纵向跑马灯的实现

//自定义view

public class VerticalMarqueeView extends View {

    public static final int DURATION_SCROLL = 2000;
    public static final int DURATION_ANIMATOR = 1000;
    private int color = Color.BLACK;
    private int textSize = 30;
    private String[] datas = null;

    private int width;
    private int height;
    private int centerX;
    private int centerY;

    private List<TextBlock> blocks = new ArrayList<TextBlock>(2);
    private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Handler handler = new Handler();
    private boolean isStopScroll = false;

    public VerticalMarqueeView(Context context, AttributeSet attrs, int defStyleAttr){
        super(context, attrs, defStyleAttr);
    }

    public VerticalMarqueeView(Context context, AttributeSet attrs){
        super(context, attrs);
    }

    public VerticalMarqueeView(Context context){
        super(context);
    }

    public VerticalMarqueeView color(int color){
        this.color = color;
        return this;
    }

    public VerticalMarqueeView textSize(int textSize){
        this.textSize = textSize;
        return this;
    }

    public VerticalMarqueeView datas(String[] datas){
        this.datas = datas;
        return this;
    }

    public void commit(){
        if(this.datas == null || datas.length == 0){
            Log.e("VerticalMarqueeView", "the datas's length is illegal");
            throw new IllegalStateException("may be not invoke the method named datas(String[])");
        }
        paint.setColor(color);
        paint.setTextSize(textSize);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if(this.datas == null || this.datas.length == 0){
            Log.e("VerticalMarqueeView", "the datas's length is illegal");
            return;
        }
        width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
        height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom();
        centerX = width / 2;
        centerY = height / 2;
        blocks.clear();
        //添加显示区域的文字块
        TextBlock block1 = new TextBlock(width, height, paint);
        block1.reset(datas[0], centerX, centerY, 0);
        blocks.add(block1);
        if(datas.length > 1){
            TextBlock block2 = new TextBlock(width, height, paint);
            block2.reset(datas[1], centerX, centerY + height, 1);
            blocks.add(block2);
        }
    }

    @Override
    protected void onDraw(Canvas canvas){
        for(int i = 0; i < blocks.size(); i++){
            blocks.get(i).draw(canvas);
        }
    }

    public void startScroll(){
        isStopScroll = false;
        if(datas == null || datas.length == 0 || datas.length == 1){
            Log.e("VerticalMarqueeView", "the datas's length is illegal");
            return;
        }
        if(!isStopScroll){
            handler.postDelayed(new Runnable(){

                @Override
                public void run(){
                    scroll();
                    if(!isStopScroll){
                        handler.postDelayed(this, DURATION_SCROLL);
                    }
                }
            }, DURATION_SCROLL);
        }
    }

    public void stopScroll(){
        this.isStopScroll = true;
    }

    private void scroll(){
        ValueAnimator animator = ValueAnimator.ofPropertyValuesHolder(PropertyValuesHolder.ofInt("scrollY", centerY, centerY - height));
        animator.setDuration(DURATION_ANIMATOR);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener(){

            @Override
            public void onAnimationUpdate(ValueAnimator animation){
                int scrollY = (int)animation.getAnimatedValue("scrollY");
                blocks.get(0).reset(scrollY);
                blocks.get(1).reset(scrollY + height);
                invalidate();
            }
        });
        animator.addListener(new Animator.AnimatorListener(){

            @Override
            public void onAnimationStart(Animator animation){
            }

            @Override
            public void onAnimationRepeat(Animator animation){
            }

            @Override
            public void onAnimationEnd(Animator animation){
                //移除第一块
                int position = blocks.get(1).getPosition();
                TextBlock textBlock = blocks.remove(0);
                //最后一个
                if(position == datas.length - 1){
                    position = 0;
                }else{
                    position ++;
                }
                textBlock.reset(datas[position], centerY + height, position);
                blocks.add(textBlock);
                invalidate();
            }

            @Override
            public void onAnimationCancel(Animator animation){
            }
        });
        animator.start();
    }

    public int getCurrentPosition(){
        if(datas == null || datas.length == 0){
            return -1;
        }
        if(datas.length == 1 && blocks.size() == 1){
            return 0;
        }
        return blocks.get(0).getPosition();
    }

    public class TextBlock {
        private int width;
        private int height;
        private String text;
        private int drawX;
        private int drawY;
        private Paint paint;
        private int position;

        public TextBlock(int width, int height, Paint paint){
            this.width = width;
            this.height = height;
            this.paint = paint;
        }

        public void reset(int centerY){
            reset(text, centerX, centerY, position);
        }

        public void reset(String text, int centerY){
            reset(text, centerX, centerY, position);
        }

        public void reset(String text, int centerY, int position){
            reset(text, centerX, centerY, position);
        }

        public void reset(String text, int centerX, int centerY, int position){
            this.text = text;
            this.position = position;
            int measureWidth = (int)paint.measureText(text);
            drawX = (width - measureWidth) / 2;
            Paint.FontMetrics metrics = paint.getFontMetrics();
            drawY = (int)(centerY + (metrics.bottom - metrics.top) / 2 - metrics.bottom);
        }

        public int getPosition(){
            return position;
        }

        public void draw(Canvas canvas){
            canvas.drawText(text, drawX, drawY, paint);
        }
    }

}

----------------------activity调用----------------------------

 //跑马灯信息显示
        vmView = (VerticalMarqueeView)view.findViewById(R.id.vmView);
        String[] datas = new String[]{
                "玩手机上瘾了？拿它戒了","没想到，女明星比我还节俭啊..","太会玩！美甲居然搞3D","日本女装大佬的“求生之路”","无屏！这才是手机的究极形态"
        };
        vmView.color(getResources().getColor(android.R.color.black))
                .textSize(sp2px(getActivity(), 15))
                .datas(datas).commit();
        vmView.startScroll();
//点击事件
 vmView.setOnClickListener(newView.OnClickListener(){

 

   @Override

   publicvoid onClick(View v){

    Toast.makeText(MainActivity.this,"当前的索引为：" + vmView.getCurrentPosition(), Toast.LENGTH_SHORT).show();

   }

  });

  

 privateint sp2px(Context context,int sp){

  floatdensity = context.getResources().getDisplayMetrics().scaledDensity;

  return(int) (sp * density +0.5f);

 }

 

 @Override

 protectedvoid onDestroy() {

  super.onDestroy();

  //必须要调用，否则内存中会一直无限循环

  vmView.stopScroll();

 }