GetAppSignByPackageName

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;  
    }  
}