10-Android 广播接收器 BroadcastReceiver

01-使用 BroadcastReceiver:

activity_main.xml:

<?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:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnSendMsg"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="发送消息" />

</LinearLayout>

MainActivity.java:

package com.example.learnbroadcastreceiver;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

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

        //1.2=================================================
        findViewById(R.id.btnSendMsg).setOnClickListener(this);
        //====================================================
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btnSendMsg:

                //1.4=================================================

                Intent i = new Intent(this,MyReceiver.class);
                i.putExtra("data","jiekexueyuan");
                sendBroadcast(i);
                //====================================================




                //1.3===================================================
//                sendBroadcast(new Intent(this,MyReceiver.class));
        }       //======================================================
    }
}

MyService.java:

package com.example.learnbroadcastreceiver;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class MyReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        //1.1======================================
        System.out.println("接收到了消息,消息的内容是：" + intent.getStringExtra("data"));
        //=========================================
    }
}

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02-动态注册和注销 BroadcastReceiver: