具有getevent的扎根android手机上的权限被拒绝

Question

I have very simple code as follows:

@Override
public void onClick(View v) 
{
  Log.i("MyApp", "Started");
  try
  {
    Process processStart = Runtime.getRuntime().exec("su");
  } 
  catch (IOException e1)
  {
    e1.printStackTrace();
  }
  String myStringArray[]= {"getevent","/dev/input/event0"};
  String line;
  try 
  {
    Process process = Runtime.getRuntime().exec(myStringArray);
    InputStreamReader inputstreamreader = new InputStreamReader(process.getInputStream());
    BufferedReader bufferedReader = new BufferedReader(inputstreamreader);
    bufferedReader.read();
    while ((line = bufferedReader.readLine()) != null) 
    {
      Log.i("MyApp", line);
    }
    InputStreamReader errstreamreader = new InputStreamReader(process.getErrorStream());
    BufferedReader errReader = new BufferedReader(errstreamreader);
    errReader.read();
    while ((line = errReader.readLine()) != null) 
    {
      Log.i("MyApp", line);
    }
  } catch(java.io.IOException e){
  }
  Log.i("MyApp", "Finished");
}
});

but I get this error:

could not open /dev/input/event0, permission denied

I get asked to grant root permission on the phone but before that it have error on logcat.

I have also tried with processStart.waitFor();

But it hangs the application there and does not move forward at all. I have tried looking the reason everywhere but could not get this to work.

I also tried with ProcessBuilder but when I use that the getevent returns nothing at all...

Answer 1

I think you have misunderstood the usage of 'su'.

Process processStart = Runtime.getRuntime().exec("su");

The above code will create a new process and execute the 'su' command, which will only make the child process to become 'root'.

Your calling process is still a normal process so that you cannot do 'getevent'. Instead you should run this super command in your 'rooted child process' like:

mProcess = new ProcessBuilder()
                        .command("/system/xbin/su")
                        .redirectErrorStream(true).start();

OutputStream out = mProcess.getOutputStream();

String cmd = "getevent /dev/input/event0 \n";
Log.d(TAG, "Native command = " + cmd);
out.write(cmd.getBytes());