はじめまして。
今、twitter4jを使用してTwitterクライアントアプリを作成しています。
複数画像をメッセージと同時に投稿したいのですが、一度ファイルを取得しているにも関わらず
ファイルが存在しないことになってしまいます。
何がいけないのでしょうか?ご教示願います。

public class TweetActivity extends Activity {

private EditText mInputText;
private Twitter mTwitter;
private Button mGazou;
private ImageView imageView,imageView2,imageView3,imageView4;
private Boolean gazou=false;
UploadedMedia media1=null;
UploadedMedia media2=null;
UploadedMedia media3=null;
UploadedMedia media4=null;
int k =0;
Uri[] multi_uri=null;
Uri uri = null;
InputStream in;
long[]mediaIds = null;
long media_id =0;

private static final int RESULT_PICK_IMAGEFILE = 1001;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.new_tweet);

    mTwitter = TwitterUtils.getTwitterInstance(this);
    //Twitter文字入力
    mInputText = (EditText) findViewById(R.id.input_text);
    //Twitter画像選択(ギャラリーから)
    mGazou = (Button)findViewById(R.id.button1);
    mGazou.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
            intent.addCategory(Intent.CATEGORY_OPENABLE);
            intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
            intent.setType("image/*");

            startActivityForResult(intent, RESULT_PICK_IMAGEFILE);
        }
    });

    findViewById(R.id.action_tweet).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //tweet();
        }
    });
}

@Override
public void onActivityResult(int requestCode, int resultCode,final Intent resultData) {

    if (requestCode != RESULT_PICK_IMAGEFILE || resultCode != RESULT_OK) {
        return;
    }

    new AsyncTask<Void, Void, Void>() {
        @Override
        protected Void doInBackground(Void... params) {
            try {
                //mTwitterはOAuth認可済みであるとする
                String message = "hello";
                ClipData clipData = resultData.getClipData();
                long[] mediaIds = new long[clipData.getItemCount()];
                for (int i = 0, length = clipData.getItemCount(); i < length; i++) {
                    ClipData.Item item = clipData.getItemAt(i);
                    mediaIds[i] = (mTwitter.uploadMedia(String.format("[filename_%d]", i + 1), getContentResolver().openInputStream(item.getUri())).getMediaId());
                }

                StatusUpdate update = new StatusUpdate(message);
                update.setMediaIds(mediaIds);
                mTwitter.updateStatus(update);

            } catch (TwitterException e) {
                e.printStackTrace();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            return null;
        }
    }.execute();
 }

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.new_tweet_menu, 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.
    switch (item.getItemId()) {
        case R.id.menu_not:
            Intent intent = new Intent(this, MainActivity.class);
            startActivity(intent);
            finish();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

ログキャットは以下のように出力されます。

04-26 05:10:17.700: E/AndroidRuntime(3099): FATAL EXCEPTION: AsyncTask #3
04-26 05:10:17.700: E/AndroidRuntime(3099): Process: android.example.shutwitter, PID: 3099
04-26 05:10:17.700: E/AndroidRuntime(3099): java.lang.RuntimeException: An error occured while executing doInBackground()
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.lang.Thread.run(Thread.java:818)
04-26 05:10:17.700: E/AndroidRuntime(3099): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.os.Handler.<init>(Handler.java:200)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.os.Handler.<init>(Handler.java:114)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.widget.Toast$TN.<init>(Toast.java:336)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.widget.Toast.<init>(Toast.java:100)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.widget.Toast.makeText(Toast.java:250)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.example.shutwitter.TweetActivity.showToast(TweetActivity.java:238)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.example.shutwitter.TweetActivity.access$1(TweetActivity.java:237)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.example.shutwitter.TweetActivity$3.doInBackground(TweetActivity.java:99)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.example.shutwitter.TweetActivity$3.doInBackground(TweetActivity.java:1)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-26 05:10:17.700: E/AndroidRuntime(3099):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-26 05:10:17.700: E/AndroidRuntime(3099):     ... 4 more