新人一枚，沒有整機環境，有什麼寫的不對歡迎批評指正，萬分感謝！
Settings主界面加載時序圖（這裏很多判斷邏輯我省略掉了。更多的是想把加載主界面流程跑通。）
這張流程圖將主fragment DashboardSummary啓動，RecyclerView數據加載刷新 顯示得較爲明白。但是對於主界面tile分類，tile排序，tile對象屬性是無法得知的。所以接下我就主要講講這兩個。
（1）先看一下主界面佈局（用繪圖畫的，比較醜見諒）
這裏有一個值得學習的是RecycleView分類加載不同的佈局，值得學習。方法在DashboardAdapter.Java裏面。
主界面對象介紹：
（1）主界面（除了Suggestion，condition）其他對象都在List<DashBoardCagtory> Categories裏面
（2） Categories 有 4個對象。4個DashBoardCagtory的title值分別是 Wireless&networks，Device，Personal，System
（3）各個Cagtories都有List<Tile> tiles 是各個DashBoardCagtorytitle下面各個tile的集合
組裝這些對象是時序圖中方法4，5，6，7，8。
5 getTilesForAction
（1）組裝Intent對象
（2）調用方法6
private static void getTilesForAction(Context context,
UserHandle user, String action, Map<Pair<String, String>, Tile> addedCache,
String defaultCategory, ArrayList<Tile> outTiles, boolean requireSettings) {
Intent intent = new Intent(action);
if (requireSettings) {
intent.setPackage(SETTING_PKG);
}
getTilesForIntent(context, user, intent, addedCache, defaultCategory, outTiles,
requireSettings, true);
}
6 getTilesForIntent
（1）利用PM查詢所有含有方法5生成的intent對象的ResolveInfo集合
（2）獲取集合中每一個Acitvity manifest配置的meta標籤name爲SETTINGS_ACTION的value值
（3）把activity name 和package 生成Intent對象
（4）將2步驟的值賦值給Tile category
（5）獲取action爲SETTINGS_ACTION的intent-filter的priority屬性
（6）將解析meta-data標籤的bundle數據賦值給Tile metaData
public static void getTilesForIntent(Context context, UserHandle user, Intent intent,
Map<Pair<String, String>, Tile> addedCache, String defaultCategory, List<Tile> outTiles,
boolean usePriority, boolean checkCategory) {
PackageManager pm = context.getPackageManager();
List<ResolveInfo> results = pm.queryIntentActivitiesAsUser(intent,
PackageManager.GET_META_DATA, user.getIdentifier());
for (ResolveInfo resolved : results) {
if (!resolved.system) {
continue;
}
ActivityInfo activityInfo = resolved.activityInfo;
Bundle metaData = activityInfo.metaData;
String categoryKey = defaultCategory;
if (checkCategory && ((metaData == null) || !metaData.containsKey(EXTRA_CATEGORY_KEY))
&& categoryKey == null) {
continue;
} else {
categoryKey = metaData.getString(EXTRA_CATEGORY_KEY);
}
Pair<String, String> key = new Pair<String, String>(activityInfo.packageName,
activityInfo.name);
Tile tile = addedCache.get(key);
if (tile == null) {
tile = new Tile();
tile.intent = new Intent().setClassName(
activityInfo.packageName, activityInfo.name);
tile.category = categoryKey;
tile.priority = usePriority ? resolved.priority : 0;
tile.metaData = activityInfo.metaData;
updateTileData(context, tile, activityInfo, activityInfo.applicationInfo,
pm);
if (DEBUG) Log.d(LOG_TAG, "Adding tile " + tile.title);
addedCache.put(key, tile);
}
if (!tile.userHandle.contains(user)) {
tile.userHandle.add(user);
}
if (!outTiles.contains(tile)) {
outTiles.add(tile);
}
}
}
7 updateTileData
（1） 解析meta-data標籤 獲取name爲 META_DATA_PREFERENCE_ICON的value值賦值給icon
（2）解析meta-data標籤 獲取name爲 META_DATA_PREFERENCE_TITLE的resource值賦值給title
（3）解析meta-data標籤 獲取name爲 META_DATA_PREFERENCE_SUMMARY的value值賦值給summary
（4）如果title爲空就獲取acitvity標籤label屬性賦值給title
（5）如果icon等於0就獲取acitvity標籤icon屬性賦值給icon
private static boolean updateTileData(Context context, Tile tile,
ActivityInfo activityInfo, ApplicationInfo applicationInfo, PackageManager pm) {
if (applicationInfo.isSystemApp()) {
int icon = 0;
CharSequence title = null;
String summary = null;
try {
Resources res = pm.getResourcesForApplication(
applicationInfo.packageName);
Bundle metaData = activityInfo.metaData;
if (res != null && metaData != null) {
if (metaData.containsKey(META_DATA_PREFERENCE_ICON)) {
icon = metaData.getInt(META_DATA_PREFERENCE_ICON);
}
if (metaData.containsKey(META_DATA_PREFERENCE_TITLE)) {
if (metaData.get(META_DATA_PREFERENCE_TITLE) instanceof Integer) {
title = res.getString(metaData.getInt(META_DATA_PREFERENCE_TITLE));
} else {
title = metaData.getString(META_DATA_PREFERENCE_TITLE);
}
}
if (metaData.containsKey(META_DATA_PREFERENCE_SUMMARY)) {
if (metaData.get(META_DATA_PREFERENCE_SUMMARY) instanceof Integer) {
summary = res.getString(metaData.getInt(META_DATA_PREFERENCE_SUMMARY));
} else {
summary = metaData.getString(META_DATA_PREFERENCE_SUMMARY);
}
}
}
} catch (PackageManager.NameNotFoundException | Resources.NotFoundException e) {
if (DEBUG) Log.d(LOG_TAG, "Couldn't find info", e);
}
if (TextUtils.isEmpty(title)) {
title = activityInfo.loadLabel(pm).toString();
}
if (icon == 0) {
icon = activityInfo.icon;
}
tile.icon = Icon.createWithResource(activityInfo.packageName, icon);
tile.title = title;
tile.summary = summary;
tile.intent = new Intent().setClassName(activityInfo.packageName,
activityInfo.name);
return true;
}
return false;
}
8 createCategory
（1）創建DashboardCategory對象
（2）利用PM查詢所有含有Tile對象categoriyKey生成的intent對象的ResolveInfo集合
（3）把acitivity label值賦值給category title屬性
（4）把解析intent-filter標籤的priority值賦值給category屬性
private static DashboardCategory createCategory(Context context, String categoryKey) {
DashboardCategory category = new DashboardCategory();
category.key = categoryKey;
PackageManager pm = context.getPackageManager();
List<ResolveInfo> results = pm.queryIntentActivities(new Intent(categoryKey), 0);
if (results.size() == 0) {
return null;
}
for (ResolveInfo resolved : results) {
if (!resolved.system) {
// Do not allow any app to add to settings, only system ones.
continue;
}
category.title = resolved.activityInfo.loadLabel(pm);
category.priority = SETTING_PKG.equals(
resolved.activityInfo.applicationInfo.packageName) ? resolved.priority : 0;
if (DEBUG) Log.d(LOG_TAG, "Adding category " + category.title);
}
return category;
}
4 getCategories
（1）調用5
（2）新建categoryMap集合
（3）遍歷tiles，判斷集合中是否有元素含有tile.category(當時我看見這個覺得google多此一舉每次這個對象都是需要new但是我後來整 理manifest發現 含有相同category的tile很多。可以看我下面整理的manifest的表格)。如果沒有就執行方法8
（4）將擁有相同屬性category的tile加入到對象DashboardCategory category對象的list<tile>集合中（我覺得google寫這個自己也蒙 蔽了。兩個相同名字， 一個是Tile裏面變量，一個是DashboardCategory對象）
（5）將categoryMap的值賦值給List <DashboardCategory>cagtories以便執行排序算法
（6）遍歷cagtories利用Collections函數和比較器TILE_COMPARATOR將category.tiles按照priority從大到小排序
（7）利用Collections函數和比較器CATEGORY_COMPARATOR將categories按照priority從大到小排序
public static List<DashboardCategory> getCategories(Context context,
HashMap<Pair<String, String>, Tile> cache) {
final long startTime = System.currentTimeMillis();
boolean setup = Global.getInt(context.getContentResolver(), Global.DEVICE_PROVISIONED, 0)
!= 0;
ArrayList<Tile> tiles = new ArrayList<>();
UserManager userManager = UserManager.get(context);
for (UserHandle user : userManager.getUserProfiles()) {
// TODO: Needs much optimization, too many PM queries going on here.
if (user.getIdentifier() == ActivityManager.getCurrentUser()) {
// Only add Settings for this user.
getTilesForAction(context, user, SETTINGS_ACTION, cache, null, tiles, true);
getTilesForAction(context, user, OPERATOR_SETTINGS, cache,
OPERATOR_DEFAULT_CATEGORY, tiles, false);
getTilesForAction(context, user, MANUFACTURER_SETTINGS, cache,
MANUFACTURER_DEFAULT_CATEGORY, tiles, false);
}
if (setup) {
getTilesForAction(context, user, EXTRA_SETTINGS_ACTION, cache, null, tiles, false);
}
}
HashMap<String, DashboardCategory> categoryMap = new HashMap<>();
for (Tile tile : tiles) {
DashboardCategory category = categoryMap.get(tile.category);
if (category == null) {
category = createCategory(context, tile.category);
if (category == null) {
Log.w(LOG_TAG, "Couldn't find category " + tile.category);
continue;
}
categoryMap.put(category.key, category);
}
category.addTile(tile);
}
ArrayList<DashboardCategory> categories = new ArrayList<>(categoryMap.values());
for (DashboardCategory category : categories) {
Collections.sort(category.tiles, TILE_COMPARATOR);
}
Collections.sort(categories, CATEGORY_COMPARATOR);
if (DEBUG_TIMING) Log.d(LOG_TAG, "getCategories took "
+ (System.currentTimeMillis() - startTime) + " ms");
return categories;
}圖表：tile
圖表：DashboardCategory
問題：summary是無法從manifest文件裏面獲取的。因爲不含有meta-data name屬性爲“com.android.settings.summary”的標籤。summary獲取方法是時序圖中方法16，17，18，31，32
16 new SummaryLoader
（1） 創建Handler對象（2） 創建異步線程（大家可以去看一下線程優先級，做app還是挺有用處的）
（3） 遍歷categories裏面每一個DashboardCategory對象裏面集合Tiles裏面每一個tile對象
（4） 發送消息執行方法17
public SummaryLoader(Activity activity, List<DashboardCategory> categories) {
mHandler = new Handler();
mWorkerThread = new HandlerThread("SummaryLoader", Process.THREAD_PRIORITY_BACKGROUND);
mWorkerThread.start();
mWorker = new Worker(mWorkerThread.getLooper());
mActivity = activity;
for (int i = 0; i < categories.size(); i++) {
List<Tile> tiles = categories.get(i).tiles;
for (int j = 0; j < tiles.size(); j++) {
Tile tile = tiles.get(j);
mWorker.obtainMessage(Worker.MSG_GET_PROVIDER, tile).sendToTarget();
}
}
}17 makeProviderW
（1）執行方法18
（2）將方法18返回的SummaryProvider對象存入到mSummaryMap中
private synchronized void makeProviderW(Tile tile) {
SummaryProvider provider = getSummaryProvider(tile);
if (provider != null) {
if (DEBUG) Log.d(TAG, "Creating " + tile);
mSummaryMap.put(provider, tile.intent.getComponent());
}
}18 getSummaryProvider（真的是厲害了，我的歌）
（1）獲取title中的meataData變量
（2）將bundle數據metaData鍵爲SettingsActivity.META_DATA_KEY_FRAGMENT的alue值賦值給clsName
（3）根據clsName反射創建class
（4）獲取name爲SUMMARY_PROVIDER_FACORY的變量Field
（5）拿到Field的值強制轉換爲SummaryProviderFactory對象
（6）返回反射類中SummaryProvider對象
private SummaryProvider getSummaryProvider(Tile tile) {
if (!mActivity.getPackageName().equals(tile.intent.getComponent().getPackageName())) {
// Not within Settings, can't load Summary directly.
// TODO: Load summary indirectly.
return null;
}
Bundle metaData = getMetaData(tile);
if (metaData == null) {
if (DEBUG) Log.d(TAG, "No metadata specified for " + tile.intent.getComponent());
return null;
}
String clsName = metaData.getString(SettingsActivity.META_DATA_KEY_FRAGMENT_CLASS);
if (clsName == null) {
if (DEBUG) Log.d(TAG, "No fragment specified for " + tile.intent.getComponent());
return null;
}
try {
Class<?> cls = Class.forName(clsName);
Field field = cls.getField(SUMMARY_PROVIDER_FACTORY);
SummaryProviderFactory factory = (SummaryProviderFactory) field.get(null);
return factory.createSummaryProvider(mActivity, this);
} catch (ClassNotFoundException e) {
if (DEBUG) Log.d(TAG, "Couldn't find " + clsName, e);
} catch (NoSuchFieldException e) {
if (DEBUG) Log.d(TAG, "Couldn't find " + SUMMARY_PROVIDER_FACTORY, e);
} catch (ClassCastException e) {
if (DEBUG) Log.d(TAG, "Couldn't cast " + SUMMARY_PROVIDER_FACTORY, e);
} catch (IllegalAccessException e) {
if (DEBUG) Log.d(TAG, "Couldn't get " + SUMMARY_PROVIDER_FACTORY, e);
}
return null;
}以NotificationApps.java爲例
public class NotificationApps extends ManageApplications {
private static class SummaryProvider implements SummaryLoader.SummaryProvider {
private final Context mContext;
private final SummaryLoader mLoader;
private final NotificationBackend mNotificationBackend;
private SummaryProvider(Context context, SummaryLoader loader) {
mContext = context;
mLoader = loader;
mNotificationBackend = new NotificationBackend();
}
@Override
public void setListening(boolean listening) {
if (listening) {
new AppCounter(mContext) {
@Override
protected void onCountComplete(int num) {
updateSummary(num);
}
@Override
protected boolean includeInCount(ApplicationInfo info) {
return mNotificationBackend.getNotificationsBanned(info.packageName,
info.uid);
}
}.execute();
}
}
private void updateSummary(int count) {
if (count == 0) {
mLoader.setSummary(this, mContext.getString(R.string.notification_summary_none));
} else {
mLoader.setSummary(this, mContext.getResources().getQuantityString(
R.plurals.notification_summary, count, count));
}
}
}
public static final SummaryLoader.SummaryProviderFactory SUMMARY_PROVIDER_FACTORY
= new SummaryLoader.SummaryProviderFactory() {
@Override
public SummaryLoader.SummaryProvider createSummaryProvider(Activity activity,
SummaryLoader summaryLoader) {
return new SummaryProvider(activity, summaryLoader);
}
};
}31 setListening
（1） 移除消息Worker.MSG_SET_LISTENING
（2） 發送消息Worker.MSG_SET_LISTENING執行方法32
public void setListening(boolean listening) {
if (mListening == listening) return;
mListening = listening;
// Unregister listeners immediately.
for (int i = 0; i < mReceivers.size(); i++) {
mActivity.unregisterReceiver(mReceivers.valueAt(i));
}
mReceivers.clear();
mWorker.removeMessages(Worker.MSG_SET_LISTENING);
mWorker.obtainMessage(Worker.MSG_SET_LISTENING, listening ? 1 : 0, 0).sendToTarget();
}32 setListeningW(注意鎖)
（1）遍歷方法18生成的mSummaryMap鍵SummaryProvider
（2）將反射fragment類中靜態內部類執行setListening方法
private synchronized void setListeningW(boolean listening) {
if (mWorkerListening == listening) return;
mWorkerListening = listening;
if (DEBUG) Log.d(TAG, "Listening " + listening);
for (SummaryProvider p : mSummaryMap.keySet()) {
try {
p.setListening(listening);
} catch (Exception e) {
Log.d(TAG, "Problem in setListening", e);
}
}
}再介紹一下Settings.java的作用
正常我們寫很多activity。是不是該這樣寫：
for(int i = 1 ; i <=需要新建activity的個數;i++) {
新建class Activityi extends SettingsActivity
}這樣做沒有什麼不對，也不會對性能有影響。但是SettingsActivity真的是爸爸，兒子們需要做的都被爸爸幹完了，所以你會發現許多空白文件。
Google就利用java靜態內部類的機制（可以去百度一下）編譯就會生成他的宿主類名$靜態內部類名 也就是我們manifest看見類似於Settings$WirelessSettings。這樣寫就避免大量白癡文件。
Google 這次7.0Settings加載邏輯大改其實對於新界面開發更容易了。只要去manifest將你的activity屬性配置好。Settings.java聲明。目前代碼邏輯就能直接把你界面加載完畢。然後你去對應的fragment實現邏輯。這樣新界面開發基本不需要改動現有邏輯。真的是厲害了，我的歌！