[andrid笔记]改进MyBatteryDemo增加电池电压和温度显示

之前的演示程序再有在按钮按下后才去注册广播接收器,才会显示出电池电压,显然这仅仅是为了演示而已,现在我们通过改进我们的演示程序,在程序一启动就能显示出当前的电池电压.

在Activity的onCreate函数中直接注册广播接收器

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    IntentFilter intentFilter=new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
    //注册接收器以获取电量信息
    registerReceiver(broadcastReceiver,intentFilter);
}

在OnCreate函数中注册Receiver后退出Activity时出现Receiver泄露.

06-08 12:54:11.378 11619-11619/com.example.test.testbattery E/ActivityThread: Activity com.example.test.testbattery.MainActivity has leaked IntentReceiver com.example.test.testbattery.MainActivity$1@d8e6cf8 that was originally registered here. Are you missing a call to unregisterReceiver()? android.app.IntentReceiverLeaked: Activity com.example.test.testbattery.MainActivity has leaked IntentReceiver com.example.test.testbattery.MainActivity$1@d8e6cf8 that was originally registered here. Are you missing a call to unregisterReceiver()?
at android.app.LoadedApk$ReceiverDispatcher.(LoadedApk.java:1361)
at android.app.LoadedApk.getReceiverDispatcher(LoadedApk.java:1142)
at android.app.ContextImpl.registerReceiverInternal(ContextImpl.java:1422)
at android.app.ContextImpl.registerReceiver(ContextImpl.java:1395)

Goole的文档说明如果是在onCreate函数中创建了receiver接收器就需要在onDestroy()函数中调用unregisterReceiver方法去取消注册.
修改代码如下:

@Override
protected void onDestroy() {
    unregisterReceiver(broadcastReceiver);
}

重写OnDestory方法出现异常

06-08 12:59:23.083 15774-15774/com.example.test.testbattery E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.test.testbattery, PID: 15774
android.util.SuperNotCalledException: Activity {com.example.test.testbattery/com.example.test.testbattery.MainActivity} did not call through to super.onDestroy()
at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4399)

解决方法：

加上super.onDestroy()代码即可解决问题。修改代码如下:

@Override
protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(broadcastReceiver);
}

至此在执行演示程序也没有再出现执行异常的log了.

增减电池电压和温度的显示

定义控件

<TextView
    android:id="@+id/textViewVoltage"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/textViewLevel"
    android:text="" />
<TextView
    android:id="@+id/textViewTemp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@id/textViewVoltage"
    android:text="" />

android:layout_below这个属性指明了该控件与另外一个控件的相对位置,这里将电压显示控件放在了电量的下方.同样的温度显示控件在电压的下方.

获取控件的id

textViewLevel = (TextView) findViewById(R.id.textViewLevel);
textViewVoltage = (TextView) findViewById(R.id.textViewVoltage);
textViewTemp = (TextView) findViewById(R.id.textViewTemp);

数值显示

public void onReceive(Context context, Intent intent) {
    //获取当前电量，如未获取具体数值，则默认为0
    batteryLevel=intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0);
    //获取最大电量，如未获取到具体数值，则默认为100
    batteryScale=intent.getIntExtra(BatteryManager.EXTRA_SCALE,100);
    //显示电量
    textViewLevel.setText("电量"+(batteryLevel*100/batteryScale)+"%");

    //获取当前的电池电压
    batteryVoltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE,0);
    textViewVoltage.setText("电压"+batteryVoltage);

    //获取当前的电池温度
    batteryTemp = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE,0);
    textViewTemp.setText("温度"+batteryTemp);
}