本文主要是介绍ADROID 2.1 架构解析 5 电池，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
5 电池
电池涉及的功能有：BatteryStatus、BatteryHealth、BatteryPresent、BatteryLevel、PlugType、BatteryVoltage、BatteryTemperature、BatteryTechnology等，它是种从下而上的表现方式，即底层电池变化后通过uevent事件向上传递电池的当前状态。
5.1 硬件调用
文件：frameworks/base/services/jni/com_android_server_BatteryService.cpp
#define POWER_SUPPLY_PATH "/sys/class/power_supply"
int register_android_server_BatteryService(JNIEnv* env)
{
...
DIR* dir = opendir(POWER_SUPPLY_PATH);
if (dir == NULL) {
LOGE("Could not open %s/n", POWER_SUPPLY_PATH);
return -1;
}
while ((entry = readdir(dir))) {
const char* name = entry->d_name;
// ignore "." and ".."
if (name[0] == '.' && (name[1] == 0 || (name[1] == '.' && name[2] == 0))) {
continue;
}
char buf[20];
// Look for "type" file in each subdirectory
snprintf(path, sizeof(path), "%s/%s/type", POWER_SUPPLY_PATH, name);
int length = readFromFile(path, buf, sizeof(buf));
if (length > 0) {
if (buf[length - 1] == '/n')
buf[length - 1] = 0;
if (strcmp(buf, "Mains") == 0) {
snprintf(path, sizeof(path), "%s/%s/online", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.acOnlinePath = strdup(path);
}
else if (strcmp(buf, "USB") == 0) {
snprintf(path, sizeof(path), "%s/%s/online", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.usbOnlinePath = strdup(path);
}
else if (strcmp(buf, "Battery") == 0) {
snprintf(path, sizeof(path), "%s/%s/status", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryStatusPath = strdup(path);
snprintf(path, sizeof(path), "%s/%s/health", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryHealthPath = strdup(path);
snprintf(path, sizeof(path), "%s/%s/present", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryPresentPath = strdup(path);
snprintf(path, sizeof(path), "%s/%s/capacity", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryCapacityPath = strdup(path);
snprintf(path, sizeof(path), "%s/%s/voltage_now", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0) {
gPaths.batteryVoltagePath = strdup(path);
// voltage_now is in microvolts, not millivolts
gVoltageDivisor = 1000;
} else {
snprintf(path, sizeof(path), "%s/%s/batt_vol", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryVoltagePath = strdup(path);
}
snprintf(path, sizeof(path), "%s/%s/temp", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0) {
gPaths.batteryTemperaturePath = strdup(path);
} else {
snprintf(path, sizeof(path), "%s/%s/batt_temp", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryTemperaturePath = strdup(path);
}
snprintf(path, sizeof(path), "%s/%s/technology", POWER_SUPPLY_PATH, name);
if (access(path, R_OK) == 0)
gPaths.batteryTechnologyPath = strdup(path);
}
}
}
closedir(dir);
扫描/sys/class/power_supply目录下的文件夹，根据其type文件里的字符串来判断是哪一种类型：Mains、USB还是Battery，然后不同的参数对应着不同的文件
jclass clazz = env->FindClass("com/android/server/BatteryService");
if (clazz == NULL) {
LOGE("Can't find com/android/server/BatteryService");
return -1;
}
gFieldIds.mAcOnline = env->GetFieldID(clazz, "mAcOnline", "Z");
gFieldIds.mUsbOnline = env->GetFieldID(clazz, "mUsbOnline", "Z");
gFieldIds.mBatteryStatus = env->GetFieldID(clazz, "mBatteryStatus", "I");
gFieldIds.mBatteryHealth = env->GetFieldID(clazz, "mBatteryHealth", "I");
gFieldIds.mBatteryPresent = env->GetFieldID(clazz, "mBatteryPresent", "Z");
gFieldIds.mBatteryLevel = env->GetFieldID(clazz, "mBatteryLevel", "I");
gFieldIds.mBatteryTechnology = env->GetFieldID(clazz, "mBatteryTechnology", "Ljava/lang/String;");
gFieldIds.mBatteryVoltage = env->GetFieldID(clazz, "mBatteryVoltage", "I");
gFieldIds.mBatteryTemperature = env->GetFieldID(clazz, "mBatteryTemperature", "I");
接口说明：
env->FindClass("com/android/server/BatteryService"); 获取指定文件的类。
env->GetFieldID(clazz, "mAcOnline", "Z"); 获取指定类的mAcOnline变量值。
以上代码的功能是：将frameworks/base/services/java/com/android/server/BatteryService.java里的各变量值存到全局变量里。
clazz = env->FindClass("android/os/BatteryManager");
if (clazz == NULL) {
LOGE("Can't find android/os/BatteryManager");
return -1;
}
gConstants.statusUnknown = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_STATUS_UNKNOWN", "I"));
gConstants.statusCharging = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_STATUS_CHARGING", "I"));
gConstants.statusDischarging = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_STATUS_DISCHARGING", "I"));
gConstants.statusNotCharging = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_STATUS_NOT_CHARGING", "I"));
gConstants.statusFull = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_STATUS_FULL", "I"));
gConstants.healthUnknown = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_UNKNOWN", "I"));
gConstants.healthGood = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_GOOD", "I"));
gConstants.healthOverheat = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_OVERHEAT", "I"));
gConstants.healthDead = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_DEAD", "I"));
gConstants.healthOverVoltage = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_OVER_VOLTAGE", "I"));
gConstants.healthUnspecifiedFailure = env->GetStaticIntField(clazz,
env->GetStaticFieldID(clazz, "BATTERY_HEALTH_UNSPECIFIED_FAILURE", "I"));
以上代码的功能是：将frameworks/base/core/java/android/os/BatteryManager.java里类的变量值存到全局变量里。
...
}
static void setBooleanField(JNIEnv* env, jobject obj, const char* path, jfieldID fieldID)
{
const int SIZE = 16;
char buf[SIZE];
jboolean value = false;
if (readFromFile(path, buf, SIZE) > 0) {
if (buf[0] == '1') {
value = true;
}
}
env->SetBooleanField(obj, fieldID, value);
}
static void setIntField(JNIEnv* env, jobject obj, const char* path, jfieldID fieldID)
{
const int SIZE = 128;
char buf[SIZE];
jint value = 0;
if (readFromFile(path, buf, SIZE) > 0) {
value = atoi(buf);
}
env->SetIntField(obj, fieldID, value);
}
static void setVoltageField(JNIEnv* env, jobject obj, const char* path, jfieldID fieldID)
{
const int SIZE = 128;
char buf[SIZE];
jint value = 0;
if (readFromFile(path, buf, SIZE) > 0) {
value = atoi(buf);
value /= gVoltageDivisor;
}
env->SetIntField(obj, fieldID, value);
}
static void android_server_BatteryService_update(JNIEnv* env, jobject obj)
{
setBooleanField(env, obj, gPaths.acOnlinePath, gFieldIds.mAcOnline);
setBooleanField(env, obj, gPaths.usbOnlinePath, gFieldIds.mUsbOnline);
setBooleanField(env, obj, gPaths.batteryPresentPath, gFieldIds.mBatteryPresent);
setIntField(env, obj, gPaths.batteryCapacityPath, gFieldIds.mBatteryLevel);
setVoltageField(env, obj, gPaths.batteryVoltagePath, gFieldIds.mBatteryVoltage);
setIntField(env, obj, gPaths.batteryTemperaturePath, gFieldIds.mBatteryTemperature);
const int SIZE = 128;
char buf[SIZE];
if (readFromFile(gPaths.batteryStatusPath, buf, SIZE) > 0)
env->SetIntField(obj, gFieldIds.mBatteryStatus, getBatteryStatus(buf));
else
env->SetIntField(obj, gFieldIds.mBatteryStatus,
gConstants.statusUnknown);
if (readFromFile(gPaths.batteryHealthPath, buf, SIZE) > 0)
env->SetIntField(obj, gFieldIds.mBatteryHealth, getBatteryHealth(buf));
if (readFromFile(gPaths.batteryTechnologyPath, buf, SIZE) > 0)
env->SetObjectField(obj, gFieldIds.mBatteryTechnology, env->NewStringUTF(buf));
}
static JNINativeMethod sMethods[] = {
/* name, signature, funcPtr */
{"native_update", "()V", (void*)android_server_BatteryService_update},
};
接口说明：
env->SetIntField(obj, fieldID, value); 将指定类的变量以整型付值。
env->SetBooleanField(obj, fieldID, value); 将指定类的变量以布尔付值。
以上代码的功能是：
将全局变量的值付给frameworks/base/core/java/android/os/BatteryManager.java里类的变量；并且将ative_update与android_server_BatteryService_update绑定。
5.2 电池服务
文件：frameworks/base/services/java/com/android/server/BatteryService.java
mUEventObserver.startObserving("SUBSYSTEM=power_supply");
private UEventObserver mUEventObserver = new UEventObserver() {
@Override
public void onUEvent(UEventObserver.UEvent event) {
update();
}
};
监控uevent事件，响应SUBSYSTEM=power_supply的事件。
private synchronized final void update() {
native_update();
...
if (mAcOnline) {
mPlugType = BatteryManager.BATTERY_PLUGGED_AC;
} else if (mUsbOnline) {
mPlugType = BatteryManager.BATTERY_PLUGGED_USB;
} else {
mPlugType = BATTERY_PLUGGED_NONE;
}
...
sendIntent();
...
}
private final void sendIntent() {
// Pack up the values and broadcast them to everyone
Intent intent = new Intent(Intent.ACTION_BATTERY_CHANGED);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
try {
mBatteryStats.setOnBattery(mPlugType == BATTERY_PLUGGED_NONE, mBatteryLevel);
} catch (RemoteException e) {
// Should never happen.
}
int icon = getIcon(mBatteryLevel);
intent.putExtra(BatteryManager.EXTRA_STATUS, mBatteryStatus);
intent.putExtra(BatteryManager.EXTRA_HEALTH, mBatteryHealth);
intent.putExtra(BatteryManager.EXTRA_PRESENT, mBatteryPresent);
intent.putExtra(BatteryManager.EXTRA_LEVEL, mBatteryLevel);
intent.putExtra(BatteryManager.EXTRA_SCALE, BATTERY_SCALE);
intent.putExtra(BatteryManager.EXTRA_ICON_SMALL, icon);
intent.putExtra(BatteryManager.EXTRA_PLUGGED, mPlugType);
intent.putExtra(BatteryManager.EXTRA_VOLTAGE, mBatteryVoltage);
intent.putExtra(BatteryManager.EXTRA_TEMPERATURE, mBatteryTemperature);
intent.putExtra(BatteryManager.EXTRA_TECHNOLOGY, mBatteryTechnology);
if (false) {
Log.d(TAG, "updateBattery level:" + mBatteryLevel +
" scale:" + BATTERY_SCALE + " status:" + mBatteryStatus +
" health:" + mBatteryHealth + " present:" + mBatteryPresent +
" voltage: " + mBatteryVoltage +
" temperature: " + mBatteryTemperature +
" technology: " + mBatteryTechnology +
" AC powered:" + mAcOnline + " USB powered:" + mUsbOnline +
" icon:" + icon );
}
ActivityManagerNative.broadcastStickyIntent(intent, null);
}
以上代码的功能是：
通过native_update();更新各状态变量的值，如：
private boolean mAcOnline;
private boolean mUsbOnline;
private int mBatteryStatus;
private int mBatteryHealth;
private boolean mBatteryPresent;
private int mBatteryLevel;
private int mBatteryVoltage;
private int mBatteryTemperature;
private String mBatteryTechnology;
private boolean mBatteryLevelCritical;
然后通过：
intent.putExtra(BatteryManager.EXTRA_STATUS, mBatteryStatus);
intent.putExtra(BatteryManager.EXTRA_HEALTH, mBatteryHealth);
intent.putExtra(BatteryManager.EXTRA_PRESENT, mBatteryPresent);
intent.putExtra(BatteryManager.EXTRA_LEVEL, mBatteryLevel);
intent.putExtra(BatteryManager.EXTRA_SCALE, BATTERY_SCALE);
intent.putExtra(BatteryManager.EXTRA_ICON_SMALL, icon);
intent.putExtra(BatteryManager.EXTRA_PLUGGED, mPlugType);
intent.putExtra(BatteryManager.EXTRA_VOLTAGE, mBatteryVoltage);
intent.putExtra(BatteryManager.EXTRA_TEMPERATURE, mBatteryTemperature);
intent.putExtra(BatteryManager.EXTRA_TECHNOLOGY, mBatteryTechnology);
ActivityManagerNative.broadcastStickyIntent(intent, null);
发布给各实体窗口取用，EXTRA_STATUS等对应的字符是：
文件：frameworks/base/core/java/android/os/BatteryManager.java
public static final String EXTRA_STATUS = "status";
public static final String EXTRA_HEALTH = "health";
public static final String EXTRA_PRESENT = "present";
public static final String EXTRA_LEVEL = "level";
public static final String EXTRA_SCALE = "scale";
public static final String EXTRA_ICON_SMALL = "icon-small";
public static final String EXTRA_PLUGGED = "plugged";
public static final String EXTRA_VOLTAGE = "voltage";
public static final String EXTRA_TEMPERATURE = "temperature";
public static final String EXTRA_TECHNOLOGY = "technology";
5.3 显示电池状态
文件：packages/apps/DeskClock/src/com/android/deskclock/DeskClock.java
private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (Intent.ACTION_DATE_CHANGED.equals(action)) {
refreshDate();
} else if (Intent.ACTION_BATTERY_CHANGED.equals(action)) {
handleBatteryUpdate(
intent.getIntExtra("status", BATTERY_STATUS_UNKNOWN),
intent.getIntExtra("level", 0));
} else if (Intent.ACTION_DOCK_EVENT.equals(action)) {
int state = intent.getIntExtra(Intent.EXTRA_DOCK_STATE, -1);
if (DEBUG) Log.d(LOG_TAG, "ACTION_DOCK_EVENT, state=" + state);
if (state == Intent.EXTRA_DOCK_STATE_UNDOCKED) {
if (mLaunchedFromDock) {
// moveTaskToBack(false);
finish();
}
mLaunchedFromDock = false;
}
}
}
};
// Adapted from KeyguardUpdateMonitor.java
private void handleBatteryUpdate(int plugStatus, int batteryLevel) {
final boolean pluggedIn = (plugStatus == BATTERY_STATUS_CHARGING || plugStatus == BATTERY_STATUS_FULL);
if (pluggedIn != mPluggedIn) {
setWakeLock(pluggedIn);
if (pluggedIn) {
// policy: update weather info when attaching to power
requestWeatherDataFetch();
}
}
if (pluggedIn != mPluggedIn || batteryLevel != mBatteryLevel) {
mBatteryLevel = batteryLevel;
mPluggedIn = pluggedIn;
refreshBattery();
}
}
private void refreshBattery() {
if (mBatteryDisplay == null) return;
if (mPluggedIn /* || mBatteryLevel < LOW_BATTERY_THRESHOLD */) {
mBatteryDisplay.setCompoundDrawablesWithIntrinsicBounds(
0, 0, android.R.drawable.ic_lock_idle_charging, 0);
mBatteryDisplay.setText(
getString(R.string.battery_charging_level, mBatteryLevel));
mBatteryDisplay.setVisibility(View.VISIBLE);
} else {
mBatteryDisplay.setVisibility(View.INVISIBLE);
}
}
由以上代码可知，程序通过接收广播信息，获取电池的当前节数：intent.getIntExtra("level", 0));，然后再将其显示。
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