<span>1. </span>Integer    (整数)
<span>2. </span>Float      (浮点数)
<span>3. </span>String     (字符串)
<span>4. </span>Boolean    (布尔值)
<span>5. </span>Array      (数组)
<span>6. </span>Object     (对象)

<span><?php </span><span>$a</span>=<span>6.66666</span>;
<span>$b</span>=(integer)<span>$a</span>;
<span>echo</span><span>$b</span>;</span>

echo <span>floor</span>(<span>4.3</span>);   <span>// 输出4 </span>
echo <span>floor</span>(<span>9.999</span>); <span>// 输出9</span>

echo <span>ceil</span>(<span>4.3</span>);    <span>// 输出5 </span>
echo <span>ceil</span>(<span>9.999</span>);  <span>// 输出10</span>

echo <span>round</span>(<span>3.4</span>);         <span>// 输出3 </span>
echo <span>round</span>(<span>3.5</span>);         <span>// 输出4 </span>
echo <span>round</span>(<span>3.6</span>);         <span>// 输出4 </span>
echo <span>round</span>(<span>3.6</span>, <span>0</span>);      <span>// 输出4 </span>
echo <span>round</span>(<span>1.95583</span>, <span>2</span>);  <span>// 输出1.96 </span>
echo <span>round</span>(<span>1241757</span>, -<span>3</span>); <span>// 输出1242000 </span>
echo <span>round</span>(<span>5.045</span>, <span>2</span>);    <span>// 输出5.04 </span>
echo <span>round</span>(<span>5.055</span>, <span>2</span>);    <span>// 输出5.06</span>

按照 @Yash Kadiya 的建议，我选择了平台特定代码。

在这里发布，快乐编码！：

颤动

import ''dart:convert'';
import ''dart:io'';

import ''package:flutter/material.dart'';
import ''package:flutter/services.dart'';
import ''package:get/get.dart'';

void main() async {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      title: ''Secure App'',theme: ThemeData(
        primarySwatch: Colors.blue,),home: HomePage(),);
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {

  String encryptedData = '''';
  String decryptedData = '''';

  static const encryptionChannel = const MethodChannel(''enc/dec'');

  Future<void> encryptData(String encrypted,String key) async {
    try {
      var result = await encryptionChannel.invokeMethod(
        ''encrypt'',{
          ''data'': jsonString,''key'': key,},);
      print(''RETURNED FROM PLATFORM'');
      print(result);
      setState(() {
        encryptedData = result;
      });
    } on PlatformException catch (e) {
      print(''${e.message}'');
    }
  }

  Future<void> decryptData(String encrypted,String key) async {
    try {
      var result = await encryptionChannel.invokeMethod(''decrypt'',{
        ''data'': encrypted,});
      print(''RETURNED FROM PLATFORM'');
      print(result);
      setState(() {
        decryptedData = result;
      });
    } on PlatformException catch (e) {
      print(''${e.message}'');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.center,children: [
            MaterialButton(
              child: Text(''Encrypt Data''),onPressed: () {
                encryptData(''data to be encrypted'',''16 character long key'');
              },MaterialButton(
              child: Text(''Decrypt Data''),onPressed: () {
                decryptData(''data to be decrypted'',''16 character long key'');
                // same key used to encrypt
              },Text(encryptedData),Text(decryptedData),],);
  }
}

安卓

MainActivity.kt

package com.example.secureapp;

import android.util.Log
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel

class MainActivity: FlutterActivity() {
    private val CHANNEL = "enc/dec";

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger,CHANNEL).setMethodCallHandler{call,result ->
            if(call.method.equals("encrypt")){
                val data = call.argument<String>("data")
                val key = call.argument<String>("key")
                val cipher = CryptoHelper.encrypt(data,key)
                result.success(cipher)
            }else if(call.method.equals("decrypt")){
                val data = call.argument<String>("data")
                val key = call.argument<String>("key")
                val jsonString = CryptoHelper.decrypt(data,key)
                result.success(jsonString)
            }else{
                result.notImplemented()
            }
        }
    }
}

CryptoHelper.java

package com.example.secureapp;

import android.util.Base64;
import android.util.Log;
import java.security.NoSuchAlgorithmException;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class CryptoHelper {
    static String keyValue;
    private final IvParameterSpec ivSpec;
    private final SecretKeySpec keySpec;
    private Cipher cipher;
    private final static String ivKey = "RF22SW76BV83EDH8"; //16 char secret key

    public CryptoHelper() {
        ivSpec = new IvParameterSpec(ivKey.getBytes());
        keySpec = new SecretKeySpec(keyValue.getBytes(),"AES");
        try {
            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            e.printStackTrace();
        }
    }

    public static String encrypt(String valueToEncrypt,String key) throws Exception {
        keyValue = key;
        CryptoHelper enc = new CryptoHelper();
        return Base64.encodeToString(enc.encryptInternal(valueToEncrypt),Base64.DEFAULT);
    }

    public static String decrypt(String valueToDecrypt,String key) throws Exception {
        keyValue = key;
        CryptoHelper enc = new CryptoHelper();
        return new String(enc.decryptInternal(valueToDecrypt));
    }

    private byte[] encryptInternal(String text) throws Exception {
        if (text == null || text.length() == 0) {
            throw new Exception("Empty string");
        }
        byte[] encrypted;
        try {
            cipher.init(Cipher.ENCRYPT_MODE,keySpec,ivSpec);
            encrypted = cipher.doFinal(text.getBytes());
        } catch (Exception e) {
            throw new Exception("[encrypt] " + e.getMessage());
        }
        return encrypted;
    }

    private byte[] decryptInternal(String code) throws Exception {
        if (code == null || code.length() == 0) {
            throw new Exception("Empty string");
        }
        byte[] decrypted;
        try {
            cipher.init(Cipher.DECRYPT_MODE,ivSpec);
            decrypted = cipher.doFinal(Base64.decode(code,Base64.DEFAULT));
        } catch (Exception e) {
            throw new Exception("[decrypt] " + e.getMessage());
        }
        return decrypted;
    }
}

IOS

在 ios 端使用 CryptoSwift 库

Podfile（将此添加到 podfile）

  pod ''CryptoSwift''

然后运行pod install

AppDelegate.swift

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
    override func application(
        _ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        
        let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
        
        let encryptionChannel = FlutterMethodChannel(name: "enc/dec",binaryMessenger: controller.binaryMessenger)
        encryptionChannel.setMethodCallHandler({
          [weak self] (call: FlutterMethodCall,result: FlutterResult) -> Void in
          // Note: this method is invoked on the UI thread.
            if(call.method == "encrypt"){
                guard let args = call.arguments as? [String : Any] else {return}
                let data = args["data"] as! String
                let key = args["key"] as! String
                let encryptedString = CryptoHelper.encrypt(dataFromFlutter: data,keyFromFlutter: key)
                self?.encrypt(result: result,encrypted: encryptedString!)
                return
            }else if(call.method == "decrypt"){
                guard let args = call.arguments as? [String : Any] else {return}
                let data = args["data"] as! String
                let key = args["key"] as! String
                let decryptedString = CryptoHelper.decrypt(dataFromFlutter: data,keyFromFlutter: key)
                self?.decrypt(result: result,decrypted: decryptedString!)
                return
            }else{
                result(FlutterMethodNotImplemented)
                return
            }
        })

        GeneratedPluginRegistrant.register(with: self)
        return super.application(application,didFinishLaunchingWithOptions: launchOptions)
    }
    
    private func encrypt(result: FlutterResult,encrypted: String) {
        result(encrypted)
    }
    
    private func decrypt(result: FlutterResult,decrypted: String) {
        result(decrypted)
    }
    
}

CryptoHelper.swift

import Foundation
import CryptoSwift

var keyValue :String!

class CryptoHelper{
    private static let iv = "RF22SW76BV83EDH8";
    // ENC
    public static func encrypt(dataFromFlutter :String,keyFromFlutter :String) -> String? {
        do{
            let encrypted: Array<UInt8> = try AES(key: keyFromFlutter,iv: iv,padding: .pkcs5).encrypt(Array(dataFromFlutter.utf8))
            return encrypted.toBase64()
        }catch{
            return "DATA ERROR"
        }
    }
    
    // DEC
    public static func decrypt(dataFromFlutter :String,keyFromFlutter :String) -> String? {
        do{
            let data = Data(base64Encoded: dataFromFlutter)
            let decrypted = try AES(key: keyFromFlutter,padding: .pkcs5).decrypt(data!.bytes)
            return String(data: Data(decrypted),encoding: .utf8)
        }catch{
            return "DATA ERROR"
        }
    }
}