am bfbdceff: Grey out App Check setting when no verifiers exist

 from unknown sources. You agree that you are solely responsible for any

 damage to your phone or loss of data that may result from using

 these apps.</string>

    <!-- Applications settings screen, setting check box title. If checked, the system will send package verification requests to package verifiers on the device who will ultimately allow or reject the installation of applications. -->

    <!-- Applications settings screen, setting check box title. If checked, the system will send package verification requests to package verifiers on the device who will ultimately allow or reject the installation of applications. [CHAR LIMIT=30] -->

    <string name="verify_applications">App check</string>

    <!-- Applications settings screen, setting check box summary. This is the summary for "App Check" checkbox. -->

    <!-- Applications settings screen, setting check box summary. This is the summary for "App Check" checkbox. [CHAR LIMIT=none] -->

    <string name="verify_applications_summary">Disallow or warn before installation of apps that may cause harm</string>

    <!-- Applications settings screen, setting check box title. If checked, applications show more settings options. -->

    <string name="advanced_settings">Advanced settings</string>

import android.content.Context;

import android.content.DialogInterface;

import android.content.Intent;

import android.content.pm.PackageManager;

import android.content.pm.ResolveInfo;

import android.net.Uri;

import android.os.Bundle;

import android.os.UserHandle;

import android.os.Vibrator;

import com.android.internal.widget.LockPatternUtils;

import java.util.ArrayList;

import java.util.List;

/**

 * Gesture lock pattern settings.

    private static final String KEY_TOGGLE_INSTALL_APPLICATIONS = "toggle_install_applications";

    private static final String KEY_TOGGLE_VERIFY_APPLICATIONS = "toggle_verify_applications";

    private static final String KEY_POWER_INSTANTLY_LOCKS = "power_button_instantly_locks";

    private static final String PACKAGE_MIME_TYPE = "application/vnd.android.package-archive";

    DevicePolicyManager mDPM;

        mToggleAppInstallation.setChecked(isNonMarketAppsAllowed());

        // Package verification

        mToggleVerifyApps = (CheckBoxPreference) findPreference(

            KEY_TOGGLE_VERIFY_APPLICATIONS);

        mToggleVerifyApps = (CheckBoxPreference) findPreference(KEY_TOGGLE_VERIFY_APPLICATIONS);

        if (isVerifierInstalled()) {

            mToggleVerifyApps.setChecked(isVerifyAppsEnabled());

        } else {

            mToggleVerifyApps.setChecked(false);

            mToggleVerifyApps.setEnabled(false);

        }

        return root;

    }

                                      Settings.Global.PACKAGE_VERIFIER_ENABLE, 1) > 0;

    }

    private boolean isVerifierInstalled() {

        final PackageManager pm = getPackageManager();

        final Intent verification = new Intent(Intent.ACTION_PACKAGE_NEEDS_VERIFICATION);

        verification.setType(PACKAGE_MIME_TYPE);

        verification.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

        final List<ResolveInfo> receivers = pm.queryBroadcastReceivers(verification, 0);

        return (receivers.size() > 0) ? true : false;

    }

    private void warnAppInstallation() {

        // TODO: DialogFragment?

        mWarnInstallApps = new AlertDialog.Builder(getActivity()).setTitle(