Record the processing when Android enters the system folder, selects a file, and then returns

Enter the system folder code:

        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        /** fileType是一个字符串，用来筛选文件类型  */
        /** "image/*" 图片 */
        /** "video/*" 视频 */
        /** "audio/*" 音频 */
        /** "*/*"     无筛选 */
        intent.setType(fileType);
        startActivityForResult(intent, READ_REQUEST_CODE);

Then receive the returned data in the onActivityResult() method of Activity.

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case READ_REQUEST_CODE:
                if (data != null && resultCode == RESULT_OK) {
                    Uri uri = data.getData();
                    String path = FileUtil.getPath(HomeActivity.this, uri);
                }
                break;
        }
    }

The main processing is in the FileUtil class. Uri obtained after Android 4.4 is in a special format, so it needs to be dealt with separately.

package cn.droidlover.xdroidmvp.demo.util;

import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.os.SystemClock;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.FileProvider;
import android.text.TextUtils;
import androidx.annotation.RequiresApi;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.DecimalFormat;
import java.util.List;
import java.util.Objects;

import cn.droidlover.xdroidmvp.demo.BuildConfig;

public class FileUtil {
    public static String readFileSize(String path) {
        return readableFileSize(new File(path).length());
    }

    public static String readableFileSize(long size) {
        if (size <= 0)
            return "0";
        final String[] units = new String[]{"B", "KB", "MB", "GB", "TB"};
        int digitGroups = (int) (Math.log10(size) / Math.log10(1024));
        return new DecimalFormat("#,##0.#").format(size / Math.pow(1024, digitGroups)) + " " + units[digitGroups];
    }

    /**
     * file --> uri
     *
     * @param context
     * @param file
     * @return
     */
    public static Uri getUriFromFile(Context context, File file) {
        if (context == null || file == null) {
            throw new NullPointerException();
        }
        Uri uri;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            uri = FileProvider.getUriForFile(context.getApplicationContext(), BuildConfig.APPLICATION_ID + ".fileprovider", file);
        } else {
            uri = Uri.fromFile(file);
        }
        return uri;
    }

    /**
     * 专为Android4.4设计的从Uri获取文件绝对路径，以前的方法已不好使
     */
    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    public static String getPath(final Context context, final Uri uri) {

        final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
        // DocumentProvider
        if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
            // ExternalStorageProvider
            //一些三方的文件浏览器会进入到这个方法中，例如ES
            //QQ文件管理器不在此列
            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);
                if (!TextUtils.isEmpty(id)) {
                    if (id.startsWith("raw:")) {
                        return id.replaceFirst("raw:", "");
                    } else if (id.contains("msf:")) {
                        return getMSFFile(uri, id, context);
                    } else {
                        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 = getDocumentId(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);
            }
        } else if ("content".equalsIgnoreCase(uri.getScheme())) {// MediaStore (and general)
            // Return the remote address
            if (isGooglePhotosUri(uri))
                return uri.getLastPathSegment();
            if (isQQMediaDocument(uri)) {
                String path = uri.getPath();
                File fileDir = Environment.getExternalStorageDirectory();
                File file = new File(fileDir, path.substring("/QQBrowser".length(), path.length()));
                return file.exists() ? file.toString() : null;
            }
            return getDataColumn(context, uri, null, null);
        } else if ("file".equalsIgnoreCase(uri.getScheme())) {// File
            return uri.getPath();
        }
        return null;
    }

    /**
     * Get the value of the data column for this Uri. This is useful for
     * MediaStore Uris, and other file-based ContentProviders.
     *
     * @param context       The context.
     * @param uri           The Uri to query.
     * @param selection     (Optional) Filter used in the query.
     * @param selectionArgs (Optional) Selection arguments used in the query.
     * @return The value of the _data column, which is typically a file path.
     */
    public static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {
        Cursor cursor = null;
        final String column = MediaStore.MediaColumns.DATA;
        final String[] projection = {column};
        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
            if (cursor != null && cursor.moveToFirst()) {
                final int column_index = cursor.getColumnIndexOrThrow(column);
                Logger.getInstence().e(cursor.getString(column_index) + column_index);
                return cursor.getString(column_index);
            }
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return null;
    }


    public static String getRealPathFromURI(Context context, Uri contentUri) {
        return getDataColumn(context, contentUri, null, null);
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is ExternalStorageProvider.
     */
    public static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is DownloadsProvider.
     */
    public static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is MediaProvider.
     */
    public static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }


    /**
     * 使用第三方qq文件管理器打开
     *
     * @param uri
     * @return
     */
    public static boolean isQQMediaDocument(Uri uri) {
        return "com.tencent.mtt.fileprovider".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is Google Photos.
     */
    public static boolean isGooglePhotosUri(Uri uri) {
        return "com.google.android.apps.photos.content".equals(uri.getAuthority());
    }

    public static String getAbsoluteImagePath(Context context, Uri uri) {
        String[] proj = {MediaStore.Images.Media.DATA};
        CursorLoader loader = new CursorLoader(context, uri, proj, null, null, null);
        Cursor cursor = loader.loadInBackground();
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
        cursor.moveToFirst();
        return cursor.getString(column_index);
    }

    public static String getMSFFile(Uri uri, String id, Context context) {
        if (id != null && id.startsWith("msf:")) {
            File dir = new File(context.getCacheDir().getAbsolutePath());
            if (!dir.exists()) {
                dir.mkdirs();
            }

            final File file = new File(dir, SystemClock.uptimeMillis() + "." + Objects.requireNonNull(context.getContentResolver().getType(uri)).split("/")[1]);
            Logger.getInstence().e("path : " + file.getAbsolutePath());
            try (
                    final InputStream inputStream = context.getContentResolver().openInputStream(uri);
                    OutputStream output = new FileOutputStream(file)) {
                final byte[] buffer = new byte[4 * 1024]; // or other buffer size
                int read;
                while ((read = inputStream.read(buffer)) != -1) {
                    output.write(buffer, 0, read);
                }
                output.flush();
                output.close();
                return file.getPath();
            } catch (IOException ex) {
                ex.printStackTrace();
                Logger.getInstence().e(ex.getMessage());
            }
        }
        return null;
    }

    private static void deleteTempFile(Context context) {
        final File[] files = context.getCacheDir().listFiles();
        if (files != null) {
            for (final File file : files) {
                file.delete();
            }
        }
    }
}

The main reason is to make a judgment as shown in the figure below, and obtain the file address according to different situations. If the obtained Uri link ends with (msf: number), the link to the cache file is obtained by copying the file out of a cache file. You need to delete the cached file after use, the method is deleteTemoFile in FileUtil.

The above is to record the problems during a use process, there may be deficiencies or better methods, please leave a message, thank you.