flutter 用 encrypt: ^5.0.1例子即可
key
iv 可以用自定义字符串：IV _ivAes = IV.fromUtf8(“1234456812344568”);

java
对应的key与iv也要用同样的字符串：
String key = “12344568123445681234456812344568”
String iv = “1234456812344568”;
没加密过的字符串转化为byte[]：
// key
byte[] keyByte = key.getBytes(StandardCharsets.UTF_8);
// iv
byte[] ivByte = iv.getBytes(StandardCharsets.UTF_8);
加密过的字符串则要同时解密后再用:
byte[] keyByte = Base64.decodeBase64(key);
byte[] ivByte = Base64.decodeBase64(iv.getBytes(StandardCharsets.UTF_8));

java javax.crypto.BadPaddingException: pad block corrupted问题解决
我用的是Java\jdk-12.0.1，security下没有两个jar包。试了如下办法，成功解密

		Cipher的填空("AES/OFB/PKCS7Padding", "BC");只中间有OFB和CFB有用，第三个不能用NoPadding

		//Cipher cipher = Cipher.getInstance("AES/OFB/PKCS5Padding", "BC");//成功了
		//Cipher cipher = Cipher.getInstance("AES/CFB/ISO10126Padding", "BC");//成功了
		//Cipher cipher = Cipher.getInstance("AES/CFB/PKCS5Padding", "BC");//成功了
		//Cipher cipher = Cipher.getInstance("AES/OFB/ISO10126Padding", "BC");//成功了
		Cipher cipher = Cipher.getInstance("AES/OFB/PKCS7Padding", "BC");//成功
		//Cipher cipher = Cipher.getInstance("AES/CFB/ISO10126Padding", "BC");//成功了