如何解决如何解决错误`java.net.ConnectException：无法连接到localhost / 127.0.0.1：8000`
我目前正在使用android-studio和Kotlin开发应用程序，以及使用django-rest-framework的API系统。
我想使用Android模拟器访问本地服务器127.0.0.1，以从API方法中获取一些价值。
我检查了堆栈溢出站点和其他站点中的一些问题，并设置了代码以引用某些文章，例如在AndroidManifest.xml中添加一些代码，制作network_security_config.xml，更改以下内容的代理Android emulator，并在Django rest framework项目中更改一些代码。
即使我在本地服务器上命中一个端点，我也会遇到类似以下的错误代码：
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)
如何解决此错误？
以下是代码：
Android项目
模拟器设置
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>
network_security_config.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
}
}
}
build.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
project / settings.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.",}
android-studio：3.3.2
python：3.7.5
django-cors-headers：2.4.0
djangorestframework：3.8.2
解决方法
尝试打开cmd，然后在上面写上ipconfig
之后，您获得了本地IP地址，然后尝试输入代码
例如，您从cmd中获取了192.168.1.2，然后将其放入代码中，如下所示：
HitAPITask().execute("http://192.168.1.2/api/name/")
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