BatteryService学习摘要

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BatteryService学习摘要

1）JNI(Java Native Interface)

中文为JAVA本地调用。从Java1.1开始，Java Native Interface(JNI)标准成为java平台的一部分，它允许Java代码和其他语言写的代码进行交互。

2）UEventObserver的使用

Android很多事件都是通过uevent跟kernel来异步通信的。其中类UEventObserver是核心。

UEventObserver接收kernel的uevent信息的抽象类。

类UEventObserver提供了三个接口给子类来调用：

(1) onUEvent(UEvent event)
       子类必须重写这个onUEvent来处理uevent。
(2) startObserving(String match)
       启动进程，要提供一个字符串参数。
(3) stopObserving()
       停止进程。

//在BatteryService.java中
mUEventObserver.startObserving("SUBSYSTEM=power_supply");

     private UEventObserver mUEventObserver = new UEventObserver() {
        @Override
        public void onUEvent(UEventObserver.UEvent event) {
            update();
        }
     };
     在UEvent thread中会不停调用 update()方法，来更新电池的信息数据。

3）关机

// shut down gracefully if our battery is critically low and we are not powered.

// wait until the system has booted before attempting to display the shutdown dialog.

if (mBatteryLevel == 0 && !isPowered() && ActivityManagerNative.isSystemReady()) {

Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);

intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);

intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);//if a task is already running for the activity

// you are now starting, then a new activity will not be started; instead,

// the current task will simply be brought to the front of the screen with

// the state it was last in.

//This flag can not be used when the caller is requesting a result from the activity being launched.

mContext.startActivity(intent);

}

4）SystemClock.elapsedRealtime()

Returns milliseconds since boot, including time spent in sleep.

5）EventLog.writeEvent()

EventLog.writeEvent(EventLogTags.BATTERY_LEVEL,mBatteryLevel, mBatteryVoltage, mBatteryTemperature);

6）Intent Flag

intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY //If set, when sending a broadcast only registered receivers will be called -- no BroadcastReceiver components will be launched.

| Intent.FLAG_RECEIVER_REPLACE_PENDING);

ActivityManagerNative.broadcastStickyIntent(intent, null);

7)logBatteryStats()方法

IBinder batteryInfoService = ServiceManager.getService(BATTERY_STATS_SERVICE_NAME);

if (batteryInfoService == null) return;

DropBoxManager db = (DropBoxManager) mContext.getSystemService(Context.DROPBOX_SERVICE);

if (db == null || !db.isTagEnabled("BATTERY_DISCHARGE_INFO")) return;

File dumpFile = null;

FileOutputStream dumpStream = null;

try {

// dump the service to a file

dumpFile = new File(DUMPSYS_DATA_PATH + BATTERY_STATS_SERVICE_NAME + ".dump");

dumpStream = new FileOutputStream(dumpFile);

batteryInfoService.dump(dumpStream.getFD(), DUMPSYS_ARGS);

FileUtils.sync(dumpStream);

// add dump file to drop box

db.addFile("BATTERY_DISCHARGE_INFO", dumpFile, DropBoxManager.IS_TEXT);

} catch (RemoteException e) {

Slog.e(TAG, "failed to dump battery service", e);

} catch (IOException e) {

Slog.e(TAG, "failed to write dumpsys file", e);

} finally {

// make sure we clean up

if (dumpStream != null) {

try {

dumpStream.close();

} catch (IOException e) {

Slog.e(TAG, "failed to close dumpsys output stream");

}

if (dumpFile != null && !dumpFile.delete()) {

Slog.e(TAG, "failed to delete temporary dumpsys file: "

+ dumpFile.getAbsolutePath());

}

8)dump(FileDescriptor fd, PrintWriter pw, String[] args)方法

if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.DUMP)

!= PackageManager.PERMISSION_GRANTED) {

pw.println("Permission Denial: can't dump Battery service from from pid="

+ Binder.getCallingPid()

+ ", uid=" + Binder.getCallingUid());

return;

}

9)接收到 BatteryService 发送出来的电池信息

需要注册一个 Intent 为Intent.ACTION_BATTERY_CHANGED 的 BroadcastReceiver 注册方法如下：

IntentFilter mIntentFilter = new IntentFilter();

mIntentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);

registerReceiver(mIntentReciver,mIntentFilter);

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver(){

@Override

public void onReceive(Context context, Intent intent){

//TODO Auto-generated method stub String action = intent.getAction();

If(action.equals(Intent.ACTION_BATTERY_CHANGED)){

int nVoltaget = intent.getIntExtra(“voltage”,0);

if(nVoltage!=0){ mVoltage.setText(“v:” + nVoltage + “mV-Success…”);}

else{

mVoltage.setText(“V: “+nVoltage+”mV-fall…”);

}

(10) stat_sys_battery_charge.xml

<level-list xmlns:android="http://schemas.android.com/apk/res/android">

<animation-list

xmlns:android="http://schemas.android.com/apk/res/android"

android:oneshot="false">

</animation-list>

</item>

<animation-list

xmlns:android="http://schemas.android.com/apk/res/android"

android:oneshot="false">

</animation-list>

</item>

...

<animation-list

xmlns:android="http://schemas.android.com/apk/res/android"

android:oneshot="false">

</animation-list>

</item>

</level-list>

========================

参考资料

JNI http://baike.baidu.com/view/1272329.html?wtp=tt

Uevent http://www.cnblogs.com/qclzdh/archive/2011/06/13/2080166.html

有关Linux的.a .so 和.o文件 http://apps.hi.baidu.com/share/detail/23484800