Android 将文件保存到外部存储

Question

我在 Android 应用程序上创建目录并将文件保存到其中时遇到了一些问题。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();

但它引发了异常：

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);

如果我设置filename 为： "MyApp/MediaTag-"+objectId+" 它正在工作，但是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。那么你知道我做错了什么吗？

还有另一个问题：有什么方法可以使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磁盘驱动器时代码>？

Answer 1

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();
    }
}

，并将其添加到清单中

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

编辑：通过使用此行，您将能够在图库视图中看到保存的图像。

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

也看看这个链接 http://rajareddypolam.wordpress.com/?p=3&预览=真

Answer 2

RajaReddy 提供的代码不再适用于 KitKat

这个代码可以（2 处更改）：

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);
                }
    });

}

Answer 3

更新 2018，SDK >= 23。

现在您还应该检查用户是否已授予外部存储权限，方法是：

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);
    }
}

当然，在 AndroidManifest.xml 中添加:

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

Answer 4

的许可：

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

您需要获得此方法

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
}

Answer 5

确保您的应用程序具有适当的权限，可以写入外部存储： http://developer.android.com/reference/android/Manifest.permission.html#WRITE_EXTERNAL_STORAGE

它在你的清单文件中应该看起来像这样：

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

Answer 6

试试这个：

1. 检查外部存储设备
2. 写入文件
3. 读取文件

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");
    }
}

Answer 7

我创建了一个用于保存位图的 AsyncTask。

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)
            {
            }
        }
    }
}

Answer 8

从 android10 开始，旧的保存文件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 -到画廊/

Answer 9

可能会抛出异常，因为没有 MediaCard 子目录。您应该检查路径中的所有目录是否存在。

关于文件的可见性：如果您将名为 .nomedia 的文件放入目录中，您就是在告诉 Android 您不希望它扫描其中的媒体文件，并且它们不会出现在图库中。

Answer 10

对于 API 级别 23 (Marshmallow) 及更高版本，除了清单中的使用权限之外，还应该实现弹出权限，并且用户需要在运行时使用应用程序时授予它。

下面，有一个示例将 hello world! 保存为图片目录中 Test 目录中 myFile.txt 文件的内容。

在清单中：

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

您要创建文件的位置：

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();
 }

Answer 11

自 android 4.4 文件保存已更改。它

ContextCompat.getExternalFilesDirs(context, name);

返回一个数组。

当 name 为 null 时，

第一个值类似于 /storage/emulated/0/Android/com.my.package/files

第二个值类似于
/storage/extSdCard/Android/com.my.package/files

单个项目数组部分，但它演示了它是如何工作的：

android 4.3 及以下版本它重新调整了一些杂乱代码的

    /** 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;
        }

Answer 12

这段代码工作得很好&也曾参与 KitKat 的工作。欣赏@RajaReddy PolamReddy
此处添加了更多步骤，并且在图库上也可见。

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();
    }

}

这是画廊中可见的媒体扫描仪。

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);
}

Answer 13

点击此处查看完整说明和源代码

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);
  }
}