3 files changed, 106 insertions, 0 deletions
diff --git a/android/src/main/kotlin/net/mullvad/mullvadvpn/ui/widget/MtuCell.kt b/android/src/main/kotlin/net/mullvad/mullvadvpn/ui/widget/MtuCell.kt
new file mode 100644
index 0000000000..eb1463cd45
--- /dev/null
+++ b/android/src/main/kotlin/net/mullvad/mullvadvpn/ui/widget/MtuCell.kt
@@ -0,0 +1,91 @@
+package net.mullvad.mullvadvpn.ui.widget
+
+import android.content.Context
+import android.text.Editable
+import android.text.TextWatcher
+import android.util.AttributeSet
+import android.view.LayoutInflater
+import android.widget.EditText
+import android.widget.TextView
+import kotlin.properties.Delegates.observable
+import net.mullvad.mullvadvpn.R
+
+private const val MIN_MTU_VALUE = 1280
+private const val MAX_MTU_VALUE = 1420
+
+class MtuCell : Cell {
+    private val input =
+        (LayoutInflater.from(context).inflate(R.layout.mtu_edit_text, null) as EditText).apply {
+            val width = resources.getDimensionPixelSize(R.dimen.cell_input_width)
+            val height = resources.getDimensionPixelSize(R.dimen.cell_input_height)
+
+            layoutParams = LayoutParams(width, height, 0.0f)
+
+            addTextChangedListener(InputWatcher())
+            setOnFocusChangeListener { _, newHasFocus -> hasFocus = newHasFocus }
+        }
+
+    private val validInputColor = context.getColor(R.color.white)
+    private val invalidInputColor = context.getColor(R.color.red)
+
+    var value: Int?
+        get() = input.text.toString().trim().toIntOrNull()
+        set(value) = input.setText(value?.toString() ?: "")
+
+    var onSubmit: ((Int?) -> Unit)? = null
+
+    var hasFocus by observable(false) { _, oldValue, newValue ->
+        if (oldValue == true && newValue == false) {
+            val mtu = value
+
+            if (mtu == null || (mtu >= MIN_MTU_VALUE && mtu <= MAX_MTU_VALUE)) {
+                onSubmit?.invoke(mtu)
+            }
+        }
+    }
+
+    constructor(context: Context) : super(context, TextView(context)) {}
+
+    constructor(context: Context, attributes: AttributeSet) :
+        super(context, attributes, TextView(context)) {}
+
+    constructor(context: Context, attributes: AttributeSet, defaultStyleAttribute: Int) :
+        super(context, attributes, defaultStyleAttribute, TextView(context)) {}
+
+    constructor(
+        context: Context,
+        attributes: AttributeSet,
+        defaultStyleAttribute: Int,
+        defaultStyleResource: Int
+    ) : super(
+        context,
+        attributes,
+        defaultStyleAttribute,
+        defaultStyleResource,
+        TextView(context)
+    ) {}
+
+    init {
+        cell.setEnabled(false)
+        cell.addView(input)
+
+        footer?.text =
+            context.getString(R.string.wireguard_mtu_footer, MIN_MTU_VALUE, MAX_MTU_VALUE)
+    }
+
+    inner class InputWatcher : TextWatcher {
+        override fun beforeTextChanged(text: CharSequence, start: Int, count: Int, after: Int) {}
+
+        override fun onTextChanged(text: CharSequence, start: Int, count: Int, after: Int) {}
+
+        override fun afterTextChanged(text: Editable) {
+            val value = text.toString().trim().toIntOrNull()
+
+            if (value != null && value >= MIN_MTU_VALUE && value <= MAX_MTU_VALUE) {
+                input.setTextColor(validInputColor)
+            } else {
+                input.setTextColor(invalidInputColor)
+            }
+        }
+    }
+}
diff --git a/android/src/main/res/layout/mtu_edit_text.xml b/android/src/main/res/layout/mtu_edit_text.xml
new file mode 100644
index 0000000000..05fce42e7d
--- /dev/null
+++ b/android/src/main/res/layout/mtu_edit_text.xml
@@ -0,0 +1,13 @@
+<EditText xmlns:android="http://schemas.android.com/apk/res/android"
+          android:paddingHorizontal="4dp"
+          android:background="@drawable/cell_input_background"
+          android:digits="0123456789"
+          android:inputType="number"
+          android:singleLine="true"
+          android:imeOptions="flagNoPersonalizedLearning"
+          android:textCursorDrawable="@drawable/cell_input_cursor"
+          android:gravity="center"
+          android:hint="@string/hint_default"
+          android:textColorHint="@color/white80"
+          android:textColor="@color/white"
+          android:textSize="20sp" />
diff --git a/android/src/main/res/values/dimensions.xml b/android/src/main/res/values/dimensions.xml
index 2e60d27cec..c4ebc722ad 100644
--- a/android/src/main/res/values/dimensions.xml
+++ b/android/src/main/res/values/dimensions.xml
@@ -18,6 +18,8 @@
     <dimen name="cell_horizontal_padding">16dp</dimen>
     <dimen name="cell_label_horizontal_padding">8dp</dimen>
     <dimen name="cell_label_vertical_padding">17dp</dimen>
+    <dimen name="cell_input_width">80dp</dimen>
+    <dimen name="cell_input_height">34dp</dimen>
     <dimen name="cell_footer_top_padding">8dp</dimen>
     <dimen name="cell_footer_horizontal_padding">24dp</dimen>
     <dimen name="chevron_width">14dp</dimen>