工具下载地址

签名工具下载地址：

https://developers.weixin.qq.com/doc/oplatform/Downloads/Android_Resource.html

什么时候使用呢？

当你去申请开发者账号的时候，如果是android应用，则需要你填写包名和签名。

它到底做了什么呢？

我们把这个apk下载下来吧，然后反编译一下。

点击按钮，调用签名方法

MainAct.this.getSign(str);

获取签名

Signature[] arrayOfSignature = getRawSignature((Context)this, paramString);

paramString这个是包名

如何获取到签名的呢？

PackageManager packageManager = paramContext.getPackageManager();
 return ((PackageInfo)packageManager).signatures;

这两行是主要代码了

再回到前面获取的地方如何处理？

stdout(MD5.getMessageDigest(arrayOfSignature[b].toByteArray()));

转成MD5值，然后输出，就如上图所示了。

完整的反编译代码

package com.tencent.mm.openapi;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.Signature;
import android.os.Bundle;
import android.text.ClipboardManager;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainAct extends Activity {
  private Button copyBtn;
  
  private TextView errorTv;
  
  private Button getBtn;
  
  private EditText pkgNameEt;
  
  private TextView resultTv;
  
  private void errout(String paramString) {
    this.errorTv.append(String.valueOf(paramString) + "\n");
  }
  
  private Signature[] getRawSignature(Context paramContext, String paramString) {
    Context context = null;
    if (paramString == null || paramString.length() == 0) {
      errout("getSignature, packageName is null");
      return (Signature[])context;
    } 
    PackageManager packageManager = paramContext.getPackageManager();
    try {
      PackageInfo packageInfo = packageManager.getPackageInfo(paramString, 64);
      if (packageInfo == null) {
        errout("info is null, packageName = " + paramString);
        return (Signature[])context;
      } 
    } catch (android.content.pm.PackageManager.NameNotFoundException nameNotFoundException) {
      errout("NameNotFoundException");
      return (Signature[])context;
    } 
    return ((PackageInfo)packageManager).signatures;
  }
  
  private void getSign(String paramString) {
    Signature[] arrayOfSignature = getRawSignature((Context)this, paramString);
    if (arrayOfSignature == null || arrayOfSignature.length == 0) {
      errout("signs is null");
      return;
    } 
    int i = arrayOfSignature.length;
    byte b = 0;
    while (true) {
      if (b < i) {
        stdout(MD5.getMessageDigest(arrayOfSignature[b].toByteArray()));
        b++;
        continue;
      } 
      return;
    } 
  }
  
  private void showDialog() {
    AlertDialog.Builder builder = new AlertDialog.Builder((Context)this);
    builder.setCancelable(false);
    builder.setTitle(2130968584).setMessage(2130968585);
    builder.setPositiveButton(2130968582, null);
    builder.setNegativeButton(2130968583, new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface param1DialogInterface, int param1Int) {
            MainAct.this.finish();
          }
        });
    builder.show();
  }
  
  private void stdout(String paramString) {
    this.resultTv.append(String.valueOf(paramString) + "\n");
    this.copyBtn.setVisibility(0);
  }
  
  public void onCreate(Bundle paramBundle) {
    super.onCreate(paramBundle);
    setContentView(2130903040);
    this.pkgNameEt = (EditText)findViewById(2131034112);
    this.resultTv = (TextView)findViewById(2131034114);
    this.errorTv = (TextView)findViewById(2131034115);
    this.getBtn = (Button)findViewById(2131034113);
    this.getBtn.setOnClickListener(new View.OnClickListener() {
          public void onClick(View param1View) {
            MainAct.this.resultTv.setText("");
            MainAct.this.errorTv.setText("");
            MainAct.this.copyBtn.setVisibility(8);
            String str = MainAct.this.pkgNameEt.getText().toString();
            if (str != null && str.length() > 0)
              MainAct.this.getSign(str); 
          }
        });
    this.copyBtn = (Button)findViewById(2131034116);
    this.copyBtn.setVisibility(8);
    this.copyBtn.setOnClickListener(new View.OnClickListener() {
          public void onClick(View param1View) {
            ((ClipboardManager)MainAct.this.getSystemService("clipboard")).setText(MainAct.this.resultTv.getText().toString().trim());
            Toast.makeText((Context)MainAct.this, 2130968581, 1).show();
          }
        });
    showDialog();
  }
}

MD5.java

package com.tencent.mm.openapi;

import java.security.MessageDigest;

public final class MD5 {
  public static final String getMessageDigest(byte[] paramArrayOfbyte) {
    // Byte code:
    //   0: bipush #16
    //   2: newarray char
    //   4: astore_1
    //   5: aload_1
    //   6: dup
    //   7: iconst_0
    //   8: ldc 48
    //   10: castore
    //   11: dup
    //   12: iconst_1
    //   13: ldc 49
    //   15: castore
    //   16: dup
    //   17: iconst_2
    //   18: ldc 50
    //   20: castore
    //   21: dup
    //   22: iconst_3
    //   23: ldc 51
    //   25: castore
    //   26: dup
    //   27: iconst_4
    //   28: ldc 52
    //   30: castore
    //   31: dup
    //   32: iconst_5
    //   33: ldc 53
    //   35: castore
    //   36: dup
    //   37: bipush #6
    //   39: ldc 54
    //   41: castore
    //   42: dup
    //   43: bipush #7
    //   45: ldc 55
    //   47: castore
    //   48: dup
    //   49: bipush #8
    //   51: ldc 56
    //   53: castore
    //   54: dup
    //   55: bipush #9
    //   57: ldc 57
    //   59: castore
    //   60: dup
    //   61: bipush #10
    //   63: ldc 97
    //   65: castore
    //   66: dup
    //   67: bipush #11
    //   69: ldc 98
    //   71: castore
    //   72: dup
    //   73: bipush #12
    //   75: ldc 99
    //   77: castore
    //   78: dup
    //   79: bipush #13
    //   81: ldc 100
    //   83: castore
    //   84: dup
    //   85: bipush #14
    //   87: ldc 101
    //   89: castore
    //   90: dup
    //   91: bipush #15
    //   93: ldc 102
    //   95: castore
    //   96: pop
    //   97: ldc 'MD5'
    //   99: invokestatic getInstance : (Ljava/lang/String;)Ljava/security/MessageDigest;
    //   102: astore_2
    //   103: aload_2
    //   104: aload_0
    //   105: invokevirtual update : ([B)V
    //   108: aload_2
    //   109: invokevirtual digest : ()[B
    //   112: astore_0
    //   113: aload_0
    //   114: arraylength
    //   115: istore_3
    //   116: iload_3
    //   117: iconst_2
    //   118: imul
    //   119: newarray char
    //   121: astore_2
    //   122: iconst_0
    //   123: istore #4
    //   125: iconst_0
    //   126: istore #5
    //   128: iload #4
    //   130: iload_3
    //   131: if_icmplt -> 145
    //   134: new java/lang/String
    //   137: astore_0
    //   138: aload_0
    //   139: aload_2
    //   140: invokespecial <init> : ([C)V
    //   143: aload_0
    //   144: areturn
    //   145: aload_0
    //   146: iload #4
    //   148: baload
    //   149: istore #6
    //   151: iload #5
    //   153: iconst_1
    //   154: iadd
    //   155: istore #7
    //   157: aload_2
    //   158: iload #5
    //   160: aload_1
    //   161: iload #6
    //   163: iconst_4
    //   164: iushr
    //   165: bipush #15
    //   167: iand
    //   168: caload
    //   169: i2c
    //   170: castore
    //   171: iload #7
    //   173: iconst_1
    //   174: iadd
    //   175: istore #5
    //   177: aload_2
    //   178: iload #7
    //   180: aload_1
    //   181: iload #6
    //   183: bipush #15
    //   185: iand
    //   186: caload
    //   187: i2c
    //   188: castore
    //   189: iinc #4, 1
    //   192: goto -> 128
    //   195: astore_0
    //   196: aconst_null
    //   197: astore_0
    //   198: goto -> 143
    // Exception table:
    //   from	to	target	type
    //   97	122	195	java/lang/Exception
    //   134	143	195	java/lang/Exception
  }
  
  public static final byte[] getRawDigest(byte[] paramArrayOfbyte) {
    try {
      MessageDigest messageDigest = MessageDigest.getInstance("MD5");
      messageDigest.update(paramArrayOfbyte);
      paramArrayOfbyte = messageDigest.digest();
    } catch (Exception exception) {
      exception = null;
    } 
    return (byte[])exception;
  }
}