BroadcastReceiver-监听电量并将其显示在屏幕上

上个博客我展示了如何监听电量变化，但是那个过于简陋，没有将电量显示到屏幕上的功能。

这个功能看起来似乎当然没什么用，但是却是之后学习的基础。

package com.example.broadcastapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private TextView mBatteryLevelText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //
        initView();
        registerBatteryReceiver();

    }

    private void initView() {
        mBatteryLevelText = (TextView) this.findViewById(R.id.battery_level);
    }

    private void registerBatteryReceiver() {
        //2.收听电量变化
        IntentFilter intentFilter = new IntentFilter();
        //3.设置频道
        intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
        //4.
        BatteryLevelReceiver batteryLevelReceiver = new BatteryLevelReceiver();
        //5.注册广播
        this.registerReceiver(batteryLevelReceiver,intentFilter);
    }

    //1.首先创建一个广播接收者，继承自 BroadcastReceiver
    private class BatteryLevelReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            Log.d(TAG,"收到了电量变化的广播 action is =="+ action);
            if (mBatteryLevelText != null) {
                mBatteryLevelText.setText("当前电量："+intent.getIntExtra(BatteryManager.EXTRA_LEVEL,0));
            }
        }

    }
}