Android 如何读取APK 签名信息

package com.test.mytest;

import java.io.ByteArrayInputStream;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.Iterator;
import java.util.List;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.util.Log;

public class MyTestClass1 {

public void CheckSignature(Context context){
byte[] signature  = getSign(context);
String publickey = getPublicKey(signature);
Log.d("CheckSignature", "publickey = " + publickey);
}

private byte[] getSign(Context context) {
PackageManager pm = context.getPackageManager();
List<PackageInfo> apps = pm.getInstalledPackages(PackageManager.GET_SIGNATURES);
Iterator<PackageInfo> iter = apps.iterator();
while (iter.hasNext()) {
PackageInfo info = iter.next();
String packageName = info.packageName;
//按包名读取签名
if (packageName.equals("com.example.resign_test")) {
return info.signatures[0].toByteArray();
}
}
return null;
}

public static String getPublicKey(byte[] signature) {
try {
CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
X509Certificate cert = (X509Certificate) certFactory.generateCertificate(new ByteArrayInputStream(signature));
return cert.getPublicKey().toString();
} catch (CertificateException e) {
e.printStackTrace();
}
return null;
}
}