什么是最简单的方法从android.net.Uri对象持有一个文件:类型转换为java.io.File对象在Android?
我尝试了下面的方法，但不管用:
File file = new File(Environment.getExternalStorageDirectory(), "read.me");
Uri uri = Uri.fromFile(file);
File auxFile = new File(uri.toString());
assertEquals(file.getAbsolutePath(), auxFile.getAbsolutePath());
编辑:对不起，我之前应该测试得更好。这应该可以工作:
new File(new URI(androidURI.toString()));
URI是java.net.URI。
你想要的是…
new File(uri.getPath());
．.． ,而不是……
new File(uri.toString());
笔记
对于android.net.Uri对象，它被命名为uri并完全按照问题中创建，uri. tostring()返回一个“file:///mnt/sdcard/myPicture.jpg”格式的字符串，而uri. getpath()返回一个“/mnt/sdcard/myPicture.jpg”格式的字符串。 我知道在Android系统中文件存储有一些细微差别。在这个回答中，我的意图是准确地回答提问者所问的问题，而不是深究其中的细微差别。
在寻找了很长一段时间后，这对我来说是有效的:
File file = new File(getPath(uri));
public String getPath(Uri uri)
{
String[] projection = { MediaStore.Images.Media.DATA };
Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
if (cursor == null) return null;
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToFirst();
String s=cursor.getString(column_index);
cursor.close();
return s;
}
对于那些在这里寻找图像解决方案的人，特别是在这里。
private Bitmap getBitmapFromUri(Uri contentUri) {
String path = null;
String[] projection = { MediaStore.Images.Media.DATA };
Cursor cursor = getContentResolver().query(contentUri, projection, null, null, null);
if (cursor.moveToFirst()) {
int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
path = cursor.getString(columnIndex);
}
cursor.close();
Bitmap bitmap = BitmapFactory.decodeFile(path);
return bitmap;
}
这些对我都没用。我发现这是可行的解决方案。但我的情况仅限于图像。
String[] filePathColumn = { MediaStore.Images.Media.DATA };
Cursor cursor = getActivity().getContentResolver().query(uri, filePathColumn, null, null, null);
cursor.moveToFirst();
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
String filePath = cursor.getString(columnIndex);
cursor.close();
文件imageToUpload =新文件(新URI(androidURI.toString()));如果这是你在外部存储中创建的文件，则有效。
例如file:///storage/emulated/0/(一些目录和文件名)
我是这样做的:
try {
readImageInformation(new File(contentUri.getPath()));
} catch (IOException e) {
readImageInformation(new File(getRealPathFromURI(context,
contentUri)));
}
public static String getRealPathFromURI(Context context, Uri contentUri) {
String[] proj = { MediaStore.Images.Media.DATA };
Cursor cursor = context.getContentResolver().query(contentUri, proj,
null, null, null);
int column_index = cursor
.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToFirst();
return cursor.getString(column_index);
}
所以基本上首先我尝试使用一个文件，即相机拍摄的照片，并保存在SD卡上。这对返回的图像不起作用: 意图photoPickerIntent =新的意图(Intent. action_pick); 在这种情况下，需要通过getRealPathFromURI()函数将Uri转换为真实路径。 所以结论是，这取决于你想转换为File的Uri类型。
使用
InputStream inputStream = getContentResolver().openInputStream(uri);
直接复制文件。还看到:
https://developer.android.com/guide/topics/providers/document-provider.html
@CommonsWare解释得很好。我们真的应该采用他提出的解决方案。
顺便说一下，当查询ContentResolver时，我们唯一可以依赖的信息是文件的名称和大小，如下所述: 检索文件信息| Android开发人员
正如您所看到的，这里有一个接口OpenableColumns，它只包含两个字段:DISPLAY_NAME和SIZE。
在我的例子中，我需要检索关于JPEG图像的EXIF信息，并在发送到服务器之前根据需要旋转它。为此，我使用ContentResolver和openInputStream()将文件内容复制到临时文件中。
public String getRealPathFromURI（Uri uri） {
String result;
Cursor cursor = getContentResolver().query(uri, null, null, null, null);
if (cursor == null) {
result = uri.getPath();
cursor.close();
return result;
}
cursor.moveToFirst();
int idx = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
result = cursor.getString(idx);
cursor.close();
return result;
}
然后使用从URI中获取文件:
File finalFile = newFile(getRealPathFromURI(uri));
——希望能帮到你----
安卓 + Kotlin
为Kotlin Android扩展添加依赖项: 实现“androidx.core: core-ktx: {latestVersion}’ 从uri获取文件: uri.toFile ()
使用Kotlin甚至更容易:
val file = File(uri.path)
或者如果你在Android上使用Kotlin扩展:
val file = uri.toFile()
更新: 对于图像，它返回“Uri缺少'file' scheme: content://”
谢谢你的评论
最好的解决方案
创建一个简单的FileUtil类，用于创建、复制和重命名文件
我使用了uri.toString()和uri.getPath()，但不适合我。 我终于找到了这个解。
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.provider.OpenableColumns;
import android.util.Log;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class FileUtil {
private static final int EOF = -1;
private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
private FileUtil() {
}
public static File from(Context context, Uri uri) throws IOException {
InputStream inputStream = context.getContentResolver().openInputStream(uri);
String fileName = getFileName(context, uri);
String[] splitName = splitFileName(fileName);
File tempFile = File.createTempFile(splitName[0], splitName[1]);
tempFile = rename(tempFile, fileName);
tempFile.deleteOnExit();
FileOutputStream out = null;
try {
out = new FileOutputStream(tempFile);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
if (inputStream != null) {
copy(inputStream, out);
inputStream.close();
}
if (out != null) {
out.close();
}
return tempFile;
}
private static String[] splitFileName(String fileName) {
String name = fileName;
String extension = "";
int i = fileName.lastIndexOf(".");
if (i != -1) {
name = fileName.substring(0, i);
extension = fileName.substring(i);
}
return new String[]{name, extension};
}
private static String getFileName(Context context, Uri uri) {
String result = null;
if (uri.getScheme().equals("content")) {
Cursor cursor = context.getContentResolver().query(uri, null, null, null, null);
try {
if (cursor != null && cursor.moveToFirst()) {
result = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (cursor != null) {
cursor.close();
}
}
}
if (result == null) {
result = uri.getPath();
int cut = result.lastIndexOf(File.separator);
if (cut != -1) {
result = result.substring(cut + 1);
}
}
return result;
}
private static File rename(File file, String newName) {
File newFile = new File(file.getParent(), newName);
if (!newFile.equals(file)) {
if (newFile.exists() && newFile.delete()) {
Log.d("FileUtil", "Delete old " + newName + " file");
}
if (file.renameTo(newFile)) {
Log.d("FileUtil", "Rename file to " + newName);
}
}
return newFile;
}
private static long copy(InputStream input, OutputStream output) throws IOException {
long count = 0;
int n;
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
while (EOF != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
}
在代码中使用FileUtil类
try {
File file = FileUtil.from(MainActivity.this,fileUri);
Log.d("file", "File...:::: uti - "+file .getPath()+" file -" + file + " : " + file .exists());
} catch (IOException e) {
e.printStackTrace();
}
通过下面的代码，我能够获得adobe应用程序共享pdf文件作为流，并保存到android应用程序路径
Android.Net.Uri fileuri =
(Android.Net.Uri)Intent.GetParcelableExtra(Intent.ExtraStream);
fileuri i am getting as {content://com.adobe.reader.fileprovider/root_external/
data/data/com.adobe.reader/files/Downloads/sample.pdf}
string filePath = fileuri.Path;
filePath I am gettings as root_external/data/data/com.adobe.reader/files/Download/sample.pdf
using (var stream = ContentResolver.OpenInputStream(fileuri))
{
byte[] fileByteArray = ToByteArray(stream); //only once you can read bytes from stream second time onwards it has zero bytes
string fileDestinationPath ="<path of your destination> "
convertByteArrayToPDF(fileByteArray, fileDestinationPath);//here pdf copied to your destination path
}
public static byte[] ToByteArray(Stream stream)
{
var bytes = new List<byte>();
int b;
while ((b = stream.ReadByte()) != -1)
bytes.Add((byte)b);
return bytes.ToArray();
}
public static string convertByteArrayToPDF(byte[] pdfByteArray, string filePath)
{
try
{
Java.IO.File data = new Java.IO.File(filePath);
Java.IO.OutputStream outPut = new Java.IO.FileOutputStream(data);
outPut.Write(pdfByteArray);
return data.AbsolutePath;
}
catch (System.Exception ex)
{
return string.Empty;
}
}
扩展基于@Jacek kwiecievik回答转换图像uri文件
fun Uri.toImageFile(context: Context): File? {
val filePathColumn = arrayOf(MediaStore.Images.Media.DATA)
val cursor = context.contentResolver.query(this, filePathColumn, null, null, null)
if (cursor != null) {
if (cursor.moveToFirst()) {
val columnIndex = cursor.getColumnIndex(filePathColumn[0])
val filePath = cursor.getString(columnIndex)
cursor.close()
return File(filePath)
}
cursor.close()
}
return null
}
如果我们使用File(uri.getPath())，它将不起作用
如果我们使用扩展从android-ktx，它仍然不能工作，因为 https://github.com/android/android-ktx/blob/master/src/main/java/androidx/core/net/Uri.kt
在这种情况下，特别是在Android上，使用字节的方式通常更快。
有了这个，我通过设置一个类FileHelper来解决这个问题，它被赋予了处理通过流从/向文件读取/写入字节的责任，以及一个类UriHelper，它被赋予了计算Uri路径和权限的责任。
就我们所知，字符串。getBytes((charset == null) ?DEFAULT_CHARSET:charset)可以帮助我们将你想要的字符串转换为你需要的字节。
如何让UriHelper和FileHelper你复制一个图片的Uri到一个文件，你可以运行:
FileHelper.getInstance().copy(UriHelper.getInstance().toFile(uri_of_a_picture)
, FileHelper.getInstance().createExternalFile(null, UriHelper.getInstance().generateFileNameBasedOnTimeStamp()
+ UriHelper.getInstance().getFileName(uri_of_a_picture, context), context)
);
关于我的UriHelper:
public class UriHelper {
private static UriHelper INSTANCE = new UriHelper();
public static UriHelper getInstance() {
return INSTANCE;
}
@SuppressLint("SimpleDateFormat")
public String generateFileNameBasedOnTimeStamp() {
return new SimpleDateFormat("yyyyMMdd_hhmmss").format(new Date()) + ".jpeg";
}
/**
* if uri.getScheme.equals("content"), open it with a content resolver.
* if the uri.Scheme.equals("file"), open it using normal file methods.
*/
//
public File toFile(Uri uri) {
if (uri == null) return null;
Logger.d(">>> uri path:" + uri.getPath());
Logger.d(">>> uri string:" + uri.toString());
return new File(uri.getPath());
}
public DocumentFile toDocumentFile(Uri uri) {
if (uri == null) return null;
Logger.d(">>> uri path:" + uri.getPath());
Logger.d(">>> uri string:" + uri.toString());
return DocumentFile.fromFile(new File(uri.getPath()));
}
public Uri toUri(File file) {
if (file == null) return null;
Logger.d(">>> file path:" + file.getAbsolutePath());
return Uri.fromFile(file); //returns an immutable URI reference representing the file
}
public String getPath(Uri uri, Context context) {
if (uri == null) return null;
if (uri.getScheme() == null) return null;
Logger.d(">>> uri path:" + uri.getPath());
Logger.d(">>> uri string:" + uri.toString());
String path;
if (uri.getScheme().equals("content")) {
//Cursor cursor = context.getContentResolver().query(uri, new String[] {MediaStore.Images.ImageColumns.DATA}, null, null, null);
Cursor cursor = context.getContentResolver().query(uri, null, null, null, null);
if (cursor == null) {
Logger.e("!!! cursor is null");
return null;
}
if (cursor.getCount() >= 0) {
Logger.d("... the numbers of rows:" + cursor.getCount()
+ "and the numbers of columns:" + cursor.getColumnCount());
if (cursor.isBeforeFirst()) {
while (cursor.moveToNext()) {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i<cursor.getColumnCount(); i++) {
stringBuilder.append("... iterating cursor.getString(" + i +"(" + cursor.getColumnName(i) + ")):" + cursor.getString(i));
stringBuilder.append("\n");
}
Logger.d(stringBuilder.toString());
}
} else {
cursor.moveToFirst();
do {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i<cursor.getColumnCount(); i++) {
stringBuilder.append("... iterating cursor.getString(" + i +"(" + cursor.getColumnName(i) + ")):" + cursor.getString(i));
stringBuilder.append("\n");
}
Logger.d(stringBuilder.toString());
} while (cursor.moveToNext());
}
path = uri.getPath();
cursor.close();
Logger.d("... content scheme:" + uri.getScheme() + " and return:" + path);
return path;
} else {
path = uri.getPath();
Logger.d("... content scheme:" + uri.getScheme()
+ " but the numbers of rows in the cursor is < 0:" + cursor.getCount()
+ " and return:" + path);
return path;
}
} else {
path = uri.getPath();
Logger.d("... not content scheme:" + uri.getScheme() + " and return:" + path);
return path;
}
}
public String getFileName(Uri uri, Context context) {
if (uri == null) return null;
if (uri.getScheme() == null) return null;
Logger.d(">>> uri path:" + uri.getPath());
Logger.d(">>> uri string:" + uri.toString());
String path;
if (uri.getScheme().equals("content")) {
//Cursor cursor = context.getContentResolver().query(uri, new String[] {MediaStore.Images.ImageColumns.DATA}, null, null, null);
Cursor cursor = context.getContentResolver().query(uri, null, null, null, null);
if (cursor == null) {
Logger.e("!!! cursor is null");
return null;
}
if (cursor.getCount() >= 0) {
Logger.d("... the numbers of rows:" + cursor.getCount()
+ "and the numbers of columns:" + cursor.getColumnCount());
if (cursor.isBeforeFirst()) {
while (cursor.moveToNext()) {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i<cursor.getColumnCount(); i++) {
stringBuilder.append("... iterating cursor.getString(" + i +"(" + cursor.getColumnName(i) + ")):" + cursor.getString(i));
stringBuilder.append("\n");
}
Logger.d(stringBuilder.toString());
}
} else {
cursor.moveToFirst();
do {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i<cursor.getColumnCount(); i++) {
stringBuilder.append("... iterating cursor.getString(" + i +"(" + cursor.getColumnName(i) + ")):" + cursor.getString(i));
stringBuilder.append("\n");
}
Logger.d(stringBuilder.toString());
} while (cursor.moveToNext());
}
cursor.moveToFirst();
path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.ImageColumns.DISPLAY_NAME));
cursor.close();
Logger.d("... content scheme:" + uri.getScheme() + " and return:" + path);
return path;
} else {
path = uri.getLastPathSegment();
Logger.d("... content scheme:" + uri.getScheme()
+ " but the numbers of rows in the cursor is < 0:" + cursor.getCount()
+ " and return:" + path);
return path;
}
} else {
path = uri.getLastPathSegment();
Logger.d("... not content scheme:" + uri.getScheme() + " and return:" + path);
return path;
}
}
}
关于我的FileHelper:
public class FileHelper {
private static final String DEFAULT_DIR_NAME = "AmoFromTaiwan";
private static final int DEFAULT_BUFFER_SIZE = 1024;
private static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
private static final int EOF = -1;
private static FileHelper INSTANCE = new FileHelper();
public static FileHelper getInstance() {
return INSTANCE;
}
private boolean isExternalStorageWritable(Context context) {
/*
String state = Environment.getExternalStorageState();
return Environment.MEDIA_MOUNTED.equals(state);
*/
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (context.checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
return true;
} else {
Logger.e("!!! checkSelfPermission() not granted");
return false;
}
} else { //permission is automatically granted on sdk<23 upon installation
return true;
}
}
private boolean isExternalStorageReadable(Context context) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (context.checkSelfPermission(android.Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
return true;
} else {
Logger.e("!!! checkSelfPermission() not granted");
return false;
}
} else { //permission is automatically granted on sdk<23 upon installation
return true;
}
}
@SuppressLint("SimpleDateFormat")
private String generateFileNameBasedOnTimeStamp() {
return new SimpleDateFormat("yyyyMMdd_hhmmss").format(new Date()) + ".jpeg";
}
public File createExternalFile(String dir_name, String file_name, Context context) {
String dir_path;
String file_path;
File dir ;
File file;
if (!isExternalStorageWritable(context)) {
Logger.e("!!! external storage not writable");
return null;
}
if (dir_name == null) {
dir_path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).getAbsolutePath() + File.separator + DEFAULT_DIR_NAME;
} else {
dir_path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).getAbsolutePath() + File.separator + dir_name;
}
Logger.d("... going to access an external dir:" + dir_path);
dir = new File(dir_path);
if (!dir.exists()) {
Logger.d("... going to mkdirs:" + dir_path);
if (!dir.mkdirs()) {
Logger.e("!!! failed to mkdirs");
return null;
}
}
if (file_name == null) {
file_path = dir_path + File.separator + generateFileNameBasedOnTimeStamp();
} else {
file_path = dir_path + File.separator + file_name;
}
Logger.d("... going to return an external dir:" + file_path);
file = new File(file_path);
if (file.exists()) {
Logger.d("... before creating to delete an external dir:" + file.getAbsolutePath());
if (!file.delete()) {
Logger.e("!!! failed to delete file");
return null;
}
}
return file;
}
public File createInternalFile(String dir_name, String file_name, Context context) {
String dir_path;
String file_path;
File dir ;
File file;
if (dir_name == null) {
dir = new ContextWrapper(context).getDir(DEFAULT_DIR_NAME, Context.MODE_PRIVATE);
} else {
dir = new ContextWrapper(context).getDir(dir_name, Context.MODE_PRIVATE);
}
dir_path = dir.getAbsolutePath();
Logger.d("... going to access an internal dir:" + dir_path);
if (!dir.exists()) {
Logger.d("... going to mkdirs:" + dir_path);
if (!dir.mkdirs()) {
Logger.e("!!! mkdirs failed");
return null;
}
}
if (file_name == null) {
file = new File(dir, generateFileNameBasedOnTimeStamp());
} else {
file = new File(dir, file_name);
}
file_path = file.getAbsolutePath();
Logger.d("... going to return an internal dir:" + file_path);
if (file.exists()) {
Logger.d("... before creating to delete an external dir:" + file.getAbsolutePath());
if (!file.delete()) {
Logger.e("!!! failed to delete file");
return null;
}
}
return file;
}
public File getExternalFile(String dir_name, String file_name, Context context) {
String dir_path;
String file_path;
File file;
if (!isExternalStorageWritable(context)) {
Logger.e("!!! external storage not writable");
return null;
}
if (dir_name == null) {
dir_path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).getAbsolutePath() + File.separator + DEFAULT_DIR_NAME;
} else {
dir_path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).getAbsolutePath() + File.separator + dir_name;
}
if (file_name == null) {
file_path = dir_path;
} else {
file_path = dir_path + File.separator + file_name;
}
Logger.d("... going to return an external file:" + file_path);
file = new File(file_path);
if (file.exists()) {
Logger.d("... file exists:" + file.getAbsolutePath());
} else {
Logger.e("!!! file does't exist:" + file.getAbsolutePath());
}
return file;
}
public File getInternalFile(String dir_name, String file_name, Context context) {
String file_path;
File dir ;
File file;
if (dir_name == null) {
dir = new ContextWrapper(context).getDir(DEFAULT_DIR_NAME, Context.MODE_PRIVATE);
} else {
dir = new ContextWrapper(context).getDir(dir_name, Context.MODE_PRIVATE);
}
if (file_name == null) {
file = new File(dir.getAbsolutePath());
} else {
file = new File(dir, file_name);
}
file_path = file.getAbsolutePath();
Logger.d("... going to return an internal dir:" + file_path);
if (file.exists()) {
Logger.d("... file exists:" + file.getAbsolutePath());
} else {
Logger.e("!!! file does't exist:" + file.getAbsolutePath());
}
return file;
}
private byte[] readBytesFromFile(File file) {
Logger.d(">>> path:" + file.getAbsolutePath());
FileInputStream fis;
long file_length;
byte[] buffer;
int offset = 0;
int next = 0;
if (!file.exists()) {
Logger.e("!!! file doesn't exists");
return null;
}
if (file.length() > Integer.MAX_VALUE) {
Logger.e("!!! file length is out of max of int");
return null;
} else {
file_length = file.length();
}
try {
fis = new FileInputStream(file);
//buffer = new byte[(int) file_length];
buffer = new byte[(int) file.length()];
long time_start = System.currentTimeMillis();
while (true) {
Logger.d("... now next:" + next + " and offset:" + offset);
if (System.currentTimeMillis() - time_start > 1000) {
Logger.e("!!! left due to time out");
break;
}
next = fis.read(buffer, offset, (buffer.length-offset));
if (next < 0 || offset >= buffer.length) {
Logger.d("... completed to read");
break;
}
offset += next;
}
//if (offset < buffer.length) {
if (offset < (int) file_length) {
Logger.e("!!! not complete to read");
return null;
}
fis.close();
return buffer;
} catch (IOException e) {
e.printStackTrace();
Logger.e("!!! IOException");
return null;
}
}
public byte[] readBytesFromFile(File file, boolean is_fis_fos_only) {
if (file == null) return null;
if (is_fis_fos_only) {
return readBytesFromFile(file);
}
Logger.d(">>> path:" + file.getAbsolutePath());
FileInputStream fis;
BufferedInputStream bis;
ByteArrayOutputStream bos;
byte[] buf = new byte[(int) file.length()];
int num_read;
if (!file.exists()) {
Logger.e("!!! file doesn't exists");
return null;
}
try {
fis = new FileInputStream(file);
bis = new BufferedInputStream(fis);
bos = new ByteArrayOutputStream();
long time_start = System.currentTimeMillis();
while (true) {
if (System.currentTimeMillis() - time_start > 1000) {
Logger.e("!!! left due to time out");
break;
}
num_read = bis.read(buf, 0, buf.length); //1024 bytes per call
if (num_read < 0) break;
bos.write(buf, 0, num_read);
}
buf = bos.toByteArray();
fis.close();
bis.close();
bos.close();
return buf;
} catch (FileNotFoundException e) {
e.printStackTrace();
Logger.e("!!! FileNotFoundException");
return null;
} catch (IOException e) {
e.printStackTrace();
Logger.e("!!! IOException");
return null;
}
}
/**
* streams (InputStream and OutputStream) transfer binary data
* if to write a string to a stream, must first convert it to bytes, or in other words encode it
*/
public boolean writeStringToFile(File file, String string, Charset charset) {
if (file == null) return false;
if (string == null) return false;
return writeBytesToFile(file, string.getBytes((charset == null) ? DEFAULT_CHARSET:charset));
}
public boolean writeBytesToFile(File file, byte[] data) {
if (file == null) return false;
if (data == null) return false;
FileOutputStream fos;
BufferedOutputStream bos;
try {
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos);
bos.write(data, 0, data.length);
bos.flush();
bos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
Logger.e("!!! IOException");
return false;
}
return true;
}
/**
* io blocks until some input/output is available.
*/
public boolean copy(File source, File destination) {
if (source == null || destination == null) return false;
Logger.d(">>> source:" + source.getAbsolutePath() + ", destination:" + destination.getAbsolutePath());
try {
FileInputStream fis = new FileInputStream(source);
FileOutputStream fos = new FileOutputStream(destination);
byte[] buffer = new byte[(int) source.length()];
int len;
while (EOF != (len = fis.read(buffer))) {
fos.write(buffer, 0, len);
}
if (true) { //debug
byte[] copies = readBytesFromFile(destination);
if (copies != null) {
int copy_len = copies.length;
Logger.d("... stream read and write done for " + copy_len + " bytes");
}
}
return destination.length() != 0;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}
public void list(final String path, final String end, final List<File> files) {
Logger.d(">>> path:" + path + ", end:" + end);
File file = new File(path);
if (file.isDirectory()) {
for (File child : file.listFiles()){
list(child.getAbsolutePath(), end, files);
}
} else if (file.isFile()) {
if (end.equals("")) {
files.add(file);
} else {
if (file.getName().endsWith(end)) files.add(file);
}
}
}
public String[] splitFileName(File file, String split) {
String path;
String ext;
int lastIndexOfSplit = file.getAbsolutePath().lastIndexOf(split);
if (lastIndexOfSplit < 0) {
path = file.getAbsolutePath();
ext = "";
} else {
path = file.getAbsolutePath().substring(0, lastIndexOfSplit);
ext = file.getAbsolutePath().substring(lastIndexOfSplit);
}
return new String[] {path, ext};
}
public File rename(File old_file, String new_name) {
if (old_file == null || new_name == null) return null;
Logger.d(">>> old file path:" + old_file.getAbsolutePath() + ", new file name:" + new_name);
File new_file = new File(old_file, new_name);
if (!old_file.equals(new_file)) {
if (new_file.exists()) { //if find out previous file/dir at new path name exists
if (new_file.delete()) {
Logger.d("... succeeded to delete previous file at new abstract path name:" + new_file.getAbsolutePath());
} else {
Logger.e("!!! failed to delete previous file at new abstract path name");
return null;
}
}
if (old_file.renameTo(new_file)) {
Logger.d("... succeeded to rename old file to new abstract path name:" + new_file.getAbsolutePath());
} else {
Logger.e("!!! failed to rename old file to new abstract path name");
}
} else {
Logger.d("... new and old file have the equal abstract path name:" + new_file.getAbsolutePath());
}
return new_file;
}
public boolean remove(final String path, final String end) {
Logger.d(">>> path:" + path + ", end:" + end);
File file = new File(path);
boolean result = false;
if (file.isDirectory()) {
for (File child : file.listFiles()){
result = remove(child.getAbsolutePath(), end);
}
} else if (file.isFile()) {
if (end.equals("")) {
result = file.delete();
} else {
if (file.getName().endsWith(end)) result = file.delete();
}
} else {
Logger.e("!!! child is not file or directory");
}
return result;
}
@TargetApi(Build.VERSION_CODES.O)
public byte[] readNIOBytesFromFile(String path) throws IOException {
Logger.d(">>> path:" + path);
if (!Files.exists(Paths.get(path), LinkOption.NOFOLLOW_LINKS)) {
Logger.e("!!! file doesn't exists");
return null;
} else {
return Files.readAllBytes(Paths.get(path));
}
}
@TargetApi(Build.VERSION_CODES.O)
public File writeNIOBytesToFile(String dir, String name, byte[] data) {
Logger.d(">>> dir:" + dir + ", name:" + name);
Path path_dir;
Path path_file;
try {
if (!Files.exists(Paths.get(dir), LinkOption.NOFOLLOW_LINKS)) {
Logger.d("... make a dir");
path_dir = Files.createDirectories(Paths.get(dir));
if (path_dir == null) {
Logger.e("!!! failed to make a dir");
return null;
}
}
path_file = Files.write(Paths.get(name), data);
return path_file.toFile();
} catch (IOException e) {
e.printStackTrace();
Logger.e("!!! IOException");
return null;
}
}
@TargetApi(Build.VERSION_CODES.O)
public void listNIO(final String dir, final String end, final List<File> files) throws IOException {
Logger.d(">>> dir:" + dir + ", end:" + end);
Files.walkFileTree(Paths.get(dir), new FileVisitor<Path>() {
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
Logger.d("... file:" + dir.getFileName());
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
Logger.d("... file:" + file.getFileName());
if (end.equals("")) {
files.add(file.toFile());
} else {
if (file.endsWith(end)) files.add(file.toFile());
}
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) {
Logger.d("... file:" + file.getFileName());
if (end.equals("")) {
files.add(file.toFile());
} else {
if (file.endsWith(end)) files.add(file.toFile());
}
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
Logger.d("... file:" + dir.getFileName());
return FileVisitResult.CONTINUE;
}
});
}
/**
* recursion
*/
private int factorial (int x) {
if (x > 1) return (x*(factorial(x-1)));
else if (x == 1) return x;
else return 0;
}
}
添加onActivityResult，获取docx或pdf文件
var imageUriPath = ""
imageUriPath =
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
val split = (imageUri.path ? : "").split(":") //split the path.
split[1]
} else {
imageUri.path ? : ""
}
val file = File(imageUriPath)
如果你有一个符合DocumentContract的Uri，那么你可能不想使用File。 如果你在kotlin上，使用DocumentFile来做你在旧世界中使用File来做的事情，并使用ContentResolver来获取流。
其他的东西几乎都肯定会坏。
使用内容解析器获取输入流
InputStream inputStream = getContentResolver().openInputStream(uri);
然后将输入流复制到文件中
FileUtils.copyInputStreamToFile(inputStream, file);
样品使用方法:
private File toFile(Uri uri) throws IOException {
String displayName = "";
Cursor cursor = getContentResolver().query(uri, null, null, null, null);
if(cursor != null && cursor.moveToFirst()){
try {
displayName = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));
}finally {
cursor.close();
}
}
File file = File.createTempFile(
FilenameUtils.getBaseName(displayName),
"."+FilenameUtils.getExtension(displayName)
);
InputStream inputStream = getContentResolver().openInputStream(uri);
FileUtils.copyInputStreamToFile(inputStream, file);
return file;
}
uri.toString()给我:"content://com.google.android.apps.nbu.files.provider/1/file%3A%2F%2F%2Fstorage%2Femulated%2F0%2FDownload%2Fbackup.file"
uri.getPath()给我:“/1/文件:///存储/模拟/0/下载/备份文件。”
new File(uri.getPath())给我“/1/ File:/storage/ emululated /0/Download/backup.file”。
所以如果你有一个文件的访问权限，想要避免使用ContentResolver或直接读取文件，答案是:
private String uriToPath( Uri uri )
{
File backupFile = new File( uri.getPath() );
String absolutePath = backupFile.getAbsolutePath();
return absolutePath.substring( absolutePath.indexOf( ':' ) + 1 );
}
为简化回答，跳过错误处理
你可以使用这个函数从uri中获取文件在新的android和旧的
fun getFileFromUri(context: Context, uri: Uri?): File? {
uri ?: return null
uri.path ?: return null
var newUriString = uri.toString()
newUriString = newUriString.replace(
"content://com.android.providers.downloads.documents/",
"content://com.android.providers.media.documents/"
)
newUriString = newUriString.replace(
"/msf%3A", "/image%3A"
)
val newUri = Uri.parse(newUriString)
var realPath = String()
val databaseUri: Uri
val selection: String?
val selectionArgs: Array<String>?
if (newUri.path?.contains("/document/image:") == true) {
databaseUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI
selection = "_id=?"
selectionArgs = arrayOf(DocumentsContract.getDocumentId(newUri).split(":")[1])
} else {
databaseUri = newUri
selection = null
selectionArgs = null
}
try {
val column = "_data"
val projection = arrayOf(column)
val cursor = context.contentResolver.query(
databaseUri,
projection,
selection,
selectionArgs,
null
)
cursor?.let {
if (it.moveToFirst()) {
val columnIndex = cursor.getColumnIndexOrThrow(column)
realPath = cursor.getString(columnIndex)
}
cursor.close()
}
} catch (e: Exception) {
Log.i("GetFileUri Exception:", e.message ?: "")
}
val path = realPath.ifEmpty {
when {
newUri.path?.contains("/document/raw:") == true -> newUri.path?.replace(
"/document/raw:",
""
)
newUri.path?.contains("/document/primary:") == true -> newUri.path?.replace(
"/document/primary:",
"/storage/emulated/0/"
)
else -> return null
}
}
return if (path.isNullOrEmpty()) null else File(path)
}
另一种方法是创建一个临时文件。做那件事:
fun createTmpFileFromUri(context: Context, uri: Uri, fileName: String): File? {
return try {
val stream = context.contentResolver.openInputStream(uri)
val file = File.createTempFile(fileName, "", context.cacheDir)
org.apache.commons.io.FileUtils.copyInputStreamToFile(stream,file)
file
} catch (e: Exception) {
e.printStackTrace()
null
}
}
我们使用Apache公共库FileUtils类。将它添加到您的项目:
implementation "commons-io:commons-io:2.7"
注意，MAKE SURE在使用后调用file.delete()。 查阅更多资料。
要正确地使用context uri获取文件， 感谢来自@Mohsents， @Bogdan Kornev， @CommonsWare， @Juan Camilo Rodriguez的回答Durán;
我从uri中创建了一个inputStream，并使用这个iStream创建了一个临时文件，最后我能够从这个文件中提取uri和路径。
fun createFileFromContentUri(fileUri : Uri) : File{
var fileName : String = ""
fileUri.let { returnUri ->
requireActivity().contentResolver.query(returnUri,null,null,null)
}?.use { cursor ->
val nameIndex = cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME)
cursor.moveToFirst()
fileName = cursor.getString(nameIndex)
}
// For extract file mimeType
val fileType: String? = fileUri.let { returnUri ->
requireActivity().contentResolver.getType(returnUri)
}
val iStream : InputStream = requireActivity().contentResolver.openInputStream(fileUri)!!
val outputDir : File = context?.cacheDir!!
val outputFile : File = File(outputDir,fileName)
copyStreamToFile(iStream, outputFile)
iStream.close()
return outputFile
}
fun copyStreamToFile(inputStream: InputStream, outputFile: File) {
inputStream.use { input ->
val outputStream = FileOutputStream(outputFile)
outputStream.use { output ->
val buffer = ByteArray(4 * 1024) // buffer size
while (true) {
val byteCount = input.read(buffer)
if (byteCount < 0) break
output.write(buffer, 0, byteCount)
}
output.flush()
}
}
}
使用这个来写入文件，它为我工作时，gif的uri是由GBoard提供的，我必须在我的应用程序数据复制该gif。
try {
String destinationFilePath = getExternalFilesDir("gifs") + "/tempFile.txt";
InputStream inputStream = getContentResolver().openInputStream(uri);
OutputStream outputStream = new FileOutputStream(destinationFilePath);
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
inputStream.close();
outputStream.close();
}
catch (Exception e) {
e.printStackTrace();
}
一些库需要文件对象的过程，如改造，一些图像编辑器等。 将URI转换为文件对象或任何类似的东西，我们有一种方法，这是支持所有android旧版本和即将到来的版本。
步骤1:
你必须在FilesDir中创建一个新文件，这个文件对于其他与我们的文件和扩展名相同的应用程序是不可读的。
步骤2:
您必须通过使用InputStream复制URI的内容来创建一个文件。
File f = getFile(getApplicationContext(), uri);
public static File getFile(Context context, Uri uri) throws IOException {
File destinationFilename = new File(context.getFilesDir().getPath() + File.separatorChar + queryName(context, uri));
try (InputStream ins = context.getContentResolver().openInputStream(uri)) {
createFileFromStream(ins, destinationFilename);
} catch (Exception ex) {
Log.e("Save File", ex.getMessage());
ex.printStackTrace();
}
return destinationFilename;
}
public static void createFileFromStream(InputStream ins, File destination) {
try (OutputStream os = new FileOutputStream(destination)) {
byte[] buffer = new byte[4096];
int length;
while ((length = ins.read(buffer)) > 0) {
os.write(buffer, 0, length);
}
os.flush();
} catch (Exception ex) {
Log.e("Save File", ex.getMessage());
ex.printStackTrace();
}
}
private static String queryName(Context context, Uri uri) {
Cursor returnCursor =
context.getContentResolver().query(uri, null, null, null, null);
assert returnCursor != null;
int nameIndex = returnCursor.getColumnIndex(OpenableColumns.DISPLAY_NAME);
returnCursor.moveToFirst();
String name = returnCursor.getString(nameIndex);
returnCursor.close();
return name;
}
科特林 2022
suspend fun Context.createFileFromAsset(assetName: String, fileName: String): File? {
return withContext(Dispatchers.IO) {
runCatching {
val stream = assets.open(assetName)
val file = File(cacheDir.absolutePath, fileName)
org.apache.commons.io.FileUtils.copyInputStreamToFile(stream, file)
file
}.onFailure { Timber.e(it) }.getOrNull()
}
}
处理完文件后，请确保对其调用.delete()。向@Mohsent致敬
经过大量的搜索和尝试不同的方法，我发现这个方法适用于不同的Android版本: 首先复制这个函数:
fun getRealPathFromUri(context: Context, contentUri: Uri): String {
var cursor: Cursor? = null
try {
val proj: Array<String> = arrayOf(MediaStore.Images.Media.DATA)
cursor = context.contentResolver.query(contentUri, proj, null, null, null)
val columnIndex = cursor?.getColumnIndexOrThrow(MediaStore.Images.Media.DATA)
cursor?.moveToFirst()
return columnIndex?.let { cursor?.getString(it) } ?: ""
} finally {
cursor?.close()
}
}
然后，生成一个像这样的文件:
File(getRealPathFromUri(context, uri))
