Kotlin DSL Component: Building AlertDialogs using Kotlin DSL (#95)

Author: julianfalcionelli

app/src/main/java/com/rocketinsights/android/ui/MainFragment.kt

@@ -25,6 +25,7 @@ import com.rocketinsights.android.extensions.setupActionBar
 import com.rocketinsights.android.extensions.show
 import com.rocketinsights.android.extensions.showToast
 import com.rocketinsights.android.extensions.viewBinding
+import com.rocketinsights.android.ui.components.dialog
 import com.rocketinsights.android.viewmodels.MainMessageState
 import com.rocketinsights.android.viewmodels.MainViewModel
 import com.rocketinsights.android.viewmodels.PhotoViewModel
@@ -113,10 +114,33 @@ class MainFragment : Fragment(R.layout.fragment_main) {
                 setFadeThroughTransition()
                 item.onNavDestinationSelected(findNavController())
             }
+            R.id.dialog -> {
+                showDslDialog()
+                true
+            }
             else -> super.onOptionsItemSelected(item)
         }
     }
 
+    private fun showDslDialog() {
+        dialog {
+            titleRes = R.string.dialog_title
+            contentRes = R.string.dialog_content
+            cancelable = false
+            positiveText = "Positive"
+            negativeText = "Negative"
+            positiveAction = {
+                requireContext().showToast("Positive Action Clicked")
+            }
+            negativeAction = {
+                requireContext().showToast("Negative Action Clicked")
+            }
+            dismissAction = {
+                requireContext().showToast("Alert Dismissed")
+            }
+        }
+    }
+
     private fun setupControls() {
         binding.stockImage.setOnClickListener {
             val extras = FragmentNavigatorExtras(

app/src/main/java/com/rocketinsights/android/ui/components/DialogDsl.kt

@@ -0,0 +1,106 @@
+package com.rocketinsights.android.ui.components
+
+import android.app.Activity
+import android.content.Context
+import android.view.View
+import androidx.annotation.StringRes
+import androidx.appcompat.app.AlertDialog
+import androidx.fragment.app.Fragment
+import com.google.android.material.dialog.MaterialAlertDialogBuilder
+
+/**
+ * DialogDsl is an example of how to create components using Kotlin DSL. The main advantage of this
+ * is the reduction of the boilerplate code, and therefore improves the readability of our code.
+ *
+ * These components make sense when it is actually used in many parts of our code and/or it is a
+ * very customizable component.
+ */
+@DslMarker
+annotation class DslDialog
+
+@DslDialog
+class DialogBuilder(
+    val context: Context,
+    val setup: DialogBuilder.() -> Unit = {}
+) {
+
+    @StringRes
+    var titleRes: Int? = null
+    var title: String? = null
+
+    @StringRes
+    var contentRes: Int? = null
+    var content: String? = null
+
+    @StringRes
+    var positiveTextRes: Int? = null
+    var positiveText: String? = null
+
+    @StringRes
+    var negativeTextRes: Int? = null
+    var negativeText: String? = null
+
+    var customLayout: View? = null
+
+    var positiveAction: (() -> Unit)? = null
+    var negativeAction: (() -> Unit)? = null
+    var dismissAction: (() -> Unit)? = null
+
+    var cancelable: Boolean = true
+
+    fun build(): AlertDialog {
+        setup()
+
+        return MaterialAlertDialogBuilder(context).apply {
+            quartus(title, { setTitle(it) }, titleRes, { setTitle(it) })
+            quartus(content, { setMessage(it) }, contentRes, { setMessage(it) })
+
+            customLayout?.let {
+                setView(it)
+            }
+
+            negativeAction?.let { action ->
+                quartus(
+                    negativeText, { setNegativeButton(it) { _, _ -> action.invoke() } },
+                    negativeTextRes, { setNegativeButton(it) { _, _ -> action.invoke() } }
+                )
+            }
+
+            positiveAction?.let { action ->
+                quartus(
+                    positiveText, { setPositiveButton(it) { _, _ -> action.invoke() } },
+                    positiveTextRes, { setPositiveButton(it) { _, _ -> action.invoke() } }
+                )
+            }
+
+            dismissAction?.let {
+                setOnDismissListener {
+                    dismissAction?.invoke()
+                }
+            }
+
+            setCancelable(cancelable)
+        }.create()
+    }
+}
+
+private fun <T, U> Any.quartus(
+    primaryValue: T?,
+    primaryAction: ((T) -> Unit)? = null,
+    secondaryValue: U?,
+    secondaryAction: ((U) -> Unit)? = null
+) {
+    primaryValue?.let {
+        primaryAction?.invoke(it)
+    } ?: run {
+        secondaryValue?.let {
+            secondaryAction?.invoke(it)
+        }
+    }
+}
+
+fun Fragment.dialog(setup: DialogBuilder.() -> Unit) =
+    DialogBuilder(requireContext(), setup = setup).build().show()
+
+fun Activity.dialog(setup: DialogBuilder.() -> Unit) =
+    DialogBuilder(this, setup = setup).build().show()

app/src/main/res/menu/main_menu.xml

@@ -17,6 +17,9 @@
         <item
             android:id="@+id/calendar_fragment"
             android:title="@string/calendar" />
+        <item
+            android:id="@+id/dialog"
+            android:title="@string/dialog" />
         <item
             android:id="@+id/menu_login"
             android:title="@string/login" />

app/src/main/res/values/strings.xml

@@ -83,4 +83,9 @@
     <string name="lottie">Lottie</string>
     <string name="property">Property</string>
     <string name="container">Container</string>
+
+    <!-- Dialog -->
+    <string name="dialog">Dsl Dialog</string>
+    <string name="dialog_title">Dialog Title</string>
+    <string name="dialog_content">Dialog Content</string>
 </resources>