java - 下载图片会覆盖上一张图片

Question

void downloadFile(){



    try {
        Bundle bundle = getIntent().getExtras();
        String[] imageUrls = bundle.getStringArray(Extra.IMAGES);
        //  Log.v(imageUrls, "Creating view...");
        int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);

        URL url = new URL(imageUrls[pagerPosition]);
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        urlConnection.setRequestMethod("GET");
        urlConnection.setDoOutput(true);

        //connect
        urlConnection.connect();

        //set the path where we want to save the file
        File SDCardRoot = Environment.getExternalStorageDirectory();
        //create a new file, to save the downloaded file
        File file = new File(SDCardRoot,"image.png");

        FileOutputStream fileOutput = new FileOutputStream(file);

        //Stream used for reading the data from the internet
        InputStream inputStream = urlConnection.getInputStream();

        //this is the total size of the file which we are downloading
        totalSize = urlConnection.getContentLength();

        runOnUiThread(new Runnable() {
            public void run() {
                pb.setMax(totalSize);
            }
        });

        //create a buffer...
        byte[] buffer = new byte[1024];
        int bufferLength = 0;

        while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
            fileOutput.write(buffer, 0, bufferLength);
            downloadedSize += bufferLength;
            // update the progressbar //
            runOnUiThread(new Runnable() {
                public void run() {
                    pb.setProgress(downloadedSize);
                    float per = ((float)downloadedSize/totalSize) * 100;
                    cur_val.setText("Downloaded " + downloadedSize + "KB / " + totalSize + "KB (" + (int)per + "%)" );
                }
            });
        }
        //close the output stream when complete //
        fileOutput.close();
        runOnUiThread(new Runnable() {
            public void run() {
                // pb.dismiss(); // if you want close it..
            }
        });

    } catch (final MalformedURLException e) {
        showError("Error : MalformedURLException " + e);
        e.printStackTrace();
    } catch (final IOException e) {
        showError("Error : IOException " + e);
        e.printStackTrace();
    }
    catch (final Exception e) {
        showError("Error : Please check your internet connection " + e);
    }
}

嗨，我正在使用此功能从 URL 下载图像，效果很好。但它会覆盖以前下载的图像..

File file = new File(SDCardRoot,"image.png");

如何在上面一行中的每个新下载中更改名称..它不接受任何非字符串的内容。

任何帮助都会很棒。

Answer 1

这是因为您总是使用相同的名称image.png保存图像，使用当前日期时间更改名称所以改变这个

File file = new File(SDCardRoot,"image.png");

至

SimpleDateFormat formatter = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss");
Date now = new Date();
String fileName = "image" + formatter.format(now) + ".png";
File file = new File(SDCardRoot,fileName);

编辑
您还可以使用日历作为

Calendar calendar = Calendar.getInstance();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss");
String fileName = "image" + formatter.format(calendar.getTime()) + ".png";
File file = new File(SDCardRoot,fileName);