Android shell command has strange behavior (“input tap x y”)

Question

Sorry for maybe silly question, but I spent almost two days trying figure out the problem.

I have this sample code where I emulate screen touch by invoking shell command "input tap 807 730". And it works.

public class DisableRequest extends Thread {
    @Override
    public void run() {
        super.run();
        StringBuffer output = new StringBuffer();

        try {
            Thread.sleep(3000);

            Process p = Runtime.getRuntime().exec("input tap 807 730");
            p.waitFor();

            BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String line = "";

            while ((line = reader.readLine()) != null) {
                output.append(line + "\n");
            }
        } catch (Exception e) {
            Log.v("INPUT_TEST", "Error : " + e.toString());
        }

        String response = output.toString();
        Log.v("INPUT_TEST", "Response : " + response);

    }

}

I have two cases.

1 ) I invoke this code in onCreate(). In this case all work excellent. For a test I have a big button all over the screen and I can see how this button is clicked after command.

2 ) I invoke this code also in onCreate() but after that I invoke this code to open dialog to request Device Administrator.

private void askForAdministrator() {
    //Begin enabling device administrator
    Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
    ComponentName deviceAdminComponentName = new ComponentName(this, MyAdminReceiver.class);
    intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, deviceAdminComponentName);
    intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "You must enable device administration for certain features"
            + " of the app to function.");

    //I thought that this would start the activity that lets the user
    //choose whether to enable the app as a device admin
    startActivityForResult(intent, ACTIVATION_REQUEST);
}

Here's what happened next:

1) Dialog, it has two buttons, opened. I know that the numbers 801 and 730 are coordinates of button "Activate". I got these numbers from enabling "Show pointer location" in "Developer options" when I clicked on "Activate" button of that Device Administrator dialog.

2) After delay (2 sec) I can see in logcat that my thread did work.

3) The button "Activate" didn't get any touches/clicks. WHY?

So my question is WHY?

BUT, if I will invoke input command using ADB like this

./adb shell input tap 807 730

then the "Activate" button will get touche. So why my command from thread didn't work.

Answer 1

The shell you can reach from within an app is sandboxed. You can not send input events to system dialogs for obvious security reasons. You can bypass this on a rooted device by executing the command as superuser.