017.Binder 程序示例之 Java 篇
本文基于 AOSP Android10 r41 源码环境
本文示例程序可以在 https://github.com/yuandaimaahao/AndroidFrameworkTutorial/tree/main/3.Binder/src/BinderJavaDemo 下载到
本文给出一个简单的 binder java 示例程序，后文的分析会基于该示例程序：
# 1. 定义 aidl 协议文件
在 device/jelly/rice14 目录下创建 BinderJavaDemo/com/yuandaima 三个文件夹，然后在 device/jelly/rice14/BinderJavaDemo/com/yuandaima 目录下创建 IHelloService.aidl
//IHelloService.aidl
package com.yuandaima;
interface IHelloService
{
void sayhello();
int sayhello_to(String name);
}
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将 aidl 编译为 java 文件：
在系统源码下：
source build/envsetup.sh
# 选择合适的 product
lunch
# 进入项目目录
aidl IHelloService.aidl
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即可生成对应的 Java 文件
# 2. 实现 Hello 服务服务端类
在 device/jelly/rice14/BinderJavaDemo/com/yuandaima 目录下创建 HelloService.java：
//HelloService.java
package com.yuandaima;
import android.util.Log;
public class HelloService extends IHelloService.Stub {
private static final String TAG = "HelloService";
private int cnt1 = 0;
private int cnt2 = 0;
public void sayhello() throws android.os.RemoteException {
cnt1++;
Log.i(TAG, "sayhello : cnt = "+cnt1);
}
public int sayhello_to(java.lang.String name) throws android.os.RemoteException {
cnt2++;
Log.i(TAG, "sayhello_to "+name+" : cnt = "+cnt2);
return cnt2;
}
}
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HelloService 服务端类需要继承 IHelloService.Stub，内部实现 sayhello 和 sayhelloto 两个方法。
# 3.实现服务端
在 device/jelly/rice14/BinderJavaDemo/com/yuandaima 目录下创建 Server.java
//Server.java
package com.yuandaima;
import android.util.Log;
import android.os.ServiceManager;
public class Server {
private static final String TAG = "BinderServer";
public static void main(String args[]) {
/* add Service */
Log.i(TAG, "add hello service");
ServiceManager.addService("hello", new HelloService());
//app_process 启动 Java 进程时，会启动 binder 线程用于获取和解析 binder 消息，应用程序无需关心 binder 消息的获取和解析工作
while (true) {
try {
Thread.sleep(100);
} catch (Exception e){}
}
}
}
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# 4.实现客户端
在 device/jelly/rice14/BinderJavaDemo/com/yuandaima 目录下创建 Client.java
//Client.java
package com.yuandaima;
import android.util.Log;
import android.os.ServiceManager;
import android.os.IBinder;
public class Client {
private static final String TAG = "BinderClient";
public static void main(String args[])
{
//获取服务
IBinder binder = ServiceManager.getService("hello");
if (binder == null)
{
Log.i(TAG, "can not get hello service");
return;
}
//转换接口
IHelloService svr = IHelloService.Stub.asInterface(binder);
//发起远程调用
try {
svr.sayhello();
Log.i(TAG, "call sayhello");
} catch (Exception e) {
}
try {
int cnt = svr.sayhello_to("hello");
Log.i(TAG, "call sayhello_to " + " : cnt = " + cnt);
} catch (Exception e) {
System.out.println("call sayhello_to , err :"+e);
Log.i(TAG, "call sayhello_to , err : "+e);
}
}
}
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# 5. 编译运行
编写 Android.bp 文件：
java_library {
name: "BinderClient",
installable: true,
srcs: [ "Client.java",
"HelloService.java",
"IHelloService.java" ],
}
java_library {
name: "BinderServer",
installable: true,
srcs: [ "Server.java",
"HelloService.java",
"IHelloService.java" ],
}
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接着把 jar 包 push 到模拟器上并执行：
# 将项目源码放到系统源码下
# 在项目目录下执行
mm
# 将 jar 包 push 到虚拟机上
cd out/target/product/generic_x86_64/system/framework
adb push BinderClient.jar /data/local/tmp
adb push BinderServer.jar /data/local/tmp
# 进入模拟器 shell 环境
adb shell
# 执行 java 程序
export CLASSPATH=/data/local/tmp/BinderClient.jar:/data/local/tmp/BinderServer.jar
# 启动服务端
app_process /data/local/tmp com.yuandaima.Server &
# 启动客户端
app_process /data/local/tmp com.yuandaima.Client
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查看 log：
logcat | grep "BinderServer"
02-15 12:20:20.493 4171 4171 I BinderServer: add hello service
logcat | grep "BinderClient"
02-15 12:20:43.169 4183 4183 I BinderClient: call sayhello
02-15 12:20:43.169 4183 4183 I BinderClient: call sayhello_to : cnt = 1
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