Android 保存文件到外部存储器

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Make sure your app has the proper permissions to be allowed to write to external storage: http://developer.android.com/reference/android/Manifest.permission.html#WRITE_EXTERNAL_STORAGE

It should look something like this in your manifest file:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

小开

最佳答案

Use this function to save your bitmap in SD card

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();
}
}

and add this in manifest

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

EDIT: By using this line you will be able to see saved images in the gallery view.

sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED,
Uri.parse("file://" + Environment.getExternalStorageDirectory())));

look at this link also http://rajareddypolam.wordpress.com/?p=3&preview=true

小开

Probably exception is thrown because there is no MediaCard subdir. You should check if all dirs in the path exist.

About visibility of your files: if you put file named .nomedia in your dir you are telling Android that you don't want it to scan it for media files and they will not appear in the gallery.

小开

Try This :

Check External storage device
Write File
Read File

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");
}
}

小开

The code presented by RajaReddy no longer works for KitKat

This one does (2 changes):

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);
}
});


}

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This code is Working great & Worked on KitKat as well. Appreciate @RajaReddy PolamReddy
Added few more steps here and also Visible on Gallery as well.

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();
}


}

This is Media scanner to Visible in Gallery.

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);
}

小开

since android 4.4 file saving has been changed. there is

ContextCompat.getExternalFilesDirs(context, name);

it retuns an array.

when name is null

the first value is like /storage/emulated/0/Android/com.my.package/files

the second value is like /storage/extSdCard/Android/com.my.package/files

android 4.3 and less it retuns a single item array

parts of little messy code but it demonstrates how it works:

    /** 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;
}

小开

I have created an AsyncTask for saving bitmaps.

public class BitmapSaver extends AsyncTask<Void, Void, Void>
{
public static final String TAG ="BitmapSaver";


private Bitmap bmp;


private Context ctx;


private File pictureFile;


public BitmapSaver(Context paramContext , Bitmap paramBitmap)
{
ctx = paramContext;


bmp = paramBitmap;
}


/** Create a File for saving an image or video */
private  File getOutputMediaFile()
{
// To be safe, you should check that the SDCard is mounted
// using Environment.getExternalStorageState() before doing this.
File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
+ "/Android/data/"
+ ctx.getPackageName()
+ "/Files");


// This location works best if you want the created images to be shared
// between applications and persist after your app has been uninstalled.


// Create the storage directory if it does not exist
if (! mediaStorageDir.exists()){
if (! mediaStorageDir.mkdirs()){
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("ddMMyyyy_HHmm").format(new Date());
File mediaFile;
String mImageName="MI_"+ timeStamp +".jpg";
mediaFile = new File(mediaStorageDir.getPath() + File.separator + mImageName);
return mediaFile;


}
protected Void doInBackground(Void... paramVarArgs)
{
this.pictureFile = getOutputMediaFile();


if (this.pictureFile == null) { return null; }


try
{
FileOutputStream localFileOutputStream = new FileOutputStream(this.pictureFile);
this.bmp.compress(Bitmap.CompressFormat.PNG, 90, localFileOutputStream);
localFileOutputStream.close();
}
catch (FileNotFoundException localFileNotFoundException)
{
return null;
}
catch (IOException localIOException)
{
}
return null;
}


protected void onPostExecute(Void paramVoid)
{
super.onPostExecute(paramVoid);


try
{
//it will help you broadcast and view the saved bitmap in Gallery
this.ctx.sendBroadcast(new Intent("android.intent.action.MEDIA_MOUNTED", Uri
.parse("file://" + Environment.getExternalStorageDirectory())));


Toast.makeText(this.ctx, "File saved", 0).show();


return;
}
catch (Exception localException1)
{
try
{
Context localContext = this.ctx;
String[] arrayOfString = new String[1];
arrayOfString[0] = this.pictureFile.toString();
MediaScannerConnection.scanFile(localContext, arrayOfString, null,
new MediaScannerConnection.OnScanCompletedListener()
{
public void onScanCompleted(String paramAnonymousString ,
Uri paramAnonymousUri)
{
}
});
return;
}
catch (Exception localException2)
{
}
}
}
}

小开

You need a permission for this

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

and method:

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
}

小开

Update 2018, SDK >= 23.

Now you should also check if the user has granted permission to external storage by using:

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);
}
}

and of course, add in the AndroidManifest.xml:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

小开

Click Here for full description and source code

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);
}
}

小开

For API level 23 (Marshmallow) and later, additional to uses-permission in manifest, pop up permission should also be implemented, and user needs to grant it while using the app in run-time.

Below, there is an example to save hello world! as content of myFile.txt file in Test directory inside picture directory.

In the manifest:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Where you want to create the file:

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();
}

小开

Old way of saving files might not work with new versions of android, starting with android10.

 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")
}
}

Reference- https://www.simplifiedcoding.net/android-save-bitmap-to-gallery/