java - 创建一个未索引的文件夹导致 IOException

Question

我想创建一个 App 应该用来保存其所有文件的主文件夹。如果目录已经存在，则应忽略文件夹创建

这是我的尝试

public static void createFolder() {
        String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
        String baseAppDir = "MyAppFolder";
        String fileHider = ".nomedia";
        File mainDirectory = new File(baseDir + File.separator + baseAppDir);

        if (!(mainDirectory.exists())) {
            mainDirectory.mkdirs();

            File outputFile = new File(mainDirectory, fileHider);

            try {
                FileOutputStream fos = new FileOutputStream(outputFile);
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }

不幸的是不起作用，得到这个错误并且没有创建文件夹

12-07 17:16:01.127: W/System.err(1855): java.io.FileNotFoundException: /storage/sdcard/MyAppFolder/.nomedia: open failed: ENOENT (No such file or directory)
12-07 17:16:01.167: W/System.err(1855):     at libcore.io.IoBridge.open(IoBridge.java:409)
12-07 17:16:01.167: W/System.err(1855):     at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
12-07 17:16:01.177: W/System.err(1855):     at java.io.FileOutputStream.<init>(FileOutputStream.java:73)
  ....

我的 list

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="it.myapp.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="18" />

    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_GPS" />
    <uses-permission android:name="android.permission.ACCESS_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.FLASHLIGHT" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.SEND_SMS" />
    <uses-permission android:name="android.permission.CALL_PHONE" />
    <uses-permission android:name="android.permission.READ_CONTACTS" />
    <uses-permission android:name="android.permission.READ_CALENDAR" />
    <uses-permission android:name="android.permission.VIBRATE" />
    <uses-permission android:name="android.permission.USE_CREDENTIALS" />
    <uses-permission android:name="android.permission.WRITE_CALENDAR" />
    <uses-permission android:name="android.permission.WRITE_SOCIAL_STREAM" />
    <uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />


    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="it.myapp.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

编辑

在主 Activity 中，如果我尝试在 createFolder() 上使用带有 printstacktrace 的 try catch，我会收到此错误日志

12-07 18:28:26.090: W/dalvikvm(3335): Exception Ljava/lang/NullPointerException; thrown while initializing Lit/myapp/test/FileArchiveManager;
12-07 18:28:26.210: W/System.err(3335): java.lang.ExceptionInInitializerError
12-07 18:28:26.220: W/System.err(3335):     at it.myapp.test.MainActivity.onCreate(MainActivity.java:19)
12-07 18:28:26.220: W/System.err(3335):     at android.app.Activity.performCreate(Activity.java:5243)
12-07 18:28:26.230: W/System.err(3335):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
12-07 18:28:26.240: W/System.err(3335):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
12-07 18:28:26.240: W/System.err(3335):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
12-07 18:28:26.240: W/System.err(3335):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
12-07 18:28:26.250: W/System.err(3335):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
12-07 18:28:26.250: W/System.err(3335):     at android.os.Handler.dispatchMessage(Handler.java:102)
12-07 18:28:26.260: W/System.err(3335):     at android.os.Looper.loop(Looper.java:137)
12-07 18:28:26.260: W/System.err(3335):     at android.app.ActivityThread.main(ActivityThread.java:4998)
12-07 18:28:26.280: W/System.err(3335):     at java.lang.reflect.Method.invokeNative(Native Method)
12-07 18:28:26.280: W/System.err(3335):     at java.lang.reflect.Method.invoke(Method.java:515)
12-07 18:28:26.280: W/System.err(3335):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
12-07 18:28:26.290: W/System.err(3335):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
12-07 18:28:26.290: W/System.err(3335):     at dalvik.system.NativeStart.main(Native Method)
12-07 18:28:26.300: W/System.err(3335): Caused by: java.lang.NullPointerException: name == null
12-07 18:28:26.310: W/System.err(3335):     at java.io.File.<init>(File.java:150)
12-07 18:28:26.310: W/System.err(3335):     at java.io.File.<init>(File.java:124)
12-07 18:28:26.320: W/System.err(3335):     at android.os.Environment.buildPath(Environment.java:812)
12-07 18:28:26.320: W/System.err(3335):     at android.os.Environment.buildPaths(Environment.java:796)
12-07 18:28:26.330: W/System.err(3335):     at android.os.Environment$UserEnvironment.buildExternalStoragePublicDirs(Environment.java:199)
12-07 18:28:26.330: W/System.err(3335):     at android.os.Environment.getExternalStoragePublicDirectory(Environment.java:538)
12-07 18:28:26.340: W/System.err(3335):     at it.myapp.test.utility.FileArchiveManager.<clinit>(FileArchiveManager.java:17)
12-07 18:28:26.340: W/System.err(3335):     ... 15 more

Answer 1

添加WRITE_EXTERNAL_STORAGE 权限。如果您的应用可以写入 getExternalFilesDir()，但不能写入外部存储的其他地方，这应该意味着:

1. 您正在 Android 4.4+ 上进行测试，并且

2. 您没有WRITE_EXTERNAL_STORAGE权限