Vincent Mimoun-Prat Vincent Mimoun-Prat - 3 months ago 22
Android Question

Android automatic horizontally scrolling TextView

I am trying to implement a single-line text view that will scroll automatically. But I unfortunatly cannot get it to work. The AutoScrollTextView is declared inside a LinearLayout (width and height = fill_parent). The class basically uses a Handler that calls itself to scroll by a given amount. I have simplified the code to only show a text view that should be scrolling by 5 pixels every second.

The log output is correct, the getScrollX() method returns the appropriate scrollX position.

If I don't call

requestLayout()
, nothing gets drawn.
invalidate()
has no effect.

Would anybody have a clue?

public class AutoScrollTextView extends TextView {

public AutoScrollTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setSingleLine();
setEllipsize(null);
setText("Single-line text view that scrolls automatically if the text is too long to fit in the widget");
}

// begin to scroll the text from the original position
public void startScrolling() {
scrollHandler.sendEmptyMessage(0);
}

private Handler scrollHandler = new Handler() {
private static final int REFRESH_INTERVAL = 1000;

public void handleMessage(Message msg) {
scrollBy(5, 0);
requestLayout();
Log.debug("Scrolled to " + getScrollX() + " px");
sendEmptyMessageDelayed(0, REFRESH_INTERVAL);
}
};
}

Answer

If you don't need to sub-class the TextView, you can try this in your layout file:

    <TextView
        android:text="Single-line text view that scrolls automatically if the text is too long to fit in the widget" 
        android:singleLine="true" 
        android:ellipsize="marquee"
        android:marqueeRepeatLimit ="marquee_forever"
        android:focusable="true"
        android:focusableInTouchMode="true" 
        android:scrollHorizontally="true"
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content"/>