如何摆脱异常 "IOException: File '... ... ... .pdf' cannot be written to"

Question

我想从 link 下载 PDF 文件并在 pdf-reader 中打开它。为此，我指出：

在宣言中：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

在classAppAsyncTasks.java:

public static class FileLoadingTask extends AsyncTask<Void, Void, File> {

    private static final String LOG_TAG = "FileLoadingTask";

    public FileLoadingTask(final Context cxt,
                           final JSONOrder order,
                           final FileLoadingListener listener) {

    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        createPdLoading(pdLoading);
        this.url = mOrder.getPreviewlink();
        this.extStorageDirectory = Environment.getExternalStorageDirectory().toString();
        this.folder = new File(extStorageDirectory, "Download");
        this.folder.mkdir();
        this.fileName = mOrder.getOrdercode() + ".pdf";
        this.file = new File(this.folder, this.fileName);
        fileLoadingListener.onBegin();
    }

    @Override
    protected File doInBackground(Void... params) {
        try {
            FileUtils.copyURLToFile(new URL(url), file);
        } catch (IOException e) {        
            throwable = e;
        }
        return file;
    }

    @Override
    protected void onPostExecute(File file) {
        super.onPostExecute(file);
        pdLoading.dismiss();
        fileLoadingListener.onEnd(file);
        if (throwable != null) {
            fileLoadingListener.onFailure(throwable);
        } else {
            fileLoadingListener.onSuccess();
        }
    }            
    public interface FileLoadingListener {

        void onBegin();               
        void onSuccess();              
        void onFailure(Throwable cause);                
        void onEnd(File file);                
    }
}

但是，不会将文件写入内部媒体 - 抛出异常：

IOException: File 'storage/emulated/0/Download/...pdf' cannot be written to

如何摆脱这个异常？

Answer 1

这个解决方案是可行的。我在代码中包含了检查外部存储器写入权限的说明。正如 Tejas Pandya and Dhaval Patel 所建议的那样。

为此，我的onPreExecute()方法添加如下：

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            while (checkPermissions()) {
            }
        }
        createPdLoading(pdLoading);
        ... ... ... ... ...
    }

方法 checkPermissions() returns 如果没有将文件写入外部存储器的权限，则值 "true"，如果有 - "false"，如果有。

    @RequiresApi(api = Build.VERSION_CODES.M)
    private boolean checkPermissions() {
        switch (App.getCurFragContext().checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
            case PackageManager.PERMISSION_DENIED:
                fileLoadingListener.requestPermissions();
                return true;
            default:
                return false;
        }
    }

我向 FileLoadingListener 接口添加了一个 requestPermissions() 方法。它从 checkPermissions() 方法调用并具有以下实现：

    @Override
    public void requestPermissions() {
        ActivityCompat.requestPermissions(
                (Activity) mActivity,
                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                App.MY_PERMISSIONS_REQUEST_WRITE);
    }

如何摆脱异常 "IOException: File '... ... ... .pdf' cannot be written to"

How to get rid of an exception "IOException: File '... ... ... .pdf' cannot be written to"

android

file

ioexception