Created
August 7, 2015 11:59
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Auto-Scrolling TextView
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| <com.mydomain.myproject.ScrollTextView | |
| android:id="@+id/scroll_text" | |
| android:layout_width="match_parent" | |
| android:layout_height="wrap_content" | |
| android:singleLine="true" /> |
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| public class MyActivity { | |
| @Override | |
| public void onCreate(Bundle savedInstanceState) { | |
| // ... | |
| final ScrollTextView scrollText = (ScrollTextView) findViewById(R.id.scroll_text); | |
| scrollText.addMessage("Message #1"); | |
| scrollText.addMessage("Message #2"); | |
| scrollText.addMessage("Message #3"); | |
| // ... | |
| } | |
| } |
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| /** | |
| * ScrollTextView | |
| */ | |
| public class ScrollTextView extends TextView { | |
| // scrolling feature | |
| private Scroller mSlr; | |
| // scroll speed | |
| private float mScrollSpeed = 200f; | |
| // the X offset when paused | |
| private int mXPaused = 0; | |
| // whether it's being paused | |
| private boolean mPaused = true; | |
| // messages | |
| private LinkedList<Message> mMessages; | |
| // current message | |
| private String mMessage; | |
| private int mRepeatTimes = 0; | |
| /* | |
| * constructor | |
| */ | |
| public ScrollTextView(Context context) { | |
| this(context, null); | |
| // customize the TextView | |
| setSingleLine(); | |
| setEllipsize(null); | |
| setVisibility(INVISIBLE); | |
| } | |
| /* | |
| * constructor | |
| */ | |
| public ScrollTextView(Context context, AttributeSet attrs) { | |
| this(context, attrs, android.R.attr.textViewStyle); | |
| // customize the TextView | |
| setSingleLine(); | |
| setEllipsize(null); | |
| setVisibility(INVISIBLE); | |
| } | |
| /* | |
| * constructor | |
| */ | |
| public ScrollTextView(Context context, AttributeSet attrs, int defStyle) { | |
| super(context, attrs, defStyle); | |
| // customize the TextView | |
| setSingleLine(); | |
| setEllipsize(null); | |
| setVisibility(INVISIBLE); | |
| } | |
| /** | |
| * add message to messages pool | |
| * @param message String | |
| * @param repeatTimes int | |
| */ | |
| public void addMessage(String message, int repeatTimes) { | |
| if (mMessages == null) { | |
| mMessages = new LinkedList<>(); | |
| } | |
| mMessages.add(new Message(message, repeatTimes)); | |
| if (mMessage == null) { | |
| mMessage = message; | |
| mRepeatTimes = repeatTimes; | |
| } | |
| startScroll(); | |
| } | |
| public void addMessage(String message) { | |
| addMessage(message, 1); | |
| } | |
| /** | |
| * begin to scroll the text from the original position | |
| */ | |
| public void startScroll() { | |
| if (mMessage == null) | |
| return; | |
| // set text | |
| if (getText() == null || !getText().equals(mMessage)) { | |
| setVisibility(INVISIBLE); | |
| setText(mMessage); | |
| } | |
| // begin from the very right side | |
| mXPaused = -1 * getWidth(); | |
| // assume it's paused | |
| mPaused = true; | |
| resumeScroll(); | |
| } | |
| /** | |
| * resume the scroll from the pausing point | |
| */ | |
| public void resumeScroll() { | |
| if (!mPaused) | |
| return; | |
| // Do not know why it would not scroll sometimes | |
| // if setHorizontallyScrolling is called in constructor. | |
| setHorizontallyScrolling(true); | |
| // use LinearInterpolator for steady scrolling | |
| mSlr = new Scroller(this.getContext(), new LinearInterpolator()); | |
| setScroller(mSlr); | |
| int scrollingLen = calculateScrollingLen(); | |
| int distance = scrollingLen - (getWidth() + mXPaused); | |
| int duration = (int) (1000f * distance / mScrollSpeed); | |
| setVisibility(VISIBLE); | |
| mSlr.startScroll(mXPaused, 0, distance, 0, duration); | |
| invalidate(); | |
| mPaused = false; | |
| } | |
| /** | |
| * calculate the scrolling length of the text in pixel | |
| * | |
| * @return the scrolling length in pixels | |
| */ | |
| private int calculateScrollingLen() { | |
| TextPaint tp = getPaint(); | |
| Rect rect = new Rect(); | |
| String strTxt = getText().toString(); | |
| tp.getTextBounds(strTxt, 0, strTxt.length(), rect); | |
| int scrollingLen = rect.width() + getWidth(); | |
| rect = null; | |
| return scrollingLen; | |
| } | |
| /** | |
| * pause scrolling the text | |
| */ | |
| public void pauseScroll() { | |
| if (null == mSlr) | |
| return; | |
| if (mPaused) | |
| return; | |
| mPaused = true; | |
| // abortAnimation sets the current X to be the final X, | |
| // and sets isFinished to be true | |
| // so current position shall be saved | |
| mXPaused = mSlr.getCurrX(); | |
| mSlr.abortAnimation(); | |
| } | |
| @Override | |
| /* | |
| * override the computeScroll to restart scrolling when finished so as that | |
| * the text is scrolled forever | |
| */ | |
| public void computeScroll() { | |
| super.computeScroll(); | |
| if (null == mSlr) return; | |
| if (mSlr.isFinished() && !mPaused) { | |
| if (--mRepeatTimes > 0) { | |
| startScroll(); | |
| return; | |
| } | |
| if (mMessages != null && !mMessages.isEmpty()) { | |
| mMessage = mMessages.getFirst().getMessage(); | |
| mRepeatTimes = mMessages.getFirst().getRepeatTimes(); | |
| mMessages.removeFirst(); | |
| startScroll(); | |
| return; | |
| } | |
| mMessage = null; | |
| mRepeatTimes = 0; | |
| } | |
| } | |
| public float getScrollSpeed() { | |
| return mScrollSpeed; | |
| } | |
| public void setScrollSpeed(float scrollSpeed) { | |
| mScrollSpeed = scrollSpeed; | |
| } | |
| public boolean isPaused() { | |
| return mPaused; | |
| } | |
| class Message { | |
| private String mMessage; | |
| private int mRepeatTimes = 1; | |
| public Message(String message) { | |
| mMessage = message; | |
| } | |
| public Message(String message, int repeatTimes) { | |
| mMessage = message; | |
| mRepeatTimes = repeatTimes; | |
| } | |
| public String getMessage() { | |
| return mMessage; | |
| } | |
| public int getRepeatTimes() { | |
| return mRepeatTimes; | |
| } | |
| } | |
| } |
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