Andy Dennis

《第一行代码》第六章 Broadcast

由于主要在acitivity_main.xml和MainActivity.kt, 这里一般只展示这两个
然后其他资源请自行到第一行代码——Android(第3版)图灵社区下载

6.2 接受系统广播

6.2.1动态注册监听时间变化

这个程序主要是MainActivity.kt文件起作用

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast

class MainActivity : AppCompatActivity() {

    lateinit var  timeChangeReceiver: TimeChangeReceiver
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val intentFilter = IntentFilter()
        //接受时间变化的广播
        intentFilter.addAction("android.intent.action.TIME_TICK")
        timeChangeReceiver = TimeChangeReceiver()
        registerReceiver(timeChangeReceiver, intentFilter)
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(timeChangeReceiver)
    }

    inner class TimeChangeReceiver : BroadcastReceiver() {

        override fun onReceive(context: Context?, intent: Intent?) {
            Toast.makeText(context, "Time has change", Toast.LENGTH_SHORT).show()
        }
    }
}

6.2.2 静态注册实现开机启动

新建BootCompleteReceiver.kt

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.widget.Toast

class BootCompleteReceiver: BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        Toast.makeText(context, "Boot Complete", Toast.LENGTH_SHORT).show()
    }
}

然后要去AndroidManifest.xml配置一下


<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.broadcasttest">

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

    <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/AppTheme"
        tools:ignore="GoogleAppIndexingWarning">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            intent-filter>
        activity>

        <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            intent-filter>
        receiver>


    application>
manifest>

6.3 发送自定义广播

6.3.1 发送标准广播

新建MyBroadcastReceiver.kt

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.widget.Toast

class MyBroadcastReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context?, text: Intent?) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show()
    }
}

AndroidManifest.xml


<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.broadcasttest">

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

    <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/AppTheme"
        tools:ignore="GoogleAppIndexingWarning">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            intent-filter>
        activity>

        <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            intent-filter>
        receiver>

        <receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            tools:ignore="ExportedReceiver">
            <intent-filter android:priority="100">
                <action android:name="com.example.broadcasttest.MY_BROADCAST"/>
            intent-filter>
        receiver>

    application>
manifest>

activity_main.xml


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send Broadcast"
        tools:ignore="HardcodedText" />

LinearLayout>

mainActivity.kt

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        button.setOnClickListener{
            val intent = Intent("com.example.broadcasttest.MY_BROADCAST")
            intent.setPackage(packageName)
            sendBroadcast(intent)
        }
    }
}

6.3.2 发送有序广播

新建AnotherBroadcastReceiver.kt

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.widget.Toast

class AnotherBroadcastReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        Toast.makeText(context, "received in AnotherBroadcastReceiver", Toast.LENGTH_SHORT).show()
    }

}

在AnroidManifest.xml中添加
AndroidManifest.xml


<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.broadcasttest">

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

    <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/AppTheme"
        tools:ignore="GoogleAppIndexingWarning">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            intent-filter>
        activity>

        <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            intent-filter>
        receiver>

        <receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            tools:ignore="ExportedReceiver">
            <intent-filter android:priority="100">
                <action android:name="com.example.broadcasttest.MY_BROADCAST"/>
            intent-filter>
        receiver>

        <receiver
            android:name=".AnotherBroadcastReceiver"
            android:enabled="true"
            android:exported="true"
            tools:ignore="ExportedReceiver">
            <intent-filter>
                <action android:name="com.example.broadcasttest.MY_BROADCAST" />
            intent-filter>
        receiver>
    application>
manifest>

MainActivity.kt

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        button.setOnClickListener{
            val intent = Intent("com.example.broadcasttest.MY_BROADCAST")
            intent.setPackage(packageName)
            sendOrderedBroadcast(intent, null) //区别的一句
        }
    }
}

我们再来好事一点。
设置一下MyBroadcastReceiver的优先数
其实之前的也已经写了

修改一下MyBroadcastReceiver.kt的代码如下:

package com.example.broadcasttest

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.widget.Toast

class MyBroadcastReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context?, text: Intent?) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show()
        //添加下面这一句
        abortBroadcast()
    }
}

运行发现只有MyBroadcastReceiver能接受到广播并提示了。

6.4实现强制下线功能

（这个练习7.3.3还会增加记住用户名和密码的功能）

点击ok后退出到登录界面

新建ActivityCollector.kt

package com.example.broadcasttest

import android.app.Activity

object ActivityCollector {

    private val activities = ArrayList<Activity>()
    fun addActivity(activity: Activity) {
        activities.add(activity)
    }

    fun removeActivity(activity: Activity) {
        activities.remove(activity)
    }

    fun finishAll(){
        for (activity in activities){
            if (!activity.isFinishing){
                activity.finish()
            }
        }
     activities.clear()
    }
}

新建BaseActivity.kt

package com.example.broadcasttest


import android.app.AlertDialog
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity

open class BaseActivity : AppCompatActivity() {

    lateinit var receiver: ForceOfflineReceiver

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        ActivityCollector.addActivity(this)
    }

    override fun onResume() {
        super.onResume()
        val intentFilter = IntentFilter()
        intentFilter.addAction("com.example.broadcastbestpractice.FORCE_OFFLINE")
        receiver = ForceOfflineReceiver()
        registerReceiver(receiver, intentFilter)
    }

    override fun onPause() {
        super.onPause()
        unregisterReceiver(receiver)
    }

    override fun onDestroy() {
        super.onDestroy()
        ActivityCollector.removeActivity(this)
    }

    inner class ForceOfflineReceiver : BroadcastReceiver() {

        override fun onReceive(context: Context, intent: Intent) {
            AlertDialog.Builder(context).apply {
                setTitle("Warning")
                setMessage("You are forced to be offline. Please try to login again.")
                setCancelable(false)
                setPositiveButton("OK") { _, _ ->
                    ActivityCollector.finishAll() // 销毁所有Activity
                    val i = Intent(context, LoginActivity::class.java)
                    context.startActivity(i) // 重新启动LoginActivity
                }
                show()
            }
        }
    }
}

新建activity_login.xml


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="60dp">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Account:" />

        <EditText
            android:id="@+id/accountEdit"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical" />
    LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="60dp">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Password:"
            tools:ignore="HardcodedText" />

        <EditText
            android:id="@+id/passwordEdit"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"
            android:inputType="textPassword" />
    LinearLayout>

    <Button
        android:id="@+id/login"
        android:layout_width="200dp"
        android:layout_height="60dp"
        android:layout_gravity="center_horizontal"
        android:text="Login"
        tools:ignore="HardcodedText" />

LinearLayout>

新建LoginActivity.kt

package com.example.broadcasttest

import android.content.Intent
import android.os.Bundle
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_login.*


class LoginActivity : BaseActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        login.setOnClickListener {
            val account = accountEdit.text.toString()
            val password = passwordEdit.text.toString()
            //用户名是admin，密码是123456
            if (account == "admin" && password == "123456"){
                val intent = Intent(this, MainActivity::class.java)
                startActivity(intent)
                finish()
            } else {
                Toast.makeText(this, "account or password is invalid", Toast.LENGTH_SHORT).show()
            }
        }

    }
}