问removeDialog()、dismissDialog()和()的区别

EN

public final class OptionsPreference extends PreferenceActivity implements DialogInterface.OnClickListener
{
private AlertDialog noInternetDialog = null;
//...

    @Override
    protected void onPause()
    {
        if (this.noInternetDialog != null)
        {
            Log.d(LOG_TAG, "Destroying noInternetDialog...");
            this.noInternetDialog.dismiss(); // X?
            removeDialog(DIALOG_NOINTERNET); // X?
            dismissDialog(DIALOG_NOINTERNET); // X?
            this.noInternetDialog = null;
        }
        super.onPause();
    }

    @Override
    protected final Dialog onCreateDialog(final int id)
    {
        switch (id)
        {
            case DIALOG_NOINTERNET:
            {
                final AlertDialog.Builder _builder = new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_info).setMessage(R.string.str_nointernet);
                _builder.setCancelable(false);
                _builder.setPositiveButton(R.string.str_wifisettings, this);
                _builder.setNeutralButton(R.string.str_ok, this);
                this.noInternetDialog = _builder.create();
                if (!isFinishing())
                {
                    this.noInternetDialog.show();
                }
                return this.noInternetDialog;
            }
// ...
}