Android: unable to create a directory in default pictures folder

问题

This is the code i am using to create a folder in the default pictures folder:

File imagesFolder = new File(Environment.DIRECTORY_PICTURES, "/images");
if (!imagesFolder.exists()) {
Log.d("if imagesFolder exists - 1", "False");
imagesFolder.mkdirs();
} else {
Log.d("if imagesFolder exists - 1", "True");
}
if (!imagesFolder.exists()) {
Log.d("if imagesFolder exists - 2", "False");
imagesFolder.mkdirs();
} else {
Log.d("if imagesFolder exists - 2", "True");
}

in log i am getting:

False

False

for the 1st time the directory is not present, hence False but then immediately i am creating it using mkdirs(), hence i expect the 2nd log to be True but even that is False and my application crashed because of NullPointerException in the later part of the code

Please help

Thank You

回答1:

You are using Environment.DIRECTORY_PICTURES the wrong way. It's just a String constant like "Pictures" but not a path. You need to get the path via Environment.getExternalStoragePublicDirectory(string)

File pictureFolder = Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES
        );
File imagesFolder = new File(pictureFolder, "images");
// etc

回答2:

To generate a folder at first you need to add permission at AndroidMinifest.xml

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

Now call following method to create a new folder with in which Directory you want to create your folder(this name should exist in Environment. list) and your folder name.

File outputDirectory = GetPhotoDirectory(Environment.DIRECTORY_PICTURES, "YourFolder");

Generate your folder by this method

public static File GetDirectory(String inWhichFolder, String yourFolderName ) {
    File outputDirectory = null;

    String externalStorageState = Environment.getExternalStorageState();
    if (externalStorageState.equals(Environment.MEDIA_MOUNTED)) {

        File pictureDirectory = Environment.getExternalStoragePublicDirectory(inWhichFolder);

        outputDirectory = new File(pictureDirectory, yourFolderName);
        if (!outputDirectory.exists()) {
            if (!outputDirectory.mkdirs()) {
                Log.e(LogHelper.LogTag, "Failed to create directory: " + outputDirectory.getAbsolutePath());
                outputDirectory = null;
            }
        }
    }
    return outputDirectory;
}

If you want to create a file under your newly created folder then you can use below code

public static Uri GenerateTimeStampPhotoFileUri(File outputDirectory, String fileName){
    Uri photoFileUri = null;

    if(outputDirectory!=null) {
        File photoFile = new File(outputDirectory, fileName);
        photoFileUri = Uri.fromFile(photoFile);
    }
    return photoFileUri;
}

Call to create a file after creating the folder with File Directory. It will return your file Uri

Uri fileUri = GenerateTimeStampPhotoFileUri(outputDirectory, fileName);

来源：https://stackoverflow.com/questions/12598567/android-unable-to-create-a-directory-in-default-pictures-folder

标签

android

mkdirs