前言：

不赘述android studio，flutter和安卓环境搭建。不熟悉的自行百度

1.使用android studio创建flutter的plugin

file->new->new flutter project->选择flutter点击next

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之后选择plugin，点create

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2.插件目录

android，example，iOS，lib
首先运行一下exmple，然后使用studio打开exmple中的android项目，在安卓项目的TestPlugin类中加入获取电量的方法

// 获取电量
           "getPlatformBattery" -> {
               context?.let { result.success(getBatteryPercentage(it)) }
           }

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fun getBatteryPercentage(context: Context): Int {
        return if (Build.VERSION.SDK_INT >= 21) {
            val bm = context.getSystemService(BATTERY_SERVICE) as BatteryManager
            bm.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)
        } else {
            val iFilter = IntentFilter(Intent.ACTION_BATTERY_CHANGED)
            val batteryStatus: Intent? = context.registerReceiver(null, iFilter)
            val level =
                batteryStatus?.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) ?: -1
            val scale =
                batteryStatus?.getIntExtra(BatteryManager.EXTRA_SCALE, -1) ?: -1
            val batteryPct = level / scale.toDouble()
            (batteryPct * 100).toInt()
        }
    }

注意：可以看到需要context参数

4.实现ActivityAware接口

class TestFlutterPlugin : FlutterPlugin, MethodCallHandler, ActivityAware{
private var context: Context? = null
 override fun onAttachedToActivity(binding: ActivityPluginBinding) {
        context = binding.activity
    }

    override fun onDetachedFromActivityForConfigChanges() {
        context = null
    }

    override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
        context = binding.activity
    }

    override fun onDetachedFromActivity() {
        context = null
    }
}

5.example中调用

String _platformBattery= 'Unknown';
@override
  void initState() {
    super.initState();
    initPlatformState();
    initBattery();
  }

 Future<void> initBattery() async {
   String platformBattery;
   try {
     platformBattery = await TestFlutterPlugin.platformBattery?? 'Unknown platform version';
   } on Exception {
     platformBattery = 'Failed to get platform version.';
   }
   if (!mounted) return;
   setState(() {
     _platformBattery = platformBattery;
   });
 }

完事，关于上传pub可以百度，私人插件本地引用看example