java.io.FileNotFoundException：/storage/emulated/0/downloadedfilem.jpg（权限被拒绝） [英] java.io.FileNotFoundException: /storage/emulated/0/downloadedfilem.jpg (Permission denied)

问题描述

我正在尝试使用Android中的Async任务下载和存储图像，当点击下载按钮时出现以下错误。

i am trying to download and store image using Async task in android , when clicking download button getting following error.

    W/System.err: java.io.FileNotFoundException: /storage/emulated/0/downloadedfilem.jpg (Permission denied)
12-07 11:01:00.120 28478-28540/myoracle.com.quotes W/System.err:     at java.io.FileOutputStream.open(Native Method)
12-07 11:01:00.120 28478-28540/myoracle.com.quotes W/System.err:     at java.io.FileOutputStream.<init>(FileOutputStream.java:221)
12-07 11:01:00.120 28478-28540/myoracle.com.quotes W/System.err:     at java.io.FileOutputStream.<init>(FileOutputStream.java:108)
12-07 11:01:00.120 28478-28540/myoracle.com.quotes W/System.err:     at myoracle.com.quotes.WallpaperDeatilsActivity$ImageDownload.doInBackground(WallpaperDeatilsActivity.java:113)
12-07 11:01:00.120 28478-28540/myoracle.com.quotes W/System.err:     at myoracle.com.quotes.WallpaperDeatilsActivity$ImageDownload.doInBackground(WallpaperDeatilsActivity.java:91)

WallpaperActivity.java

class ImageDownload extends AsyncTask<String, String, String> {

    @Override
    protected String doInBackground(String... params) {
        int count;
        try {

            String root = Environment.getExternalStorageDirectory().toString();

            System.out.println("Downloading");
            URL url = new URL(params[0]);

            URLConnection conection = url.openConnection();
            conection.connect();
            // getting file length
            int lenghtOfFile = conection.getContentLength();

            // input stream to read file - with 8k buffer
            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            // Output stream to write file
            System.out.println(root);
            OutputStream output = new FileOutputStream(root+"/downloadedfilem.jpg");
            byte data[] = new byte[1024];
            long total = 0;
            while ((count = input.read(data)) != -1) {
                total += count;
                // writing data to file
                output.write(data, 0, count);
                System.out.println(count);
            }
            // flushing output
            output.flush();
            // closing streams
            output.close();
           input.close();

        } catch (Exception e) {
            e.printStackTrace();
        }

1. Android Target Api 7.1.1

清单中添加的权限

1. android .permission.READ_EXTERNAL_STORAGE

1. android.permission.READ_EXTERNAL_STORAGE

android.permission.WRITE_EXTERNAL_STORAGE

android.permission.WRITE_EXTERNAL_STORAGE

推荐答案

您需要为OS Marshmallow或更高版本添加运行时权限。
添加此代码以允许在onCreate中或在图像下载过程之前允许在splash活动中运行时操作。

You need to add runtime permission for OS Marshmallow or above. Add this code for permission to allow run time operation in splash activity in onCreate or before download process of image.

if (!checkPermission()) {
    openActivity();
} else {
    if (checkPermission()) {
        requestPermissionAndContinue();
    } else {
        openActivity();
    }
}

在 onCreate之外添加此方法

private static final int PERMISSION_REQUEST_CODE = 200;
private boolean checkPermission() {

        return ContextCompat.checkSelfPermission(this, WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED
                && ContextCompat.checkSelfPermission(this, READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED
                ;
    }

private void requestPermissionAndContinue() {
    if (ContextCompat.checkSelfPermission(this, WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED
            && ContextCompat.checkSelfPermission(this, READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {

        if (ActivityCompat.shouldShowRequestPermissionRationale(this, WRITE_EXTERNAL_STORAGE)
                && ActivityCompat.shouldShowRequestPermissionRationale(this, READ_EXTERNAL_STORAGE)) {
            AlertDialog.Builder alertBuilder = new AlertDialog.Builder(this);
            alertBuilder.setCancelable(true);
            alertBuilder.setTitle(getString(R.string.permission_necessary));
            alertBuilder.setMessage(R.string.storage_permission_is_encessary_to_wrote_event);
            alertBuilder.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCompat.requestPermissions(SplashActivity.this, new String[]{WRITE_EXTERNAL_STORAGE
                            , READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
                }
            });
            AlertDialog alert = alertBuilder.create();
            alert.show();
            Log.e("", "permission denied, show dialog");
        } else {
            ActivityCompat.requestPermissions(SplashActivity.this, new String[]{WRITE_EXTERNAL_STORAGE,
                    READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
        }
    } else {
        openActivity();
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

    if (requestCode == PERMISSION_REQUEST_CODE) {
        if (permissions.length > 0 && grantResults.length > 0) {

            boolean flag = true;
            for (int i = 0; i < grantResults.length; i++) {
                if (grantResults[i] != PackageManager.PERMISSION_GRANTED) {
                    flag = false;
                }
            }
            if (flag) {
                openActivity();
            } else {
                finish();
            }

        } else {
            finish();
        }
    } else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

private void openActivity() {
  //add your further process after giving permission or to download images from remote server.
}

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