Add a warning message to the ASM toggle.

This trigger fires if ASM is not enabled by default for
the device and the toggle is only visible if the ASM visible
flag is enabled.

Bug: 30455784
Change-Id: Id6adf8a75dbd4290f042d743689a75f496efb0c9

res/values/strings.xml

@@ -7828,4 +7828,7 @@
 
     <!-- Section title for the Domain URL app preference list [CHAR LIMIT=60]-->
     <string name="domain_url_section_title">Installed apps</string>
+
+    <!-- Warning when activating the automatic storage manager on legacy devices. [CHAR LIMIT=NONE] -->
+    <string name="automatic_storage_manager_activation_warning">Your storage is now being managed by the storage manager</string>
 </resources>

src/com/android/settings/deletionhelper/ActivationWarningFragment.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016 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.settings.deletionhelper;
+
+import android.app.AlertDialog;
+import android.app.Dialog;
+import android.app.DialogFragment;
+import android.content.DialogInterface;
+import android.os.Bundle;
+import com.android.settings.R;
+
+/**
+ * Fragment to warn the user about activating the storage manager.
+ */
+public class ActivationWarningFragment extends DialogFragment {
+    public static final String TAG = "ActivationWarningFragment";
+
+    public static ActivationWarningFragment newInstance() {
+        return new ActivationWarningFragment();
+    }
+
+    @Override
+    public Dialog onCreateDialog(Bundle savedInstanceState) {
+        return new AlertDialog.Builder(getActivity())
+                .setMessage(R.string.automatic_storage_manager_activation_warning)
+                .setPositiveButton(android.R.string.ok, null)
+                .create();
+    }
+
+}

src/com/android/settings/deletionhelper/AutomaticStorageManagerSettings.java

@@ -17,11 +17,13 @@
 package com.android.settings.deletionhelper;
 
 import android.app.Activity;
+import android.app.AlertDialog;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.res.Resources;
 import android.os.Bundle;
+import android.os.SystemProperties;
 import android.os.storage.StorageManager;
 import android.provider.Settings;
 import android.text.format.DateUtils;
@@ -55,6 +57,8 @@ public class AutomaticStorageManagerSettings extends SettingsPreferenceFragment
     private static final String KEY_DELETION_HELPER = "deletion_helper";
     private static final String KEY_FREED = "freed_bytes";
     private static final String KEY_STORAGE_MANAGER_SWITCH = "storage_manager_active";
+    private static final String STORAGE_MANAGER_ENABLED_BY_DEFAULT_PROPERTY =
+            "ro.storage_manager.enabled";
 
     private DropDownPreference mDaysToRetain;
     private Preference mFreedBytes;
@@ -126,6 +130,10 @@ public class AutomaticStorageManagerSettings extends SettingsPreferenceFragment
                 mDaysToRetain.setEnabled(checked);
                 Settings.Secure.putInt(getContentResolver(),
                         Settings.Secure.AUTOMATIC_STORAGE_MANAGER_ENABLED, checked ? 1 : 0);
+                // Only show a warning if enabling.
+                if (checked) {
+                    maybeShowWarning();
+                }
                 break;
             case KEY_DAYS:
                 Settings.Secure.putInt(getContentResolver(),
@@ -164,4 +172,15 @@ public class AutomaticStorageManagerSettings extends SettingsPreferenceFragment
         }
         return indices.length - 1;
     }
+
+    private void maybeShowWarning() {
+        // If the storage manager is on by default, we can use the normal message.
+        boolean warningUnneeded = SystemProperties.getBoolean(
+                STORAGE_MANAGER_ENABLED_BY_DEFAULT_PROPERTY, false);
+        if (warningUnneeded) {
+            return;
+        }
+        ActivationWarningFragment fragment = ActivationWarningFragment.newInstance();
+        fragment.show(getFragmentManager(), ActivationWarningFragment.TAG);
+    }
 }