Écrire un fichier dans un stockage externe sous Android

Question

Je veux créer un fichier dans une carte SD de stockage externe et y écrire. J'ai recherché sur Internet et j'ai essayé mais je n'ai pas obtenu le résultat, j'ai également ajouté l'autorisation dans le fichier Android Manifest, je le fais sur Emulator, j'essaye le code suivant et obtenir un ERRR", "Impossible de créer le fichier".

 btnWriteSDFile = (Button) findViewById(R.id.btnWriteSDFile);
btnWriteSDFile.setOnClickListener(new OnClickListener() {
    //private Throwable e;

    @Override
    public void onClick(View v) {
        // write on SD card file data from the text box
        try {
            File myFile = new File("/sdcard/mysdfile.txt");
            myFile.createNewFile();
            FileOutputStream fOut = new FileOutputStream(myFile);
            OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
            myOutWriter.append(txtData.getText());
            myOutWriter.close();
            fOut.close();

        } catch (Exception e) {
              Log.e("ERRR", "Could not create file",e);
        } 
    }// onClick
}); // btnWriteSDFile

Answer 1

Vous pouvez également le faire avec ce code.

  public class WriteSDCard extends Activity {

 private static final String TAG = "MEDIA";
 private TextView tv;

  /** Called when the activity is first created. */
@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 2

Pour écrire dans le stockage externe des appareils Lollipop+, nous avons besoin de :

1. Ajoutez l'autorisation suivante dans Manifest :

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

2. Demander une approbation de l'utilisateur :

           public static final int REQUEST_WRITE_STORAGE = 112; 
   
          private requestPermission(Activity context) {
              boolean hasPermission = (ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED);
              if (!hasPermission) {
                 ActivityCompat.requestPermissions(context,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                  REQUEST_WRITE_STORAGE);
              } else {
                // You are allowed to write external storage:
                String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/new_folder";
                File storageDir = new File(path);
                if (!storageDir.exists() && !storageDir.mkdirs()) {
                  // This should never happen - log handled exception!
                }
              }
   

3. Gérez la réponse de l'utilisateur dans Activity :

    @Override
   public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
   
        switch (requestCode)
        {
         case Preferences.REQUEST_WRITE_STORAGE: {
            if (grantResults.length > 0 && grantResults[0] ==  PackageManager.PERMISSION_GRANTED) {
              Toast.makeText(this, "The app was allowed to write to your storage!", Toast.LENGTH_LONG).show();
              // Reload the activity with permission granted or use the features what required the permission
            } else {
              Toast.makeText(this, "The app was not allowed to write to your storage. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
           }
        }
    }
   

Answer 3

Le code ci-dessous crée un répertoire Documents , puis un sous-répertoire pour l'application et y enregistre les fichiers.

 public class loadDataTooDisk extends AsyncTask<String, Integer, String> {
    String sdCardFileTxt;
    @Override
    protected String doInBackground(String... params)
    {

        //check to see if external storage is avalibel
        checkState();
        if(canW == canR == true)
        {
            //get the path to sdcard 
            File pathToExternalStorage = Environment.getExternalStorageDirectory();
            //to this path add a new directory path and create new App dir (InstroList) in /documents Dir
            File appDirectory = new File(pathToExternalStorage.getAbsolutePath()  + "/documents/InstroList");
            // have the object build the directory structure, if needed.
            appDirectory.mkdirs();
            //test to see if it is a Text file
            if ( myNewFileName.endsWith(".txt") )
            {

                //Create a File for the output file data
                File saveFilePath = new File (appDirectory, myNewFileName);
                //Adds the textbox data to the file
                try{
                    String newline = "\r\n";
                    FileOutputStream fos = new FileOutputStream (saveFilePath);
                    OutputStreamWriter OutDataWriter  = new OutputStreamWriter(fos);

                    OutDataWriter.write(equipNo.getText() + newline);
                    // OutDataWriter.append(equipNo.getText() + newline);
                    OutDataWriter.append(equip_Type.getText() + newline);
                    OutDataWriter.append(equip_Make.getText()+ newline);
                    OutDataWriter.append(equipModel_No.getText()+ newline);
                    OutDataWriter.append(equip_Password.getText()+ newline);
                    OutDataWriter.append(equipWeb_Site.getText()+ newline);
                    //OutDataWriter.append(equipNotes.getText());
                    OutDataWriter.close();

                    fos.flush();
                    fos.close();

                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}

Celui-ci construit le nom du fichier

    private String BuildNewFileName()
    { // creates a new filr name
        Time today = new Time(Time.getCurrentTimezone());
        today.setToNow();

        StringBuilder sb = new StringBuilder();

        sb.append(today.year + "");                // Year)
        sb.append("_");
        sb.append(today.monthDay + "");          // Day of the month (1-31)
        sb.append("_");
        sb.append(today.month + "");              // Month (0-11))
        sb.append("_");
        sb.append(today.format("%k:%M:%S"));      // Current time
        sb.append(".txt");                      //Completed file name

        myNewFileName = sb.toString();
        //Replace (:) with (_)
        myNewFileName = myNewFileName.replaceAll(":", "_");

        return myNewFileName;
    }

J'espère que cela t'aides! Il m'a fallu beaucoup de temps pour le faire fonctionner.

Answer 4

Vous devriez lire la documentation sur le stockage externe sur Android . Il y a une multitude de problèmes qui pourraient exister avec votre code actuel, et je pense que parcourir la documentation pourrait vous aider à les résoudre.