Java.io.IOException：即使请求了权限，仍然被拒绝访问。

Question

Java.io.IOException：即使请求了权限，仍然被拒绝访问。

javaandroidandroid-permissionsandroid-file

3

我在某些设备上（包括api 23之前和之后的设备）遇到了异常情况：

Non-fatal Exception: java.io.IOException
Permission denied

imageFile.createNewFile();

在我的AndroidManifest.xml文件中，我已经添加了权限声明：

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

在授予Manifest.permission.WRITE_EXTERNAL_STORAGE权限（api 23+）后才调用它。

String[] perms = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
if (EasyPermissions.hasPermissions(getActivity(), perms)) {
// Call it
} else {
   EasyPermissions.requestPermissions(this,
           getString(R.string.please_grant_permission),
           RC_SAVE,
           perms);
}

这是我的代码：

 File downloadsFolder = Environment.getExternalStoragePublicDirectory(
         Environment.DIRECTORY_DOWNLOADS);
 if (!downloadsFolder.exists()) {
     downloadsFolder.mkdir();
 }

 File imageFile = new File(downloadsFolder, fileName);

 if (!imageFile.exists()) {
     try {
         imageFile.createNewFile(); // Error on some devices
...

统计数据：https://imgur.com/B9noOb6 统计数据：https://imgur.com/DsoeO2B

- Yevhenii

如果用户拒绝权限，您将如何处理23+上的情况？在清单上声明是不够的。 - hemen

https://dev59.com/3KDia4cB1Zd3GeqPI8N7 - John Joe

请查看此示例 https://stackoverflow.com/questions/55816746/filedownloader-at-the-android-it-is-showing-no-errors-but-the-download-does-not/56313094#56313094 - Zack Dawood

3个回答

1

以下是适用于minSdkVersion 15和targetSdkVersion 28的解决方案。

基于您的问题，以下是可行的代码片段：

图片下载成功快照。

代码布局视图

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.zackdawood.albummanager"
        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'
}

strings.xml

<resources>
    <string name="app_name">AlbumManager</string>
    <string name="write_button">Write Image</string>
    <string name="read_button">Read Image</string>
    <string name="request_access">Request Access</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">upload.wikimedia.org</domain>
</domain-config>
</network-security-config>

GenericFileProvider.java

package com.zackdawood.albummanager;

import android.support.v4.content.FileProvider;

public class GenericFileProvider extends FileProvider {
}

FileDownloader.java

package com.zackdawood.albummanager;

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.albummanager;

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,
            android.Manifest.permission.INTERNET};

    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);
        ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);
        Log.v(TAG, "onCreate() Method invoked ");
    }

    public void write(View view) {
        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 {

            new DownloadFile().execute("https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Adler.jpg/547px-Adler.jpg", "lab_result_2019-04-06.jpg");


        }
    }

    public void read(View view) {
        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 folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);

            File directory = new File(folder + "/TB System");
            File imgFile = new File(directory, "lab_result_2019-04-06.jpg");

            Log.v(TAG, "view() Method imgfile " + imgFile.getAbsolutePath());

            Uri path = FileProvider.getUriForFile(this, BuildConfig.APPLICATION_ID + ".fileprovider", imgFile);


            Log.v(TAG, "view() Method path " + path);

            Intent imageIntent = new Intent(Intent.ACTION_VIEW);
            imageIntent.setDataAndType(path, "image/*");
            imageIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            imageIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

            try {
                startActivity(imageIntent);
            } catch (ActivityNotFoundException e) {
                Toast.makeText(MainActivity.this, "No Application available to view Image", Toast.LENGTH_SHORT).show();
            }

        }
    }

    public void request(View view) {
        ActivityCompat.requestPermissions(MainActivity.this, PERMISSIONS, 112);

    }

    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
            File folder = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);

            File directory = new File(folder + "/TB System");
            if (!directory.exists()) {
                directory.mkdir();
                Log.v(TAG, "doInBackground() Method Directory Created ");

            }

            File imgFile = new File(directory, fileName);
            Log.v(TAG, "doInBackground() imgFile invoked " + imgFile.getAbsolutePath());
            Log.v(TAG, "doInBackground() imgFile invoked " + imgFile.getAbsoluteFile());

            try {
                imgFile.createNewFile();
                Log.v(TAG, "doInBackground() file created" + imgFile);

            } catch (IOException e) {
                e.printStackTrace();
                Log.e(TAG, "doInBackground() error" + e.getMessage());
                Log.e(TAG, "doInBackground() error" + e.getStackTrace());


            }
            FileDownloader.downloadFile(fileUrl, imgFile);
            Log.v(TAG, "doInBackground() file download completed");

            return null;
        }
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <LinearLayout
        android:layout_width="395dp"
        android:layout_height="715dp"
        android:orientation="vertical"
        tools:layout_editor_absoluteX="8dp"
        tools:layout_editor_absoluteY="8dp">

        <Button
            android:id="@+id/button2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/write_button"
            android:onClick="write"/>

        <Button
            android:id="@+id/button3"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/read_button"
            android:onClick="read"/>

        <Button
            android:id="@+id/button4"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/request_access"
            android:onClick="request"/>
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

AndroidManifest.xml

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

    <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>

应用程序启动器屏幕。

读取图像输出

- Zack Dawood

0

   File imageFile = new File(downloadsFolder, fileName);
   imageFile.createNewFile();  // <<<< throws exception

在更近期的 Android 版本中，使用 File API 的限制越来越多。

在获得写入权限后，您应该使用 Storage Access Framework 通过 Intent.ACTION_CREATE_DOCUMENT 和 Outputstream 来代替 `File-API-functions。

    String proposedFileName = "MyDownloadedDocument.jpg";

    // DocumentsContract#EXTRA_INITIAL_URI
    Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT)
            .setType(IMAGE_JPEG_MIME)
            .addCategory(Intent.CATEGORY_OPENABLE)
            .putExtra(Intent.EXTRA_TITLE, proposedFileName)
            .putExtra(DocumentsContract.EXTRA_PROMPT, getString(R.string.label_save_as))
            .setFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                    | Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                    | Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION)
            ;

    startActivityForResult(intent, folderpickerCode);

在onActivityResult中，您可以进行编写。

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_SAVE_PICTURE) {
        if (resultCode == RESULT_OK) {
            final Uri outUri = (data == null) ? null : data.getData();
            OutputStream outStream = getContentResolver().openOutputStream(outUri, "w");
            // write to outStream
            outStream.close();
        } else finish();
        return;
    }

    super.onActivityResult(requestCode, resultCode, data);
}

- k3b

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Ramesh Choudhary · Accepted Answer

如果你的目标API级别是>=29，则由于新的存储更新，你可能会遇到这些错误。
解决方案适用于API级别29
在你的应用程序清单文件中将requestLegacyExternalStorage设置为true。

<application android:requestLegacyExternalStorage="true">