Android实现歌词滚动效果

public class VerticalScrollTextView extends TextView {
private Paint mPaint;
private float mX;
private Paint mPathPaint; 
public int index = 0;
private List<Sentence  list;
public float mTouchHistoryY;
private int mY; 
private float middleY;//
private static final int DY = 40; //
public VerticalScrollTextView(Context context) {
super(context);
init();
}
public VerticalScrollTextView(Context context, AttributeSet attr) {
super(context, attr);
init();
}
public VerticalScrollTextView(Context context, AttributeSet attr, int i) {
super(context, attr, i);
init();
}
private void init() {
setFocusable(true);
if(list==null){
list=new ArrayList<Sentence ();
Sentence sen=new Sentence(0," ");
list.add(0, sen);
} 
// 
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setTextSize(24);
mPaint.setColor(Color.BLACK);
mPaint.setAlpha(80);
mPaint.setTypeface(Typeface.SERIF);
// 
mPathPaint = new Paint();
mPathPaint.setAntiAlias(true);
mPathPaint.setColor(Color.RED);
mPathPaint.setTextSize(24);
mPathPaint.setTypeface(Typeface.SANS_SERIF);
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(0xEFeffff);
Paint p = mPaint;
Paint p2 = mPathPaint;
p.setTextAlign(Paint.Align.LEFT);
if (index == -1)
return;
p2.setTextAlign(Paint.Align.LEFT);
// 
canvas.drawText(list.get(index).getName(), mX, middleY, p2);
float tempY = middleY;
// 
for (int i = index - 1; i  = 0; i--) {  
tempY = tempY - DY;
if (tempY < 0) {
break;
}
canvas.drawText(list.get(i).getName(), mX, tempY, p);  
}
tempY = middleY;
//
for (int i = index + 1; i < list.size(); i++) {
// 
tempY = tempY + DY;
if (tempY   mY) {
break;
}
canvas.drawText(list.get(i).getName(), mX, tempY, p);  
}
}
protected void onSizeChanged(int w, int h, int ow, int oh) {
super.onSizeChanged(w, h, ow, oh);
mX = w * 0.3f; 
mY = h;
middleY = h * 0.5f;
}
public long updateIndex(int index) { 
if (index == -1)
return -1;
this.index=index; 
return index;
}
public List<Sentence  getList() {
return list;
}
public void setList(List<Sentence  list) {
this.list = list;
}
public void updateUI(){
new Thread(new updateThread()).start();
}
class updateThread implements Runnable {
long time = 300; 
int i=0;
public void run() {
while (true) {
long sleeptime = updateIndex(i);
time += sleeptime;
mHandler.post(mUpdateResults);
if (sleeptime == -1)
return;
try {
Thread.sleep(time);
i++;
if(i==getList().size())
{
i=0;
time = 300;
}
} catch (InterruptedException e) {   
e.printStackTrace();
}
}
}
}
Handler mHandler = new Handler();
Runnable mUpdateResults = new Runnable() {
public void run() {
invalidate(); // 
}
};
}

public class Sentence {
private String name;
private int index;
public Sentence(int index,String name){
this.name=name;
this.index=index;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getIndex() {
return index;
}
public void setIndex(int index) {
this.index = index;
}
}

<com.mypackager.ui.VerticalScrollTextView
android:id="@+id/scoll_textView"
android:layout_width="500dp"
android:layout_height="500dp"
android:text="@string/company_intrduce_text"
android:visibility="gone"
</com.mypackager.VerticalScrollTextView 

List lst=new ArrayList<Sentence ();
for(int i=0;i<8;i++){
if(i%2==0){
Sentence sen=new Sentence(i,i+1+"NanJINGXIXI");
lst.add(i, sen);
}else{
Sentence sen=new Sentence(i,i+1+"Hello world!");
lst.add(i, sen);
}
} 
play_textView.setList(lst);
play_textView.updateUI();