Android : the marquee long text don't work in my code

in my project i use sliding_Image and marquee text....but the text don't move or sometimes it move and when the image of page changes the text be refreshed... this is my code:

aBuffer="";

File myFile = new File("/mnt/sdcard/CS/T.txt");
FileInputStream fIn = null;
try {
    fIn = new FileInputStream(myFile);
} catch (FileNotFoundException e1) {
    e1.printStackTrace();
}
BufferedReader myReader = new BufferedReader(new InputStreamReader(fIn));

try {
    while ((aDataRow = myReader.readLine()) != null) {
        aBuffer += aDataRow + "\n";
    }
    Log.d("tag","is : "+aBuffer);
    myReader.close();
} catch (IOException e) {
    e.printStackTrace();
}

txv=(TextView)findViewById(R.id.textView1);
txv.setText(aBuffer);
txv.setSelected(true);
txv.setEllipsize(TruncateAt.MARQUEE);
txv.setSingleLine(true);        

and this is xml of myActivity :

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:lines="1"
    android:singleLine="true"
    android:ellipsize="marquee"
    android:fadingEdge="horizontal"
    android:marqueeRepeatLimit="marquee_forever"
    android:scrollHorizontally="true"
    android:textColor="#ff4500" />