如何在Android中选择文件并计算其哈希(SHA-256)

Question

我想计算一个文件的哈希(SHA-256(。此文件是从使用Intent实现的选择器中选择的。如何计算路径如下所示的文件的哈希。

意向用途：

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

在onActivityResult((中，我获得的路径如下：

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，但都不起作用。

Answer 1

以下代码来自如何从URI 获取完整文件路径

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());
}
}