Android：从firebase下载的dex无法正常工作：“找不到用于dex位置的原始dex文件”

如何解决Android：从firebase下载的dex无法正常工作：“找不到用于dex位置的原始dex文件”

我是Android开发的新手，我正在尝试从Firebase存储下载动态加载dex文件（因此可以在不更新应用本身的情况下即时更改它）。我正在尝试关注this Medium Article。

但是DexClassloader总是会出现此错误，这似乎是错误下载（下载后文件大小为0MB）的症状：

E/System: java.io.IOException: No original dex files found for dex location /data/user/0/com.example.calculator/cache/Calc1387497247.dex
        at dalvik.system.DexFile.openDexFileNative(Native Method)
        at dalvik.system.DexFile.openDexFile(DexFile.java:367)
        at dalvik.system.DexFile.<init>(DexFile.java:148)
        at dalvik.system.DexFile.loadDex(DexFile.java:219)
        at dalvik.system.DexPathList.loadDexFile(DexPathList.java:362)
        at dalvik.system.DexPathList.makeElements(DexPathList.java:313)
        at dalvik.system.DexPathList.makeDexElements(DexPathList.java:263)
        at dalvik.system.DexPathList.<init>(DexPathList.java:126)
        at dalvik.system.BaseDexClassLoader.<init>(BaseDexClassLoader.java:48)
        at dalvik.system.DexClassLoader.<init>(DexClassLoader.java:57)
        at com.example.calculator.MainActivity.onCreate(MainActivity.java:64)
        at android.app.Activity.performCreate(Activity.java:6679)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
        at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2618)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6119)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

我从中篇文章的linked github project中获得了dex。 只是构建项目，然后解压缩并使用dex文件（我尝试使用整个apk，但同样失败） 看起来它下载正常，并且可以在检查时找到临时文件。

我已经尝试了几个stackoverflow问题中的建议。 ex1 ex2 但是什么都没有。

下载后我能够测试文件的大小，它显示临时文件为0 MB。因此，它必须下载不正确，并且该错误是其症状。

我认为我不是唯一尝试遵循本文的人。 因此，如果任何人都有修复程序，或者可以指出我正在运行的github示例项目的方向，将不胜感激。

源代码：MainActivity.java

package com.example.calculator;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.FirebaseApp;
import com.google.firebase.storage.FileDownloadTask;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;

import dalvik.system.DexClassLoader;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FirebaseApp.initializeApp(this);

        FirebaseStorage storage = FirebaseStorage.getInstance();

        // Create a storage reference from our app
        StorageReference storageRef = storage.getReference();


        StorageReference gsReference = storage.getReferenceFromUrl("gs://dcl-demo.appspot.com/Calc.dex");



        Log.e("Cache Dir: ",getCacheDir().getAbsolutePath());

        try {
            File outputDir = getCacheDir().getAbsoluteFile(); // context being the Activity pointer
            File localFile = File.createTempFile("Calc",".dex",outputDir);

            gsReference.getFile(localFile);

            Log.e("Local File Path: ",localFile.getAbsolutePath());
            Log.e("Local File Name: ",localFile.getName());

            File file = new File(localFile.getAbsolutePath());
            if(file.exists()) {
                Log.e("THE FILE EXISTS: ","EXISTS");
            }

            final DexClassLoader classLoader = new DexClassLoader(localFile.getAbsolutePath(),getCacheDir().getAbsolutePath(),null,this.getClass().getClassLoader());

            try {
               Class<?> myOwnClass = classLoader.loadClass("com.example.calculator.DynamicCalculator");
                Method addMethod = myOwnClass.getmethod("add",Double.class,Double.class);
                double result = (double) addMethod.invoke(null,5.0,3.0);

                Log.e("Returned Result: ",String.valueOf(result));

            } catch (Exception e) {
               e.printstacktrace();
            }


            } catch (Exception e) {
                e.printstacktrace();
            }

    }}

BuildGradle（应用程序）：

    apply plugin: 'com.android.application'
    apply plugin: 'com.google.gms.google-services'
    
    android {
        compileSdkVersion 29
        buildToolsversion "30.0.0"
    
        defaultConfig {
            applicationId "com.example.calculator"
            minSdkVersion 23
            targetSdkVersion 29
            versionCode 1
            versionName "1.0"
    
            testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        }
    
        buildTypes {
            debug {
                minifyEnabled false
            }
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'),'proguard-rules.pro'
            }
        }
    
    }
    
    dependencies {
        implementation filetree(dir: 'libs',include: ['*.jar'])
    
        implementation 'androidx.appcompat:appcompat:1.2.0'
        implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
        //implementation 'com.google.firebase:firebase-analytics:17.5.0'
        implementation 'com.google.firebase:firebase-storage:19.2.0'
        testImplementation 'junit:junit:4.12'
        androidTestImplementation 'androidx.test.ext:junit:1.1.2'
        androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    }

BuildGradle（项目）：

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    
    repositories {
        google()
        jcenter()
        
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.0.1'
        classpath 'com.google.gms:google-services:4.3.3'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
        
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

AndroidManifest：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.calculator">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>