android上的FileDownloader它没有显示错误，但下载没有开始
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【中文标题】android上的FileDownloader它没有显示错误，但下载没有开始【英文标题】：FileDownloader at the android it is showing no errors but the download does not start 【发布时间】：2019-09-12 23:10:12 【问题描述】：我正在尝试下载一个简单的.pdf 文件，我尝试过日志但没有错误，什么也没有。我尝试调试，但直到昨天它仍然像魅力一样工作，但今天不是，我没有在这部分代码中进行任何更改。
我基于这个问题和答案在 SO。
https://***.com/a/24748227/9560126
下面是代码。
有时在 LogCat 上它只向我显示类似这样的消息。
com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:251) FileDownloader.downloadFile
在这行代码。
inputStream = urlConnection.getInputStream();
Url连接代码。
urlConnection.getResponseCode()
它正在返回405
MainActivity.java
String newEntry = "http://www.axmag.com/download/pdfurl-guide.pdf";
new DownloadFile().execute(newEntry, "maven.pdf");
private static class DownloadFile extends AsyncTask<String, Void, Void>
@Override
protected Void doInBackground(String... strings)
String fileUrl = strings[0]; // -> http://maven.apache.org/maven-1.x/maven.pdf
String fileName = strings[1]; // -> maven.pdf
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File folder = new File(extStorageDirectory, "testthreepdf");
folder.mkdir();
File pdfFile = new File(folder, fileName);
try
pdfFile.createNewFile();
catch (IOException e)
e.printStackTrace();
FileDownloader.downloadFile(fileUrl, pdfFile);
return null;
FileDownloader.java
public class FileDownloader
private static final int MEGABYTE = 1024 * 1024;
public static void downloadFile(String fileUrl, File directory)
try
URL url = new URL(fileUrl);
HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.connect();
InputStream inputStream;
inputStream = urlConnection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream(directory);
int totalSize = urlConnection.getContentLength();
byte[] buffer = new byte[MEGABYTE];
int bufferLength = 0;
while((bufferLength = inputStream.read(buffer))>0 )
fileOutputStream.write(buffer, 0, bufferLength);
fileOutputStream.close();
catch (FileNotFoundException e)
e.printStackTrace();
catch (MalformedURLException e)
e.printStackTrace();
catch (IOException e)
e.printStackTrace();
AndroidManifest.XML
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
【问题讨论】：
【参考方案1】：解决方案如下，这应该可以解决您的问题。与 API 28 Android Permissions 相关的更改使您的旧代码过时了
访问屏幕
输出
代码快照
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.zackdawood">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
<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"
android:networkSecurityConfig="@xml/network_security_config">
<provider
android:name=".GenericFileProvider"
android:authorities="$applicationId.fileprovider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/external_files"/>
</provider>
<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>
GenericFileProvider.java
package com.zackdawood;
import android.support.v4.content.FileProvider;
public class GenericFileProvider extends FileProvider
FileDownloader.java
package com.zackdawood;
import android.util.Log;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class FileDownloader
private static final String TAG = "FileDownloader";
private static final int MEGABYTE = 1024 * 1024;
public static void downloadFile(String fileUrl, File directory)
try
Log.v(TAG, "downloadFile() invoked ");
Log.v(TAG, "downloadFile() fileUrl " + fileUrl);
Log.v(TAG, "downloadFile() directory " + directory);
URL url = new URL(fileUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream(directory);
int totalSize = urlConnection.getContentLength();
byte[] buffer = new byte[MEGABYTE];
int bufferLength = 0;
while ((bufferLength = inputStream.read(buffer)) > 0)
fileOutputStream.write(buffer, 0, bufferLength);
fileOutputStream.close();
Log.v(TAG, "downloadFile() completed ");
catch (FileNotFoundException e)
e.printStackTrace();
Log.e(TAG, "downloadFile() error" + e.getMessage());
Log.e(TAG, "downloadFile() error" + e.getStackTrace());
catch (MalformedURLException e)
e.printStackTrace();
Log.e(TAG, "downloadFile() error" + e.getMessage());
Log.e(TAG, "downloadFile() error" + e.getStackTrace());
catch (IOException e)
e.printStackTrace();
Log.e(TAG, "downloadFile() error" + e.getMessage());
Log.e(TAG, "downloadFile() error" + e.getStackTrace());
MainActivity.java
package com.zackdawood;
import android.content.ActivityNotFoundException;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
import java.io.File;
import java.io.IOException;
public class MainActivity extends AppCompatActivity
private static final String TAG = "MainActivity";
private static final String[] PERMISSIONS = android.Manifest.permission.READ_EXTERNAL_STORAGE, android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
private static boolean hasPermissions(Context context, String... permissions)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null)
for (String permission : permissions)
if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED)
return false;
return true;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.v(TAG, "onCreate() Method invoked ");
ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);
public void request(View view)
ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);
public void view(View view)
Log.v(TAG, "view() Method invoked ");
if (!hasPermissions(MainActivity.this, PERMISSIONS))
Log.v(TAG, "download() Method DON'T HAVE PERMISSIONS ");
Toast t = Toast.makeText(getApplicationContext(), "You don't have read access !", Toast.LENGTH_LONG);
t.show();
else
File d = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS); // -> filename = maven.pdf
File pdfFile = new File(d, "maven.pdf");
Log.v(TAG, "view() Method pdfFile " + pdfFile.getAbsolutePath());
Uri path = FileProvider.getUriForFile(this, BuildConfig.APPLICATION_ID + ".fileprovider", pdfFile);
Log.v(TAG, "view() Method path " + path);
Intent pdfIntent = new Intent(Intent.ACTION_VIEW);
pdfIntent.setDataAndType(path, "application/pdf");
pdfIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
pdfIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
try
startActivity(pdfIntent);
catch (ActivityNotFoundException e)
Toast.makeText(MainActivity.this, "No Application available to view PDF", Toast.LENGTH_SHORT).show();
Log.v(TAG, "view() Method completed ");
public void download(View view)
Log.v(TAG, "download() Method invoked ");
if (!hasPermissions(MainActivity.this, PERMISSIONS))
Log.v(TAG, "download() Method DON'T HAVE PERMISSIONS ");
Toast t = Toast.makeText(getApplicationContext(), "You don't have write access !", Toast.LENGTH_LONG);
t.show();
else
Log.v(TAG, "download() Method HAVE PERMISSIONS ");
//new DownloadFile().execute("http://maven.apache.org/maven-1.x/maven.pdf", "maven.pdf");
new DownloadFile().execute("http://www.axmag.com/download/pdfurl-guide.pdf", "maven.pdf");
Log.v(TAG, "download() Method completed ");
private class DownloadFile extends AsyncTask<String, Void, Void>
@Override
protected Void doInBackground(String... strings)
Log.v(TAG, "doInBackground() Method invoked ");
String fileUrl = strings[0]; // -> http://maven.apache.org/maven-1.x/maven.pdf
String fileName = strings[1]; // -> maven.pdf
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
File pdfFile = new File(folder, fileName);
Log.v(TAG, "doInBackground() pdfFile invoked " + pdfFile.getAbsolutePath());
Log.v(TAG, "doInBackground() pdfFile invoked " + pdfFile.getAbsoluteFile());
try
pdfFile.createNewFile();
Log.v(TAG, "doInBackground() file created" + pdfFile);
catch (IOException e)
e.printStackTrace();
Log.e(TAG, "doInBackground() error" + e.getMessage());
Log.e(TAG, "doInBackground() error" + e.getStackTrace());
FileDownloader.downloadFile(fileUrl, pdfFile);
Log.v(TAG, "doInBackground() file download completed");
return null;
字符串.xml
<resources>
<string name="app_name">DemoInternalDownload</string>
<string name="action_settings">Settings</string>
<string name="file_view">File View</string>
<string name="file_download">File Download</string>
<string name="file_request">Request Access Again</string>
</resources>
external_files.xml
<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
<external-path name="external_files" path="."/>
</paths>
network_security_config.xml
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="true">
<domain includeSubdomains="true">maven.apache.org</domain>
<domain includeSubdomains="true">www.axmag.com</domain>
</domain-config>
</network-security-config>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_
tools:context=".MainActivity">
<LinearLayout
android:layout_
android:layout_
android:orientation="vertical">
<Button
android:id="@+id/button3"
android:layout_
android:layout_
android:layout_marginTop="200px"
android:onClick="download"
android:text="@string/file_download" />
<Button
android:id="@+id/button4"
android:layout_
android:layout_
android:layout_marginTop="200px"
android:onClick="view"
android:text="@string/file_view" />
<Button
android:id="@+id/button5"
android:layout_
android:layout_
android:layout_marginTop="200px"
android:onClick="request"
android:text="@string/file_request" />
</LinearLayout>
</android.support.design.widget.CoordinatorLayout>
build.gradle
apply plugin: 'com.android.application'
android
compileSdkVersion 28
defaultConfig
applicationId "com.zackdawood"
minSdkVersion 15
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 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
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'
【讨论】：
download(View view)方法从来没有被调用过，我还在学习android，请大家帮忙 @XavitojCheema 如果您单击 FileView 按钮，则将调用 View 方法。 android:onClick 属性触发事件。 谢谢，我确实跳过了用 XML 文件编写的部分。 @ZackDawood 我应该怎么做才能允许所有http url？
类似的，我尝试过 react-native，使用 rn-fetch-blob，但似乎不起作用以上是关于android上的FileDownloader它没有显示错误，但下载没有开始的主要内容，如果未能解决你的问题，请参考以下文章