Android 呼吸燈流程分析(一)
阿新 • • 發佈：2018-12-30
一、Android 呼吸燈的使用
在講呼吸燈實現流程之前，我們先看一下如何使用它。
Android提供了呼吸燈的介面，我們可以通過該介面，控制呼吸燈的閃爍頻率和佔空比。具體程式碼如下：
通過該程式，便能自由控制呼吸燈的佔空比與頻率。package com.example.test; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.app.Activity; import android.app.Notification; import android.app.NotificationManager; public class MainActivity extends Activity { Button working; EditText ledOn; EditText ledOff; final int ID_LED=19871103; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ledOn = (EditText)findViewById(R.id.LedOn); ledOff = (EditText)findViewById(R.id.LedOff); working = (Button)findViewById(R.id.bu1); working.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { // TODO Auto-generated method stub NotificationManager nm=(NotificationManager)getSystemService(NOTIFICATION_SERVICE); Notification notification = new Notification(); notification.ledARGB = 0xffff0000; //這裡是顏色，我們可以嘗試改變，理論上0xFFff0000是紅色 // notification.ledOnMS = 350; // notification.ledOffMS = 300; notification.ledOnMS = Integer.parseInt((ledOn.getText().toString())); notification.ledOffMS = Integer.parseInt((ledOff.getText().toString())); notification.flags = Notification.FLAG_SHOW_LIGHTS; nm.notify(ID_LED, notification); } }); //nm.cancel(ID_LED); } }
二、Android上層呼吸燈的實現
1、NotificationManager
(1).在apk中我們填充了結構notification，並呼叫了nm.notify。很顯然，找到了關鍵點NotificationManager，對應檔案為：
frameworks/base/core/java/android/app/NotificationManager.java
(2).在NotificationManager.java中找到了我們的呼叫方法notify。 對應如下：
抓取到關鍵點：enqueueNotificationWithTag。它位於類NotificationManagerService.java中，具體位置如下：public void notify(int id, Notification notification) 107 { 108 notify(null, id, notification); 109 } 110 111 /** 112 * Post a notification to be shown in the status bar. If a notification with 113 * the same tag and id has already been posted by your application and has not yet been 114 * canceled, it will be replaced by the updated information. 115 * 116 * @param tag A string identifier for this notification. May be {@code null}. 117 * @param id An identifier for this notification. The pair (tag, id) must be unique 118 * within your application. 119 * @param notification A {@link Notification} object describing what to 120 * show the user. Must not be null. 121 */ 122 public void notify(String tag, int id, Notification notification) 123 { 124 int[] idOut = new int[1]; 125 INotificationManager service = getService(); 126 String pkg = mContext.getPackageName(); 127 if (notification.sound != null) { 128 notification.sound = notification.sound.getCanonicalUri(); 129 } 130 if (localLOGV) Log.v(TAG, pkg + ": notify(" + id + ", " + notification + ")"); 131 try { 132 service.enqueueNotificationWithTag(pkg, tag, id, notification, idOut, 133 UserHandle.myUserId()); 134 if (id != idOut[0]) { 135 Log.w(TAG, "notify: id corrupted: sent " + id + ", got back " + idOut[0]); 136 } 137 } catch (RemoteException e) { 138 } 139 }
frameworks/base/services/java/com/android/server/NotificationManagerService.java
(3).NotificationManagerService
進入類NotificationManagerService.java，找到我們在NotificationManager.java中呼叫的方法：enqueueNotificationWithTag，如下：
public void enqueueNotificationWithTag(String pkg, String tag, int id, Notification notification,
956 int[] idOut, int userId)
957 {
958 enqueueNotificationInternal(pkg, Binder.getCallingUid(), Binder.getCallingPid(),
959 tag, id, notification, idOut, userId);
960 }
961
962 private final static int clamp(int x, int low, int high) {
963 return (x < low) ? low : ((x > high) ? high : x);
964 }
965
966 // Not exposed via Binder; for system use only (otherwise malicious apps could spoof the
967 // uid/pid of another application)
968 public void enqueueNotificationInternal(String pkg, int callingUid, int callingPid,
969 String tag, int id, Notification notification, int[] idOut, int userId)
970 {
971 if (DBG) {
972 Slog.v(TAG, "enqueueNotificationInternal: pkg=" + pkg + " id=" + id + " notification=" + notification);
973 }
974 checkCallerIsSystemOrSameApp(pkg);
975 final boolean isSystemNotification = ("android".equals(pkg));
976
977 userId = ActivityManager.handleIncomingUser(callingPid,
978 callingUid, userId, true, false, "enqueueNotification", pkg);
979 UserHandle user = new UserHandle(userId);
980
981 // Limit the number of notifications that any given package except the android
982 // package can enqueue. Prevents DOS attacks and deals with leaks.
983 if (!isSystemNotification) {1321 if ((notification.flags & Notification.FLAG_SHOW_LIGHTS) != 0
1322 && canInterrupt) {
1323 mLights.add(r);
1324 updateLightsLocked();
1325 } else {
1326 if (old != null
1327 && ((old.notification.flags & Notification.FLAG_SHOW_LIGHTS) != 0)) {
1328 updateLightsLocked();
1329 }
1330 } private LightsService.Light mNotificationLight;
1602 if (mNotificationPulseEnabled) {
1603 // pulse repeatedly
1604 ///M: log lights information
1605 Log.d(TAG, "notification setFlashing ledOnMS = "+ledOnMS + " ledOffMS = "+ ledOffMS);
1606 mNotificationLight.setFlashing(ledARGB, LightsService.LIGHT_FLASH_TIMED,
1607 ledOnMS, ledOffMS);
1608 ///M:
1609 } else {
1610 // pulse only once
1611 mNotificationLight.pulse(ledARGB, ledOnMS);
1612 }(4).LightsService
LightsService的位置如下：
frameworks/base/services/java/com/android/server/LightsService.java
在LightsService中，通過方法：setFlashing 呼叫：setLightLocked，最終到達了JNI的setLight_native；
116 private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode) {
117 if (color != mColor || mode != mMode || onMS != mOnMS || offMS != mOffMS) {
118 if (DEBUG) Slog.v(TAG, "setLight #" + mId + ": color=#"
119 + Integer.toHexString(color));
120 mColor = color;
121 mMode = mode;
122 mOnMS = onMS;
123 mOffMS = offMS;
124 setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);
125 }
126 } 通過方法setLight_native，進入到了JNI層中，位置如下：
frameworks/base/services/jni/com_android_server_LightsService.cpp
在方法：setLight_native中，一樣的進行了相關的判斷、接受上層賦值.之後根據引數，呼叫了對應的set_light:
127 ALOGD("setLight_native: light=%d, colorARGB=0x%x, flashMode=%d, onMS=%d, offMS=%d, brightnessMode=%d",
128 light, colorARGB, flashMode, onMS, offMS, brightnessMode);
129
130#if defined(MTK_AAL_SUPPORT)
131 if (light == LIGHT_INDEX_BACKLIGHT) {
132 if (AALClient::getInstance().setBacklightColor(colorARGB & 0x00ffffff) == 0)
133 return;
134 ALOGW("Fail to set backlight from AAL service");
135 }
136#endif
137
138 devices->lights[light]->set_light(devices->lights[light], &state);3.HAL
呼吸燈的HAL層對應位置如下：
mediatek/hardware/liblights/lights.c
我們在NotificationManager下來的set_light對應為：
open_lights下的：
584 }
585 else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) {
586 set_light = set_light_notifications;
587 }set_light_notifications ----> handle_speaker_battery_locked ----> set_speaker_light_locked
在函式set_speaker_light_locked中，最後判斷我們要控制的led是red，green還是blue，從我的範例上看，我傳入的led引數為0xffff0000，對應為red。於是，進入如下的 red：
465 if (red) {
466 blink_green(0, 0, 0);
467 blink_blue(0, 0, 0);
468 blink_red(red, onMS, offMS);
469 }
470 else if (green) {
471 blink_red(0, 0, 0);
472 blink_blue(0, 0, 0);
473 blink_green(green, onMS, offMS);
474 }
475 else if (blue) {
476 blink_red(0, 0, 0);
477 blink_green(0, 0, 0);
478 blink_blue(blue, onMS, offMS);
479 }
480 else {
481 blink_red(0, 0, 0);
482 blink_green(0, 0, 0);
483 blink_blue(0, 0, 0);
484 }上層傳下來的的level值為0，則直接關閉RED_LED_FILE（char const*const RED_LED_FILE = "/sys/class/leds/red/brightness"）
248 if (nowStatus == 0) {
249 write_int(RED_LED_FILE, 0);
250 }251 else if (nowStatus == 1) {
252// write_int(RED_LED_FILE, level); // default full brightness
253 write_str(RED_TRIGGER_FILE, "timer");
254 while (((access(RED_DELAY_OFF_FILE, F_OK) == -1) || (access(RED_DELAY_OFF_FILE, R_OK|W_OK) == -1)) && i<10) {
255 ALOGD("RED_DELAY_OFF_FILE doesn't exist or cannot write!!\n");
256 led_wait_delay(5);//sleep 5ms for wait kernel LED class create led delay_off/delay_on node of fs
257 i++;
258 }
259 write_int(RED_DELAY_OFF_FILE, offMS);
260 write_int(RED_DELAY_ON_FILE, onMS);
261 }262 else {
263 write_str(RED_TRIGGER_FILE, "none");
264 write_int(RED_LED_FILE, 255); // default full brightness
265 } 到處Andoid上層的呼吸燈基本上就這個。
在HAL中最後，點亮，關閉和閃爍呼吸燈，點亮和關閉呼吸燈都是直接操作裝置介面： RED_LED_FILE = "/sys/class/leds/red/brightness";
閃爍則相對複雜一些，接下來驅動部分就以閃爍為為範例進行講解。