Stay discoverable in Bluetooth settings and pairing pages

There are two problems with the Bluetooth settings and pairing pages
that are fixed by this CL:

(1) We advertise on the page that the local device is visible to other
devices, but that only lasts for the length of the default timeout (120
seconds) for the local adapter being in discoverable mode.

(2) Both the BluetoothSettings and BluetoothPairingDetail fragments
enter discoverable mode in their onStart handler and exit it in their
onStop handler. Unfortunately when doing a fragment navigation the
onStart and onStop events interleave in a non-intuitive manner. When you
go from BluetoothSettings to BluetoothPairingDetail, we see the onStop
event for BluetoothSettings *after* the onStart event for
BluetoothPairingDetail, and similarly when going back from
BluetoothSettings to BluetoothPairingDetail. What this means in practice
is that if you go to the BluetoothSettings page, the device will be
discoverable, but once you navigate to BluetoothPairingDetail or back
again you won't be discoverable again until you go somewhere else or end
the settings activity.

This CL adds a new object called AlwaysDiscoverable which can be used to
start and stop a mode of "always being discoverable". While started, it
will listen for changes to the discoverable state, and return to
discoverable mode. This fixes (1) by returning to discoverable mode
whenever the normal timeout expires, and (2) similary by returning to
discoverable mode when we accidentally exit it due to the onStop/onStart
mismatch.

A better fix for (2) would be to avoid the "glitch" of briefly exiting
discoverable mode only to re-enter it, but the implementation of that is
a little more complicated so that's being left as future work in order
to keep this CL as small as possible.

Bug: 64130265
Test: make RunSettingsRoboTests
Change-Id: I559dd8187263ea6a0008be1a8abdfffac97cb87a

src/com/android/settings/bluetooth/AlwaysDiscoverable.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2017 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.bluetooth;
+
+import android.bluetooth.BluetoothAdapter;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.os.Handler;
+import android.support.annotation.VisibleForTesting;
+import android.util.Log;
+
+import com.android.settingslib.bluetooth.LocalBluetoothAdapter;
+
+import java.util.Timer;
+import java.util.TimerTask;
+
+/** Helper class, intended to be used by an Activity, to keep the local Bluetooth adapter in
+ *  discoverable mode indefinitely. By default setting the scan mode to
+ *  BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE will time out after some time, but some
+ *  Bluetooth settings pages would like to keep the device discoverable as long as the page is
+ *  visible. */
+public class AlwaysDiscoverable extends BroadcastReceiver {
+    private static final String TAG = "AlwaysDiscoverable";
+
+    private Context mContext;
+    private LocalBluetoothAdapter mLocalAdapter;
+    private IntentFilter mIntentFilter;
+
+    @VisibleForTesting
+    boolean mStarted;
+
+    public AlwaysDiscoverable(Context context, LocalBluetoothAdapter localAdapter) {
+        mContext = context;
+        mLocalAdapter = localAdapter;
+        mIntentFilter = new IntentFilter();
+        mIntentFilter.addAction(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED);
+    }
+
+    /** After calling start(), consumers should make a matching call to stop() when they no longer
+     * wish to enforce discoverable mode. */
+    public void start() {
+        if (mStarted) {
+            return;
+        }
+        mContext.registerReceiver(this, mIntentFilter);
+        mStarted = true;
+        if (mLocalAdapter.getScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
+            mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+        }
+    }
+
+    public void stop() {
+        if (!mStarted) {
+            return;
+        }
+        mContext.unregisterReceiver(this);
+        mStarted = false;
+        mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE);
+    }
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        String action = intent.getAction();
+        if (action != BluetoothAdapter.ACTION_SCAN_MODE_CHANGED) {
+            return;
+        }
+        if (mLocalAdapter.getScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
+            mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+        }
+    }
+}

src/com/android/settings/bluetooth/BluetoothPairingDetail.java

@@ -53,6 +53,8 @@ public class BluetoothPairingDetail extends DeviceListPreferenceFragment impleme
     BluetoothProgressCategory mAvailableDevicesCategory;
     @VisibleForTesting
     FooterPreference mFooterPreference;
+    @VisibleForTesting
+    AlwaysDiscoverable mAlwaysDiscoverable;
 
     private boolean mInitialScanStarted;
 
@@ -64,6 +66,7 @@ public class BluetoothPairingDetail extends DeviceListPreferenceFragment impleme
     public void onActivityCreated(Bundle savedInstanceState) {
         super.onActivityCreated(savedInstanceState);
         mInitialScanStarted = false;
+        mAlwaysDiscoverable = new AlwaysDiscoverable(getContext(), mLocalAdapter);
     }
 
     @Override
@@ -79,7 +82,7 @@ public class BluetoothPairingDetail extends DeviceListPreferenceFragment impleme
         super.onStop();
 
         // Make the device only visible to connected devices.
-        mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE);
+        mAlwaysDiscoverable.stop();
         disableScanning();
     }
 
@@ -132,9 +135,7 @@ public class BluetoothPairingDetail extends DeviceListPreferenceFragment impleme
                         R.string.bluetooth_preference_found_devices,
                         BluetoothDeviceFilter.UNBONDED_DEVICE_FILTER, mInitialScanStarted);
                 updateFooterPreference(mFooterPreference);
-                // mLocalAdapter.setScanMode is internally synchronized so it is okay for multiple
+                mAlwaysDiscoverable.start();
-                // threads to execute.
-                mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
                 enableScanning();
                 break;
 

src/com/android/settings/bluetooth/BluetoothSettings.java

@@ -84,6 +84,7 @@ public class BluetoothSettings extends DeviceListPreferenceFragment implements I
     FooterPreference mFooterPreference;
     private Preference mPairingPreference;
     private BluetoothEnabler mBluetoothEnabler;
+    private AlwaysDiscoverable mAlwaysDiscoverable;
 
     private SwitchBar mSwitchBar;
 
@@ -115,6 +116,9 @@ public class BluetoothSettings extends DeviceListPreferenceFragment implements I
                 mMetricsFeatureProvider, Utils.getLocalBtManager(activity),
                 MetricsEvent.ACTION_BLUETOOTH_TOGGLE);
         mBluetoothEnabler.setupSwitchController();
+        if (mLocalAdapter != null) {
+            mAlwaysDiscoverable = new AlwaysDiscoverable(getContext(), mLocalAdapter);
+        }
     }
 
     @Override
@@ -161,7 +165,9 @@ public class BluetoothSettings extends DeviceListPreferenceFragment implements I
         }
 
         // Make the device only visible to connected devices.
-        mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE);
+        if (mAlwaysDiscoverable != null) {
+            mAlwaysDiscoverable.stop();
+        }
 
         if (isUiRestricted()) {
             return;
@@ -192,7 +198,9 @@ public class BluetoothSettings extends DeviceListPreferenceFragment implements I
                 mPairedDevicesCategory.addPreference(mPairingPreference);
                 updateFooterPreference(mFooterPreference);
 
-                mLocalAdapter.setScanMode(BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+                if (mAlwaysDiscoverable != null) {
+                    mAlwaysDiscoverable.start();
+                }
                 return; // not break
 
             case BluetoothAdapter.STATE_TURNING_OFF:

tests/robotests/src/com/android/settings/bluetooth/AlwaysDiscoverableTest.java

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2017 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.bluetooth;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.bluetooth.BluetoothAdapter;
+import android.content.Context;
+import android.content.Intent;
+
+import com.android.settings.TestConfig;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+import com.android.settingslib.bluetooth.LocalBluetoothAdapter;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class AlwaysDiscoverableTest {
+    @Mock
+    private LocalBluetoothAdapter mLocalAdapter;
+
+    @Mock
+    private Context mContext;
+
+    private AlwaysDiscoverable mAlwaysDiscoverable;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mAlwaysDiscoverable = new AlwaysDiscoverable(mContext, mLocalAdapter);
+    }
+
+    @Test
+    public void isStartedWithoutStart() {
+        assertThat(mAlwaysDiscoverable.mStarted).isFalse();
+    }
+
+    @Test
+    public void isStartedWithStart() {
+        mAlwaysDiscoverable.start();
+        assertThat(mAlwaysDiscoverable.mStarted).isTrue();
+    }
+
+    @Test
+    public void isStartedWithStartStop() {
+        mAlwaysDiscoverable.start();
+        mAlwaysDiscoverable.stop();
+        assertThat(mAlwaysDiscoverable.mStarted).isFalse();
+    }
+
+    @Test
+    public void stopWithoutStart() {
+        mAlwaysDiscoverable.stop();
+        // expect no crash
+        verify(mLocalAdapter, never()).setScanMode(anyInt());
+    }
+
+    @Test
+    public void startSetsModeAndRegistersReceiver() {
+        when(mLocalAdapter.getScanMode()).thenReturn(BluetoothAdapter.SCAN_MODE_NONE);
+        mAlwaysDiscoverable.start();
+        verify(mLocalAdapter).setScanMode(eq(BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE));
+        verify(mContext).registerReceiver(eq(mAlwaysDiscoverable), any());
+    }
+
+    @Test
+    public void stopUnregistersReceiver() {
+        mAlwaysDiscoverable.start();
+        mAlwaysDiscoverable.stop();
+        verify(mContext).unregisterReceiver(mAlwaysDiscoverable);
+    }
+
+    @Test
+    public void resetsToDiscoverableModeWhenScanModeChanges() {
+        mAlwaysDiscoverable.start();
+        verify(mLocalAdapter, times(1)).setScanMode(
+                BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+
+        sendScanModeChangedIntent(BluetoothAdapter.SCAN_MODE_CONNECTABLE,
+                BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+
+        verify(mLocalAdapter, times(2)).setScanMode(
+                BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
+    }
+
+    private void sendScanModeChangedIntent(int newMode, int previousMode) {
+        when(mLocalAdapter.getScanMode()).thenReturn(newMode);
+        Intent intent = new Intent(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED);
+        intent.putExtra(BluetoothAdapter.EXTRA_SCAN_MODE, newMode);
+        intent.putExtra(BluetoothAdapter.EXTRA_PREVIOUS_SCAN_MODE, previousMode);
+        mAlwaysDiscoverable.onReceive(mContext, intent);
+    }
+}

tests/robotests/src/com/android/settings/bluetooth/BluetoothPairingDetailTest.java

@@ -85,6 +85,7 @@ public class BluetoothPairingDetailTest {
         mFragment.mLocalAdapter = mLocalAdapter;
         mFragment.mLocalManager = mLocalManager;
         mFragment.mDeviceListGroup = mPreferenceGroup;
+        mFragment.mAlwaysDiscoverable = new AlwaysDiscoverable(mContext, mLocalAdapter);
     }
 
     @Test