WRITE_EXTERNAL_STORAGE not working on lollipop eve

问题:

I'm trying to save images from the apps local data folders to external storage. My manifest contains the following (before the manifest's application tags):

<uses-sdk android:minSdkVersion="14" android:targetSdkVersion="23" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="18"/>

When I try the following

try {
        InputStream in = new FileInputStream(filePath);
        File outPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        File outFile = new File(outPath, "mypicture.jpg");


        //try fails at this line
        OutputStream out = new FileOutputStream(outFile);

        byte[] buf = new byte[1024];
        int len;

        while ((len = in.read(buf)) > 0) {
            out.write(buf, 0, len);
        }

        in.close();
        in = null;
        out.flush();
        out.close();
        out = null;
} catch (IOException e) {
    e.printStackTrace();
}

I get this error:

java.io.FileNotFoundException: /storage/emulated/0/Pictures/mypicture.jpg: open failed: EACCES (Permission denied)

I've also tried a slightly different output path instead:

 String sdCardPath = Environment.getExternalStorageDirectory() + "/MyFolder";
 new File(sdCardPath).mkdirs();
 File outFile = new File(sdCardPath, "mypicture.jpg");

but that gives me an error too:

java.io.FileNotFoundException: /storage/emulated/0/MyFolder/mypicture.jpg: open failed: ENOENT (No such file or directory)

The device is running Android 4.4.2, so shouldn't need to request permissions at runtime (as far as I'm aware it can't request them).

Is there something else that could be missing in order to allow saving a file to external storage?

回答1:

The cause of the issue was an external library pulled in via gradle which had its own manifest requesting <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="18">

My own manifest only worked if maxSdkVersion="18" was NOT included, and so the manifest merger adding that param caused this error. My solution was to change my own manifest to:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="23" tools:replace="android:maxSdkVersion" />

I assume that the maxSdkVersion="18" meant that any devices running SDK 19-22 could not have this permission (with 23+ being able to request it at runtime).

回答2:

It shoudn't be necessary, but try to add this permission in you Manifest.

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

Sometimes Android trolls us.

回答3:

try this:

 String root = Environment.getExternalStorageDirectory().toString();
File myDir = new File(root + "/MyFolder");    
myDir.mkdirs();
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String fname = "Image-" + n + ".jpg";

File file = new File (myDir, fname);
if (file.exists ()) file.delete (); 
file.createNewFile();
try {
       FileOutputStream out = new FileOutputStream(file);
       FileInputStream in = new FileInputStream(filePath);
        byte[] buf = new byte[1024];
        int len;

        while ((len = in.read(buf)) > 0) {
            out.write(buf, 0, len);
        }

        in.close();
        out.flush();
        out.close();

} catch (Exception e) {
       e.printStackTrace();
}

also add both read and write permission to the manifest

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

回答4:

In Android 6, you need to request permission at runtime. If you run on 4.4, still have that error, I think you have not create folder yet.

 String sdCardPath = Environment.getExternalStorageDirectory() + "/MyFolder";
 new File(sdCardPath) .mkdirs(); //create folders where write files
 File outFile = new File(sdCardPath, "mypicture.jpg");