fragment-ktx: Add Fragment.addOnBackPressedCallback

Author: osipxd

fragment-ktx/README.md

@@ -31,7 +31,11 @@ dependencies {
 
 ## Extensions
 
-> Extensions will be listed here
+Extensions for `Fragment`:
+
+- `Fragment.addOnBackPressedCallback(enabled: Boolean = true, onBackPressed: OnBackPressedCallback.() -> Unit)`
+  
+  Create and add a new `OnBackPressedCallback` tied to `Fragment.viewLifecycleOwner` that calls `onBackPressed` in `OnBackPressedCallback.handleOnBackPressed`.
 
 ## Contributing
 

fragment-ktx/build.gradle.kts

@@ -12,4 +12,6 @@ description = "A set of extensions in addition to androidx fragment-ktx"
 dependencies {
     api(jetbrains.kotlin.stdlib)
     api(androidx.fragment.ktx)
+    api(androidx.activity)
+    api(androidx.annotation)
 }

fragment-ktx/src/main/kotlin/OnBackPressedCallback.kt

@@ -0,0 +1,40 @@
+// Public API
+@file:Suppress("unused")
+
+package com.redmadrobot.extensions.fragment
+
+import androidx.activity.OnBackPressedCallback
+import androidx.annotation.MainThread
+import androidx.fragment.app.Fragment
+
+/**
+ * Create and add a new [OnBackPressedCallback] tied to [Fragment.getViewLifecycleOwner]
+ * that calls [onBackPressed] in [OnBackPressedCallback.handleOnBackPressed].
+ *
+ * Callback should be added in [Fragment.onAttach] or later. Callbacks are tied to [Fragment.getViewLifecycleOwner] so
+ * it will only be added when the fragment view's Lifecycle is [androidx.lifecycle.Lifecycle.State.STARTED].
+ * ```
+ *  class FormEntryFragment : Fragment() {
+ *      override fun onAttach(context: Context) {
+ *          super.onAttach(context)
+ *          addOnBackPressedCallback {
+ *              showAreYouSureDialog()
+ *          }
+ *      }
+ *  }
+ * ```
+ * @param enabled Callback state. By default is `true`.
+ * @return Created callback. You can manage it using [OnBackPressedCallback.setEnabled] and
+ * [OnBackPressedCallback.remove].
+ * @see OnBackPressedCallback
+ * @see androidx.activity.OnBackPressedDispatcher
+ */
+@MainThread
+public inline fun Fragment.addOnBackPressedCallback(
+    enabled: Boolean = true,
+    crossinline onBackPressed: OnBackPressedCallback.() -> Unit
+): OnBackPressedCallback {
+    return object : OnBackPressedCallback(enabled) {
+        override fun handleOnBackPressed() = onBackPressed()
+    }.also { requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner, it) }
+}