Android Studio

Chapter 8

How to work with

menus and preferences

Chapter 8

How to work with menus and preferences

Objectives

Applied

1. Given the specifications for a menu that contains one or more

items, define the menu and its items and handle the events that

occur when users select those items.

2. Given the specifications for the preferences for an app, use a

fragment to allow the user to set those preferences.

Objectives

Applied

Given the specifications for a menu that contains one or more items, define the menu and its items and handle the events that occur when users select those items.

Given the specifications for the preferences for an app, use a fragment to allow the user to set those preferences.

Objectives (continued)

Knowledge

1. Name and describe the most common type of menu.

2. Distinguish between an action item and the action overflow

item.

3. Describe how Android decides whether to display an item as

an action item or a menu item.

4. Explain how to use an intent to start an activity.

5. In general, explain how the Preferences API works and list one

of its benefits.

Objectives (continued)

Knowledge

Name and describe the most common type of menu.

Distinguish between an action item and the action overflow item.

Describe how Android decides whether to display an item as an action item or a menu item.

Explain how to use an intent to start an activity.

In general, explain how the Preferences API works and list one of its benefits.

An activity with an options menu

that has two items

An activity with an options menu that has two items

The same options menu displayed from an

action overflow icon

The same options menu displayed from an action overflow icon

Two action items displayed as text

Two action items displayed as icons

Two action items displayed as text

Two action items displayed as icons

One action icon and an overflow action icon

One action icon and an overflow action icon

Three types of menus

 An options menu typically drops down from the action

overflow icon as shown earlier. However, it can also be

displayed across the bottom of the screen as shown earlier.

 A floating context menu appears as a floating list of menu

items when a user performs a long click on the widget.

Alternately, contextual action mode can display action items

that apply to the selected item or items.

 A popup menu usually appears as a list below a widget or

action item.

Three types of menus

An options menu typically drops down from the action overflow icon as shown earlier. However, it can also be displayed across the bottom of the screen as shown earlier.

A floating context menu appears as a floating list of menu items when a user performs a long click on the widget. Alternately, contextual action mode can display action items that apply to the selected item or items.

A popup menu usually appears as a list below a widget or action item.

The file that contains the XML for the menu

res\menu\activity_tip_calculator.xml

The XML for the menu

<menu xmlns:android=

"http://schemas.android.com/apk/res/android">

<item android:id="@+id/menu_settings"

android:title="@string/ menu_settings"

android:icon="@drawable/ic_settings"

android:showAsAction="ifRoom" />

<item android:id="@+id/menu_about"

android:title="@string/menu_about"

android:icon="@drawable/ic_about"

android:showAsAction="never" />

</menu>

The file that contains the XML for the menu

res\menu\activity_tip_calculator.xml

The XML for the menu

<menu xmlns:android=

"http://schemas.android.com/apk/res/android">

<item android:id="@+id/menu_settings"

android:title="@string/menu_settings"

android:icon="@drawable/ic_settings"

android:showAsAction="ifRoom" />

<item android:id="@+id/menu_about"

android:title="@string/menu_about"

android:icon="@drawable/ic_about"

android:showAsAction="never" />

</menu>

Some attributes of a menu item

title

icon

showAsAction

orderInCategory

Typical values for the showAsAction attribute

always

never

ifRoom

Some attributes of a menu item

title

icon

showAsAction

orderInCategory

Typical values for the showAsAction attribute

always

never

ifRoom

The location of the icon files for the items

res\drawable-xhdpi\ic_settings.png

res\drawable-xhdpi\ic_about.png

A directory that has standard icons for API 23

\sdk\platforms\android-23\data\res\drawable-xhdpi

The location of the icon files for the items

res\drawable-xhdpi\ic_settings.png

res\drawable-xhdpi\ic_about.png

A directory that has standard icons for API 23

\sdk\platforms\android-23\data\res\drawable-xhdpi

The code that displays the menu

@Override

public boolean onCreateOptionsMenu(Menu menu) {

getMenuInflater().inflate(

R.menu.activity_tip_calculator, menu);

return true;

}

The code that displays the menu

@Override

public boolean onCreateOptionsMenu(Menu menu) {

getMenuInflater().inflate(

R.menu.activity_tip_calculator, menu);

return true;

}

The code that handles the menu item events

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.menu_settings:

Toast.makeText(this, "Settings",

Toast.LENGTH_SHORT).show();

return true;

case R.id.menu_about:

Toast.makeText(this, "About",

Toast.LENGTH_SHORT).show();

return true;

default:

return super.onO ptionsItemSelected(item);

}

}

The code that handles the menu item events

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.menu_settings:

Toast.makeText(this, "Settings",

Toast.LENGTH_SHORT).show();

return true;

case R.id.menu_about:

Toast.makeText(this, "About",

Toast.LENGTH_SHORT).show();

return true;

default:

return super.onOptionsItemSelected(item);

}

}

Code that starts a new activity

Two statements

Intent settings = new Intent(

getApplicationContext(), SettingsActivity.class);

startActivity(settings);

One statement

startActivity(new Intent(

getApplicationContext(), SettingsActivity.class));

Code that starts a new activity

Two statements

Intent settings = new Intent(

getApplicationContext(), SettingsActivity.class);

startActivity(settings);

One statement

startActivity(new Intent(

getApplicationContext(), SettingsActivity.class));

Code that uses menu items to start new activities

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.menu_settings:

startActivity(new Intent(

getApplicationContext(),

SettingsActivity.class));

return true;

case R.id.menu_about:

startActivity(new Intent(

getApplicationContext(),

AboutActivity.class));

return true;

default:

return super.onOptionsItemSelected(item);

}

}

Code that uses menu items to start new activities

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.menu_settings:

startActivity(new Intent(

getApplicationContext(),

SettingsActivity.class));

return true;

case R.id.menu_about:

startActivity(new Intent(

getApplicationContext(),

AboutActivity.class));

return true;

default:

return super.onOptionsItemSelected(item);

}

}

The Settings activity

The Settings activity

The dialog for the “Rounding?” item

The dialog for the “Rounding?” item

The file that contains the XML for the

preferences

res\xml\preferences.xml

The XML for the preferences

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

<PreferenceScreen xmlns:android=

"http://schemas.android.com/apk/res/android">

<CheckBoxPreference

android:key="pref_remember_percent"

android:title="@string/remember_percent_title"

android:summary="@string/remember_percent_summary"

android:defaultValue="true" />

<ListPreference

android:key="pref_rounding"

android:title="@string/rounding_title"

android:summary="@string/rounding_summary"

android:dialogTitle="@string/rounding_title"

android:entries="@array/rounding_keys"

android:entryValues="@array/rounding_values"

android:defaultValue="@string/rounding_default" />

</PreferenceScreen>

The file that contains the XML for the preferences

res\xml\preferences.xml

The XML for the preferences

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

<PreferenceScreen xmlns:android=

"http://schemas.android.com/apk/res/android">

<CheckBoxPreference

android:key="pref_remember_percent"

android:title="@string/remember_percent_title"

android:summary="@string/remember_percent_summary"

android:defaultValue="true" />

<ListPreference

android:key="pref_rounding"

android:title="@string/rounding_title"

android:summary="@string/rounding_summary"

android:dialogTitle="@string/rounding_title"

android:entries="@array/rounding_keys"

android:entryValues="@array/rounding_values"

android:defaultValue="@string/rounding_default" />

</PreferenceScreen>

Some attributes for all Preference elements

key

title

summary

defaultValue

Some attributes for a ListPreference element

dialogTitle

entries

entryValues

Some attributes for all Preference elements

key

title

summary

defaultValue

Some attributes for a ListPreference element

dialogTitle

entries

entryValues

The SettingsFragment class

package com.murach.tipcalculator;

import android.os.Bundle;

import android.preference.PreferenceFragment;

public class SettingsFragment

extends PreferenceFragment {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

// Load the preferences from an XML resource

addPreferencesFromResource(R.xml.preferences);

}

}

The SettingsFragment class

package com.murach.tipcalculator;

import android.os.Bundle;

import android.preference.PreferenceFragment;

public class SettingsFragment

extends PreferenceFragment {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

// Load the preferences from an XML resource

addPreferencesFromResource(R.xml.preferences);

}

}

The SettingsActivity class

package com.murach.tipcalculator;

import android.app.Activity;

import android.os.Bundle;

public class SettingsActivity extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

// Display the fragment as the main content

getFragmentManager()

.beginTransaction()

.replace(android.R.id.content,

new SettingsFragment())

.commit();

}

}

The SettingsActivity class

package com.murach.tipcalculator;

import android.app.Activity;

import android.os.Bundle;

public class SettingsActivity extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

// Display the fragment as the main content

getFragmentManager()

.beginTransaction()

.replace(android.R.id.content,

new SettingsFragment())

.commit();

}

}

How to work with preferences

Step 1: Define the instance variables

private SharedPreferences prefs;

private boolean rememberTipPercent = true;

private int rounding = ROUND_NONE;

Step 2: Set the default values (onCreate)

PreferenceManager.setDefaultValues(

this, R.xml.preferences, false);

Step 3: Get the SharedPreferences object (onCreate)

prefs = PreferenceManager.getDefaultSharedPreferences(this);

Step 4: Get the preferences (onResume)

rememberTipPercent = prefs.getBoolean(

"pref_remember_percent ", true);

rounding = Integer.parseInt(

prefs.getString("pref_rounding", "0"));

How to work with preferences

Step 1: Define the instance variables

private SharedPreferences prefs;

private boolean rememberTipPercent = true;

private int rounding = ROUND_NONE;

Step 2: Set the default values (onCreate)

PreferenceManager.setDefaultValues(

this, R.xml.preferences, false);

Step 3: Get the SharedPreferences object (onCreate)

prefs = PreferenceManager.getDefaultSharedPreferences(this);

Step 4: Get the preferences (onResume)

rememberTipPercent = prefs.getBoolean(

"pref_remember_percent", true);

rounding = Integer.parseInt(

prefs.getString("pref_rounding", "0"));

Some methods of the SharedPreferences object

getBoolean(key, default)

getString(key, default)

getInt(key, default)

getLong(key, default)

getFloat(key, default)

Some methods of the SharedPreferences object

getBoolean(key, default)

getString(key, default)

getInt(key, default)

getLong(key, default)

getFloat(key, default)

Use the “Remember Tip Percent” preference

in the onResume method

if (rememberTipPercent) {

tipPercent = prefs.getFloat("tipPercent", 0.15f);

}

else {

tipPercent = 0.15f;

}

Use the “Remember Tip Percent” preference in the onResume method

if (rememberTipPercent) {

tipPercent = prefs.getFloat("tipPercent", 0.15f);

}

else {

tipPercent = 0.15f;

}

Use the “Rounding” preference

in the calculateAndDisplay method

float tipPercentToDisplay = 0;

if (rounding == ROUND_NONE) {

tipAmount = billAmount * tipPercent;

totalAmount = billAmount + tipAmount;

tipPercentToDisplay = tipPercent;

}

else if (rounding == ROUND_TIP) {

tipAmount = StrictMath.round(billAmount * tipPercent);

totalAmount = billAmount + tipAmount;

tipPercentToDisplay = tipAmount / billAmount;

}

else if (rounding == ROUND_TOTAL) {

float tipNotRounded = billAmount * tipPercent;

totalAmount = StrictMath.round(

billAmount + tipNotRounded);

tipAmount = totalAmount - billAmount;

tipPercentToDisplay = tipAmount / billAmount;

}

Use the “Rounding” preference in the calculateAndDisplay method

float tipPercentToDisplay = 0;

if (rounding == ROUND_NONE) {

tipAmount = billAmount * tipPercent;

totalAmount = billAmount + tipAmount;

tipPercentToDisplay = tipPercent;

}

else if (rounding == ROUND_TIP) {

tipAmount = StrictMath.round(billAmount * tipPercent);

totalAmount = billAmount + tipAmount;

tipPercentToDisplay = tipAmount / billAmount;

}

else if (rounding == ROUND_TOTAL) {

float tipNotRounded = billAmount * tipPercent;

totalAmount = StrictMath.round(

billAmount + tipNotRounded);

tipAmount = totalAmount - billAmount;

tipPercentToDisplay = tipAmount / billAmount;

}

A Settings activity that uses categories

A Settings activity that uses categories

The XML for the preferences

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

<PreferenceScreen

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

<PreferenceCategory

android:title="@string/percent_category_title"

android:key="pref_percent_category">

<CheckBoxPreference

android:key="pref_remember_percent"

android:title="@string/forget_remember_title"

android:summary="@string/forget_remember_summary"

android:defaultValue="fa lse" />

<ListPreference

android:key="pref_default_percent"

android:title="@string/default_percent_title"

android:summary="@string/default_percent_summary"

android:dialogTitle="@string/default_percent_ title"

android:entries="@array/default_percent_keys"

android:entryValues="@array/default_percent_values"

android:defaultValue=

"@string/default_percent_default" />

</PreferenceCategory>

...

</PreferenceScreen>

The XML for the preferences

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

<PreferenceScreen

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

<PreferenceCategory

android:title="@string/percent_category_title"

android:key="pref_percent_category">

<CheckBoxPreference

android:key="pref_remember_percent"

android:title="@string/forget_remember_title"

android:summary="@string/forget_remember_summary"

android:defaultValue="false" />

<ListPreference

android:key="pref_default_percent"

android:title="@string/default_percent_title"

android:summary="@string/default_percent_summary"

android:dialogTitle="@string/default_percent_title"

android:entries="@array/default_percent_keys"

android:entryValues="@array/default_percent_values"

android:defaultValue=

"@string/default_percent_default" />

</PreferenceCategory>

...

</PreferenceScreen>

A Settings activity that uses dependencies

The dependency attribute

dependency

A Settings activity that uses dependencies

The dependency attribute

dependency

The XML for the preferences

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

<PreferenceScreen

xmlns:android="http://schemas.an droid.com/apk/res/android">

<PreferenceCategory

android:title="@string/percent_category_title"

android:key="pref_percent_category">

<CheckBoxPreference

android:key="pref_forget_percent"

android:title="@string/forget_percent_title"

android:summary="@string/forget_percent_summary"

android:defaultValue="false" />

<ListPreference

android:key="pref_default_percent"

android:title="@string/default_percent_title"

android:summary="@string/default_percent_summary"

android:dependency="pref_forget_percent"

android:dialogTitle="@string/default_percent_title"

android:entries="@array/defaul t_percent_keys"

android:entryValues="@array/default_percent_values"

android:defaultValue="

@string/default_percent_default" />

</PreferenceCategory>

...

</PreferenceScreen>

The XML for the preferences

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

<PreferenceScreen

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

<PreferenceCategory

android:title="@string/percent_category_title"

android:key="pref_percent_category">

<CheckBoxPreference

android:key="pref_forget_percent"

android:title="@string/forget_percent_title"

android:summary="@string/forget_percent_summary"

android:defaultValue="false" />

<ListPreference

android:key="pref_default_percent"

android:title="@string/default_percent_title"

android:summary="@string/default_percent_summary"

android:dependency="pref_forget_percent"

android:dialogTitle="@string/default_percent_title"

android:entries="@array/default_percent_keys"

android:entryValues="@array/default_percent_values"

android:defaultValue="

@string/default_percent_default" />

</PreferenceCategory>

...

</PreferenceScreen>

A class that works with preferences

package com.murach.tipcalculator;

import android.content.SharedPreferences;

import android.content.SharedPreferences.

OnSharedPreferenceChangeListener;

import android.os.Bundle;

import android.preference.Preference ;

import android.preference.PreferenceFragment;

import android.preference.PreferenceManager;

public class SettingsFragment extends PreferenceFragment

implements OnSharedPreferenceChangeListener {

private SharedPreferences prefs;

private boolean rememberPercent;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

addPreferencesFromResource(R.xml.preferences);

prefs = PreferenceManager.getDefaultSharedPreferences

(getActivity());

}

A class that works with preferences

package com.murach.tipcalculator;

import android.content.SharedPreferences;

import android.content.SharedPreferences.

OnSharedPreferenceChangeListener;

import android.os.Bundle;

import android.preference.Preference;

import android.preference.PreferenceFragment;

import android.preference.PreferenceManager;

public class SettingsFragment extends PreferenceFragment

implements OnSharedPreferenceChangeListener {

private SharedPreferences prefs;

private boolean rememberPercent;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

addPreferencesFromResource(R.xml.preferences);

prefs = PreferenceManager.getDefaultSharedPreferences

(getActivity());

}

A class that works with preferences (continued)

@Override

public void onResume() {

super.onResume();

rememberPercent = prefs.getBoolean(

"pref_remember_percent", true);

this.setDefaultPercentPreference(rememberPercent);

prefs.registerOnSharedPreferenceChangeListener(this);

}

private void setDefaultPercentPreference(

boolean rememberPercent) {

Preference defaultPercent =

findPreference("pref_default_percent");

if (rememberPercent) {

defaultPercent.setEnabled(false);

} else {

defaultPercent.setEnabled(true);

}

}

@Override

public void onPause() {

prefs.unregisterOnSharedPreferenceChangeListener(this);

super.onPause();

}

A class that works with preferences (continued)

@Override

public void onResume() {

super.onResume();

rememberPercent = prefs.getBoolean(

"pref_remember_percent", true);

this.setDefaultPercentPreference(rememberPercent);

prefs.registerOnSharedPreferenceChangeListener(this);

}

private void setDefaultPercentPreference(

boolean rememberPercent) {

Preference defaultPercent =

findPreference("pref_default_percent");

if (rememberPercent) {

defaultPercent.setEnabled(false);

} else {

defaultPercent.setEnabled(true);

}

}

@Override

public void onPause() {

prefs.unregisterOnSharedPreferenceChangeListener(this);

super.onPause();

}

A class that works with preferences (continued)

@Override

public void onSharedPreferenceChanged(SharedPreferences prefs,

String key) {

if (key.equals("pref_remember_percent")) {

rememberPercent = prefs.getBoolean(key, true);

}

this.setDefaultPercentPreference(rememberPercent);

}

}

A class that works with preferences (continued)

@Override

public void onSharedPreferenceChanged(SharedPreferences prefs,

String key) {

if (key.equals("pref_remember_percent")) {

rememberPercent = prefs.getBoolean(key, true);

}

this.setDefaultPercentPreference(rememberPercent);

}

}

11/19/15 10:18 AM Chapter 8 slides Slide 1