如何解决错误“java.net.ConnectException：无法连接到 localhost/127.0.0.1:8000”

我目前正在开发一个应用程序android-studio with Kotlin和一个API系统使用django-rest-framework.

我想访问我的本地服务器127.0.0.1使用 android 模拟器从 API 方法中获取一些值。

我在堆栈溢出网站和其他网站上检查了一些问题，并参考一些文章设置了我的代码，例如在AndroidManifest.xml，制作一个network_security_config.xml，更改代理Android emulator并更改一些代码Django rest framework项目。

即使当我到达本地服务器中的端点时，我也会收到如下错误代码：

2020-10-07 22:37:39.318 7247-7247/com.sample.apitest I/System.out: checked
2020-10-07 22:37:39.358 7247-7280/com.sample.apitest D/NetworkSecurityConfig: Using Network Security Config from resource network_security_config debugBuild: true
2020-10-07 22:37:39.392 7247-7280/com.sample.apitest W/System.err: java.net.ConnectException: Failed to connect to localhost/127.0.0.1:8000
2020-10-07 22:37:39.394 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.io.RealConnection.connectSocket(RealConnection.java:143)
2020-10-07 22:37:39.394 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.io.RealConnection.connect(RealConnection.java:112)
2020-10-07 22:37:39.394 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:184)
2020-10-07 22:37:39.395 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:126)
2020-10-07 22:37:39.395 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:95)
2020-10-07 22:37:39.395 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:281)
2020-10-07 22:37:39.396 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:224)
2020-10-07 22:37:39.396 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:461)
2020-10-07 22:37:39.396 7247-7280/com.sample.apitest W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:127)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at com.sample.apitest.MainActivity$HitAPITask.doInBackground(MainActivity.kt:49)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at com.sample.apitest.MainActivity$HitAPITask.doInBackground(MainActivity.kt:39)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:333)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
2020-10-07 22:37:39.397 7247-7280/com.sample.apitest W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
2020-10-07 22:37:39.398 7247-7280/com.sample.apitest W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
2020-10-07 22:37:39.398 7247-7280/com.sample.apitest W/System.err:     at java.lang.Thread.run(Thread.java:764)

我该如何解决这个错误？

以下是代码：

安卓项目

emulator settings

AndroidManifest.xml

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

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

    <application
            android:networkSecurityConfig="@xml/network_security_config"
            android:usesCleartextTraffic="true"

            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"
            tools:ignore="GoogleAppIndexingWarning"
            tools:targetApi="n">
        <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>

网络安全配置.xml

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <domain-config cleartextTrafficPermitted="true">
        <domain includeSubdomains="true">localhost</domain>
    </domain-config>
</network-security-config>

MainActivity.kt

package com.sample.apitest

import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import org.json.JSONException
import org.json.JSONObject
import java.io.BufferedReader
import java.io.IOException
import java.io.InputStreamReader
import java.net.HttpURLConnection
import java.net.MalformedURLException
import java.net.URL

class MainActivity : AppCompatActivity() {

    var name: TextView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        name = findViewById(R.id.textView)
        val button = findViewById<Button>(R.id.button)

        button.setOnClickListener {
            println("checked")
            HitAPITask().execute("http://localhost:8000/api/name/")

        }
    }

    inner class HitAPITask : AsyncTask<String, String, String>() {

        override fun doInBackground(vararg params: String?): String? {
            var connection: HttpURLConnection? = null
            var reader: BufferedReader? = null
            val buffer: StringBuffer

            try {
                val url = URL(params[0])
                connection = url.openConnection() as HttpURLConnection
                connection.connect()

                val stream = connection.inputStream
                reader = BufferedReader(InputStreamReader(stream))
                buffer = StringBuffer()
                var line: String?
                while (true) {
                    line = reader.readLine()
                    if (line == null) {
                        break
                    }
                    buffer.append(line)
                }

                var jsonText = buffer.toString()

                val jsonObj = JSONObject(jsonText)
                val plant_name: String = jsonObj.getString("name")

                return plant_name
            } catch (e: MalformedURLException) {
                e.printStackTrace()
            } catch (e: IOException) {
                e.printStackTrace()
            } catch (e: JSONException) {
                e.printStackTrace()
            } finally {
                connection?.disconnect()
                try {
                    reader?.close()
                } catch (e: IOException) {
                    e.printStackTrace()
                }
            }
            return null
        }

        override fun onPostExecute(result: String?) {
            super.onPostExecute(result)
            if (result == null) return

            name!!.text = result
        }
    }
}

构建.gradle

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.sample.apitest"
        minSdkVersion 16
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:2.0.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Django Rest框架项目

项目/设置.py

    #...      

INSTALLED_APPS = [
    #...
    'corsheaders',
]

MIDDLEWARE = [
    #...
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.common.CommonMiddleware',
]

CORS_ORIGIN_WHITELIST = [
    'http://10.0.2.2:8000'
]

API端点

[ Method = GET ] http://127.0.0.1:8000/api/name/

    {
      "name": "myName.",
    }

安卓工作室：3.3.2

蟒蛇：3.7.5

django-cors-headers：2.4.0

djangorest框架：3.8.2

尝试打开cmd然后写入ipconfig在上面 之后你得到了你的本地IP地址然后尝试添加你的代码

例如，您从 cmd 获得 192.168.1.2，然后将其放入您的代码中，如下所示：

HitAPITask().execute("http://192.168.1.2/api/name/")