Effective Navigation in Android
Today we are covering effective navigation in android. One of the very first steps to designing and developing an Android application is to determine what users are able to see and do with the app. Once you know what kinds of data users are interacting with in the app, the next step is to design the interactions that allow users to navigate across, into, and back out from the different pieces of content within the app.
This class shows you how to plan out the high-level screen hierarchy for your application and then choose appropriate forms of navigation to allow users to effectively and intuitively traverse your content. Each lesson covers various stages in the interaction design process for navigation in Android applications, in roughly chronological order. After going through the lessons in this class, you should be able to apply the methodology and navigation paradigms outlined here to your own applications, providing a coherent navigation experience for your users.
====================================================================
CollectionDemoActivity.class
-------------------------------------------------------------------------------------------------------------
import android.app.ActionBar;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.app.TaskStackBuilder;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class CollectionDemoActivity extends FragmentActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments representing
* each object in a collection. We use a {@link android.support.v4.app.FragmentStatePagerAdapter}
* derivative, which will destroy and re-create fragments as needed, saving and restoring their
* state in the process. This is important to conserve memory and is a best practice when
* allowing navigation between objects in a potentially large collection.
*/
DemoCollectionPagerAdapter mDemoCollectionPagerAdapter;
/**
* The {@link android.support.v4.view.ViewPager} that will display the object collection.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_collection_demo);
// Create an adapter that when requested, will return a fragment representing an object in
// the collection.
//
// ViewPager and its adapters use support library fragments, so we must use
// getSupportFragmentManager.
mDemoCollectionPagerAdapter = new DemoCollectionPagerAdapter(getSupportFragmentManager());
// Set up action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home button should show an "Up" caret, indicating that touching the
// button will take the user one step up in the application's hierarchy.
actionBar.setDisplayHomeAsUpEnabled(true);
// Set up the ViewPager, attaching the adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mDemoCollectionPagerAdapter);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This is called when the Home (Up) button is pressed in the action bar.
// Create a simple intent that starts the hierarchical parent activity and
// use NavUtils in the Support Package to ensure proper handling of Up.
Intent upIntent = new Intent(this, MainActivity.class);
if (NavUtils.shouldUpRecreateTask(this, upIntent)) {
// This activity is not part of the application's task, so create a new task
// with a synthesized back stack.
TaskStackBuilder.from(this)
// If there are ancestor activities, they should be added here.
.addNextIntent(upIntent)
.startActivities();
finish();
} else {
// This activity is part of the application's task, so simply
// navigate up to the hierarchical parent activity.
NavUtils.navigateUpTo(this, upIntent);
}
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A {@link android.support.v4.app.FragmentStatePagerAdapter} that returns a fragment
* representing an object in the collection.
*/
public static class DemoCollectionPagerAdapter extends FragmentStatePagerAdapter {
public DemoCollectionPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = new DemoObjectFragment();
Bundle args = new Bundle();
args.putInt(DemoObjectFragment.ARG_OBJECT, i + 1); // Our object is just an integer :-P
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
// For this contrived example, we have a 100-object collection.
return 100;
}
@Override
public CharSequence getPageTitle(int position) {
return "OBJECT " + (position + 1);
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DemoObjectFragment extends Fragment {
public static final String ARG_OBJECT = "object";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_collection_object, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
Integer.toString(args.getInt(ARG_OBJECT)));
return rootView;
}
}
}
===============================================================
MainActivity.class
---------------------------------------------------------------------------------------------------
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
* three primary sections of the app. We use a {@link android.support.v4.app.FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
/**
* The {@link ViewPager} that will display the three primary sections of the app, one at a
* time.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home/Up button should not be enabled, since there is no hierarchical
// parent.
actionBar.setHomeButtonEnabled(false);
// Specify that we will be displaying tabs in the action bar.
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// When swiping between different app sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by the adapter.
// Also specify this Activity object, which implements the TabListener interface, as the
// listener for when this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mAppSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new LaunchpadSectionFragment();
default:
// The other sections of the app are dummy placeholders.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
fragment.setArguments(args);
return fragment;
}
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
return "Section " + (position + 1);
}
}
/**
* A fragment that launches other parts of the demo application.
*/
public static class LaunchpadSectionFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
// Demonstration of a collection-browsing activity.
rootView.findViewById(R.id.demo_collection_button)
.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
startActivity(intent);
}
});
// Demonstration of navigating to external activities.
rootView.findViewById(R.id.demo_external_activity)
.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Create an intent that asks the user to pick a photo, but using
// FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET, ensures that relaunching
// the application from the device home screen does not return
// to the external activity.
Intent externalActivityIntent = new Intent(Intent.ACTION_PICK);
externalActivityIntent.setType("image/*");
externalActivityIntent.addFlags(
Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
startActivity(externalActivityIntent);
}
});
return rootView;
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
=============================================================
------------------------------------------------------------------------------------
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--
This title strip will display the currently visible page title, as well as the page
titles for adjacent pages.
-->
<android.support.v4.view.PagerTitleStrip android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:background="#33b5e5"
android:textColor="#fff"
android:paddingTop="4dp"
android:paddingBottom="4dp" />
</android.support.v4.view.ViewPager>
==============================================================
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
==========================================================
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/text1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:textSize="128sp"
android:padding="32dp" />
===========================================================
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/text1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:textSize="24sp"
android:padding="32dp" />
=========================================================
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center">
<Button android:id="@+id/demo_collection_button"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="@string/demo_collection"/>
<Button android:id="@+id/demo_external_activity"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/demo_external_activity" />
</LinearLayout>
</FrameLayout>
Today we are covering effective navigation in android. One of the very first steps to designing and developing an Android application is to determine what users are able to see and do with the app. Once you know what kinds of data users are interacting with in the app, the next step is to design the interactions that allow users to navigate across, into, and back out from the different pieces of content within the app.
This class shows you how to plan out the high-level screen hierarchy for your application and then choose appropriate forms of navigation to allow users to effectively and intuitively traverse your content. Each lesson covers various stages in the interaction design process for navigation in Android applications, in roughly chronological order. After going through the lessons in this class, you should be able to apply the methodology and navigation paradigms outlined here to your own applications, providing a coherent navigation experience for your users.
====================================================================
CollectionDemoActivity.class
-------------------------------------------------------------------------------------------------------------
import android.app.ActionBar;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.app.TaskStackBuilder;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class CollectionDemoActivity extends FragmentActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments representing
* each object in a collection. We use a {@link android.support.v4.app.FragmentStatePagerAdapter}
* derivative, which will destroy and re-create fragments as needed, saving and restoring their
* state in the process. This is important to conserve memory and is a best practice when
* allowing navigation between objects in a potentially large collection.
*/
DemoCollectionPagerAdapter mDemoCollectionPagerAdapter;
/**
* The {@link android.support.v4.view.ViewPager} that will display the object collection.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_collection_demo);
// Create an adapter that when requested, will return a fragment representing an object in
// the collection.
//
// ViewPager and its adapters use support library fragments, so we must use
// getSupportFragmentManager.
mDemoCollectionPagerAdapter = new DemoCollectionPagerAdapter(getSupportFragmentManager());
// Set up action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home button should show an "Up" caret, indicating that touching the
// button will take the user one step up in the application's hierarchy.
actionBar.setDisplayHomeAsUpEnabled(true);
// Set up the ViewPager, attaching the adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mDemoCollectionPagerAdapter);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This is called when the Home (Up) button is pressed in the action bar.
// Create a simple intent that starts the hierarchical parent activity and
// use NavUtils in the Support Package to ensure proper handling of Up.
Intent upIntent = new Intent(this, MainActivity.class);
if (NavUtils.shouldUpRecreateTask(this, upIntent)) {
// This activity is not part of the application's task, so create a new task
// with a synthesized back stack.
TaskStackBuilder.from(this)
// If there are ancestor activities, they should be added here.
.addNextIntent(upIntent)
.startActivities();
finish();
} else {
// This activity is part of the application's task, so simply
// navigate up to the hierarchical parent activity.
NavUtils.navigateUpTo(this, upIntent);
}
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A {@link android.support.v4.app.FragmentStatePagerAdapter} that returns a fragment
* representing an object in the collection.
*/
public static class DemoCollectionPagerAdapter extends FragmentStatePagerAdapter {
public DemoCollectionPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = new DemoObjectFragment();
Bundle args = new Bundle();
args.putInt(DemoObjectFragment.ARG_OBJECT, i + 1); // Our object is just an integer :-P
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
// For this contrived example, we have a 100-object collection.
return 100;
}
@Override
public CharSequence getPageTitle(int position) {
return "OBJECT " + (position + 1);
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DemoObjectFragment extends Fragment {
public static final String ARG_OBJECT = "object";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_collection_object, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
Integer.toString(args.getInt(ARG_OBJECT)));
return rootView;
}
}
}
===============================================================
MainActivity.class
---------------------------------------------------------------------------------------------------
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
* three primary sections of the app. We use a {@link android.support.v4.app.FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
/**
* The {@link ViewPager} that will display the three primary sections of the app, one at a
* time.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home/Up button should not be enabled, since there is no hierarchical
// parent.
actionBar.setHomeButtonEnabled(false);
// Specify that we will be displaying tabs in the action bar.
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// When swiping between different app sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by the adapter.
// Also specify this Activity object, which implements the TabListener interface, as the
// listener for when this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mAppSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new LaunchpadSectionFragment();
default:
// The other sections of the app are dummy placeholders.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
fragment.setArguments(args);
return fragment;
}
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
return "Section " + (position + 1);
}
}
/**
* A fragment that launches other parts of the demo application.
*/
public static class LaunchpadSectionFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
// Demonstration of a collection-browsing activity.
rootView.findViewById(R.id.demo_collection_button)
.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
startActivity(intent);
}
});
// Demonstration of navigating to external activities.
rootView.findViewById(R.id.demo_external_activity)
.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Create an intent that asks the user to pick a photo, but using
// FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET, ensures that relaunching
// the application from the device home screen does not return
// to the external activity.
Intent externalActivityIntent = new Intent(Intent.ACTION_PICK);
externalActivityIntent.setType("image/*");
externalActivityIntent.addFlags(
Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
startActivity(externalActivityIntent);
}
});
return rootView;
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
=============================================================
------------------------------------------------------------------------------------
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--
This title strip will display the currently visible page title, as well as the page
titles for adjacent pages.
-->
<android.support.v4.view.PagerTitleStrip android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:background="#33b5e5"
android:textColor="#fff"
android:paddingTop="4dp"
android:paddingBottom="4dp" />
</android.support.v4.view.ViewPager>
==============================================================
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
==========================================================
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/text1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:textSize="128sp"
android:padding="32dp" />
===========================================================
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/text1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:textSize="24sp"
android:padding="32dp" />
=========================================================
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center">
<Button android:id="@+id/demo_collection_button"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginBottom="16dp"
android:text="@string/demo_collection"/>
<Button android:id="@+id/demo_external_activity"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/demo_external_activity" />
</LinearLayout>
</FrameLayout>
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