diff --git a/packages/SystemUI/res-keyguard/layout/keyguard_pin_view.xml b/packages/SystemUI/res-keyguard/layout/keyguard_pin_view.xml
index 02cb2bcfad819..a22a56fb3c610 100644
--- a/packages/SystemUI/res-keyguard/layout/keyguard_pin_view.xml
+++ b/packages/SystemUI/res-keyguard/layout/keyguard_pin_view.xml
@@ -20,171 +20,166 @@
 <com.android.keyguard.KeyguardPINView
         xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:androidprv="http://schemas.android.com/apk/res-auto"
-        android:id="@+id/keyguard_pin_view"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/keyguard_pin_view"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         androidprv:layout_maxWidth="@dimen/keyguard_security_width"
         android:orientation="vertical"
         >
-    <LinearLayout
-            android:id="@+id/pin_container"
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@+id/pin_container"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_marginBottom="8dp"
+        android:layout_weight="1"
+        android:layoutDirection="ltr"
+        android:orientation="vertical">
+
+        <!-- Set this to be just above key1. It would be better to introduce a barrier above
+             key1/key2/key3, then place this View above that. Sadly, that doesn't work (the Barrier
+             drops to the bottom of the page, and key1/2/3 all shoot up to the top-left). In any
+             case, the Flow should ensure that key1/2/3 all have the same top, so this should be
+             fine. -->
+        <com.android.keyguard.AlphaOptimizedRelativeLayout
+            android:id="@+id/row0"
             android:layout_width="match_parent"
-            android:layout_height="0dp"
-            android:orientation="vertical"
-            android:layout_weight="1"
-            android:layoutDirection="ltr"
-            android:layout_marginBottom="8dp"
-            >
-      <Space
-          android:layout_width="match_parent"
-          android:layout_height="0dp"
-          android:layout_weight="1"
-          />
-      <com.android.keyguard.AlphaOptimizedRelativeLayout
-          android:id="@+id/row0"
-          android:layout_width="match_parent"
-          android:layout_height="wrap_content"
-          android:paddingBottom="@dimen/num_pad_entry_row_margin_bottom"
-          >
+            android:layout_height="wrap_content"
+            android:paddingBottom="@dimen/num_pad_entry_row_margin_bottom"
+            androidprv:layout_constraintBottom_toTopOf="@id/key1"
+            androidprv:layout_constraintEnd_toEndOf="parent"
+            androidprv:layout_constraintStart_toStartOf="parent"
+
+            androidprv:layout_constraintTop_toTopOf="parent"
+            androidprv:layout_constraintVertical_bias="1.0">
+
             <com.android.keyguard.PasswordTextView
-                    android:id="@+id/pinEntry"
-                    android:layout_width="@dimen/keyguard_security_width"
-                    android:layout_height="@dimen/keyguard_password_height"
-                    style="@style/Widget.TextView.Password"
-                    android:layout_centerHorizontal="true"
-                    android:layout_marginRight="72dp"
-                    androidprv:scaledTextSize="@integer/scaled_password_text_size"
-                    android:contentDescription="@string/keyguard_accessibility_pin_area"
-                    />
+                android:id="@+id/pinEntry"
+                style="@style/Widget.TextView.Password"
+                android:layout_width="@dimen/keyguard_security_width"
+                android:layout_height="@dimen/keyguard_password_height"
+                android:layout_centerHorizontal="true"
+                android:layout_marginRight="72dp"
+                android:contentDescription="@string/keyguard_accessibility_pin_area"
+                androidprv:scaledTextSize="@integer/scaled_password_text_size" />
         </com.android.keyguard.AlphaOptimizedRelativeLayout>
-        <LinearLayout
-                android:id="@+id/row1"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:orientation="horizontal"
-                android:layout_gravity="center_horizontal"
-                android:layout_marginBottom="@dimen/num_pad_row_margin_bottom"
-                >
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key1"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="1"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key2"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="2"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key3"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="3"
-                    />
-        </LinearLayout>
-        <LinearLayout
-                android:id="@+id/row2"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:orientation="horizontal"
-                android:layout_gravity="center_horizontal"
-                android:layout_marginBottom="@dimen/num_pad_row_margin_bottom"
-                >
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key4"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="4"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key5"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="5"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key6"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="6"
-                    />
-        </LinearLayout>
-        <LinearLayout
-                android:id="@+id/row3"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:orientation="horizontal"
-                android:layout_gravity="center_horizontal"
-                android:layout_marginBottom="@dimen/num_pad_row_margin_bottom"
-                >
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key7"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="7"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key8"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="8"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key9"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="9"
-                    />
-        </LinearLayout>
-        <LinearLayout
-                android:id="@+id/row4"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:orientation="horizontal"
-                android:layout_gravity="center_horizontal"
-                >
-            <com.android.keyguard.NumPadButton
-                    android:id="@+id/delete_button"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    android:contentDescription="@string/keyboardview_keycode_delete"
-                    style="@style/NumPadKey.Delete"
-                    />
-            <com.android.keyguard.NumPadKey
-                    android:id="@+id/key0"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    android:layout_marginEnd="@dimen/num_pad_key_margin_end"
-                    androidprv:textView="@+id/pinEntry"
-                    androidprv:digit="0"
-                    />
-            <com.android.keyguard.NumPadButton
-                    android:id="@+id/key_enter"
-                    android:layout_width="@dimen/num_pad_key_width"
-                    android:layout_height="match_parent"
-                    style="@style/NumPadKey.Enter"
-                    android:contentDescription="@string/keyboardview_keycode_enter"
-                    />
-        </LinearLayout>
-    </LinearLayout>
+
+        <androidx.constraintlayout.helper.widget.Flow
+            android:id="@+id/flow1"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            android:orientation="horizontal"
+
+            androidprv:constraint_referenced_ids="key1,key2,key3,key4,key5,key6,key7,key8,key9,delete_button,key0,key_enter"
+
+            androidprv:flow_horizontalGap="@dimen/num_pad_key_margin_end"
+
+            androidprv:flow_horizontalStyle="packed"
+            androidprv:flow_maxElementsWrap="3"
+
+            androidprv:flow_verticalGap="@dimen/num_pad_entry_row_margin_bottom"
+            androidprv:flow_verticalStyle="packed"
+            androidprv:flow_verticalBias="1.0"
+
+            androidprv:flow_wrapMode="aligned"
+
+            androidprv:layout_constraintTop_toTopOf="parent"
+            androidprv:layout_constraintBottom_toBottomOf="parent"
+            androidprv:layout_constraintEnd_toEndOf="parent"
+            androidprv:layout_constraintStart_toStartOf="parent" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key1"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="1"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key2"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="2"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key3"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="3"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key4"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="4"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key5"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="5"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key6"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="6"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key7"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="7"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key8"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="8"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key9"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="9"
+            androidprv:textView="@+id/pinEntry" />
+
+
+        <com.android.keyguard.NumPadButton
+            android:id="@+id/delete_button"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            style="@style/NumPadKey.Delete"
+            android:contentDescription="@string/keyboardview_keycode_delete"
+            />
+
+        <com.android.keyguard.NumPadKey
+            android:id="@+id/key0"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            androidprv:digit="0"
+            androidprv:textView="@+id/pinEntry" />
+
+        <com.android.keyguard.NumPadButton
+            android:id="@+id/key_enter"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
+            style="@style/NumPadKey.Enter"
+            android:contentDescription="@string/keyboardview_keycode_enter"
+            />
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
+
+
+
     <include layout="@layout/keyguard_eca"
              android:id="@+id/keyguard_selector_fade_container"
              android:layout_width="match_parent"
diff --git a/packages/SystemUI/res-keyguard/values-land/donottranslate.xml b/packages/SystemUI/res-keyguard/values-land/donottranslate.xml
new file mode 100644
index 0000000000000..9912b699507eb
--- /dev/null
+++ b/packages/SystemUI/res-keyguard/values-land/donottranslate.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2021 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<resources xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
+    <string name="num_pad_key_ratio">1.51</string>
+</resources>
diff --git a/packages/SystemUI/res-keyguard/values/donottranslate.xml b/packages/SystemUI/res-keyguard/values/donottranslate.xml
index a4d0ff7269a22..878c0172c3ff3 100644
--- a/packages/SystemUI/res-keyguard/values/donottranslate.xml
+++ b/packages/SystemUI/res-keyguard/values/donottranslate.xml
@@ -26,4 +26,6 @@
 
     <!-- Skeleton string format for displaying the time in 24-hour format. -->
     <string name="clock_24hr_format">Hm</string>
+
+    <string name="num_pad_key_ratio">1</string>
 </resources>
diff --git a/packages/SystemUI/res-keyguard/values/styles.xml b/packages/SystemUI/res-keyguard/values/styles.xml
index 72b027af1bf68..ea769c6a64103 100644
--- a/packages/SystemUI/res-keyguard/values/styles.xml
+++ b/packages/SystemUI/res-keyguard/values/styles.xml
@@ -37,6 +37,10 @@
       <item name="android:colorControlNormal">@null</item>
       <item name="android:colorControlHighlight">?android:attr/colorAccent</item>
       <item name="android:background">@drawable/num_pad_key_background</item>
+
+      <!-- Default values for NumPadKey used in a ConstraintLayout. -->
+      <item name="layout_constraintDimensionRatio">@string/num_pad_key_ratio</item>
+      <item name="layout_constraintWidth_max">@dimen/num_pad_key_width</item>
     </style>
     <style name="Widget.TextView.NumPadKey.Digit"
            parent="@android:style/Widget.DeviceDefault.TextView">
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardPINView.java b/packages/SystemUI/src/com/android/keyguard/KeyguardPINView.java
index 8fc4240e1054d..82ade7aa18066 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardPINView.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardPINView.java
@@ -22,15 +22,14 @@ import android.util.AttributeSet;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.animation.AnimationUtils;
-import android.widget.LinearLayout;
+
+import androidx.constraintlayout.widget.ConstraintLayout;
 
 import com.android.internal.jank.InteractionJankMonitor;
 import com.android.settingslib.animation.AppearAnimationUtils;
 import com.android.settingslib.animation.DisappearAnimationUtils;
 import com.android.systemui.R;
 
-import java.util.List;
-
 /**
  * Displays a PIN pad for unlocking.
  */
@@ -40,10 +39,6 @@ public class KeyguardPINView extends KeyguardPinBasedInputView {
     private final DisappearAnimationUtils mDisappearAnimationUtils;
     private final DisappearAnimationUtils mDisappearAnimationUtilsLocked;
     private ViewGroup mContainer;
-    private ViewGroup mRow0;
-    private ViewGroup mRow1;
-    private ViewGroup mRow2;
-    private ViewGroup mRow3;
     private int mDisappearYTranslation;
     private View[][] mViews;
 
@@ -82,30 +77,38 @@ public class KeyguardPINView extends KeyguardPinBasedInputView {
     }
 
     private void updateMargins() {
+        // Re-apply everything to the keys...
         int bottomMargin = mContext.getResources().getDimensionPixelSize(
-                R.dimen.num_pad_row_margin_bottom);
-
-        for (ViewGroup vg : List.of(mRow1, mRow2, mRow3)) {
-            ((LinearLayout.LayoutParams) vg.getLayoutParams()).setMargins(0, 0, 0, bottomMargin);
-        }
-
-        bottomMargin = mContext.getResources().getDimensionPixelSize(
                 R.dimen.num_pad_entry_row_margin_bottom);
-        ((LinearLayout.LayoutParams) mRow0.getLayoutParams()).setMargins(0, 0, 0, bottomMargin);
+        int rightMargin = mContext.getResources().getDimensionPixelSize(
+                R.dimen.num_pad_key_margin_end);
+        String ratio = mContext.getResources().getString(R.string.num_pad_key_ratio);
 
-        if (mEcaView != null) {
-            int ecaTopMargin = mContext.getResources().getDimensionPixelSize(
-                    R.dimen.keyguard_eca_top_margin);
-            int ecaBottomMargin = mContext.getResources().getDimensionPixelSize(
-                    R.dimen.keyguard_eca_bottom_margin);
-            ((LinearLayout.LayoutParams) mEcaView.getLayoutParams()).setMargins(0, ecaTopMargin,
-                    0, ecaBottomMargin);
+        // mView contains all Views that make up the PIN pad; row0 = the entry test field, then
+        // rows 1-4 contain the buttons. Iterate over all views that make up the buttons in the pad,
+        // and re-set all the margins.
+        for (int row = 1; row < 5; row++) {
+            for (int column = 0; column < 3; column++) {
+                View key = mViews[row][column];
+
+                ConstraintLayout.LayoutParams lp =
+                        (ConstraintLayout.LayoutParams) key.getLayoutParams();
+
+                lp.dimensionRatio = ratio;
+
+                // Don't set any margins on the last row of buttons.
+                if (row != 4) {
+                    lp.bottomMargin = bottomMargin;
+                }
+
+                // Don't set margins on the rightmost buttons.
+                if (column != 2) {
+                    lp.rightMargin = rightMargin;
+                }
+
+                key.setLayoutParams(lp);
+            }
         }
-
-        View entryView = findViewById(R.id.pinEntry);
-        ViewGroup.LayoutParams lp = entryView.getLayoutParams();
-        lp.height = mContext.getResources().getDimensionPixelSize(R.dimen.keyguard_password_height);
-        entryView.setLayoutParams(lp);
     }
 
     @Override
@@ -113,13 +116,9 @@ public class KeyguardPINView extends KeyguardPinBasedInputView {
         super.onFinishInflate();
 
         mContainer = findViewById(R.id.pin_container);
-        mRow0 = findViewById(R.id.row0);
-        mRow1 = findViewById(R.id.row1);
-        mRow2 = findViewById(R.id.row2);
-        mRow3 = findViewById(R.id.row3);
         mViews = new View[][]{
                 new View[]{
-                        mRow0, null, null
+                        findViewById(R.id.row0), null, null
                 },
                 new View[]{
                         findViewById(R.id.key1), findViewById(R.id.key2),
@@ -188,9 +187,6 @@ public class KeyguardPINView extends KeyguardPinBasedInputView {
     private void enableClipping(boolean enable) {
         mContainer.setClipToPadding(enable);
         mContainer.setClipChildren(enable);
-        mRow1.setClipToPadding(enable);
-        mRow2.setClipToPadding(enable);
-        mRow3.setClipToPadding(enable);
         setClipChildren(enable);
     }
 
diff --git a/packages/SystemUI/src/com/android/keyguard/NumPadButton.java b/packages/SystemUI/src/com/android/keyguard/NumPadButton.java
index 57407f1f34c0b..99f9558fe5d02 100644
--- a/packages/SystemUI/src/com/android/keyguard/NumPadButton.java
+++ b/packages/SystemUI/src/com/android/keyguard/NumPadButton.java
@@ -59,7 +59,9 @@ public class NumPadButton extends AlphaOptimizedImageButton {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 
         // Set width/height to the same value to ensure a smooth circle for the bg, but shrink
-        // the height to match the old pin bouncer
+        // the height to match the old pin bouncer.
+        // This is only used for PIN/PUK; the main PIN pad now uses ConstraintLayout, which will
+        // force our width/height to conform to the ratio in the layout.
         int width = getMeasuredWidth();
 
         boolean shortenHeight = mAnimator == null
diff --git a/packages/SystemUI/src/com/android/keyguard/NumPadKey.java b/packages/SystemUI/src/com/android/keyguard/NumPadKey.java
index 232c6fc990681..e79ea9a44843e 100644
--- a/packages/SystemUI/src/com/android/keyguard/NumPadKey.java
+++ b/packages/SystemUI/src/com/android/keyguard/NumPadKey.java
@@ -175,7 +175,9 @@ public class NumPadKey extends ViewGroup {
         measureChildren(widthMeasureSpec, heightMeasureSpec);
 
         // Set width/height to the same value to ensure a smooth circle for the bg, but shrink
-        // the height to match the old pin bouncer
+        // the height to match the old pin bouncer.
+        // This is only used for PIN/PUK; the main PIN pad now uses ConstraintLayout, which will
+        // force our width/height to conform to the ratio in the layout.
         int width = getMeasuredWidth();
 
         boolean shortenHeight = mAnimator == null