让我告诉你第一件事你不能删除DCIM文件夹，因为它是一个系统文件夹。当你在手机上手动删除它时，它会删除该文件夹的内容，但不会删除DCIM文件夹。您可以通过以下方法删除其内容:

根据评论更新

File dir = new File(Environment.getExternalStorageDirectory()+"Dir_name_here"); 
if (dir.isDirectory()) 
{
    String[] children = dir.list();
    for (int i = 0; i < children.length; i++)
    {
       new File(dir, children[i]).delete();
    }
}

看到android.os。FileUtils，它隐藏在API 21上

public static boolean deleteContents(File dir) {
    File[] files = dir.listFiles();
    boolean success = true;
    if (files != null) {
        for (File file : files) {
            if (file.isDirectory()) {
                success &= deleteContents(file);
            }
            if (!file.delete()) {
                Log.w("Failed to delete " + file);
                success = false;
            }
        }
    }
    return success;
}

来源:https://android.googlesource.com/platform/frameworks/base/ + /主/核心/ java / android / os / FileUtils.java # 414

我知道的最安全的代码:

private boolean recursiveRemove(File file) {
    if(file == null  || !file.exists()) {
        return false;
    }

    if(file.isDirectory()) {
        File[] list = file.listFiles();

        if(list != null) {

            for(File item : list) {
                recursiveRemove(item);
            }

        }
    }

    if(file.exists()) {
        file.delete();
    }

    return !file.exists();
}

检查文件是否存在，处理空值，检查目录是否被实际删除

这是kotlin选项。它运行得很好。

fun executeDelete(context: Context, paths: List<String>): Int {
    return try {
        val files = paths.map { File(it) }
        val fileCommands = files.joinToString(separator = " ") {
            if (it.isDirectory) "'${it.absolutePath}/'" else "'${it.absolutePath}'"
        }
        val command = "rm -rf $fileCommands"
        val process = Runtime.getRuntime().exec(arrayOf("sh", "-c", command))
        val result = process.waitFor()
        if (result == 0) {
            context.rescanPaths(paths)
        }
        result
    } catch (e: Exception) {
        -1
    }
}

//避免在一行中多次调用，它可以删除整个文件夹内容

fun Context.rescanPaths(paths: List<String>, callback: (() -> Unit)? = null) {
if (paths.isEmpty()) {
    callback?.invoke()
    return
}

var cnt = paths.size
MediaScannerConnection.scanFile(applicationContext, paths.toTypedArray(), null) { _, _ ->
    if (--cnt == 0) {
        callback?.invoke()
    }
}
}

这里是一个非递归的实现，只是为了好玩:

/**
 * Deletes the given folder and all its files / subfolders.
 * Is not implemented in a recursive way. The "Recursively" in the name stems from the filesystem command
 * @param root The folder to delete recursively
 */
public static void deleteRecursively(final File root) {
    LinkedList<File> deletionQueue = new LinkedList<>();
    deletionQueue.add(root);

    while(!deletionQueue.isEmpty()) {
        final File toDelete = deletionQueue.removeFirst();
        final File[] children = toDelete.listFiles();
        if(children == null || children.length == 0) {
            // This is either a file or an empty directory -> deletion possible
            toDelete.delete();
        } else {
            // Add the children before the folder because they have to be deleted first
            deletionQueue.addAll(Arrays.asList(children));
            // Add the folder again because we can't delete it yet.
            deletionQueue.addLast(toDelete);
        }
    }
}

private static void deleteRecursive(File dir)
{
    //Log.d("DeleteRecursive", "DELETEPREVIOUS TOP" + dir.getPath());
    if (dir.isDirectory())
    {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++)
        {
            File temp = new File(dir, children[i]);
            deleteRecursive(temp);
        }

    }

    if (dir.delete() == false)
    {
        Log.d("DeleteRecursive", "DELETE FAIL");
    }
}