Android四大组件之广播BroadcastReceiver详解

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btnSend"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:insetTop="16dp"
        android:text="发松" />
</LinearLayout>

package com.aaa.btdemo02;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
    //定义对象；村长：一样权威，光辉的存在,拿着大喇叭，讲话;
    Button btnSend;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main); //取值
        btnSend=(Button) findViewById(R.id.btnSend);
        //这对这个按钮做监听事件;发送信息，大喇叭...
        btnSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent=new Intent();
                //设置intent的动作;后面字符串是自定义的
                intent.setAction("android.intent.action.receiverdata");
                intent.putExtra("msg","羊村各位村民开会了");
                MainActivity.this.sendBroadcast(intent);
            }
        });
    }
}

package com.aaa.btdemo02;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.text.TextUtils;
import android.util.Log;
public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        //接受广播
        if(intent==null)return;
        //intent:接受从主端传递过来的数据，action数据；
        String action=intent.getAction();
        //针对上述做判断;第一个判断是否为空也可以写成action.isEmpty
        if(!TextUtils.isEmpty(action)&&"android.intent.action.receiverdata".equals(action)){
            String msg=intent.getStringExtra("msg");//不习惯可以使用Bundle
            Log.i("喜洋洋-->",msg);
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.aaa.btdemo02">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Btdemo02">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <cateGory android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <receiver android:name=".MyReceiver"
            android:exported="true">
            <intent-filter>
                <!-- 自定义的action名 -->
                <action android:name="android.intent.action.receiverdata"/>
            </intent-filter>
        </receiver>
    </application>

</manifest>