最近做了一些关于Android Native 编程相关的东西，在这篇文章中我将介绍如何在Android application中调用Native executable。至于如何编写Native executable和如何打包native到apk中，之前我都有文章介绍这里就不再重复了。
我写了一个Demo程序，演示如何在Android Application中调用Native executable。该示例中：
- 可以调用系统自带的executable，例如“/system/bin/ls”；
- 可以调用自己编写的Native executable，放置在apk的assets目录下；
- 可以调用从远程服务器下载的Native executable；
接下来详细介绍代码的实现，在这里我们主要用到了android.os.Exec，但是android.os.Exec不被包含在android.jar中，因此只能通过java反射机制来实现。
以下代码实现了一个通用的exec函数：
private String exec(String arg0, String arg1, String arg2) {
try {
// android.os.Exec is not included in android.jar so we need to use reflection.
Class execClass = Class.forName("android.os.Exec");
Method createSubprocess = execClass.getMethod("createSubprocess",
String.class, String.class, String.class, int[].class);
Method waitFor = execClass.getMethod("waitFor", int.class);
// Executes the command.
// NOTE: createSubprocess() is asynchronous.
int[] pid = new int[1];
FileDescriptor fd = (FileDescriptor)createSubprocess.invoke(
null, arg0, arg1, arg2, pid);
// Reads stdout.
// NOTE: You can write to stdin of the command using new FileOutputStream(fd).
FileInputStream in = new FileInputStream(fd);
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String output = "";
try {
String line;
while ((line = reader.readLine()) != null) {
output += line + "\n";
}
} catch (IOException e) {
// It seems IOException is thrown when it reaches EOF.
}
// Waits for the command to finish.
waitFor.invoke(null, pid[0]);
return output;
} catch (ClassNotFoundException e) {
throw new RuntimeException(e.getMessage());
} catch (SecurityException e) {
throw new RuntimeException(e.getMessage());
} catch (NoSuchMethodException e) {
throw new RuntimeException(e.getMessage());
} catch (IllegalArgumentException e) {
throw new RuntimeException(e.getMessage());
} catch (IllegalAccessException e) {
throw new RuntimeException(e.getMessage());
} catch (InvocationTargetException e) {
throw new RuntimeException(e.getMessage());
}
}
以下代码实现如何执行assets中的Native executable程序：
private int getassetsfile(String fileName, String tagFile) {
int retVal = 0;
try {
File dir = new File(tagFile);
if (dir.exists()) {
dir.delete();
}
InputStream in = this.getAssets().open(fileName);
if(in.available() == 0) {
return retVal;
}
FileOutputStream out = new FileOutputStream(tagFile);
int read;
byte[] buffer = new byte[4096];
while ((read = in.read(buffer)) > 0) {
out.write(buffer, 0, read);
}
out.close();
in.close();
retVal = 1;
return retVal;
} catch (IOException e) {
throw new RuntimeException(e.getMessage());
}
}
以下代码实现如何执行远程服务器上的Native executable程序：
private void download(String urlStr, String localPath) {
try {
URL url = new URL(urlStr);
HttpURLConnection urlconn = (HttpURLConnection)url.openConnection();
urlconn.setRequestMethod("GET");
urlconn.setInstanceFollowRedirects(true);
urlconn.connect();
InputStream in = urlconn.getInputStream();
FileOutputStream out = new FileOutputStream(localPath);
int read;
byte[] buffer = new byte[4096];
while ((read = in.read(buffer)) > 0) {
out.write(buffer, 0, read);
}
out.close();
in.close();
urlconn.disconnect();
} catch (MalformedURLException e) {
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
throw new RuntimeException(e.getMessage());
}
}
总结下：
通常有三种方法把Native executable放置到手机上：1.assets；2.via network；3.via pc use adb。在本例子中前两种方法都有实现，至于第三种我相信地球人都知道。
下载演示程序：DemoNativeExe_apk (212)
下载源代码：DemoNativeExeSrc (305)
转载请注明： 转载自iT人 – theiter
本文链接地址: 在Android上运行native可执行程序
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