Cleanup to screensaver settings for O

Reworked the way screensaver settings are laid out for O. Instead of
using the options menu and dialogs to navigate screensaver options,
there are now two rows: one row for the screensaver choice and
optionally its own settings, and one row for the "when to show" setting.
And now there's a nice obvious button you can press to preview your
choices.

Test: 'export ROBOTEST_FILTER="RadioButtonListFragmentTest";\
mmm -j20 packages/apps/Settings/tests/robotests'

Bug: 35031991
Change-Id: Ie7d2055fb45f6dfe72e34cb9598d9a25f7bee75a

src/com/android/settings/dream/CurrentDreamPicker.java

@@ -0,0 +1,117 @@
+/*
+ * 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.dream;
+
+
+import android.content.ComponentName;
+import android.content.Context;
+import android.graphics.drawable.Drawable;
+import com.android.internal.logging.nano.MetricsProto;
+import com.android.settings.widget.RadioButtonPickerFragment;
+import com.android.settingslib.dream.DreamBackend;
+import com.android.settingslib.dream.DreamBackend.DreamInfo;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public final class CurrentDreamPicker extends RadioButtonPickerFragment {
+
+    private DreamBackend mBackend;
+
+    @Override
+    public void onAttach(Context context) {
+        super.onAttach(context);
+
+        mBackend = DreamBackend.getInstance(context);
+    }
+
+    @Override
+    public int getMetricsCategory() {
+        return MetricsProto.MetricsEvent.DREAM;
+    }
+
+    @Override
+    protected boolean setDefaultKey(String key) {
+        Map<String, ComponentName> componentNameMap = getDreamComponentsMap();
+        if (componentNameMap.get(key) != null) {
+            mBackend.setActiveDream(componentNameMap.get(key));
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    protected String getDefaultKey() {
+        return mBackend.getActiveDream().flattenToString();
+    }
+
+    @Override
+    protected List<? extends CandidateInfo> getCandidates() {
+        final List<DreamCandidateInfo> candidates;
+        candidates = mBackend.getDreamInfos().stream()
+                .map(DreamCandidateInfo::new)
+                .collect(Collectors.toList());
+
+        return candidates;
+    }
+
+    @Override
+    protected void onSelectionPerformed(boolean success) {
+        super.onSelectionPerformed(success);
+
+        getActivity().finish();
+    }
+
+    private Map<String, ComponentName> getDreamComponentsMap() {
+        Map<String, ComponentName> comps = new HashMap<>();
+        mBackend.getDreamInfos()
+                .forEach((info) ->
+                        comps.put(info.componentName.flattenToString(), info.componentName));
+
+        return comps;
+    }
+
+    private static final class DreamCandidateInfo extends CandidateInfo {
+        private final CharSequence name;
+        private final Drawable icon;
+        private final String key;
+
+        DreamCandidateInfo(DreamInfo info) {
+            super(true);
+
+            name = info.caption;
+            icon = info.icon;
+            key = info.componentName.flattenToString();
+        }
+
+        @Override
+        public CharSequence loadLabel() {
+            return name;
+        }
+
+        @Override
+        public Drawable loadIcon() {
+            return icon;
+        }
+
+        @Override
+        public String getKey() {
+            return key;
+        }
+    }
+}