本身就是一个广播接收器（BroadcastReceiver），因此我们最初企图直接用这个Widget接受ACTION_BATTERY_CHANGED广播并作出反应，但却发现这个接收器并不会接受电池更新的广播（不论我们在配置文件中配置与否）。所以只能另寻出路，我们想到，可以使用一个单独的为本Widget服务的Service，该Service检测到电池电量更新后就更新桌面的Widget显示。
Broadcast Action: This is a sticky broadcast containing the charging state, level, and other information about the battery. See BatteryManager for documentation on the contents of the Intent.
You can not receive this through components declared in manifests, only by explicitly registering for it with Context.registerReceiver(). See ACTION_BATTERY_LOW, ACTION_BATTERY_OKAY, ACTION_POWER_CONNECTED, and ACTION_POWER_DISCONNECTED for distinct battery-related broadcasts that are sent and can be received through manifest receivers.
This is a protected intent that can only be sent by the system.
package com.billhoo.study;
import android.app.Notification; //通知，即显示在屏幕左上角的小图标
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;
import android.os.IBinder;
public class MonitorService extends Service {
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onStart(Intent intent, int startId) {
// 定义电池电量更新广播的过滤器,只接受带有ACTION_BATTERRY_CHANGED事件的Intent
IntentFilter batteryChangedReceiverFilter = new IntentFilter();
batteryChangedReceiverFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
// 向系统注册batteryChangedReceiver接收器，本接收器的实现见代码字段处
registerReceiver(batteryChangedReceiver, batteryChangedReceiverFilter);
// 实例化Notification通知的管理器，即字段notification manager
notifyManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// 由于初始化本服务时系统可能没有发出ACTION_BATTERY_CHANGED广播，那么刚才注册的那个接收器将不会在本服务启动时被激活，这种情况下就无法显示当前电量，因此在这里添加一个匿名广播接收器。
new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
int level = intent.getIntExtra("level", 0); //电池电量等级
int scale = intent.getIntExtra("scale", 100); //电池满时百分比
int status = intent.getIntExtra("status", 0); //电池状态
// 若正在充电
if (status == BatteryManager.BATTERY_STATUS_CHARGING)
notification = getNotification(getChargingIcon(level * 100 / scale),
"电池监控", System.currentTimeMillis(), "电池电量", "正在充电");
else
notification = getNotification(getStateIcon(level * 100 / scale),
"电池监控", System.currentTimeMillis(), "电池电量", "请及时充电");
//向系统发送此通知，为方便起见，通知ID简单设为0
notifyManager.notify(0, notification);
}
};
}
@Override
public void onDestroy() {
//当本服务终止时，通过通知ID注销左上角的通知
notifyManager.cancel(0);
}
// --------------------------------------私有方法------------------------------
// 获得一个notification
private Notification getNotification(int notificationIcon, String tickerText,
long when, String contentTitle, String contentText) {
// 定义该notification的扩展文本和intent
Notification notification = new Notification(notificationIcon, tickerText,
when);
Context context = getApplicationContext();
Intent notificationIntent = new Intent(context, BatteryInfo.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
notificationIntent, 0);
notification.setLatestEventInfo(context, contentTitle, contentText,
contentIntent);
// 设置本状态出现在“正在进行”而非“通知”栏目，不允许用户清除状态图标
notification.flags |= Notification.FLAG_ONGOING_EVENT;
return notification;
}
// 获得对应的电池状态图标
private int getStateIcon(int batteryHealth) {
if (batteryHealth >= 0 || batteryHealth <= 100)
return batteryStateIcons[batteryHealth]; //这里是为了方便起见而硬编码的资源数组，直接从R.java文件中提取的十六进制资源ID
return R.drawable.stat_sys_battery_unknown;
}
// 获得对应的充电状态图标
private int getChargingIcon(int batteryHealth) {
if (batteryHealth >= 0 && batteryHealth < 5)
return R.drawable.stat_sys_battery_charge_anim0;
if (batteryHealth >= 5 && batteryHealth < 10)
return R.drawable.stat_sys_battery_charge_anim01;
if (batteryHealth >= 10 && batteryHealth < 15)
return R.drawable.stat_sys_battery_charge_anim02;
if (batteryHealth >= 15 && batteryHealth < 20)
return R.drawable.stat_sys_battery_charge_anim03;
if (batteryHealth >= 20 && batteryHealth < 25)
return R.drawable.stat_sys_battery_charge_anim04;
if (batteryHealth >= 25 && batteryHealth < 30)
return R.drawable.stat_sys_battery_charge_anim05;
if (batteryHealth >= 30 && batteryHealth < 35)
return R.drawable.stat_sys_battery_charge_anim06;
if (batteryHealth >= 35 && batteryHealth < 40)
return R.drawable.stat_sys_battery_charge_anim07;
if (batteryHealth >= 40 && batteryHealth < 45)
return R.drawable.stat_sys_battery_charge_anim08;
if (batteryHealth >= 45 && batteryHealth < 50)
return R.drawable.stat_sys_battery_charge_anim09;
if (batteryHealth >= 50 && batteryHealth < 55)
return R.drawable.stat_sys_battery_charge_anim10;
if (batteryHealth >= 55 && batteryHealth < 60)
return R.drawable.stat_sys_battery_charge_anim11;
if (batteryHealth >= 60 && batteryHealth < 65)
return R.drawable.stat_sys_battery_charge_anim12;
if (batteryHealth >= 65 && batteryHealth < 70)
return R.drawable.stat_sys_battery_charge_anim13;
if (batteryHealth >= 70 && batteryHealth < 75)
return R.drawable.stat_sys_battery_charge_anim14;
if (batteryHealth >= 75 && batteryHealth < 80)
return R.drawable.stat_sys_battery_charge_anim15;
if (batteryHealth >= 80 && batteryHealth < 85)
return R.drawable.stat_sys_battery_charge_anim16;
if (batteryHealth >= 85 && batteryHealth < 90)
return R.drawable.stat_sys_battery_charge_anim17;
if (batteryHealth >= 90 && batteryHealth < 95)
return R.drawable.stat_sys_battery_charge_anim18;
if (batteryHealth >= 95 && batteryHealth < 100)
return R.drawable.stat_sys_battery_charge_anim19;
if (batteryHealth == 100)
return R.drawable.stat_sys_battery_charge_animfull;
return R.drawable.stat_sys_battery_unknown;
}
// -------------------------------私有字段--------------------------------------
private NotificationManager notifyManager = null;
private Notification notification = null;
//这里是为了方便起见而硬编码的icon资源数组，直接从R.java文件中提取的十六进制资源ID，本数组的0号元素0x7f020002表示资源stat_sys_battery_0.png（见附件），以后累加。不同配置的ID可能不同，请读者自行修改。
private int batteryStateIcons[] = { 0x7f020002, 0x7f020003, 0x7f020004,
0x7f020005, 0x7f020006, 0x7f020007, 0x7f020008, 0x7f020009, 0x7f02000a,
0x7f02000b, 0x7f02000c, 0x7f02000d, 0x7f02000e, 0x7f02000f, 0x7f020010,
0x7f020011, 0x7f020012, 0x7f020013, 0x7f020014, 0x7f020015, 0x7f020016,
0x7f020017, 0x7f020018, 0x7f020019, 0x7f02001a, 0x7f02001b, 0x7f02001c,
0x7f02001d, 0x7f02001e, 0x7f02001f, 0x7f020020, 0x7f020021, 0x7f020022,
0x7f020023, 0x7f020024, 0x7f020025, 0x7f020026, 0x7f020027, 0x7f020028,
0x7f020029, 0x7f02002a, 0x7f02002b, 0x7f02002c, 0x7f02002d, 0x7f02002e,
0x7f02002f, 0x7f020030, 0x7f020031, 0x7f020032, 0x7f020033, 0x7f020034,
0x7f020035, 0x7f020036, 0x7f020037, 0x7f020038, 0x7f020039, 0x7f02003a,
0x7f02003b, 0x7f02003c, 0x7f02003d, 0x7f02003e, 0x7f02003f, 0x7f020040,
0x7f020041, 0x7f020042, 0x7f020043, 0x7f020044, 0x7f020045, 0x7f020046,
0x7f020047, 0x7f020048, 0x7f020049, 0x7f02004a, 0x7f02004b, 0x7f02004c,
0x7f02004d, 0x7f02004e, 0x7f02004f, 0x7f020050, 0x7f020051, 0x7f020052,
0x7f020053, 0x7f020054, 0x7f020055, 0x7f020056, 0x7f020057, 0x7f020058,
0x7f020059, 0x7f02005a, 0x7f02005b, 0x7f02005c, 0x7f02005d, 0x7f02005e,
0x7f02005f, 0x7f020060, 0x7f020061, 0x7f020062, 0x7f020063, 0x7f020064,
0x7f020065, 0x7f02007b };
// 接受电池信息更新的广播
private BroadcastReceiver batteryChangedReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
int level = intent.getIntExtra("level", 0);
int scale = intent.getIntExtra("scale", 100);
int status = intent.getIntExtra("status", 0);
// 若正在充电
if (status == BatteryManager.BATTERY_STATUS_CHARGING)
notification = getNotification(getChargingIcon(level * 100 / scale),
"Battery Monitor", System.currentTimeMillis(), "电池电量", "正在充电");
else
notification = getNotification(getStateIcon(level * 100 / scale),
"Battery Monitor", System.currentTimeMillis(), "电池电量", "请及时充电");
notifyManager.notify(0, notification);
}
};
}