[移动开发]android动态注册广播获取电量信息

运行结果如图：

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Step1：xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="当前电池的电量是："
            android:textSize="25dp"/>
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

在MainActivity中通过意图过滤器来注册广播.?IntentFilter?是对意图进行过滤的，就是我想要接收哪些广播,不想接收哪些广播,主要过滤Intent中Action,?Data和Category的字段。intentFilter.addAction(Intent.ACTION_?BATTERY_?_CHANGED);中Intent的参数ACTION_?_BATTERY_?_CHANGED.通过看源码知这是一一个系统级别广播，作用就是获取当明电池的信息;
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Step2：MainActivity

package com.example.broadcastapplication1;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends Activity implements MyReceiver.Mylistener {
    MyReceiver myReceiver;
    private TextView textView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView=(TextView)findViewById(R.id.textView);
        IntentFilter intentFilter=new IntentFilter();
        intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
        myReceiver=new MyReceiver();
        registerReceiver(myReceiver,intentFilter);
        myReceiver.setMylistener(this);
    }

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

    @Override
    public void onlistener(String level) {
        textView.setText("当前电池的电量是："+level+"%");
    }
}

Step3：定义一个MyReceiver继承BroadcastReceiver，重写onReceive()方法，在方法中获取电量的信息。

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package com.example.broadcastapplication1 ;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        int level=intent.getIntExtra("level",0);
        mylistener.onlistener(level+"");
        System.out.println("当前电池的电量是："+level+"%");
        Bundle bundle=intent.getExtras();
        int current=bundle.getInt("level");
        int total=bundle.getInt("scale");
        if (current*1.0/total<0.5){
            Toast.makeText(context,"电池电量不足60%，请充电",Toast.LENGTH_SHORT).show();
        }else {

            Toast.makeText(context,"电池电量大于60%",Toast.LENGTH_SHORT).show();
        }
//        if (level<60){
//            Toast.makeText(context,"电池电量不足60%，请充电！",Toast.LENGTH_LONG).show();
//        }
    }
    public Mylistener mylistener;
    public interface Mylistener{
        public void onlistener(String level);
    }
   public void setMylistener(Mylistener mylistener) {
       this.mylistener = mylistener;
   }
}

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判断电量代码如下：

 System.out.println("当前电池的电量是："+level+"%");
        Bundle bundle=intent.getExtras();
        int current=bundle.getInt("level",0);
        int total=bundle.getInt("scale",0);
        if (current*1.0/total<0.6){
            Toast.makeText(context,"电池电量不足60%，请充电",Toast.LENGTH_SHORT).show();
        }else {

            Toast.makeText(context,"电池电量大于60%",Toast.LENGTH_SHORT).show();
        }
    }