampleActivity extends TabActivity {

@Override




TabHost tabHost = getTabHost(); // The activity TabHost

TabHost.TabSpec spec;

Intent intent = new Intent(TabLayoutExampleActivity.this, LinearLayout.class);

spec = tabHost.newTabSpec("linear layout").setIndicator("Linear", null).setContent(intent);

tabHost.addTab(spec);

intent = new Intent(TabLayoutExampleActivity.this, TableLayout.class);

spec = tabHost.newTabSpec("table layout").setIndicator("Table",null).setContent(intent);


}


@Override












}

extend TabActivity


@Override












}

the XML file containing the TabHost, TabWidget, FrameLayout


@Override




TabHost tabHost = getTabHost();








}

Reference to the Activity's TabHost (which was defined in XML)


@Override












}

Reusable TabSpec for each Tab.


@Override












}

The TabSpec tells the TabHost what views represent thetab contents and what the tab buttons should look like.


@Override









Intent intent = new Intent(TabLayoutExampleActivity.this, TableLayout.class);



}

Remember from the previous lecture, this is how we use an Intent object to start another Activity


@Override












}

Refer to this TabActivity's tab host (which will contain the actual tabs)


@Override












}

Create a new tab spec, give it the id "linear layout"


@Override












}

Set the label for the tab (label the user sees) to "Linear". And


@Override












}

We're not using an image for the tabs, so null for this argument


@Override












}

Fill the FrameLayout to hold the Activity specified by this intent


@Override












}

Add the tab to the tabHost, it will now show up in the UI


@Override












}

To add another tab, let's do this all over again!

TabLayout - Rules

• � TabHost must have the id @android:id/tabhost

• �The TabWidget must have the id �@android:id/tabs

• �The FrameLayout must have the id �@android:id/tabcontent

TabHost - useful methods

• setCurrentTab(int)o make this tab the active tab, making it visible in the

UI

• setOnTabChangedListener(OnTabChangedListener)o react to when the active tab changes

Activity LifeCycle

• During the life of an activity, the system calls a core set

of lifecycle methods in a sequence.

• Implementing your activity lifecycle methods properly ensures your app behaves gracefully in many ways, including that it:o Does not crash if the user receives a phone call or switches to another app while

using your app.o Does not consume valuable system resources when the user is not actively

using it.o Does not lose the user's progress if they leave your app and return to it at a later

time.

Activity Lifecycle

• A nice picture of activity lifecycle

• http://developer.android.com/reference/android/app/Activity.html

Activity LifeCycle - onCreate()

• Called when the activity is first created.

• this is where you should do all of your normal static set up: create views, bind data to lists, etc.

• provides you with a Bundle containing the activity's previously frozen state, if there was one.

• always followed by onStart().

Activity LifeCycle - onStart()

• called when the activity is becoming visible to the user

• followed by o onResume() if the activity comes to the foreground

Activity LifeCycle - onRestart()

• called after your activity has been stopped, prior to it being started again

• always followed by onStart()

• called when the activity will start interacting with the user

• at this point your activity is at the top of the activity stack, with user input going to it

• Always followed by onPause()

Activity LifeCycle - onResume()

• called when the system is about to start resuming a previous activity

• this is typically used to commit unsaved changes to persistent data, stop animations and other things that may be consuming CPU, etc

• implementations of this method must be very quick because the next activity will not be resumed until this method returns

• followed by o onResume() if the activity returns back to the fronto onStop() if it becomes invisible to the user.

Activity LifeCycle - onPause()

• called when the activity is no longer visible to the user because another activity has been resumed and is covering this one

• this may happen either because a new activity is being started, an existing one is being brought in front of this one, or this one is being destroyed

• followed by o onRestart() if this activity is coming back to interact with

the usero onDestroy() if this activity is going away

Activity LifeCycle - onStop()

• the final call you receive before your activity is destroyed

• this can happen either because o the activity is finishing (someone called finish() )o the system is temporarily destroying this instance of

the activity due to low memory

• you can distinguish between these two scenarios with the isFinishing() method

Activity LifeCycle - onDestroy()

Reading Assignment

• Please read page 0 – 710 by next class. Pay more attention on the section of Large-Screen Strategies and Tactics.

• We are going to talk about Fragment next week.

Configuration Changes

• In your app, you can detect when the configuration of the device changeso screen orientation, keyboard availability, and

language

• In default, the system will try to handle the changes for you, unless you specify that you want to handle them yourself

Configuration Changes - Manifest

• to specify that, you want to handle orientation and keyboard availability changes by yourself

• open the manifest file and add the bold line<activity

android:configChanges="orientation|keyboardHidden"

android:name=".OnConfigurationChangedExampleActivity"

android:label="@string/app_name" >

<intent-filter>

<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />

</intent-filter>

</activity>

Configuration Changes - Manifest

• This specifies one or more configuration changes that the activity will handle itself when the orientation changes and when keyboard availability changes.

<activity

android:configChanges="orientation|keyboardHidden"

android:name=".OnConfigurationChangedExampleActivity"


<intent-filter>

<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />

</intent-filter>

</activity>

Configuration Changes - Event

Then, to react to the orientation change event, add this method to your Activity

@Override

public void onConfigurationChanged(Configuration newConfig) {

super.onConfigurationChanged(newConfig);

if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {

/* ... */

}

else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {

/* ... */

}

}

Passing Data between Activities

When you start Activity B from Activity A, you may want to send data to Activity B

Activity A Activity B

startActivity B

send some data to B also

Passing Data between Activities

Activity A - onCreate()

Intent intent = new Intent(this,

SecondActivity.class);

Bundle bundle = new Bundle();

bundle.putString("fname","John");

bundle.putString("lname", "Doe");

bundle.putInt("age", 18);

intent.putExtras(bundle);

startActivity(intent);

Activity B - onCreate()

Intent intent = getIntent();

Bundle bundle = intent.getExtras();

if(bundle != null) {

edit1.setText(bundle.getString("fname"));

edit2.setText(bundle.getString("lname"));

int age= bundle.getInt("age");

}

Explicit Intent vs Implicit Intent

• An Intent encapsulates a request, made to Android, for some activity or other receiver to do something.

• If the activity you intend to launch is one of your own, you may find it simplest to create an explicit Intent.o new Intent(this, MyListViewActivity.class);

• You can also start up activities from the operating system or third-party apps using implicit intent.o Implicit intent works a lot like the Web HTTP.

Implicit Intent

• Implicit Intent o Action + URI (“data”)o these are almost exactly analogous to HTTP verbs (POST,

GET) and URLs — the action is the verb, and the “ data” is a Uri, such as http://commonsware.com

• android.intent.action:o MAINo MUSIC_PLAYERo VIEWo WEB_SEARCH

URIs

• Uniform Resource Identifier that identifies an abstract or physical resource, as specified by RFC 2396.

• The URI class can both parse URI strings into parts and compose URI strings from parts.

• There are 4 main parts to a URIo Scheme, port, host, and path

• http://developer.android.com/reference/java/net/URI.html

http://www.ietf.org/rfc/rfc2396.txt

URIs - Examples - Hierarchical

http://mobile.cs.fsu.edu/androidhttp://twitter.comfile:///tmp/android.txt

scheme host port path

http mobile.cs.fsu.edu 80 android

http twitter.com

file /tmp/android.txt

URIs - Examples - Opaque

mailto:robots.example.com

scheme scheme-specific part

mailto robots.example.com

URIs - Parsing URIs

URI uri = Uri.parse("http://www.google.com");

String scheme = uri.getScheme();

String host = uri.getHost();

int port = uri.getPort();

String path = uri.getPath();

String schemeSpecificPart = uri.getSchemeSpecificPart();

Intent Filters

To inform the system which implicit intents they can handle, activities, services, and broadcast receivers can have one or more intent filters

• each filter describes a capability of the component, a set of intents that the component is willing to receive

• it filters in intents of a desired type, while filtering out unwanted intents — but only unwanted implicit intents (those that don't name a target class)

Intent Filters

• explicit intento always delivered to its target, no matter what it

contains; the filter is not consulted

• implicit intento delivered to a component only if it can pass through

one of the component's filters

Intent Filters

• explicit intento always delivered to its target, no matter what it

contains; the filter is not consulted

• implicit intento delivered to a component only if it can pass through

one of the component's filters

We have seen this before!new Intent(A.this, B.class)

Intent Filters

How does Android know that you may want to open the YouTube app when you try to watch a video on YouTube?

Using Intent Filters

We will create an app that can be used to launch links at

o http://mobile.cs.fsu.edu

http://mobile.cs.fsu.edu/

Intent Filters

<activity

android:name=".MyActivity"


<intent-filter>

<data

android:scheme="http"

android:host="mobile.cs.fsu.edu" />

<action android:name="android.intent.action.VIEW" />

<category android:name="android.intent.category.DEFAULT"></category>

<category android:name="android.intent.category.BROWSABLE"></category>

</intent-filter>

</activity>

Intent Filters

<activity



<intent-filter>

<data






</intent-filter>

</activity>

Intent Filters

<activity



<intent-filter>

<data






</intent-filter>

</activity>

Intent Filters

<activity



<intent-filter>

<data android:scheme="http"





</intent-filter>

</activity>

Display data to the user. Generic action you can use on a piece of data to get the most reasonable thing to occur

Intent Filters

<activity



<intent-filter>

<data






</intent-filter>

</activity>

Set if the Activity should be an option for the default action on a piece of data.

Intent Filters

<activity



<intent-filter>

<data





<category android:name="android.intent.category.BROWSABLE">

</category>

</intent-filter>

</activity>

Activities that can be safely invoked from a browser must support this category. It's required here.

Intent Filters

<activity



<intent-filter>

<data





<category android:name="android.intent.category.BROWSABLE">

</category>

</intent-filter>

</activity>

This is an Implicit Intent!

References

• The Busy Coder's Guide to Android Development - Mark Murphy

• Android Developers

• The Mobile Lab at Florida State University

http://commonsware.com/

http://commonsware.com/

http://developer.android.com/

http://en.wikipedia.org/wiki/Event-driven_programming

Documents

Mobile Programming Lecture 5 Composite Views, Activities, Intents and Filters