Add a null home activity to Shell.apk

In configurations where AOSP Settings.apk is not included, there might
not be any home activity. E.g. CSI doesn't have Settings.apk.

This CL adds a null home activity to Shell.apk, which is in CSI,
so the framework can be in a sane state. Without such null home
activity in CSI, package manager fails to install any APKs.

Bug: 148044842
Test: $ lunch csi_arm64-userdebug; m -j
      # Flash CSI to a Pixel (with AVB disabled) and reboot
      $ m DeviceHealthChecks
      $ adb install $OUT/testcases/DeviceHealthTests/arm64/DeviceHealthTests.apk
      Performing Streamed Install
      Success

Change-Id: I87999e30298bbe42af64f28e88fc6dc5975f1ca3
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index af2569d..618f52e 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -265,6 +265,22 @@
                   android:excludeFromRecents="true"
                   android:exported="false" />
 
+        <!--
+        The following is used as a no-op/null home activity when
+        no other MAIN/HOME activity is present (e.g., in CSI).
+        -->
+        <activity android:name=".NullHome"
+                  android:excludeFromRecents="true"
+                  android:label=""
+                  android:screenOrientation="nosensor">
+            <!-- The priority here is set to be lower than that for Settings -->
+            <intent-filter android:priority="-1100">
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.HOME" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+        </activity>
+
         <receiver
             android:name=".BugreportReceiver"
             android:permission="android.permission.DUMP">
diff --git a/packages/Shell/res/layout/null_home_finishing_boot.xml b/packages/Shell/res/layout/null_home_finishing_boot.xml
new file mode 100644
index 0000000..5f9563a
--- /dev/null
+++ b/packages/Shell/res/layout/null_home_finishing_boot.xml
@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2020 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
+  -->
+<FrameLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="#80000000"
+    android:forceHasOverlappingRendering="false">
+    <LinearLayout
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:layout_gravity="center"
+        android:layout_marginStart="16dp"
+        android:layout_marginEnd="16dp">
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:textSize="40sp"
+            android:textColor="?android:attr/textColorPrimary"
+            android:text="@*android:string/android_start_title"/>
+        <ProgressBar
+            style="@android:style/Widget.Material.ProgressBar.Horizontal"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12.75dp"
+            android:colorControlActivated="?android:attr/textColorPrimary"
+            android:indeterminate="true"/>
+    </LinearLayout>
+</FrameLayout>
diff --git a/packages/Shell/src/com/android/shell/NullHome.java b/packages/Shell/src/com/android/shell/NullHome.java
new file mode 100644
index 0000000..bd97561
--- /dev/null
+++ b/packages/Shell/src/com/android/shell/NullHome.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+package com.android.shell;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.util.Log;
+
+/**
+ * This covers the fallback case where no launcher is available.
+ * Usually Settings.apk has one fallback home activity.
+ * Settings.apk, however, is not part of CSI, which needs to be
+ * standalone (bootable and testable).
+ */
+public class NullHome extends Activity {
+    private static final String TAG = "NullHome";
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        Log.i(TAG, "onCreate");
+        setContentView(R.layout.null_home_finishing_boot);
+    }
+
+    protected void onDestroy() {
+        super.onDestroy();
+        Log.i(TAG, "onDestroy");
+    }
+}