mobile programming lecture 6

Mobile ProgrammingLecture 6

Fragments, Permissions, BroadcastReceivers

Agenda

• Dynamic UI

• LayoutInflater

• Fragments

• Permissions

• BroadcastReceiver

Building the UI Dynamically

So far we've been creating UIs that are defined before runtime

There are some cases where you will need to build the UI dynamically

Consider this XML layout file

Building the UI Dynamically<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent" >

<TableRow

android:layout_width="wrap_content"

android:layout_height="wrap_content" >

<TextView

android:layout_height="wrap_content"

android:text="Medium Text"

android:textAppearance="?android:attr/textAppearanceMedium" />

</TableRow>

<TableRow

</TableRow>

</TableLayout>

Now let's look at Java code that can build a similar UI at runtime

<TableLayout android:layout_width="match_parent"

<TableRow

<TextView

android:text="Medium Text"/>

</TableRow>

<TableRow

</TableRow>

</TableLayout>

public void onCreate(Bundle state) {

super.onCreate(savedInstanceState);

TableLayout layout = new TableLayout(this);

TableRow row = new TableRow(this);

TextView tv = new TextView(this);

tv.setText("Medium Text");

row.addView(tv);

layout.addView(row);

row = new TableRow(this);

setContentView(layout);

<TableRow

<TextView

</TableRow>

<TableRow

</TableRow>

</TableLayout>

row.addView(tv);

This argument asks for a Context, e.g.this or getApplicationContext()

<TableRow

<TextView

</TableRow>

<TableRow

</TableRow>

</TableLayout>

row.addView(tv);

"this" refers to the instance of whichever class the code is currently in!

<TableRow

<TextView

</TableRow>

<TableRow

</TableRow>

</TableLayout>

row.addView(tv);

In this case, it would refer to your Activity (since you know that onCreate() is a method of an Activity)

You can't add the same child element twice!

This is an easy way to get a Force Close

LayoutInflater

• instantiates a layout XML file into its corresponding View objects

• use getLayoutInflater()

LayoutInflater

@Override

setContentView(R.layout.main);

@Override

LayoutInflater inflater =

getLayoutInflater();

setContentView(

inflater.inflate(R.layout.main, null));

LayoutInflater

@Override

setContentView(

Gives you the same result

LayoutInflater

@Override

setContentView(

Second argument is of type ViewGroup

LayoutInflater

@Override

setContentView(

Use it if you want to embed the first argument into the second argument

Fragments

• A Fragment represents a behavior or a portion of user interface in an Activity.

• Add multiple fragments to a screen to avoid switching activities

• Fragments have their own lifecycle, state, and back stack

• Fragments require API Level 11 or greater

Fragments - Lifecycle

A fragment must always be embedded in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle.

• http://developer.android.com/guide/components/fragments.html

onCreateView() is the one we'll be focusing on for now ...

Fragments - Steps for Creating One

1. You must create a subclass of Fragment1. Fragment, ListFragment, etc

2. You must implement onCreateView()1. onCreateView() must return a View

i.e. @Override public View onCreateView( /* required args */)

Fragments - onCreateView()

There are two ways to return a view in your implementation of onCreateView()

1. Use the LayoutInflater argument to instantiate a predefined layout XML file

public class MyFragment extends Fragment {

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle state)

{return inflater.inflate(R.layout.example_fragment, container, false);

extend Fragment, not Activity

The XML layout file to instantiate

The ViewGroup to insert it into

Passing true would create a redundant ViewGroup, so pass false for now

2. Build a UI dynamically and return the root View

{ScrollView scroller = new ScrollView(getActivity());TextView text = new TextView(getActivity());scroller.addView(text);text.setText("Sample Text");

return scroller;

You've seen most of this before!

return scroller;

Last time we used the keyword this to get the Context

return scroller;

Since we're in a Fragment here, and not an Activity ...

return scroller;

We can get the controlling Activity from within the Fragment using getActivity()

return scroller;

This is how we get the Context. Alternatively, we can say getActivity().getApplicationContext()

Fragments - Adding a Fragment

There are 2 ways to add a Fragment

1. Declare the Fragment inside of the Activity's layout file<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="match_parent"> <fragment android:name="edu.fsu.cs.mobile.example.MyFragment" android:id="@+id/list" android:tag="list_fragment" android:layout_weight="1" android:layout_width="match_parent" android:layout_height="match_parent" /> <fragment android:name="edu.fsu.cs.mobile.example.MyOtherFragment" android:id="@+id/viewer" android:tag="viewer_fragment" android:layout_weight="2" android:layout_width="match_parent" android:layout_height="match_parent" /></LinearLayout>

1. Declare the Fragment inside of the Activity's layout file

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="match_parent"> <fragment android:name="edu.fsu.cs.mobile.example.MyFragment" android:id="@+id/list" android:tag="list_fragment" android:layout_weight="1" android:layout_width="match_parent" android:layout_height="match_parent" /> <fragment android:name="edu.fsu.cs.mobile.example.MyOtherFragment" android:id="@+id/viewer" android:tag="viewer_fragment" android:layout_weight="2" android:layout_width="match_parent" android:layout_height="match_parent" /></LinearLayout>

absolute reference to your Fragment class, which includes the package name

Fragment id

Fragment TAG

This works because you return a View object in your onCreateView() method for the specified Fragment

The View then gets embedded into the UI

2. Programmatically add the Fragment to an existing ViewGroup

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

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_height="wrap_content" />

<FrameLayout

android:id="@+id/fragment_container"

</FrameLayout>

</LinearLayout>

Use a FrameLayout as a container for your Fragment

<TextView

<FrameLayout

</FrameLayout>

</LinearLayout>

Remember the id of the container ...

<TextView

<FrameLayout

</FrameLayout>

</LinearLayout>

This is main.xml layout file

public class MyActivity extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

FragmentManager manager = getFragmentManager();

FragmentTransaction trans = manager.beginTransaction();

MyFragment fragment = new MyFragment();

trans.add(R.id.fragment_container, fragment, "my_fragment");

trans.commit();

@Override

trans.commit();

This XML layout file contains the FrameLayout container

@Override

trans.commit();

FragmentManager allows you to interact with Fragments that are in an Activity

@Override

trans.commit();

FragmentTransaction allows you to perform operations on Fragments (add, remove, replace)

@Override

trans.commit();

Our Fragment doesn't exist at this point (was not specified in XML), let's create an instance of it

@Override

trans.commit();

Add our Fragment to the FrameLayout container

@Override

trans.commit();

The unique TAG for your Fragment, so that you can reference it later

@Override

trans.commit();

Update the UI

Fragments - Passing data to

You will often want to pass data from your Activity to your Fragment. You can do this several ways. From within the Activity ...

@Override

public void onCreate(Bundle savedInstance) {

super.onCreate(savedInstance);

fragment.my_custom_field = value;

fragment.setMyCustomField(value);

trans.commit();

@Override

fragment.my_custom_field = value;

fragment.setMyCustomField(value);

trans.commit();

You will need to have my_custom_field as a public field in your Fragment, and setMyCustomField() as a public method

Alternatively, you can use Fragments setArguments(Bundle) and getArguments() methods.

@Override

Bundle extras = new Bundle();

extras.putInt("selected",15);

fragment.setArguments(extras);

trans.commit();

@Override

trans.commit();

You've seen Bundle before!

@Override

trans.commit();

setArguments() takes a Bundle as an argument. This is a standard Fragment method

Then, in your Fragment, you can get the arguments using getArguments()

public class MyFragment extends Fragment{

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle state) {

Bundle args = getArguments();

return new TextView(getActivity());

@Override

public void onActivityCreated(Bundle state) {

super.onActivityCreated(state);

@Override

Bundle args and Bundle state are two separate Bundles. Ignore Bundle state for now

@Override

get the arguments that were passed by the Activity

@Override

onCreateView must return a View

@Override

You may need to get the arguments at this point in the Lifecycle instead

@Override

This is usually if you extended ListFragment instead

Fragments - How to Reference

• A Fragment is not a View!

• You can't call findViewById() in order to reference a Fragment within an Activity

• use getFragmentManager().findFragmentById() or getFragmentManager().findFragmentByTag() instead

• of course, an instance of your Fragment Manager needs to already be a part of your Activity

MyFragment fragment = (MyFragment) manager.findFragmentById(R.id.fragment_id);

MyFragment fragment = (MyFragment) manager.findFragmentByTag("my_fragment");

Fragments - Removing a Fragment

You can also remove Fragments from the UI

You can also replace one Fragment with another

@Override

MyFragment fragment = manager.findFragmentById(R.id.my_fragment);

trans.remove(fragment);

trans.commit();

@Override

trans.commit();

You can only remove it if it was added somehow. This gets a reference to a Fragment that was already added.

@Override

trans.commit();

Remove the Fragment from this Activity

Fragments - Replacing a Fragment

You can replace a Fragment by removing an existing Fragment and adding an new one. But an easier way to do this is to call replace() instead

You can also replace Fragments

@Override

trans.replace(R.id.fragment_container, fragment);

trans.commit();

@Override

trans.commit();

Reference the Fragment (if you don't already have a reference to it)

@Override

trans.commit();

Remove Fragment from the Activity

Fragments - Reference the Activity

• You can reference the controlling Activity from within the Fragment

e.g, in the onCreateView() method of the Fragment class:

View listView = getActivity().findViewById(R.id.list);

Permissions

• no application, by default, has permission to perform any operations that would adversely impact

o other applicationso the operating systemo the user

• How does the system know that this app uses these permissions?

Using Permissions

Permissions requested by your application must be specified in the Android Manifest file.

For example, here we request permission to access the Internet

How to Request Permissions

Your app doesn't request to use any permissions by default

To request to use a permission

1. Open AndroidManifest.xml

2. Click the Permissions tab at the bottom of the Editor

3. Click Add ...

4. Select Uses Permission

5. Select the permission you want to request from the drop-down list

6. Save AndroidManifest.xml

Permissions - WebView Example

A WebView is a View that allows you to load and display web page content to the user

@Override

WebView webview = (WebView) findViewById(R.id.webView1);

webview.setWebViewClient(new WebViewClient() {

@Overridepublic boolean shouldOverrideUrlLoading(WebView view, String url) {

return false;

webview.loadUrl("http://www.google.com");

Of course, this is in our XML layout file somewhere

@Override

return false;

This block of code prevents the system from opening the URL in the default browser

@Override

return false;

It has to return false, in order to load the URL in our webview instead of the default browser

@Override

public boolean shouldOverrideUrlLoading(WebView view, String url) {

return false;

The WebView will not load the URL if you don't have INTERNET permissions!, i.e.

android.permissions.INTERNET

Permissions

There are many more permissions that can be used

You can find a list of them here

Android Application Components

1. Activity

2. Broadcast Receiver

3. Content Provider

4. Service

Broadcast Receiver

• �a component that responds to system wide broadcast announcementso �Incoming SMS, MMS, Email, phone callo Battery low, Screen has turned off, or a picture was

captured.

• �think of a Broadcast receiver as a “gateway” to the other components.

• intended to very little worko Depending on the incoming event to the receiver, it

could start a Service or Activity.

Broadcast Receiver

To add a new Broadcast Receiver• open the AndroidManifest.xml file

• click on the Application tab at the bottom of the window

• under the Application Nodes section, click Add ...

• select Receiver

• in the Attributes for Receiver section, click on the Name* link

• Enter the name of your Broadcast Receivero e.g. "MyBroadcastReceiver"

• Finish

Broadcast Receiver - Manifest File

If you view AndroidManifest.xml in the XML editor, you should see something like this

Broadcast Receiver

Your new Broadcast Receiver file should look something like this

public class MyBroadcastReceiver extends BroadcastReceiver {

@Overridepublic void onReceive(Context context, Intent intent) {

Broadcast Receiver

Event listener for when a broadcast has been received.

Broadcast Receiver

How do you know which broadcasts to listen for?

Registering BroadcastReceiver

There are two ways to register a BroadcastReceiver to listen for a broadcast

1 . Adding an <intent-filter> to the Manifest file

2. Programmatically

1. To add an <intent-filter> to the Manifest and listen for a Broadcast ...

1. Open AndroidManifest.xml and click on the Application Tab at the bottom of the Window

2. Select your BroadcastReceiver

3. Click Add ...

4. Make sure "Create new element in the selected element ... " is selected, then choose Intent Filter

5. Click Add ...

6. Choose Action

7. Select the appropriate permission in the Name drop-down list

a. e.g. android.intent.action.TIME_SET

8. Save AndroidManifest.xml

Alternatively, if you view AndroidManifest.xml in the XML editor, you should see something like this

</receiver>

We need to tell the system which broadcast(s) we want to listen for. First we need to add an <intent-filter> tag

</receiver>

Place the cursor here and press Ctrl + Space

</receiver>

Select <intent-filter>

<intent-filter>

</intent-filter>

</receiver>

<intent-filter>

</intent-filter>

</receiver>

an <intent-filter> describes what this receiver should listen for

<intent-filter>

</intent-filter>

</receiver>

Place the cursor here and press Ctrl + Space

<intent-filter>

</intent-filter>

</receiver>

Select <action/>

<intent-filter><action />

</intent-filter>

</receiver>

Press Ctrl + Space again

<intent-filter>

</intent-filter>

</receiver>

Select android:name

<intent-filter>

</intent-filter>

</receiver>

Let's try receiving a broadcast for when the screen has been turned on

<intent-filter>

</intent-filter>

</receiver>

Press Ctrl + Space again

<intent-filter>

</intent-filter>

</receiver>

Select android.intent.action.TIME_SET

<intent-filter>

</intent-filter>

</receiver>

<intent-filter>

</intent-filter>

</receiver>

2. To register a BroadcastReceiver programmatically ...

public class MainActivity extends Activity {

MyBroadcastReceiver receiver;

@Override public void onCreate(Bundle savedInstanceState) {

receiver = new MyBroadcastReceiver();

IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);

registerReceiver(receiver, filter);

Create a new instance of your receiver

Create an intent filter

The receiver is now registered

BroadcastReceiver - onReceive()

@Override

public void onReceive(Context context, Intent intent) {

Intent myIntent = new Intent(context, ActivityToBeLaunched.class);

Toast.makeText(

context,

"Broadcast Received!",

Toast.LENGTH_LONG).show();

myIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

context.startActivity(myIntent);

Now let's look at our BroadcastReceiver

@Override

Toast.makeText(

context,

At this point, the broadcast has been received

@Override

Toast.makeText(

context,

Let's say we want to launch a new Activity when we receive the broadcast

@Override

Toast.makeText(

context,

And we want to show a Toast

@Override

Toast.makeText(

context,

You need to add flags to your intent this time

@Override

Toast.makeText(

context,

Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag

Unregistering BroadcastReceiver

Sometimes after you start listening for a Broadcast, you may want to STOP listening for it at some point

To UNregister a BroadcastReceiver programmatically ...

@Override

public void onPause() {

unregisterReceiver(receiver);

super.onPause();

@Override

public void onPause() {

unregisterReceiver(receiver);

super.onPause();

You will want to unregister before calling a super.onSomething() method, otherwise you may get Force Close

If you register a BroadcastReceiver programmatically, you should unregister it before your Activity is destroyed!

• otherwise you will have a "leaked" receiver

• Please call unregisterReceiver in o onPause()o onStop()o or onDestroy()

This is important

Code Examples

• BroadcastReceiverExample

• SimpleFragmentUsingXml

• SimpleFragmentProgrammatically

• FragmentActivityReferenceExample

• FragmentTransitionExample

• LayoutInflaterExample

• PermissionsExample

• ComplexFragmentsExample

• DynamicUiExample

References

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

• Android Developers

• The Mobile Lab at Florida State University

• Code Examples

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