android - 如何在 Android 中选择一个文件并计算其哈希值 (SHA-256)

Question

我想计算文件的哈希值 (SHA-256)。该文件是从使用 Intent 实现的选择器中选择的。如何计算如下获取路径的文件的哈希值。

Intent 使用:

Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
            intent.setType("*/*");
            startActivityForResult(intent, 7);

在 onActivityResult() 中，我获取的路径如下:

 if(requestCode == 7){
        if (resultCode == RESULT_OK) {
            String Path = data.getData().getPath();
       }

我尝试了 stackoverflow 上提供的各种答案，但没有一个有效。

Answer 1

以下代码来自How to get the Full file path from URI

import android.annotation.SuppressLint; 
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.provider.DocumentsContract;
import android.provider.MediaStore;

import java.net.URISyntaxException;

/**
 * Created by Aki on 1/7/2017.
 */

public class PathUtil {
    /*
     * Gets the file path of the given Uri.
     */
    @SuppressLint("NewApi")
    public static String getPath(Context context, Uri uri) throws URISyntaxException {
        final boolean needToCheckUri = Build.VERSION.SDK_INT >= 19;
        String selection = null;
        String[] selectionArgs = null;
        // Uri is different in versions after KITKAT (Android 4.4), we need to
        // deal with different Uris.
        if (needToCheckUri && DocumentsContract.isDocumentUri(context.getApplicationContext(), uri)) {
            if (isExternalStorageDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                return Environment.getExternalStorageDirectory() + "/" + split[1];
            } else if (isDownloadsDocument(uri)) {
                final String id = DocumentsContract.getDocumentId(uri);
                uri = ContentUris.withAppendedId(
                        Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));
            } else if (isMediaDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];
                if ("image".equals(type)) {
                    uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                } else if ("video".equals(type)) {
                    uri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
                } else if ("audio".equals(type)) {
                    uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
                }
                selection = "_id=?";
                selectionArgs = new String[]{ split[1] };
            }
        }
        if ("content".equalsIgnoreCase(uri.getScheme())) {
            String[] projection = { MediaStore.Images.Media.DATA };
            Cursor cursor = null;
            try {
                cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
                int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                if (cursor.moveToFirst()) {
                    return cursor.getString(column_index);
                }
            } catch (Exception e) {
            }
        } else if ("file".equalsIgnoreCase(uri.getScheme())) {
            return uri.getPath();
        }
        return 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());
    }
}