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/WhenToDreamPicker.java

@@ -0,0 +1,115 @@
+/*
+ * 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.Context;
+import android.graphics.drawable.Drawable;
+import com.android.internal.logging.nano.MetricsProto;
+import com.android.settings.R;
+import com.android.settings.widget.RadioButtonPickerFragment;
+import com.android.settingslib.dream.DreamBackend;
+import java.util.ArrayList;
+import java.util.List;
+
+public class WhenToDreamPicker extends RadioButtonPickerFragment {
+
+    private static final String TAG = "WhenToDreamPicker";
+    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 List<? extends CandidateInfo> getCandidates() {
+        final String[] entries = entries();
+        final String[] values = keys();
+        final List<WhenToDreamCandidateInfo> candidates = new ArrayList<>();
+
+        if (entries == null || entries.length <= 0) return null;
+        if (values == null || values.length != entries.length) {
+            throw new IllegalArgumentException("Entries and values must be of the same length.");
+        }
+
+        for (int i = 0; i < entries.length; i++) {
+            candidates.add(new WhenToDreamCandidateInfo(entries[i], values[i]));
+        }
+
+        return candidates;
+    }
+
+    private String[] entries() {
+        return getResources().getStringArray(R.array.when_to_start_screensaver_entries);
+    }
+
+    private String[] keys() {
+        return getResources().getStringArray(R.array.when_to_start_screensaver_values);
+    }
+
+    @Override
+    protected String getDefaultKey() {
+        return DreamSettings.getKeyFromSetting(mBackend.getWhenToDreamSetting());
+    }
+
+    @Override
+    protected boolean setDefaultKey(String key) {
+        mBackend.setWhenToDream(DreamSettings.getSettingFromPrefKey(key));
+        return true;
+    }
+
+    @Override
+    protected void onSelectionPerformed(boolean success) {
+        super.onSelectionPerformed(success);
+
+        getActivity().finish();
+    }
+
+    private final class WhenToDreamCandidateInfo extends CandidateInfo {
+        private final String name;
+        private final String key;
+
+        WhenToDreamCandidateInfo(String title, String value) {
+            super(true);
+
+            name = title;
+            key = value;
+        }
+
+        @Override
+        public CharSequence loadLabel() {
+            return name;
+        }
+
+        @Override
+        public Drawable loadIcon() {
+            return null;
+        }
+
+        @Override
+        public String getKey() {
+            return key;
+        }
+    }
+}