android - FileNotFoundException :/storage/sdcard0/Myfile. txt:打开失败:EACCES(权限被拒绝)

Question

我正在尝试在应用程序外部的外部存储文件夹中写入文件。我在 list 中添加了 WRITE_EXTERNAL_STORAGE 权限。

Stack Overflow 中也有类似的错误，但在尝试解决方案后(正如您将在我的下一行中看到的那样)，我遇到了同样的错误。

我在带有 Nexus 5X API 27 oreo rom 的模拟器和带有 Android 4.4 的华为真机上都试过了。

在两个设备中我都有同样的错误:

FileNotFoundException: /storage/sdcard0/Myfile.txt: open failed: EACCES (Permission denied)

这是我的代码:

    String content = "hello world";
    File file;
    FileOutputStream outputStream;
    try {
        file = new File(Environment.getExternalStorageDirectory().getAbsolutePath(), "MyFile.txt");
        outputStream = new FileOutputStream(file);
        outputStream.write(content.getBytes());
        outputStream.close();
    } catch (IOException e) {
        Toast.makeText(context, e.toString(), Toast.LENGTH_LONG).show();
        e.printStackTrace();
    }

list :

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

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.KILL_BACKGROUND_PROCESSES" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="18" />

<uses-feature
    android:name="android.hardware.camera.autofocus"
    android:required="false" />
<uses-feature
    android:name="android.hardware.camera"
    android:required="false" />
<uses-feature
    android:name="android.hardware.telephony"
    android:required="false" />
<uses-feature
    android:name="android.hardware.location"
    android:required="false" />
<uses-feature
    android:name="android.hardware.location.gps"
    android:required="false" />

<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=".activities.Activity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

Answer 1

对于 Android >=6.0 的设备，您必须 request permissions at runtime

对于android 4，apprently添加android:maxSdkVersion="18"会产生这个异常，尝试移除它

编辑:对于 Android 4.4 及更高版本，您不 WRITE_EXTERNAL_STORAGE IF ONLY 您想要写入外部存储，来自文档:

beginning with Android 4.4 (API level 19), it's no longer necessary for your app to request the WRITE_EXTERNAL_STORAGE permission when your app wants to write to its own application-specific directories on external storage (the directories provided by getExternalFilesDir())

否则，对于 android < 4.4，您需要为自己的应用程序特定目录添加 android:maxSdkVersion="18"外部存储