我在Android应用程序上创建目录并将文件保存到它时遇到了一些问题。我正在使用这段代码来执行此操作：
String filename = "MyApp/MediaTag/MediaTag-"+objectId+".png";
File file = new File(Environment.getExternalStorageDirectory(), filename);
FileOutputStream fos;
fos = new FileOutputStream(file);
fos.write(mediaTagBuffer);
fos.flush();
fos.close();
但这是一个例外：
java.io.FileNotFoundException：/mnt/sdcard/MyApp/MediaCard/MediaCard-0.png（没有这样的文件或目录）
在该行：fos = new FileOutputStream(file);
如果我将文件名设置为："MyApp/MediaTag-"+objectId+"它正在工作，但如果我尝试创建文件并将其保存到另一个目录，则会抛出异常。那么任何想法我做错了什么？
还有一个问题：有没有办法让我的文件在外部存储中保密，这样用户就无法在图库中看到它们，只有当他将设备连接为Disk Drive时？
答案 0 :(得分：177)
使用此功能将位图保存在SD卡
中private void SaveImage(Bitmap finalBitmap) {
String root = Environment.getExternalStorageDirectory().toString();
File myDir = new File(root + "/saved_images");
if (!myDir.exists()) {
myDir.mkdirs();
}
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String fname = "Image-"+ n +".jpg";
File file = new File (myDir, fname);
if (file.exists ())
file.delete ();
try {
FileOutputStream out = new FileOutputStream(file);
finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
}
}
并在清单
中添加此内容<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
编辑：通过使用此行，您可以在图库视图中查看已保存的图片。
sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED,
Uri.parse("file://" + Environment.getExternalStorageDirectory())));
同时查看此链接http://rajareddypolam.wordpress.com/?p=3&preview=true
答案 1 :(得分：24)
RajaReddy提供的代码不再适用于KitKat
这个（2个变化）：
private void saveImageToExternalStorage(Bitmap finalBitmap) {
String root = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString();
File myDir = new File(root + "/saved_images");
myDir.mkdirs();
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String fname = "Image-" + n + ".jpg";
File file = new File(myDir, fname);
if (file.exists())
file.delete();
try {
FileOutputStream out = new FileOutputStream(file);
finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
out.flush();
out.close();
}
catch (Exception e) {
e.printStackTrace();
}
// Tell the media scanner about the new file so that it is
// immediately available to the user.
MediaScannerConnection.scanFile(this, new String[] { file.toString() }, null,
new MediaScannerConnection.OnScanCompletedListener() {
public void onScanCompleted(String path, Uri uri) {
Log.i("ExternalStorage", "Scanned " + path + ":");
Log.i("ExternalStorage", "-> uri=" + uri);
}
});
}
答案 2 :(得分：5)
您需要获得此权限
< uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
public boolean saveImageOnExternalData(String filePath, byte[] fileData) {
boolean isFileSaved = false;
try {
File f = new File(filePath);
if (f.exists())
f.delete();
f.createNewFile();
FileOutputStream fos = new FileOutputStream(f);
fos.write(fileData);
fos.flush();
fos.close();
isFileSaved = true;
// File Saved
} catch (FileNotFoundException e) {
System.out.println("FileNotFoundException");
e.printStackTrace();
} catch (IOException e) {
System.out.println("IOException");
e.printStackTrace();
}
return isFileSaved;
// File Not Saved
}
答案 3 :(得分：4)
确保您的应用具有允许写入外部存储的适当权限：http://developer.android.com/reference/android/Manifest.permission.html#WRITE_EXTERNAL_STORAGE
它应该在您的清单文件中看起来像这样：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
答案 4 :(得分：4)
试试这个：
public class WriteSDCard extends Activity {
private static final String TAG = "MEDIA";
private TextView tv;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv = (TextView) findViewById(R.id.TextView01);
checkExternalMedia();
writeToSDFile();
readRaw();
}
/**
* Method to check whether external media available and writable. This is
* adapted from
* http://developer.android.com/guide/topics/data/data-storage.html
* #filesExternal
*/
private void checkExternalMedia() {
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
// Can read and write the media
mExternalStorageAvailable = mExternalStorageWriteable = true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
// Can only read the media
mExternalStorageAvailable = true;
mExternalStorageWriteable = false;
} else {
// Can't read or write
mExternalStorageAvailable = mExternalStorageWriteable = false;
}
tv.append("\n\nExternal Media: readable=" + mExternalStorageAvailable
+ " writable=" + mExternalStorageWriteable);
}
/**
* Method to write ascii text characters to file on SD card. Note that you
* must add a WRITE_EXTERNAL_STORAGE permission to the manifest file or this
* method will throw a FileNotFound Exception because you won't have write
* permission.
*/
private void writeToSDFile() {
// Find the root of the external storage.
// See http://developer.android.com/guide/topics/data/data-
// storage.html#filesExternal
File root = android.os.Environment.getExternalStorageDirectory();
tv.append("\nExternal file system root: " + root);
// See
// http://stackoverflow.com/questions/3551821/android-write-to-sd-card-folder
File dir = new File(root.getAbsolutePath() + "/download");
dir.mkdirs();
File file = new File(dir, "myData.txt");
try {
FileOutputStream f = new FileOutputStream(file);
PrintWriter pw = new PrintWriter(f);
pw.println("Hi , How are you");
pw.println("Hello");
pw.flush();
pw.close();
f.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
Log.i(TAG, "******* File not found. Did you"
+ " add a WRITE_EXTERNAL_STORAGE permission to the manifest?");
} catch (IOException e) {
e.printStackTrace();
}
tv.append("\n\nFile written to " + file);
}
/**
* Method to read in a text file placed in the res/raw directory of the
* application. The method reads in all lines of the file sequentially.
*/
private void readRaw() {
tv.append("\nData read from res/raw/textfile.txt:");
InputStream is = this.getResources().openRawResource(R.raw.textfile);
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr, 8192); // 2nd arg is buffer
// size
// More efficient (less readable) implementation of above is the
// composite expression
/*
* BufferedReader br = new BufferedReader(new InputStreamReader(
* this.getResources().openRawResource(R.raw.textfile)), 8192);
*/
try {
String test;
while (true) {
test = br.readLine();
// readLine() returns null if no more lines in the file
if (test == null) break;
tv.append("\n" + " " + test);
}
isr.close();
is.close();
br.close();
} catch (IOException e) {
e.printStackTrace();
}
tv.append("\n\nThat is all");
}
}
答案 5 :(得分：3)
可能会抛出异常，因为没有MediaCard子目录。您应该检查路径中是否存在所有目录。
关于文件的可见性：如果您在目录中放置了名为.nomedia的文件，则告诉Android您不希望它扫描媒体文件，它们不会出现在图库中。
答案 6 :(得分：3)
Update 2018，SDK> = 23。
现在，您还应该使用以下方法检查用户是否已授予对外部存储的权限：
class Orders extends Component {
let cancel;
state = {
orders: [],
loading: true
}
componentDidMount() {
this.asyncRequest = api.get('/orders.json', {
cancelToken: new CancelToken(function executor(c) {
// An executor function receives a cancel function as a parameter
cancel = c;
})
})
.then(response => {
const fetchedOrders = [];
if (response && response.data) {
for (let key in response.data) {
fetchedOrders.push({
id: key,
...response.data[key]
});
}
}
this.setState({ loading: false, orders: fetchedOrders });
})
.catch(error => {
this.setState({ loading: false });
// please check the syntax, I don't remember if it is throw or throw new
throw error;
});
}
componentWillUnmount() {
if (this.asyncRequest) {
cancel();
}
}
render() {
return (
<div>
{this.state.orders.map(order => {
return (<Order
key={order.id}
ingrediencies={order.ingrediencies}
price={order.price} />);
})}
</div>
);
}
}
，当然还要添加<ErrorHandler>
<Orders />
</ErrorHandler>
：
public boolean isStoragePermissionGranted() {
String TAG = "Storage Permission";
if (Build.VERSION.SDK_INT >= 23) {
if (this.checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
Log.v(TAG, "Permission is granted");
return true;
} else {
Log.v(TAG, "Permission is revoked");
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
return false;
}
}
else { //permission is automatically granted on sdk<23 upon installation
Log.v(TAG,"Permission is granted");
return true;
}
}
public void saveImageBitmap(Bitmap image_bitmap, String image_name) {
String root = Environment.getExternalStorageDirectory().toString();
if (isStoragePermissionGranted()) { // check or ask permission
File myDir = new File(root, "/saved_images");
if (!myDir.exists()) {
myDir.mkdirs();
}
String fname = "Image-" + image_name + ".jpg";
File file = new File(myDir, fname);
if (file.exists()) {
file.delete();
}
try {
file.createNewFile(); // if file already exists will do nothing
FileOutputStream out = new FileOutputStream(file);
image_bitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
}
MediaScannerConnection.scanFile(this, new String[]{file.toString()}, new String[]{file.getName()}, null);
}
}
答案 7 :(得分：2)
因为android 4.4文件保存已被更改。有
ContextCompat.getExternalFilesDirs(context, name);
它返回一个数组。
当名称为空时
第一个值类似于/storage/emulated/0/Android/com.my.package/files
第二个值就像 /storage/extSdCard/Android/com.my.package/files
android 4.3及更少它返回单个项目数组
部分小杂乱的代码，但它演示了它是如何工作的：
/** Create a File for saving an image or video
* @throws Exception */
private File getOutputMediaFile(int type) throws Exception{
// Check that the SDCard is mounted
File mediaStorageDir;
if(internalstorage.isChecked())
{
mediaStorageDir = new File(getFilesDir().getAbsolutePath() );
}
else
{
File[] dirs=ContextCompat.getExternalFilesDirs(this, null);
mediaStorageDir = new File(dirs[dirs.length>1?1:0].getAbsolutePath() );
}
// Create the storage directory(MyCameraVideo) if it does not exist
if (! mediaStorageDir.exists()){
if (! mediaStorageDir.mkdirs()){
output.setText("Failed to create directory.");
Toast.makeText(this, "Failed to create directory.", Toast.LENGTH_LONG).show();
Log.d("myapp", "Failed to create directory");
return null;
}
}
// Create a media file name
// For unique file name appending current timeStamp with file name
java.util.Date date= new java.util.Date();
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",Locale.ENGLISH) .format(date.getTime());
File mediaFile;
if(type == MEDIA_TYPE_VIDEO) {
// For unique video file name appending current timeStamp with file name
mediaFile = new File(mediaStorageDir.getPath() + File.separator + slpid + "_" + pwsid + "_" + timeStamp + ".mp4");
}
else if(type == MEDIA_TYPE_AUDIO) {
// For unique video file name appending current timeStamp with file name
mediaFile = new File(mediaStorageDir.getPath() + File.separator + slpid + "_" + pwsid + "_" + timeStamp + ".3gp");
} else {
return null;
}
return mediaFile;
}
/** Create a file Uri for saving an image or video
* @throws Exception */
private Uri getOutputMediaFileUri(int type) throws Exception{
return Uri.fromFile(getOutputMediaFile(type));
}
//usage:
try {
file=getOutputMediaFileUri(MEDIA_TYPE_AUDIO).getPath();
} catch (Exception e1) {
e1.printStackTrace();
return;
}
答案 8 :(得分：1)
对于API级别23（棉花糖）及更高版本，除了清单中的uses-permission外，还应实现弹出权限，并且用户需要在运行时使用该应用时授予它。
下面有一个示例，将hello world!作为myFile.txt文件的内容保存在图片目录内的Test目录中。
在清单中：
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
您要在哪里创建文件：
int permission = ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
String[] PERMISSIONS_STORAGE = {Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE};
if (permission != PackageManager.PERMISSION_GRANTED)
{
ActivityCompat.requestPermissions(MainActivity.this,PERMISSIONS_STORAGE, 1);
}
File myDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "Test");
myDir.mkdirs();
try
{
String FILENAME = "myFile.txt";
File file = new File (myDir, FILENAME);
String string = "hello world!";
FileOutputStream fos = new FileOutputStream(file);
fos.write(string.getBytes());
fos.close();
}
catch (IOException e) {
e.printStackTrace();
}
答案 9 :(得分：1)
从 android10 开始，旧的文件保存方式可能不适用于新版本的 android。
fun saveMediaToStorage(bitmap: Bitmap) {
//Generating a dummy file name
val filename = "${System.currentTimeMillis()}.jpg"
//Output stream
var fos: OutputStream? = null
//For devices running android >= Q
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
//getting the contentResolver
context?.contentResolver?.also { resolver ->
//Content resolver will process the contentvalues
val contentValues = ContentValues().apply {
//putting file information in content values
put(MediaStore.MediaColumns.DISPLAY_NAME, filename)
put(MediaStore.MediaColumns.MIME_TYPE, "image/jpg")
put(MediaStore.MediaColumns.RELATIVE_PATH, Environment.DIRECTORY_PICTURES)
}
//Inserting the contentValues to contentResolver and getting the Uri
val imageUri: Uri? =
resolver.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues)
//Opening an outputstream with the Uri that we got
fos = imageUri?.let { resolver.openOutputStream(it) }
}
} else {
//These for devices running on android < Q
//So I don't think an explanation is needed here
val imagesDir =
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
val image = File(imagesDir, filename)
fos = FileOutputStream(image)
}
fos?.use {
//Finally writing the bitmap to the output stream that we opened
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, it)
context?.toast("Saved to Photos")
}
}
参考 - https://www.simplifiedcoding.net/android-save-bitmap-to-gallery/
答案 10 :(得分：0)
这段代码非常好用也在使用KitKat。感谢@RajaReddy PolamReddy
此处添加了更多步骤，并且还在Gallery上添加了Visible。
public void SaveOnClick(View v){
File mainfile;
String fpath;
try {
//i.e v2:My view to save on own folder
v2.setDrawingCacheEnabled(true);
//Your final bitmap according to my code.
bitmap_tmp = v2.getDrawingCache();
File(getExternalFilesDir(Environment.DIRECTORY_PICTURES)+File.separator+"/MyFolder");
Random random=new Random();
int ii=100000;
ii=random.nextInt(ii);
String fname="MyPic_"+ ii + ".jpg";
File direct = new File(Environment.getExternalStorageDirectory() + "/MyFolder");
if (!direct.exists()) {
File wallpaperDirectory = new File("/sdcard/MyFolder/");
wallpaperDirectory.mkdirs();
}
mainfile = new File(new File("/sdcard/MyFolder/"), fname);
if (mainfile.exists()) {
mainfile.delete();
}
FileOutputStream fileOutputStream;
fileOutputStream = new FileOutputStream(mainfile);
bitmap_tmp.compress(CompressFormat.JPEG, 100, fileOutputStream);
Toast.makeText(MyActivity.this.getApplicationContext(), "Saved in Gallery..", Toast.LENGTH_LONG).show();
fileOutputStream.flush();
fileOutputStream.close();
fpath=mainfile.toString();
galleryAddPic(fpath);
} catch(FileNotFoundException e){
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
这是Media Gallery中可见的媒体扫描程序。
private void galleryAddPic(String fpath) {
Intent mediaScanIntent = new Intent("android.intent.action.MEDIA_SCANNER_SCAN_FILE");
File f = new File(fpath);
Uri contentUri = Uri.fromFile(f);
mediaScanIntent.setData(contentUri);
this.sendBroadcast(mediaScanIntent);
}
答案 11 :(得分：0)
Click Here获取完整的描述和源代码
public void saveImage(Context mContext, Bitmap bitmapImage) {
File sampleDir = new File(Environment.getExternalStorageDirectory() + "/" + "ApplicationName");
TextView tvImageLocation = (TextView) findViewById(R.id.tvImageLocation);
tvImageLocation.setText("Image Store At : " + sampleDir);
if (!sampleDir.exists()) {
createpathForImage(mContext, bitmapImage, sampleDir);
} else {
createpathForImage(mContext, bitmapImage, sampleDir);
}
}