如何使用Binder类

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aidl

服务端定义接口

1. 定义aidl文件，放在src目录下

2. 实现编译aidl后的内部类stub

Android SDK 工具会基于您的 .aidl 文件，使用 Java 编程语言生成接口。此接口拥有一个名为 Stub 的内部抽象类，用于扩展 Binder 类并实现 AIDL 接口中的方法。您必须扩展 Stub 类并实现这些方法。

3. 向客户端公开接口

实现 Service 并重写 onBind()，从而返回 Stub 类的实现。

客户端使用

1. 使用bindService()

2. 再src目录包含该aidl文件，为客户端提供使用adil权限

注意： 调用是同步的，如果服务耗时需要再子线程调用，需要考虑线程安全

传递类

目前只能传递基本类型数据，传递对象类型需要model类实现Parcelable

调用方始终捕获DeadObjectException异常

DeadObjectException

代码示例

// IRemoteService.aidlpackage com.example.android// Declare any non-default types here with import statements/** Example service interface */internal interface IRemoteService {    /** Request the process ID of this service, to do evil things with it. */    val pid:Int    /** Demonstrates some basic types that you can use as parameters     * and return values in AIDL.     */    fun basicTypes(anInt:Int, aLong:Long, aBoolean:Boolean, aFloat:Float,                 aDouble:Double, aString:String)}编译后生成IRemoteService extends Binder implements IMyService{        class Stub extends android.os.Binder implements IMyService{        // 客户端拿到Binder获得一个Proxy代理对象                private static class Proxy implements IMyService{                                }        }}

// 向客户端公开接口class RemoteService : Service() {    override fun onCreate() {        super.onCreate()    }    override fun onBind(intent: Intent): IBinder {        // Return the interface        return binder    }// 实现stub    privateval binder = object : IRemoteService.Stub() {        override fun getPid(): Int {            return Process.myPid()        }        override fun basicTypes(                anInt: Int,                aLong: Long,                aBoolean: Boolean,                aFloat: Float,                aDouble: Double,                aString: String        ) {            // Does nothing        }    }}

var iRemoteService: IRemoteService? = nullval mConnection = object : ServiceConnection {    // Called when the connection with the service is established    override fun onServiceConnected(className: ComponentName, service: IBinder) {        // Following the example above for an AIDL interface,        // this gets an instance of the IRemoteInterface, which we can use to call on the service        iRemoteService = IRemoteService.Stub.asInterface(service)    }    // Called when the connection with the service disconnects unexpectedly    override fun onServiceDisconnected(className: ComponentName) {        Log.e(TAG, "Service has unexpectedly disconnected")        iRemoteService = null    }}

绑定服务

1、扩展binder类，常规service写法。非夸进程，用于后台服务处理 2、Messenger处理跨进程。特点是不需要考虑多线程安全，它是通过handler维护的messenger会创建所有请求的队列。使用简单 3、aidl，跨进程需要考虑多线程问题。设计相对复杂

// messenger服务创建/** Command to the service to display a message  */private const val MSG_SAY_HELLO = 1class MessengerService : Service() {    /**     * Target we publish for clients to send messages to IncomingHandler.     */    private lateinit var mMessenger: Messenger    /**     * Handler of incoming messages from clients.     */    internal class IncomingHandler(            context: Context,            privateval applicationContext: Context = context.applicationContext    ) : Handler() {        override fun handleMessage(msg: Message) {            when (msg.what) {                MSG_SAY_HELLO ->                    Toast.makeText(applicationContext, "hello!", Toast.LENGTH_SHORT).show()                else -> super.handleMessage(msg)            }        }    }    /**     * When binding to the service, we return an interface to our messenger     * for sending messages to the service.     */    override fun onBind(intent: Intent): IBinder? {        Toast.makeText(applicationContext, "binding", Toast.LENGTH_SHORT).show()        mMessenger = Messenger(IncomingHandler(this))        return mMessenger.binder    }}

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