找到要修改的文件，进行修改。

这里修改apktool.yml文件，将 minSdkVersion从21【对应Android version 5.0】改为19【对应Android version 4.4】。

sdkInfo:   minSdkVersion: 21   targetSdkVersion: 28

改为

sdkInfo:   minSdkVersion: 19   targetSdkVersion: 28

 使用APKTool编译，重打包

D:\wxds450>apktool b wxdu450  D:\wxds450>echo off I: Using Apktool 2.9.1 I: Checking whether sources has changed... I: Smaling smali folder into classes.dex... I: Checking whether sources has changed... I: Smaling smali_classes2 folder into classes2.dex... I: Checking whether sources has changed... I: Smaling smali_classes3 folder into classes3.dex... I: Checking whether sources has changed... I: Smaling smali_classes4 folder into classes4.dex... I: Checking whether sources has changed... I: Smaling smali_classes5 folder into classes5.dex... I: Checking whether resources has changed... I: Building resources... I: Copying libs... (/lib) I: Copying libs... (/kotlin) I: Building apk file... I: Copying unknown files/dir... I: Built apk into: wxdu450\dist\wxdu450.apk

新的文件生成在dist目录下，将新文件更名为wxdu450_0.apk，并移动到d:\wxds450下。

打包完成后会发现指定的目录下出现了打包好的nopassword.apk文件。但是这个apk没有签名，需要重新签名之后，才能安装。

使用APKTool生成签名

生成keystore

keytool、jarsigner 工具是JAVA JDK自带的，配置好JAVA环境即可！

输入命令：keytool -genkey -alias new.keystore -keyalg RSA -validity 20000 -keystore new.keystore，然后在输入两次最低六位数的密钥口令，例如123456，下面的信息直接Enter，最后y即可。

D:\wxds450>keytool -genkey -alias new.keystore -keyalg RSA -validity 20000 -keystore new.keystore Enter keystore password: Re-enter new password: What is your first and last name?   [Unknown]: What is the name of your organizational unit?   [Unknown]: What is the name of your organization?   [Unknown]: What is the name of your City or Locality?   [Unknown]: What is the name of your State or Province?   [Unknown]: What is the two-letter country code for this unit?   [Unknown]: Is CN=Unknown, OU=Unknown, O=Unknown, L=Unknown, ST=Unknown, C=Unknown correct?   [no]:  y  Enter key password for          (RETURN if same as keystore password): Re-enter new password:  Warning: The JKS keystore uses a proprietary format. It is recommended to migrate to PKCS12 which is an industry standard format using "keytool -importkeystore -srckeystore new.keystore -destkeystore new.keystore -deststoretype pkcs12".

结果生成新文件new.keystore。

 签名APK

未签名APK不能在安卓手机上安装，想要安装则想要对齐签名。

输入命令：jarsigner -verbose -keystore new.keystore -signedjar wxdu450_sign.apkwxdu450_0.apk new.keystore然后再输入密钥库的密码短语即你之前设置的密钥口令，即可签名！

D:\wxds450>jarsigner -verbose -keystore new.keystore -signedjar wxdu450_sign.apk wxdu450_0.apk new.keystore Enter Passphrase for keystore:    adding: META-INF/MANIFEST.MF    adding: META-INF/NEW_KEYS.SF    adding: META-INF/NEW_KEYS.RSA   signing: classes.dex   signing: classes2.dex ...... ......   signing: pinyindb/pinyin_gwoyeu_mapping.xml   signing: pinyindb/pinyin_mapping.xml   signing: pinyindb/unicode_to_hanyu_pinyin.txt   signing: src/com/qq/jce/wup/wup.properties jar signed.  Warning: The signer's certificate is self-signed. No -tsa or -tsacert is provided and this jar is not timestamped. Without a timestamp, users may not be able to validate this jar after the signer certificate's expiration date (2078-10-06) or after any future revocation date. 

结果生成新文件wxdu450_sign.apk，这个新文件就可以在Android4.4手机上安装而不出现解析错误。修改之后虽然能安装成功，但也只是能安装成功，还远远没有达到真正能用的水平：点击打开应用，直接闪退。如果要真的用起来，还需要解决很多问题。