Android读写文件，适配Q以上

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

@Override
    protected 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 address
            if (isGooglePhotosUri(imageUri)) {
                return imageUri.getLastPathSegment();
            }
            return getDataColumn(context, imageUri, null, null);
        }
        // File
        else 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();
    }
}