我使用下面的code上传文件到Dropbox的。但我想检查文件上的Dropbox已经存在，以避免重复。所以，我怎么能检查文件是否已经存在或不？由于我是新来的Andr​​oid，我不知道现在该做什么

 公共类UploadFileToDropbox扩展的AsyncTask＆LT;虚空，虚空，布尔＆GT;
{

    私人DropboxAPI＆LT;＆GT; Dropbox的;
    私人字符串路径;
    私人上下文的背景下;

    公共UploadFileToDropbox（上下文的背景下，DropboxAPI＆LT;＆GT;的Dropbox，
                               字符串路径）{
        this.context = context.getApplicationContext（）;
        this.dropbox =保管箱;
        this.path =路径;
    }

    @覆盖
    保护布尔doInBackground（空... PARAMS）{
        最终文件TEMPDIR = context.getCacheDir（）;
        文件临时文件;
        FileWriter的FR;
        尝试 {
            TEMPFILE = File.createTempFile（文件，名.txt，TEMPDIR）;
            FR =新的FileWriter（临时文件）;
            fr.write（测试文件上传使用Dropbox的API为Android）;
            fr.close（）;

            的FileInputStream的FileInputStream =新的FileInputStream（临时文件）;
            dropbox.putFile（路径+为sample.txt的FileInputStream，
                    tempFile.length（），NULL，NULL）;
            tempFile.delete（）;
            返回true;
        }赶上（IOException异常E）{
            e.printStackTrace（）;
        }赶上（DropboxException E）{
            e.printStackTrace（）;
        }
        返回false;
    }

    @覆盖
    保护无效onPostExecute（布尔结果）{
        如果（结果）{
            Toast.makeText（背景下，文件上传成功！，
                    Toast.LENGTH_LONG）.show（）;
        } 其他 {
            Toast.makeText（背景下，无法上传文件，Toast.LENGTH_LONG）
                    。显示（）;
        }
    }
}
 

解决方案

 私人无效loadFiles（最后弦乐目录）{
        新的Thread（）{
            @覆盖
            公共无效的run（）{

                字符串的mpath =目录;
                进入direntEx = NULL;
                尝试 {
                    direntEx = mApi.metadata（的mpath，1000，空，真，空）;
                }赶上（DropboxException E）{
                    e.printStackTrace（）;
                }

                如果（direntEx.contents.size（）！= 0）{
                    对于（输入ENT：direntEx.contents）{
                        字符串名称= ent.fileName（）;
                          / *这里比较文件* /

                   }
                 }

                super.run（）;
            }

        }。开始（）;

    }
 

I am using following code to upload a file to Dropbox. But I want to check if the file exists on Dropbox already, to avoid duplications. So how can I check if a file already exists or not? As I am new to Android, I don't know what to do now

public class UploadFileToDropbox extends AsyncTask<Void, Void, Boolean>
{

    private DropboxAPI<?> dropbox;
    private String path;
    private Context context;

    public UploadFileToDropbox(Context context, DropboxAPI<?> dropbox,
                               String path) {
        this.context = context.getApplicationContext();
        this.dropbox = dropbox;
        this.path = path;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        final File tempDir = context.getCacheDir();
        File tempFile;
        FileWriter fr;
        try {
            tempFile = File.createTempFile("file", ".txt", tempDir);
            fr = new FileWriter(tempFile);
            fr.write("Test file uploaded using Dropbox API for Android");
            fr.close();

            FileInputStream fileInputStream = new FileInputStream(tempFile);
            dropbox.putFile(path + "sample.txt", fileInputStream,
                    tempFile.length(), null, null);
            tempFile.delete();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
        } catch (DropboxException e) {
            e.printStackTrace();
        }
        return false;
    }

    @Override
    protected void onPostExecute(Boolean result) {
        if (result) {
            Toast.makeText(context, "File Uploaded Successfully!",
                    Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(context, "Failed to upload file", Toast.LENGTH_LONG)
                    .show();
        }
    }
}

private void loadFiles(final String directory) {
        new Thread() {
            @Override
            public void run() {

                String mPath = directory;
                Entry direntEx = null;
                try {
                    direntEx = mApi.metadata(mPath, 1000, null, true, null);
                } catch (DropboxException e) {
                    e.printStackTrace();
                }

                if (direntEx.contents.size() != 0) {
                    for (Entry ent : direntEx.contents) {
                        String name = ent.fileName();
                          /*Compare file here*/

                   }
                 }

                super.run();
            }

        }.start();

    }