擷取Android裝置電池電量狀態

Android開發人員可以利用BroadcastReceiver機制，擷取電池電量變化的ACTION_BATTERY_CHANGED intent，進而擷取當前android裝置的電池狀態。
具體操作步驟：
1. 建立一個監聽ACTION_BATTERY_CHANGED事件的intentFilter。
2. 建立一個BroadcastReceiver對象，該對象可以接收broadcast intent。
3. 註冊BroadcastReceiver對象來監聽ACTION_BATTERY_CHANGED事件。
4. 在BroadcastReceiver對象中，重寫onReceive方法，在onReceive方法的傳入參數intent裡擷取需要的電池狀態資訊。

5. 在生命週期結束時，取消step4中的註冊。

package com.chen.battery;import android.os.BatteryManager;import android.os.Bundle;import android.app.Activity;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.view.Menu;import android.view.TextureView;import android.widget.TextView;public class MainActivity extends Activity {@Overrideprotected void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();}private TextView batterLevel;private BroadcastReceiver batteryLevelRcvr;private IntentFilter batteryLevelFilter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);batterLevel = (TextView)findViewById(R.id.batteryLevel);monitorBatteryState();}private void monitorBatteryState(){batteryLevelRcvr = new BroadcastReceiver(){@Overridepublic void onReceive(Context context, Intent intent) {// TODO Auto-generated method stubStringBuilder sb = new StringBuilder();int rawlevel = intent.getIntExtra("level", -1);int scale = intent.getIntExtra("scale", -1);int status = intent.getIntExtra("status", -1);int health = intent.getIntExtra("health", -1);int level = -1;if(rawlevel >= 0 && scale > 0){level = (rawlevel*100)/scale;}sb.append("電池狀態: ");sb.append(level + "%  ");switch (status) {case BatteryManager.BATTERY_STATUS_UNKNOWN:sb.append("[沒有安裝電池]");break;case BatteryManager.BATTERY_STATUS_CHARGING:sb.append("[正在充電]");break;default:if(level <= 10)sb.append("[電量過低，請充電]");else if (level <= 100) {sb.append("[未串連充電器]");}break;}sb.append(' ');batterLevel.setText(sb.toString());}};batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);registerReceiver(batteryLevelRcvr, batteryLevelFilter);}}