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Android

Android Menus in Kotlin

Menus are a common feature in Android apps. They provide a user interface component that presents app-related actions as well as navigation options. Android provides a flexible way to add and customize menus.

In this tutorial, we'll go over creating a basic options menu using Kotlin in an Android app.

Prerequisites:

  • Android Studio with Kotlin support.
  • Basic knowledge of Kotlin and Android development.

1. Set up a new project:

Open Android Studio and create a new project. Choose an empty activity template.

2. Defining the menu:

  1. Create a new directory named menu inside the res folder.
  2. Inside the menu directory, create an XML file named main_menu.xml.
  3. Add menu items:
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/action_settings"
        android:title="Settings"
        android:orderInCategory="100"
        android:showAsAction="never" />
    
    <item
        android:id="@+id/action_about"
        android:title="About"
        android:orderInCategory="101"
        android:showAsAction="never" />
</menu>

3. Inflate the menu in your Activity:

Open your MainActivity.kt:

override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(R.menu.main_menu, menu)
    return true
}

4. Handle menu item clicks:

Still in MainActivity.kt, override onOptionsItemSelected:

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.action_settings -> {
            Toast.makeText(this, "Settings selected", Toast.LENGTH_SHORT).show()
            return true
        }
        R.id.action_about -> {
            Toast.makeText(this, "About selected", Toast.LENGTH_SHORT).show()
            return true
        }
        else -> return super.onOptionsItemSelected(item)
    }
}

5. Running the App:

When you run your app and click on the three vertical dots (or the physical menu button on some devices) on the top right corner of the app, you should see the "Settings" and "About" options. When you click on them, a Toast message will appear.

6. Additional Tips:

  • The attribute android:showAsAction determines how the item will show. If you set it to "always", it will always show as a direct action in the UI. "never" means it'll be hidden under the menu.
  • For creating more advanced menus, you can nest items within <group> elements, use icons, and even create sub-menus.
  • Remember, good UX design means not overloading the user with too many options. Menus should be clear and concise.
  • Context menus and popup menus are other types of menus in Android. Context menus are usually for actions related to a specific item on the screen, while popup menus are used to display a list of items in a vertical list anchored to a view.

Menus are an integral part of Android apps, and with Kotlin, the process is more streamlined and expressive. Use them wisely to improve the navigation and functionality of your apps.

Creating options menu in Android using Kotlin

Description: Creating an options menu in Android involves overriding the onCreateOptionsMenu method and inflating a menu resource.

Code (Activity class):

class MainActivity : AppCompatActivity() {

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        menuInflater.inflate(R.menu.options_menu, menu)
        return true
    }

    // Other methods
}

Contextual menus in Android with Kotlin

Description: Contextual menus are displayed when users long-press on a view. Override onCreateContextMenu to define the menu items.

Code (Activity class):

class MainActivity : AppCompatActivity() {

    override fun onCreateContextMenu(menu: ContextMenu, v: View, menuInfo: ContextMenu.ContextMenuInfo?) {
        super.onCreateContextMenu(menu, v, menuInfo)
        menuInflater.inflate(R.menu.context_menu, menu)
    }

    // Other methods
}

Handling menu item clicks in Kotlin for Android

Description: Handle menu item clicks by overriding the onOptionsItemSelected method in your activity.

Code (Activity class):

class MainActivity : AppCompatActivity() {

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item.itemId) {
            R.id.menu_item1 -> {
                // Handle item1 click
                return true
            }
            R.id.menu_item2 -> {
                // Handle item2 click
                return true
            }
            // Other menu items
            else -> return super.onOptionsItemSelected(item)
        }
    }

    // Other methods
}

Adding icons to menu items in Android with Kotlin

Description: Include icons with menu items by specifying them in the menu resource XML file.

Code (menu resource XML):

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/menu_item1"
        android:icon="@drawable/ic_menu_item1"
        android:title="Item 1"
        app:showAsAction="ifRoom" />

    <!-- Other menu items -->

</menu>

PopupMenu usage in Android with Kotlin

Description: PopupMenu is a convenient way to display a list of items anchored to a view.

Code (Activity class):

class MainActivity : AppCompatActivity() {

    private fun showPopupMenu(view: View) {
        val popupMenu = PopupMenu(this, view)
        popupMenu.menuInflater.inflate(R.menu.popup_menu, popupMenu.menu)

        popupMenu.setOnMenuItemClickListener { item ->
            when (item.itemId) {
                R.id.popup_item1 -> {
                    // Handle popup_item1 click
                    true
                }
                R.id.popup_item2 -> {
                    // Handle popup_item2 click
                    true
                }
                else -> false
            }
        }

        popupMenu.show()
    }

    // Other methods
}

Customizing and styling menus in Android using Kotlin

Description: Customize menus by defining a custom layout for menu items or applying styles.

Code (menu resource XML with custom layout):

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/menu_item_custom"
        android:title=""
        app:actionLayout="@layout/custom_menu_item_layout"
        app:showAsAction="always" />

    <!-- Other menu items -->

</menu>

Overflow menu in Android with Kotlin

Description: The overflow menu appears when there is not enough space to display all items in the action bar.

Code (menu resource XML with overflow menu):

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/menu_item1"
        android:title="Item 1"
        app:showAsAction="ifRoom" />

    <!-- Other menu items -->

    <item
        android:id="@+id/menu_overflow"
        android:icon="@drawable/ic_overflow"
        android:title="Overflow"
        app:showAsAction="always">
        <menu>
            <item
                android:id="@+id/overflow_item1"
                android:title="Overflow Item 1" />
            <!-- Other overflow items -->
        </menu>
    </item>

</menu>

ActionMode for contextual action bars in Kotlin for Android

Description: ActionMode provides a contextual action bar for performing actions on selected items.

Code (Activity class):

class MainActivity : AppCompatActivity() {

    private var actionMode: ActionMode? = null

    override fun onContextItemSelected(item: MenuItem): Boolean {
        when (item.itemId) {
            R.id.context_menu_item_delete -> {
                // Handle delete action
                return true
            }
            // Other context menu items
            else -> return super.onContextItemSelected(item)
        }
    }

    private val actionModeCallback = object : ActionMode.Callback {
        override fun onCreateActionMode(mode: ActionMode, menu: Menu): Boolean {
            mode.menuInflater.inflate(R.menu.context_menu, menu)
            return true
        }

        override fun onPrepareActionMode(mode: ActionMode, menu: Menu): Boolean {
            // Update action mode UI if needed
            return false
        }

        override fun onActionItemClicked(mode: ActionMode, item: MenuItem): Boolean {
            // Handle action item click
            return true
        }

        override fun onDestroyActionMode(mode: ActionMode) {
            // Cleanup and reset UI
            actionMode = null
        }
    }

    // Other methods
}
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