安卓电量优化2

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电量优化

提问：拍照和图片处理他们可以放在链接充电线后再处理？
答案：图片处理。
像这些不需要及时地和用户交互的操作可以放到后面处理。
比如：360手机助手，当充上电的时候，才会自动清理手机垃圾，自动备份上传图片、联系人等到云端。

通过监控电量状态来进行电量管理。
我们可以通过下面的代码来获取手机的当前充电状态：
// It is very easy to subscribe to changes to the battery state, but you can get the current
// state by simply passing null in as your receiver. Nifty, isn’t that?
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = this.registerReceiver(null, filter);
int chargePlug = batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
boolean acCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_AC);
if (acCharge) {
Log.v(LOG_TAG,“The phone is charging!”);
}

在上面的例子演示了如何立即获取到手机的充电状态，得到充电状态信息之后，我们可以有针对性的对部分代码做优化。比如我们可以判断只有当前手机为AC充电状态时 才去执行一些非常耗电的操作。
/**

• This method checks for power by comparing the current battery state against all possible

• plugged in states. In this case, a device may be considered plugged in either by USB, AC, or

• wireless charge. (Wireless charge was introduced in API Level 17.)
  */
  private boolean checkForPower() {
  // It is very easy to subscribe to changes to the battery state, but you can get the current
  // state by simply passing null in as your receiver. Nifty, isn’t that?
  IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
  Intent batteryStatus = this.registerReceiver(null, filter);

  // There are currently three ways a device can be plugged in. We should check them all.
  int chargePlug = batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
  boolean usbCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_USB);
  boolean acCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_AC);
  boolean wirelessCharge = false;
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
  wirelessCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_WIRELESS);
  }
  return (usbCharge || acCharge || wirelessCharge);
  }

练习：Modify WaitForPowerActivity
提示用户插入手机充电，

经过优化之后，如果呈现下面的图示，说明电量消耗的性能是良好的：

另外WiFi连接下，网络传输的电量消耗要比移动网络少很多，应该尽量减少移动网络下的数据传输，多在WiFi环境下传输数据。

那么如何才能够把任务缓存起来，做到批量化执行呢？下面就轮到Job Scheduler出场了。

使用Job Scheduler，应用需要做的事情就是判断哪些任务是不紧急的，可以交给Job Scheduler来处理，Job Scheduler集中处理收到的任务，选择合适的时间，合适的网络，再一起进行执行。