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一、Android 版本
Android 13
二、low storage简介(DeviceStorageMonitorService)
设备存储监视器服务是一个模块，主要用来：
1.监视设备存储（“/ data”）。
2.每60秒扫描一次免费存储空间(谷歌默认值)
3.当设备的存储空间不足时生成“低存储”通知。 //updateNotifications
4.引导用户管理设备中安装的所有应用程序，并发送意图。 //updateBroadcasts
5.存储严重不足时显示警告对话框。
6.为AMS/PMS提供公共API以查询存储状态
三、DeviceStorageMonitorService关键代码介绍
3.1服务初始化
- DeviceStorageMonitorService初始化handler用于check
- SystemService.onStart()时，获取通知，添加devicestoragemonitor到Binder Service
- 执行check()
public DeviceStorageMonitorService(Context context) {super(context);mHandlerThread = new HandlerThread(TAG, android.os.Process.THREAD_PRIORITY_BACKGROUND);mHandlerThread.start();mHandler = new Handler(mHandlerThread.getLooper()) {@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case MSG_CHECK_LOW:checkLow();return;case MSG_CHECK_HIGH:checkHigh();return;}}};} public void onStart() {final Context context = getContext();mNotifManager = context.getSystemService(NotificationManager.class);mCacheFileDeletedObserver = new CacheFileDeletedObserver();mCacheFileDeletedObserver.startWatching();// Ensure that the notification channel is set upPackageManager packageManager = context.getPackageManager();boolean isTv = packageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK);if (isTv) {mNotifManager.createNotificationChannel(new NotificationChannel(TV_NOTIFICATION_CHANNEL_ID,context.getString(com.android.internal.R.string.device_storage_monitor_notification_channel),NotificationManager.IMPORTANCE_HIGH));}publishBinderService(SERVICE, mRemoteService);publishLocalService(DeviceStorageMonitorInternal.class, mLocalService);// Kick off pass to examine storage statemHandler.removeMessages(MSG_CHECK_LOW);mHandler.obtainMessage(MSG_CHECK_LOW).sendToTarget();}3.2 check data分区
frameworks/base/services/core/java/com/android/server/storage/DeviceStorageMonitorService.java
注意这两个方法
if (State.isEntering(State.LEVEL_LOW, oldLevel, newLevel))
if (State.isLeaving(State.LEVEL_LOW, oldLevel, newLevel))
主要逻辑是进入低内存的时候，判断之前的状态，如果之前是正常的，就发通知，如果一直处理低内存状态，就不处理，避免重发通知处理
如果是低内存到正常内存状态，那就自动把通知取消掉
@WorkerThreadprivate void checkLow() {Slog.w(TAG, "AAAAA >>> checkLow()");final StorageManager storage = getContext().getSystemService(StorageManager.class);final int seq = mSeq.get();// Check every mounted private volume to see if they're low on spacefor (VolumeInfo vol : storage.getWritablePrivateVolumes()) {Slog.w(TAG, "AAAAA >>> checkLow() updateNotifications");final File file = vol.getPath();final long fullBytes = storage.getStorageFullBytes(file);final long lowBytes = storage.getStorageLowBytes(file);//默认500M或总空间的%5// Automatically trim cached data when nearing the low threshold;// when it's within 150% of the threshold, we try trimming usage// back to 200% of the threshold.if (file.getUsableSpace() < (lowBytes * 3) / 2) {final PackageManagerInternal pm =LocalServices.getService(PackageManagerInternal.class);//lowBytes的1.5倍容量时触发freeStoragetry {pm.freeStorage(vol.getFsUuid(), lowBytes * 2, 0);} catch (IOException e) {Slog.w(TAG, e);}}// Send relevant broadcasts and show notifications based on any// recently noticed state transitions.final UUID uuid = StorageManager.convert(vol.getFsUuid());final State state = findOrCreateState(uuid);final long totalBytes = file.getTotalSpace();//data总大小final long usableBytes = file.getUsableSpace();//可使用大小int oldLevel = state.level;int newLevel;//判断是LEVEL_LOW，LEVEL_FULL还是LEVEL_NORMALif (mForceLevel != State.LEVEL_UNKNOWN) {// When in testing mode, use unknown old level to force sending// of any relevant broadcasts.oldLevel = State.LEVEL_UNKNOWN;newLevel = mForceLevel;} else if (usableBytes <= fullBytes) {newLevel = State.LEVEL_FULL;} else if (usableBytes <= lowBytes) {newLevel = State.LEVEL_LOW;} else if (StorageManager.UUID_DEFAULT.equals(uuid)&& usableBytes < BOOT_IMAGE_STORAGE_REQUIREMENT) {newLevel = State.LEVEL_LOW;} else {newLevel = State.LEVEL_NORMAL;}// Log whenever we notice drastic storage changesif ((Math.abs(state.lastUsableBytes - usableBytes) > DEFAULT_LOG_DELTA_BYTES)|| oldLevel != newLevel) {EventLogTags.writeStorageState(uuid.toString(), oldLevel, newLevel,usableBytes, totalBytes);state.lastUsableBytes = usableBytes;}//发送通知updateNotifications(vol, oldLevel, newLevel);//发送广播updateBroadcasts(vol, oldLevel, newLevel, seq);state.level = newLevel;}//没有check消息，继续60s检测一次// Loop around to check again in future; we don't remove messages since// there might be an immediate request pending.if (!mHandler.hasMessages(MSG_CHECK_LOW)) {mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_CHECK_LOW),LOW_CHECK_INTERVAL);}if (!mHandler.hasMessages(MSG_CHECK_HIGH)) {mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_CHECK_HIGH),HIGH_CHECK_INTERVAL);}} private void updateNotifications(VolumeInfo vol, int oldLevel, int newLevel) {Slog.w(TAG, "AAAAA >>> updateNotifications() oldLevel="+oldLevel+",,,,,newLevel="+newLevel);final Context context = getContext();final UUID uuid = StorageManager.convert(vol.getFsUuid());if (State.isEntering(State.LEVEL_LOW, oldLevel, newLevel)) {//调起通知Slog.w(TAG, "AAAAA >>> updateNotifications() do Notification");Intent lowMemIntent = new Intent(StorageManager.ACTION_MANAGE_STORAGE);lowMemIntent.putExtra(StorageManager.EXTRA_UUID, uuid);lowMemIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);final CharSequence title = context.getText(com.android.internal.R.string.low_internal_storage_view_title);final CharSequence details = context.getText(com.android.internal.R.string.low_internal_storage_view_text);PendingIntent intent = PendingIntent.getActivityAsUser(context, 0, lowMemIntent,PendingIntent.FLAG_IMMUTABLE, null, UserHandle.CURRENT);Notification notification =new Notification.Builder(context, SystemNotificationChannels.ALERTS).setSmallIcon(com.android.internal.R.drawable.stat_notify_disk_full).setTicker(title).setColor(context.getColor(com.android.internal.R.color.system_notification_accent_color)).setContentTitle(title).setContentText(details).setContentIntent(intent).setStyle(new Notification.BigTextStyle().bigText(details)).setVisibility(Notification.VISIBILITY_PUBLIC).setCategory(Notification.CATEGORY_SYSTEM).extend(new Notification.TvExtender().setChannelId(TV_NOTIFICATION_CHANNEL_ID)).build();notification.flags |= Notification.FLAG_NO_CLEAR;mNotifManager.notifyAsUser(uuid.toString(), SystemMessage.NOTE_LOW_STORAGE,notification, UserHandle.ALL);FrameworkStatsLog.write(FrameworkStatsLog.LOW_STORAGE_STATE_CHANGED,Objects.toString(vol.getDescription()),FrameworkStatsLog.LOW_STORAGE_STATE_CHANGED__STATE__ON);} else if (State.isLeaving(State.LEVEL_LOW, oldLevel, newLevel)) {//取消通知Slog.w(TAG, "AAAAA >>> updateNotifications() cancel Notification");mNotifManager.cancelAsUser(uuid.toString(), SystemMessage.NOTE_LOW_STORAGE,UserHandle.ALL);FrameworkStatsLog.write(FrameworkStatsLog.LOW_STORAGE_STATE_CHANGED,Objects.toString(vol.getDescription()),FrameworkStatsLog.LOW_STORAGE_STATE_CHANGED__STATE__OFF);}} private void updateBroadcasts(VolumeInfo vol, int oldLevel, int newLevel, int seq) {if (!Objects.equals(StorageManager.UUID_PRIVATE_INTERNAL, vol.getFsUuid())) {// We don't currently send broadcasts for secondary volumesreturn;}//lowStorage广播action ACTION_DEVICE_STORAGE_LOWfinal Intent lowIntent = new Intent(Intent.ACTION_DEVICE_STORAGE_LOW).addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT| Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND| Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS).putExtra(EXTRA_SEQUENCE, seq);//正常Storage广播action ACTION_DEVICE_STORAGE_OKfinal Intent notLowIntent = new Intent(Intent.ACTION_DEVICE_STORAGE_OK).addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT| Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND| Intent.FLAG_RECEIVER_VISIBLE_TO_INSTANT_APPS).putExtra(EXTRA_SEQUENCE, seq);if (State.isEntering(State.LEVEL_LOW, oldLevel, newLevel)) {//只发送一次广播ACTION_DEVICE_STORAGE_LOW，粘性广播，进程注册肯定会收到广播getContext().sendStickyBroadcastAsUser(lowIntent, UserHandle.ALL);} else if (State.isLeaving(State.LEVEL_LOW, oldLevel, newLevel)) {//恢复正常移除lowIntent粘性广播，发送normal的普通广播getContext().removeStickyBroadcastAsUser(lowIntent, UserHandle.ALL);getContext().sendBroadcastAsUser(notLowIntent, UserHandle.ALL);}final Intent fullIntent = new Intent(Intent.ACTION_DEVICE_STORAGE_FULL).addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT).putExtra(EXTRA_SEQUENCE, seq);final Intent notFullIntent = new Intent(Intent.ACTION_DEVICE_STORAGE_NOT_FULL).addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT).putExtra(EXTRA_SEQUENCE, seq);//发送FULL Storage广播ACTION_DEVICE_STORAGE_FULLif (State.isEntering(State.LEVEL_FULL, oldLevel, newLevel)) {getContext().sendStickyBroadcastAsUser(fullIntent, UserHandle.ALL);} else if (State.isLeaving(State.LEVEL_FULL, oldLevel, newLevel)) {getContext().removeStickyBroadcastAsUser(fullIntent, UserHandle.ALL);getContext().sendBroadcastAsUser(notFullIntent, UserHandle.ALL);}}
private static class State {private static final int LEVEL_UNKNOWN = -1;private static final int LEVEL_NORMAL = 0;//空间正常private static final int LEVEL_LOW = 1;//空间低private static final int LEVEL_FULL = 2;//空间满了
}3.3 低内存判断值
frameworks/base/core/java/android/os/storage/StorageManager.java
//总空间的百分比（默认是５%）和 500M 的最小值 作为最低空间提醒的标准public static final int DEFAULT_STORAGE_THRESHOLD_PERCENT_LOW = 5;private static final long DEFAULT_THRESHOLD_MAX_BYTES = DataUnit.MEBIBYTES.toBytes(500);public long getStorageLowBytes(File path) {final long lowPercent = Settings.Global.getInt(mResolver,Settings.Global.SYS_STORAGE_THRESHOLD_PERCENTAGE,DEFAULT_STORAGE_THRESHOLD_PERCENT_LOW);final long lowBytes = (path.getTotalSpace() * lowPercent) / 100;final long maxLowBytes = Settings.Global.getLong(mResolver,Settings.Global.SYS_STORAGE_THRESHOLD_MAX_BYTES, DEFAULT_THRESHOLD_MAX_BYTES);return Math.min(lowBytes, maxLowBytes);}四、查看剩余空间的方法
1、df -h 查看 data 目录空间
2、从桌面"设置"应用中查看存储
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