Handle alert when shut down device android in rooted app

I want change this message "Your phone is shut down" that appear when shut down the device.

Do you have any ideas?

My app download videos in the background, I must warn you not to switch off the device if the download is not yet finished, such as happens when you shut down Windows and is downloading updates.

In AndroidManifest.xml:

<uses-permission android:name="android.permission.PREVENT_POWER_KEY" />
<uses-permission android:name="android.permission.DEVICE_POWER"
    tools:ignore="ProtectedPermissions" />

MainActivity.java I intercept the power off button and force close system dialog and create a View custom above it

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_POWER) {
        // Do something here...
        event.startTracking(); // Needed to track long presses

        Intent closeDialog = new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
        sendBroadcast(closeDialog);
        mViewCustom.setVisibility(View.VISIBLE);

        return true;
    }
    return super.onKeyDown(keyCode, event);
}

@Override
public boolean onKeyLongPress(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_POWER) {

        return true;
    }
    return super.onKeyLongPress(keyCode, event);
}