Android组件保活，service保活

首先介绍一下android的进程. Android 进程分为两种 :其一，java层的进程，也就是在虚拟机里运行的进程，他们的父进程是zygote进程，我们平时调用的AM里面的类似getrunningprocess()方法，返回的就是这类进程信息，这类进程很容易被杀死。其二，native层的原生进程也就是linux c的进程，这类进程比较安全，其中父进程是init进程的更加安全，很难杀死，在linux里叫守护进程，像surfaceflinger(控制界面呈现)进程，一旦启动会在底层一直运行。

那么我们的目的就是要写一个守护进程实时监视自己app java层进程的情况如果被杀死就立即创建。

首先是最重要的守护程序代码 linuxC的带注释

#include #include #include #include #include #include #include #include /***守护进程的名字"/proc/pid/status"文件的第一行 linux内核把所有进程信息的节点映射在了"/proc"下*注意不同android版本 status里进程名字格式可能不一样*楼主的4.0.3是下面这行 具体的自己到/proc里看一下**/char *procdeam = "Name: com.gy.textndk";//判断进程是否还在运行int ifprocrun(char *rootpath){DIR *dir;struct dirent *ptr; //遍历文件夹需要dirent结构体int bufsize = strlen(procdeam);if((dir = opendir(rootpath)) == NULL){perror("dir opened failed\n");exit(1);}//遍历"/proc"下所有文件夹while((ptr = readdir(dir)) != NULL){if(ptr->d_type == 4){char path[128];memset(path,'\0',sizeof(path));strcpy(path,rootpath);strcat(path,"/");strcat(path,ptr->d_name);strcat(path,"/status");//判断是否存在"status" 文件if(access(path,F_OK) != -1) {int fd = open(path,O_RDONLY);char tmp_buf[bufsize];read(fd,tmp_buf,bufsize);close(fd);printf(tmp_buf,"\n");//判断进程名是否相等if(strcmp(tmp_buf,procdeam) == 0){ printf("-----------------proc is running------------------\n");return 1;}}}}return 0;}int main(){ int i;int fd;//1.创建子进程，结束父进程，子进程由init接管成为守护进程pid_t pid = fork();if(pid<0)exit(1);else if(pid>0)exit(0);//设置新的 sessionsetsid();//2.关闭所有fd管道 for(i=0;i<=48608;i++){close(i);}//3.改变工作目录到跟文件夹chdir("/");//4.umaskumask(0);//5.do sthwhile(1){if(ifprocrun("/proc") == 0){ //调用app_process 的命令 "com.gy.Autostart_Activity"这个实在manifest里注册的 intent-filter action//自己定义 这样AMS才能根据action启动你app组件 类似注册表system("am start -a com.gy.Autostart_Activity");}sleep(10); //10s判断一次 自己定}}

上面这个程序不能用arm-linux-gcc编译因为不支持 android新版的程序调用接口，用 ndk-build命令编译源码放在名叫的jni目录下

接下来就是实现把编译好的linux c守护程序打包进apk并在安装时将其释放到data目录下，便于运行。

首先将编译好的linux c程序放进assets文件夹
下面就是java层释放assets资源文件并且运行的代码，涉及jni

package com.gy.textndk;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.app.Activity;import android.content.Context;import android.util.Log;import android.widget.TextView;import android.os.Bundle;public class HelloJni extends Activity{/** Called when the activity is first created. */private static String TAG = "gy";@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);/* Create a TextView and set its content.* the text is retrieved by calling a native* function.*/TextView tv = new TextView(this);tv.setText( stringFromJNI() );setContentView(tv);StringBuilder sb = new StringBuilder();sb.append(getAppPrivateDir(this)).append("/gyarmdeomproc");copyAsset(HelloJni.this, "gyarmdeomproc", sb.toString());startproc();}/* A native method that is implemented by the* 'hello-jni' native library, which is packaged* with this application.*/public native String stringFromJNI();/* This is another native method declaration that is *not** implemented by 'hello-jni'. This is simply to show that* you can declare as many native methods in your Java code* as you want, their implementation is searched in the* currently loaded native libraries only the first time* you call them.** Trying to call this function will result in a* java.lang.UnsatisfiedLinkError exception !*/public native String unimplementedStringFromJNI();public native int startproc();/* this is used to load the 'hello-jni' library on application* startup. The library has already been unpacked into* /data/data/com.example.hellojni/lib/libhello-jni.so at* installation time by the package manager.*/static {System.loadLibrary("hello-jni");}//文件复制public static boolean copyStream(InputStream in, OutputStream out) {Log.d(TAG, "copyStream("+ in + " ," + out+ ")");try {byte[] buf = new byte[8192];int len;while ((len = in.read(buf)) > 0)out.write(buf, 0, len); } catch (Exception e) {e.printStackTrace();return false;}return true;}//获得app私有文件夹路径public static String getAppPrivateDir(Context ctx) {File dataDir = ctx.getDir("data", Context.MODE_PRIVATE);return dataDir.getAbsolutePath();}//拷贝assets资源文件到data私有文件夹下public static boolean copyAsset(Context ctx, String assetFile,String saveToFile) {Log.d(TAG, "copyAssets(" + assetFile + " -> " + saveToFile);File outputFile = new File(saveToFile);if (outputFile.exists()) {return true;}// init output stream(file)OutputStream out;try {out = new FileOutputStream(outputFile);} catch (FileNotFoundException e1) {e1.printStackTrace();return false;}boolean copyResult = false;InputStream in = null;try {in = ctx.getAssets().open(assetFile);copyResult = copyStream(in, out);Log.d(TAG, "copy " + assetFile + " - " + copyResult);} catch (IOException e1) {e1.printStackTrace();} finally {// close input stream(file)try {if (in != null)in.close();} catch (IOException e) {}}// close output stream (file)try {if (out != null)out.close();} catch (IOException e) {e.printStackTrace();}// return copy result// add file execute permissionFile fs = new File(saveToFile);try {//这句很重要 赋予文件可执行权限 不然文件无法执行 fs.setExecutable(true, true);} catch (Exception e) {e.printStackTrace();}Log.d(TAG, "copyAsset() return " + copyResult);return copyResult;}}

最后是jni的c代码很简单直接调用

/** deomproc.c** Created on: 2015年2月9日* Author: gy#include #include #include JNIEXPORT jint JNICALL Java_com_gy_textndk_HelloJni_startproc(){ system("/data/data/com.gy.textndk/app_data/gyarmdeomproc");}

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