[Method summary] operations related to file creation, reading, and deletion, and reading and deleting

[Method summary] operations related to file creation, reading, and deletion, and reading and deleting

Summarize the common methods related to a wave of File Operations (for use)

 Required permissions:

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

 

 1. Get all file names in the folder

public static List<String> getFileName(String fileName) {    List<String> fileList = new ArrayList<>();    File file = new File(fileName);    if (!file.exists()) {        return null;    }    File f[] = file.listFiles();    for (int i = 0; i < f.length; i++) {        File fs = f[i];        if (!fs.isDirectory()) {            fileList.add(fs.getName());        }    }    return fileList;}

 

 2. Create a file on the SD card

public static File createFile(String fileName) throws IOException {    File file = new File(fileName);    if (!isFileExists(file)) {        if (file.isDirectory()) {            file.mkdirs();        } else {            file.createNewFile();        }    }    return file;}

 

 3. Create a folder on the SD card

public static File createFolder(String fileName) throws IOException {    File file = new File(fileName);    if (!isFileExists(file)) {        file.mkdirs();    }    return file;}

 

 4. Read text files from the SD card

public synchronized static String readFile(String fileName) {    StringBuffer sb = new StringBuffer();    File file = new File(fileName);    String str = null;    try {        InputStream is = new FileInputStream(file);        InputStreamReader isr = new InputStreamReader(is, "UTF-8");        @SuppressWarnings("resource")        BufferedReader reader = new BufferedReader(isr);        while ((str = reader.readLine()) != null) {            sb.append(str);        }    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }    return sb.toString();}

 

 5. delete a single file

public static boolean deleteFile(String filePath) {    File file = new File(filePath);    if (file.isFile() && file.exists()) {        return file.delete();    }    return false;}

File Name of the deleted file in filePath

Return true if the file is successfully deleted; otherwise, false is returned.

 

 6. delete folders and files in their directories

Public static boolean deleteFolder (String filePath) {boolean flag = false; // if filePath does not end with a file separator, the file separator if (! FilePath. endsWith (File. separator) {filePath = filePath + File. separator;} File dirFile = new File (filePath); if (! DirFile. exists () |! DirFile. isDirectory () {return false;} flag = true; File [] files = dirFile. listFiles (); // traverse and delete all files (including subdirectories) in the folder for (File file: files) {if (file. isFile () {// Delete the sub-file flag = deleteFile (file. getAbsolutePath (); if (! Flag) break;} else {// Delete sub-directory flag = deleteFolder (file. getAbsolutePath (); if (! Flag) break;} if (! Flag) return false; // delete the empty current directory return dirFile. delete ();}

FilePath: the file path of the deleted directory
Return true if the return directory is successfully deleted; otherwise, false is returned.

 

 7. Convert the file to Base64

public static String encodeBase64File(String path) throws Exception {    byte[] videoBytes;    ByteArrayOutputStream baos = new ByteArrayOutputStream();    @SuppressWarnings("resource")    FileInputStream fis = new FileInputStream(new File(path));    byte[] buf = new byte[1024];    int n;    while (-1 != (n = fis.read(buf))) {        baos.write(buf, 0, n);    }    videoBytes = baos.toByteArray();    return Base64.encodeToString(videoBytes, Base64.NO_WRAP);}

 

 8. Convert the path from the photo album Library to the SD card path (Android 4.4 or above)

@TargetApi(Build.VERSION_CODES.KITKAT)public static String getPath(final Context context, final Uri uri) {    final boolean isOverKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;    // DocumentProvider    if (isOverKitKat && DocumentsContract.isDocumentUri(context, uri)) {        // ExternalStorageProvider        if (isExternalStorageDocument(uri)) {            final String docId = DocumentsContract.getDocumentId(uri);            final String[] split = docId.split(":");            final String type = split[0];            if ("primary".equalsIgnoreCase(type)) {                return Environment.getExternalStorageDirectory() + "/"                        + split[1];            }        }        // DownloadsProvider        else if (isDownloadsDocument(uri)) {            final String id = DocumentsContract.getDocumentId(uri);            final Uri contentUri = ContentUris.withAppendedId(                    Uri.parse("content://downloads/public_downloads"),                    Long.valueOf(id));            return getDataColumn(context, contentUri, null, null);        }        // MediaProvider        else if (isMediaDocument(uri)) {            final String docId = DocumentsContract.getDocumentId(uri);            final String[] split = docId.split(":");            final String type = split[0];            Uri contentUri = null;            if ("image".equals(type)) {                contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;            } else if ("video".equals(type)) {                contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;            } else if ("audio".equals(type)) {                contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;            }            final String selection = "_id=?";            final String[] selectionArgs = new String[]{split[1]};            return getDataColumn(context, contentUri, selection,                    selectionArgs);        }    }    // MediaStore (and general)    else if ("content".equalsIgnoreCase(uri.getScheme())) {        // Return the remote address        if (isGooglePhotosUri(uri))            return uri.getLastPathSegment();        return getDataColumn(context, uri, null, null);    }    // File    else if ("file".equalsIgnoreCase(uri.getScheme())) {        return uri.getPath();    }    return null;}

 

 The preceding method may require the support of the following auxiliary methods:

public static boolean isFileExists(File file) {    return file.exists();}

public static boolean isExternalStorageDocument(Uri uri) {    return "com.android.externalstorage.documents".equals(uri.getAuthority());}

public static boolean isDownloadsDocument(Uri uri) {    return "com.android.providers.downloads.documents".equals(uri.getAuthority());}

public static boolean isMediaDocument(Uri uri) {    return "com.android.providers.media.documents".equals(uri.getAuthority());}

public static boolean isGooglePhotosUri(Uri uri) {    return "com.google.android.apps.photos.content".equals(uri.getAuthority());}

@SuppressLint("NewApi")public static String getDataColumn(Context context, Uri uri,                                   String selection, String[] selectionArgs) {    Cursor cursor = null;    final String column = "_data";    final String[] projection = {column};    try {        cursor = context.getContentResolver().query(uri, projection,                selection, selectionArgs, null);        if (cursor != null && cursor.moveToFirst()) {            final int index = cursor.getColumnIndexOrThrow(column);            return cursor.getString(index);        }    } finally {        if (cursor != null)            cursor.close();    }    return null;}

 

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