Runtime.getRuntime（）。exec：为什么命令“ cp”不起作用？

Question

My code:

File dir = Environment.getExternalStoragePublicDirectory( Environment.DIRECTORY_DOWNLOADS );
File src = new File(dir, "test.dat");
File dst = new File(dir, "test_2.dat");

if ( src.exists() )
{
    try
    {
        Process process = Runtime.getRuntime().exec( new String[] {"cp", "-f", src.getAbsolutePath(), dst.getAbsolutePath()} );
        process.waitFor();
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
    catch (InterruptedException e)
    {
        e.printStackTrace();
    }
}

This code works (copy file) on Samsung Galaxy S3, but does not work on Amazon Kindle Fire:

java.io.IOException: Error running exec(). Command: [cp, -f, /mnt/sdcard/Download/test.dat, /mnt/sdcard/Download/test_2.dat] Working Directory: null Environment: null

Why does this happen? And how to get to execute this command copy on all devices?

Answer 1

In general it won't work because an android application doesn't have premissions to access the downloads directory. Or maybe because it can't access /bin/cp. It will work if you root your phone I think. Try the same from the adb shell prompt so you then understand why it doesn't work.

Answer 2

I have had a similar issue with replacing the bootanimation.zip and this is how I fixed it. Hope it helps somebody.

Runtime.getRuntime().exec("mount -o remount,rw system /system");
Runtime.getRuntime().exec("cp /storage/emulated/0/bootanimation/bootanimation.zip /system/media/bootanimation.zip");
Runtime.getRuntime().exec("chmod 644 /system/media/bootanimation.zip");
Runtime.getRuntime().exec("mount -o remount,ro system /system");