如何在android中为备份联系人创建一个文件夹

Question

我是android开发的新手，我正在创建android联系人备份。在这个.vcf文件将放在该文件夹中。我尝试了很多次它没用。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    backup = (Button) findViewById(R.id.btnbkp);
    restore = (Button) findViewById(R.id.btnres);

    vfile = "contacts.vcf";
    storage_path = Environment.getExternalStorageDirectory().toString() + "/" + vfile;
    f = new File(storage_path);


    backup.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            new LongOperation().execute("");

        }
    });
    restore.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final Intent intent = new Intent();

            final MimeTypeMap mime = MimeTypeMap.getSingleton();
            String tmptype = mime.getMimeTypeFromExtension("vcf");
            final File file = new File(Environment.getExternalStorageDirectory().toString() + "/contacts.vcf");

            intent.setDataAndType(Uri.fromFile(file), tmptype);
            startActivity(intent);
        }
    });

}

private class LongOperation extends AsyncTask<String, Void, String> {

    ProgressDialog progress;

    @Override
    protected void onPreExecute() {
        progress = new ProgressDialog(MainActivity.this);
        progress.setMessage("Loading.... ");
        progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progress.setIndeterminate(true);
        progress.setProgress(0);
        progress.show();
    }

    @Override
    protected String doInBackground(String... params) {
        try {
            if (!f.exists())
                f.createNewFile();
            mFileOutputStream = new FileOutputStream(storage_path, false);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        getVcardString();
        return "Executed";
    }

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(MainActivity.this, result + " Succesfully backed up", Toast.LENGTH_LONG).show();
        progress.dismiss();
    }

}

private void getVcardString() {
    vCard = new ArrayList<String>();
    cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
    if (cursor != null && cursor.getCount() > 0) {
        cursor.moveToFirst();
        for (int i = 0; i < cursor.getCount(); i++) {

            get(cursor);
            Log.d("TAG", "Contact " + (i + 1) + "VcF String is" + vCard.get(i));
            cursor.moveToNext();
        }

    } else {
        Log.d("TAG", "No Contacts in Your Phone");
    }
    try {
        mFileOutputStream.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

public void get(Cursor cursor) {
    //cursor.moveToFirst();
    String lookupKey = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.LOOKUP_KEY));
    Uri uri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_VCARD_URI, lookupKey);
    AssetFileDescriptor fd;
    try {
        fd = this.getContentResolver().openAssetFileDescriptor(uri, "r");
        FileInputStream fis = fd.createInputStream();
        byte[] buf = new byte[(int) fd.getDeclaredLength()];
        fis.read(buf);
        String vcardstring = new String(buf);
        vCard.add(vcardstring);

        mFileOutputStream.write(vcardstring.toString().getBytes());

    } catch (Exception e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

如何使用此代码

 String folder_main = "NewFolder";
 File f = new File(Environment.getExternalStorageDirectory(), folder_main);
 if (!f.exists()) {
 f.mkdirs();
 }

请告诉我......提前谢谢..

 <uses-permission android:name="android.permission.READ_CONTACTS"/>
<uses-permission android:name="android.permission.WRITE_CONTACTS"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="ANDROID.PERMISSION.READ_EXTERNAL_STORAGE"/>