Android toolbar menu fragment

Fragment Toolbar.

Manage it better.

Introduction

Since I started work commercially I met an opinion that working with Fragments is not always intuitive, at least not as much as working with Activities. Especially after watching this video your mindset in context of Fragments might change significantly. Complicated lifecycle, hard management will not change the way of thinking about it.

Few weeks ago I had to deal with really big thing. I’ve moved big app built in 95% on Activities to Fragments. I was very long way, very hard one. I’ve learnt a lot, so wanted to share this knowledge with you.

Toolbar for Fragment. What is wrong with it ?

Let’s assume that we have only one Activity with bottom navigation and the rest of views are Fragments. Normally on every Fragment change toolbar is set as supportActionBar which gives you possibilities to use methods to create, prepare, manage toolbar options menu. It looks simple, doesn’t it?
But it also creates some problems:

• Before creating new toolbar on another Fragment you need to clear the old one.
• If you are clearing it, indeed you are losing state and all data.
• When you are going back to previous Fragments you have to recreate whole action bar.

As you can see it is a very inconvenient process, hard to maintain and generates a lot of boilerplate code. Especially if you are using searchView all those disadvantages mentioned above are unacceptable.

What is the solution ?

Assuming that we have few types of toolbar in app, you can build it using Builder Pattern and handle all cases in one place. All work comes down to choosing options for your Toolbar.

Starting point is to select one of two possible solutions. First one suggests to create one Toolbar and add it from code to your views. The second, which I have chosen is to implement toolbar in every Fragment’s .xml file. Basically, it was much easier for me because it was already done (refactoring code from Activities), so code below will match the second option.

Lets create FragmentToolbar Builder which contains all options we need in our app. I’m using Kotlin to achieve it, but my Fragments are still in Java, so I had to use implementation readable for Java.

Nothing revealing, let’s add those options to our toolbar.

Create BaseFragment which will be inherited by every Fragment.

Finally we are prepared to create Toolbars for our Fragments! Now every Fragment must specify which options will be used or if the Toolbar should even exist. Following the simple example:

To more complex:

Summary

Everyone knows how much time we spend on adding menu options and how many lines in code we need to write or copy/paste. This solution saves your time and keeps code clean. No need to set toolbar as supportActionBar. You don’t have to worry about keeping state and data for menu when Fragment changes (it lives as long as your Fragment). To sum up, management is as simple as possible and fragmentManager backstack changes (adding / removing Fragments) has no effect on toolbar at all.

Personally I feel better when I’m dealing with Activities. Working with Fragments pushed me to simplify this process. So when you’ll be in the same situation — don’t fight with it, just do it by your own.

If you like my work hit clap button and let me know what you think in comments!

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Using the Android Toolbar (ActionBar) — Tutorial

Using the toolbar in Android applications. This tutorial describes how to use the toolbar widget in your Android application. It is based on Android 6.0.

1. Introduction to the toolbar

1.1. What is the toolbar (action bar)?

The toolbar bar (formerly known as action bar) is represented as of Android 5.0 via the Toolbar view group. It can be freely positioined into your layout file. It can display the activity title, icon, actions which can be triggered, additional views and other interactive items. It can also be used for navigation in your application.

Before Android 5.0 the location of the toolbar (actionbar) was hard coded to the top of the activity. It is possible to disable the toolbar via the used theme, but the default Android themes have it enabled.

The following screenshot shows the toolbar of the Google+ Android application with interactive items and a navigation bar. On top it also indicates that the user can open a navigation bar on the side of the application.

1.2. Action bar on devices lower than API 21

The toolbar has been introduced in Android 5.0 (API 21). If you want to use the toolbar on devices with an earlier Android release you can use the downport provided by the appcompat-v7 support library. To use the toolbar on such devices add a compile dependency to com.android.support:appcompat to your Gradle build file. For example:

See the following link for setting up the library v7 in your project: http://developer.android.com/tools/support-library/setup.html.

1.3. Once upon a time their was the options menu

Applications with a target SDK version less than API 11 use the options menu, if such a button is present on the device. The option menu is displayed if the user presses the Option button. The toolbar bar is superior to the options menu, as the action bar is clearly visible, while the options menu is only shown on request. In case of the options menu, the user may not recognize that options are available in the application.

2. Using the toolbar

2.1. Creating actions in the toolbar

Entries in the toolbar are typically called actions. While it is possible to create entries in the action bar via code, it is typically defined in an XML resource file.

Each menu definition is contained in a separate file in the res/menu folder. The Android tooling automatically creates a reference to menu item entries in the R file, so that the menu resource can be accessed.

An activity adds entries to the action bar in its onCreateOptionsMenu() method.

The showAsAction attribute allows you to define how the action is displayed. For example, the ifRoom attribute defines that the action is only displayed in the action bar if there is sufficient screen space available.

The MenuInflator class allows to inflate actions defined in an XML file and adds them to the action bar. MenuInflator can get accessed via the getMenuInflator() method from your activity. The following example code demonstrates the creation of actions.

While you can define the actions also in your source code, it is good practice to do this via XML files, as this results in less boilerplate code.

2.2. Reacting to action selection

If an action is selected, the onOptionsItemSelected() method in the corresponding activity is called. It receives the selected action as parameter. The usage of this method is demonstrated in the following code snippet.

2.3. Search an action in the action bar

To search for a menu item in a menu you can use the findItem() method of the Menu class. This method allows to search by id.

2.4. Changing the menu

The onCreateOptionsMenu() method is only called once. If you want to change the menu later, you have to call the invalidateOptionsMenu() method. Afterwards this onCreateOptionsMenu() method is called again.

2.5. Making the toolbar context sensitive with the contextual action mode

A contextual action mode activates a temporary toolbar that overlays the application toolbar for the duration of a particular sub-task.

The contextual action mode is typically activated by selecting an item or by long clicking on it.

To implement this, call the startActionMode() method on a viewor on your activity. This method gets an ActionMode.Callback object which is responsible for the life cycle of the contextual action bar.

You could also assign a context menu to a view via the registerForContextMenu(view) method. A context menu is also activated if the user «long presses» the view. The onCreateContextMenu() method is called every time a context menu is activated as the context menu is discarded after its usage. You should prefer the contextual action mode over the usage of context menus.

2.6. Contributing to the action bar with fragments

Fragments can also contribute entries to the toolbar bar.

To do this, call setHasOptionsMenu(true) in the onCreate() method of the fragment. The Android framework calls in this case the onCreateOptionsMenu() method in the fragment class. Here the fragment can adds menu items to the toolbar.

2.7. Changing the visibility of the toolbar bar

You can change the visibility of the toolbar at runtime. The following code demonstrates that.

You can also change the text which is displayed alongside the application icon at runtime. The following example shows that.

2.8. Assigning a Drawable

You also add a Drawable to the action bar as background via the ActionBar.setBackgroundDrawable() method.

The toolbar scales the image. Therefore it is best practice to provide a scalable drawable, e.g., a 9-patch or XML drawable.

As of Android 4.2 the background of the action bar can also be animated via an AnimationDrawable .

2.9. Dimming the navigation buttons

You can also dim the software navigation button in your Android application to have more space available. If the user touches the button of the screen, the navigation button is automatically shown again.

Dimming the navigation buttons is demonstrated by the following code snippet.

The following screenshots show an application with and without the navigation buttons.

2.10. Using immersive full screen mode

As of Android 4.4 (API 19) you can put your application into full screen mode. The first time this happens the system displays the user the info that he can restore the system bars with a downward swipe along the region where the system bars normally appear.

For example the following method also to put an activity into full screen mode.

2.11. Enabling the split toolbar

You can define that the toolbar should be automatically split by the system if not enough space is available.

You can activate this via the android:uiOptions=»SplitActionBarWhenNarrow» parameter in the declaration of your application activity in the AndroidManifest.xml file.

If this option is activated, Android has the option to split the toolbar. Whether to split is decided by the system at runtime.

3. Exercise: Using the contextual action mode

3.1. Target

In this exercise you add a contextual action mode to one of your existing applications.

3.2. Create menu resource in the res/menu folder

For this, create a new menu XML resource with the actionmode.xml file name. See ActionMode.Callback callback as demonstrated in the following example code.

In your adapter implement a LongClickListener which triggers the contextual action mode.

4. Making the action bar dynamic

4.1. Custom views in the action bar

You can also add a custom view to the action bar, for example, a button or a text field.

For this you use the setCustomView method of the ActionView class. You also have to enable the display of custom views via the setDisplayOptions() method by passing in the ActionBar.DISPLAY_SHOW_CUSTOM flag.

For example, you can define a layout file which contains a EditText element.

This layout can be assigned in an activity to the action bar via the following code. The example code also attaches a listener to the custom view.

4.2. Action view

An action view _ is a widget that appears in the _action bar as a substitute for an action item’s button. You can, for example, use this feature to replace an action item with a ProgressBar view. An action view for an action can be defined via the android:actionLayout or android:actionViewClass attribute to specify either a layout resource or widget class to use.

This replacement is depicted in the following screenshots.

The following activity replaces the icon at runtime with an action view which contains a ProgressBar view.

The following code shows the layout used for the action view.

The following code shows the XML files for the menu.

5. Action provider

5.1. What is an action provider?

An action provider defines rich menu interaction in a single component. It can generate action views, which are used in the action bar, dynamically populate sub-menus of an action and handle default action invocations.

The base class for an action provider is the ActionProvider class.

Currently the Android platform provides two action providers: the MediaRouteActionProvider and the ShareActionProvider .

5.2. Example: usage of the ShareActionProvider

The following demonstrates the usage of the ShareActionProvider . This action provider allows you to grab selected content from applications which have registered the Intent.ACTION_SEND intent.

To use ShareActionProvider , you have to define a special menu entry for it and assign an intent which contains the sharing data to it.

6. Navigation via the application icon

6.1. Application icon as home

The action bar shows an icon of your application. This is called the home icon. You can assign an action to this icon. The recommendation is to return to the main activity in your program if the user selects this icon.

If the action is selected, the onOptionsItemSelected() method is called with an action which has the android.R.id.home ID.

Before Android 4.1, you had to use the android.R.id.home ID in the onOptionMenuItemSelected() method and enable the selection of the home button. This is demonstrated by the following code in which the SecondActivity activity defines the MainActivity as home.

As of Android 4.1 you can simply set the parentActivityName in the AndroidManifest.xml file pointing to the parent activity.

6.2. Application icon as Up button

You can use the application icon also as Up button, e.g., to go to the parent activity of the current activity. The back button on the device always returns to the previous activity.

Both can be different, for example, if the user started the option to write an email from the home screen, the back button will return the user to the home screen while the Up button would return the user to the activity which shows an overview of all emails.

To enable the Up display, you can use the following code snippet in your activity.

This snippet only enables the Up display on your home icon. You need to implement the correct behavior in your activity in the onOptionsItemSelected() method. The corresponding action still has the android.R.id.home ID.

The difference between Up and the Back button can be confusing for the end user. If you decide to implement Up, in your application, it is recommended to perform some end user testing to see if the Up implementation is intuitive for them or not.

7. Exercise: Using the toolbar

This exercise demonstrates how to use the toolbar widget in your Android application.

It is based on the fragment tutorial which can be found under: https:///www.vogella.com/tutorials/AndroidFragments/article.html You have to finish this tutorial before continuing this one.

8. Exercise: Add a toolbar to your application

8.1. Add a refresh icon

Continue to use the RSS Reader project. Create a new drawable called ic_refresh via the File New Vector Asset menu entry. Select a fitting image from the provided example images.

If the fill color does not fit to your styling, open the created drawable and adjust the color.

8.2. Add menu resources

Create a new XML resource for your menu called mainmenu.xml in your menu resource folder (create one, if the folder does not exist). The resulting XML file should look similar to the following listing.

8.3. Turn off the default action bar from the styling

Disable the default action bar one via the res/values/styles.xml file.

The following styling setting assumes that RssFeedActivity extends Activity . Please double-check this.

8.4. Add a toolbar view to your activity layout

Change the layout files of your RssfeedActivity activity to also contain a toolbar entry. For this you need to wrap your existing layout definition into another LinearLayout and add the toolbar to this second layout file.

Do the same for the layout for the portrait mode.

8.5. Adjust your activity

Change your RssfeedActivity class to the following code, to configure the toolbar view.

8.6. Run the application and test the toolbar

Run your application and validate that you can select both of your actions. Ensure that a Toast is displayed if you select the different entries.

If your device or emulator has an Option menu button, you will not see the overflow menu. You need to press the Option key to see the actions which are part of the overflow menu.

8.7. Trigger an intent via the toolbar

If the action_network action is selected, trigger the intent to control the network connectivity.

9. Trigger a method in your fragments via the toolbar

In this exercise you call a method in your list fragment based on the toolbar selection. It continues to use the RSS Reader project.

Create a updateListContent method in MyListFragment .

In your RssfeedActivity class, call the new method, if the action_refresh action is selected.

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