Android Runtime.exec ("screencap") not doing anything (not working) and not giving any error

Question

Running the command: adb shell screencap /sdcard/image1.png from the command line works, and the screenshot is taken and saved in the gallery as "image1.png"

But this doesn't work grammatically when doing:

String[] commandAndArgs = new String[]{ "screencap", "/sdcard/qweqwe.
Process p = Runtime.getRuntime().exec(commandAndArgs);

No errors or exception are thrown

Full code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    try{
        String[] commandAndArgs = new String[]{ "screencap", "/sdcard/qweqwe.png" };
        Process p = Runtime.getRuntime().exec(commandAndArgs);

        String error = "error: ";
        Scanner scanner = new Scanner(p.getInputStream());
        while (scanner.hasNext()) {
            error += scanner.nextLine();
        }

        Toast.makeText(this, error, Toast.LENGTH_LONG).show();
    }catch (Exception e){
        Log.e("err", Log.getStackTraceString(e));
    }
}

Answer 1

You'll have to check if exit code of the process is equal to zero, which indicates success.

final int code = p.waitFor()
if (code != 0) {
    throw new RuntimeException("Code: " + code);
}

The other thing is that taking screenshots requires android.permission.READ_FRAME_BUFFER, which is a signature permission only granted to system apps (including ADB shell). See, if you open a shell from your app it still runs with your app's permissions. And if your app doesn't have the permission it won't work.