Android Q升级了文件系统，访问文件不仅仅是说动态权限了，有各种限制。权限什么的就不赘述了，下面介绍一下在10以上的系统中访问文件。

首先是打开文件管理器

    /*** 打开文件管理器 存储卡和外接U盘都可以访问*/public void openFileManager() {Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);intent.addCategory(Intent.CATEGORY_OPENABLE);intent.setType("text/*");startActivityForResult(intent, REQUEST_CODE_FILE);}

这个setType可以根据自己的需要，设置MIME类型，设置要访问什么类型的文件。具体MIME可以参考MIME类型-CSDN博客

然后会打开文件管理器，这里面可以访问手机存储的文件或者外插U盘内的文件，就根据自己需求选择文件就可以了。

选中的文件会在onActivityResult中返回

@Overrideprotected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {super.onActivityResult(requestCode, resultCode, data);if (resultCode == RESULT_OK && requestCode == REQUEST_CODE_FILE){//拿到需要解析的文件Uri uri = data.getData();String filePath= FileHelper.getFileAbsolutePath(this,uri);if (!TextUtils.isEmpty(filePath)){parseFile = new File(filePath);binding.tvFileName.setText(parseFile.getName());readFile();}}}

这里关键的一点就是把拿到的uri转换成filePath了，转换成路径之后就可以读文件，根据需求进行操作了。这个FileHelper转自Android打开系统文件管理器，并获取选中文件的路径，适配Android10及以上无法获取路径_intent.settype获取文件-CSDN博客

package com.......utils;import android.content.ContentResolver;
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.FileUtils;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.provider.OpenableColumns;import androidx.annotation.RequiresApi;import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;/*** ================================================* Description:通过uri获取本地文件的绝对路径* <p>* ================================================*/
public class FileHelper {/*** 根据Uri获取文件绝对路径，解决Android4.4以上版本Uri转换** @param context* @param imageUri*/public static String getFileAbsolutePath(Context context, Uri imageUri) {if (context == null || imageUri == null) {return null;}if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.KITKAT) {return getRealFilePath(context, imageUri);}if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT && android.os.Build.VERSION.SDK_INT < Build.VERSION_CODES.Q && DocumentsContract.isDocumentUri(context, imageUri)) {if (isExternalStorageDocument(imageUri)) {String docId = DocumentsContract.getDocumentId(imageUri);String[] split = docId.split(":");String type = split[0];if ("primary".equalsIgnoreCase(type)) {return Environment.getExternalStorageDirectory() + "/" + split[1];}} else if (isDownloadsDocument(imageUri)) {String id = DocumentsContract.getDocumentId(imageUri);Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));return getDataColumn(context, contentUri, null, null);} else if (isMediaDocument(imageUri)) {String docId = DocumentsContract.getDocumentId(imageUri);String[] split = docId.split(":");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;}String selection = MediaStore.Images.Media._ID + "=?";String[] selectionArgs = new String[]{split[1]};return getDataColumn(context, contentUri, selection, selectionArgs);}} // MediaStore (and general)if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q){return uriToFileApiQ(context,imageUri);}else if ("content".equalsIgnoreCase(imageUri.getScheme())) {// Return the remote addressif (isGooglePhotosUri(imageUri)) {return imageUri.getLastPathSegment();}return getDataColumn(context, imageUri, null, null);}// Fileelse if ("file".equalsIgnoreCase(imageUri.getScheme())) {return imageUri.getPath();}return null;}//此方法 只能用于4.4以下的版本private static String getRealFilePath(final Context context, final Uri uri) {if (null == uri) {return null;}final String scheme = uri.getScheme();String data = null;if (scheme == null) {data = uri.getPath();} else if (ContentResolver.SCHEME_FILE.equals(scheme)) {data = uri.getPath();} else if (ContentResolver.SCHEME_CONTENT.equals(scheme)) {String[] projection = {MediaStore.Images.ImageColumns.DATA};Cursor cursor = context.getContentResolver().query(uri, projection, null, null, null);//            Cursor cursor = context.getContentResolver().query(uri, new String[]{MediaStore.Images.ImageColumns.DATA}, null, null, null);if (null != cursor) {if (cursor.moveToFirst()) {int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);if (index > -1) {data = cursor.getString(index);}}cursor.close();}}return data;}/*** @param uri The Uri to check.* @return Whether the Uri authority is ExternalStorageProvider.*/private 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.*/private static boolean isDownloadsDocument(Uri uri) {return "com.android.providers.downloads.documents".equals(uri.getAuthority());}private static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {Cursor cursor = null;String column = MediaStore.Images.Media.DATA;String[] projection = {column};try {cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);if (cursor != null && cursor.moveToFirst()) {int index = cursor.getColumnIndexOrThrow(column);return cursor.getString(index);}} finally {if (cursor != null) {cursor.close();}}return null;}/*** @param uri The Uri to check.* @return Whether the Uri authority is MediaProvider.*/private static boolean isMediaDocument(Uri uri) {return "com.android.providers.media.documents".equals(uri.getAuthority());}/*** @param uri The Uri to check.* @return Whether the Uri authority is Google Photos.*/private static boolean isGooglePhotosUri(Uri uri) {return "com.google.android.apps.photos.content".equals(uri.getAuthority());}/*** Android 10 以上适配 另一种写法* @param context* @param uri* @return*/public static String getFileFromContentUri(Context context, Uri uri) {if (uri == null) {return null;}String filePath;String[] filePathColumn = {MediaStore.MediaColumns.DATA, MediaStore.MediaColumns.DISPLAY_NAME};ContentResolver contentResolver = context.getContentResolver();Cursor cursor = contentResolver.query(uri, filePathColumn, null,null, null);if (cursor != null) {cursor.moveToFirst();try {filePath = cursor.getString(cursor.getColumnIndex(filePathColumn[0]));return filePath;} catch (Exception e) {} finally {cursor.close();}}return "";}/*** Android 10 以上适配* @param context* @param uri* @return*/@RequiresApi(api = Build.VERSION_CODES.Q)private static String uriToFileApiQ(Context context, Uri uri) {File file = null;//android10以上转换if (uri.getScheme().equals(ContentResolver.SCHEME_FILE)) {file = new File(uri.getPath());} else if (uri.getScheme().equals(ContentResolver.SCHEME_CONTENT)) {//把文件复制到沙盒目录ContentResolver contentResolver = context.getContentResolver();Cursor cursor = contentResolver.query(uri, null, null, null, null);if (cursor.moveToFirst()) {String displayName = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));try {InputStream is = contentResolver.openInputStream(uri);File cache = new File(context.getExternalCacheDir().getAbsolutePath(), Math.round((Math.random() + 1) * 1000) + displayName);FileOutputStream fos = new FileOutputStream(cache);FileUtils.copy(is, fos);file = cache;fos.close();is.close();} catch (IOException e) {e.printStackTrace();}}}return file.getAbsolutePath();}
}