这个问题总是初始化的 num = 0 如果 file 存在,它保存 file0.jpg 而不是检查 file0.jpg 存在吗? 所以,代码工作。您应该检查直到可用:

int num = 0;
String save = at.getText().toString() + ".jpg";
File file = new File(myDir, save);
while(file.exists()) {
    save = at.getText().toString() + (num++) +".jpg";
    file = new File(myDir, save); 
}

试试这个:

File file = new File(myDir, at.getText().toString() + ".jpg"); 

for (int num = 0; file.exists(); num++) {
    file = new File(myDir, at.getText().toString() + num + ".jpg");
}

// Now save/use your file here

除了第一个答案,我还做了一些修改

private File getUniqueFileName(String folderName, String searchedFilename) {
        int num = 1;
        String extension = getExtension(searchedFilename);
        String filename = searchedFilename.substring(0, searchedFilename.lastIndexOf("."));
        File file = new File(folderName, searchedFilename);
        while (file.exists()) {
            searchedFilename = filename + "("+(num++)+")"+extension;
            file = new File(folderName, searchedFilename);
        }
        return file;
    }

int i = 0;
String save = at.getText().toString();
String filename = save +".jpg";
File f = new File(filename);
while (f.exists()) {
    i++;
    filename =save+ Integer.toString(i)+".jpg";
    f = new File(filename);
}
f.createNewFile();

您可以使用 do while 环

下面是一个使用Java 7中引入的新NIO路径API的示例

Path candidate = null;
int counter = 0;
do {
    candidate = Paths.get(String.format("%s-%d",
            path.toString(), ++counter));
} while (Files.exists(candidate));
Files.createFile(candidate);

@Tejas Trivedi 的答案使它像windows一样工作,当您碰巧下载了同一个文件多次

// This function will iteratively to find a unique file name to use when given a file: example (###).txt
//  More or less how windows will save a new file when one already exists example.txt becomes example (1).txt
//  if example.txt already exists
private File getUniqueFileName(File file) {
    File originalFile = file;
    try {
        while (file.exists()) {
            String newFileName = file.getName();
            String baseName = newFileName.substring(0, newFileName.lastIndexOf("."));
            String extension = getExtension(newFileName);

            Pattern pattern = Pattern.compile("( \\(\\d+\\))\\."); // Find ' (###).' in the file name, if it exists
            Matcher matcher = pattern.matcher(newFileName);

            String strDigits = "";
            if (matcher.find()) {
                baseName = baseName.substring(0, matcher.start(0)); // remove the (###)
                strDigits = matcher.group(0); // grab the ### we'll want to increment
                strDigits = strDigits.substring(strDigits.indexOf("(") + 1, strDigits.lastIndexOf(")")); // strip off the ' (' and ').' from the match
                // increment the found digit and convert it back to a string
                int count = Integer.parseInt(strDigits);
                strDigits = Integer.toString(count + 1);
            } else {
                strDigits = "1"; // if there is no (###) match then start with 1
            }
            file = new File(file.getParent() + "/" + baseName + " (" + strDigits + ")" + extension); // put the pieces back together
        }
        return file;
    } catch (Error e) {
        return originalFile; // Just overwrite the original file at this point...
    }

}

private String getExtension(String name) {
    return name.substring(name.lastIndexOf("."));
}

使命感 getUniqueFileName(new File('/dir/example.txt') “当”是一个例子。生成新文件时,txt已存在,目标为“/dir/example(1)”。txt'如果它也存在,它会一直递增括号之间的数字,直到找到唯一的文件,如果发生错误,它只会给出原始文件名。

我希望这能帮助那些需要在Android或其他平台上用Java生成唯一文件的人。

科特林版本:

private fun checkAndRenameIfExists(name: String): File {
    var filename = name
    val extension = "pdf"
    val root = Environment.getExternalStorageDirectory().absolutePath
    var file = File(root, "$filename.$extension")
    var n = 0
    while (file.exists()) {
        n += 1
        filename = "$name($n)"
        file = File(root, appDirectoryName + File.separator + "$filename.$extension")
    }
    return file
}

这是我用来处理这个案例的解决方案。适用于文件夹和文件。

var destination = File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "MyFolder")
 if (!destination.exists()){
     destination.mkdirs()
 } else {
     val numberOfFileAlreadyExist =
         destination.listFiles().filter { it.name.startsWith("MyFolder") }.size
     destination = File(
         Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
         "MyFolder(${numberOfFileAlreadyExist + 1})"
     )
     destination.mkdirs()
 }

祝你今天愉快!

另一个简单的逻辑解决方案是使用apachecommons.IO获取目录下的唯一文件名 WildcardFileFilter 要匹配文件名并获取给定名称的存在数量,请递增计数器。

public static String getUniqueFileName(String directory, String fileName){
  String fName = fileName.substring(0, fileName.lastIndexOf("."));
  Collection<File> listFiles = FileUtils.listFiles(new File(directory), new WildcardFileFilter(fName+"*", IOCase.INSENSITIVE), DirectoryFileFilter.DIRECTORY);
  if(listFiles.isEmpty()){
    return fName;
  }
  return fName.concat(" ("+listFiles.size()+")");
}

帮助别人。。

private File getFileName(File file) {
        if (file.exists()){
            String newFileName = file.getName();
            String simpleName = file.getName().substring(0,newFileName.indexOf("."));
            String strDigit="";

            try {
                simpleName = (Integer.parseInt(simpleName)+1+"");
                File newFile = new File(file.getParent()+"/"+simpleName+getExtension(file.getName()));
                return getFileName(newFile);
            }catch (Exception e){}

            for (int i=simpleName.length()-1;i>=0;i--){
                if (!Character.isDigit(simpleName.charAt(i))){
                    strDigit = simpleName.substring(i+1);
                    simpleName = simpleName.substring(0,i+1);
                    break;
                }
            }

            if (strDigit.length()>0){
                simpleName = simpleName+(Integer.parseInt(strDigit)+1);
            }else {
                simpleName+="1";
            }

            File newFile = new File(file.getParent()+"/"+simpleName+getExtension(file.getName()));
            return getFileName(newFile);
        }
        return file;
    }

private String getExtension(String name) {
        return name.substring(name.lastIndexOf("."));
}