Android快速索引条控件QuickIndexBar

在canvas上指定好位置，用各种画笔Paint，重要的是分析的过程。

    private Paint paint;
    private int cellWidth, cellHeight;

    private void init() {
        paint = new Paint();
        paint.setTextSize(40);
        paint.setColor(Color.WHITE);
        paint.setTypeface(Typeface.DEFAULT_BOLD);
        paint.setAntiAlias(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (cellHeight == 0) cellHeight = getMeasuredHeight() / indexs.length;
    if (cellWidth == 0) cellWidth = getMeasuredWidth();

    //分别画26个字母
    for (int i = 0; i < indexs.length; i++) {

        //先测量用此画笔画字母的大小，用一个矩形把它包裹起来，这样方便计算字母的高度
        Rect bounds = new Rect();
        paint.getTextBounds(indexs[i], 0, indexs[i].length(), bounds);

        //计算画每个字母的起始坐标
        float x = cellWidth / 2 - paint.measureText(indexs[i]) / 2;
        float y = cellHeight / 2 + bounds.height() / 2 + i * cellHeight;
        canvas.drawText(indexs[i], x, y, paint);
    }

    }

    private int lastIndex = -1;
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int x = (int) event.getX();
//        if (x >= 0 && x <= cellWidth) {  //只对quickindexbar的触摸事件有效
//            return false;
//        }
        int y = (int) event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                if (isSameIndex(y / cellHeight)) break;


                String word = indexs[((int) (y / cellHeight))];
                lastIndex = y / cellHeight;
                if (mIndexChangedListener != null) {
                    mIndexChangedListener.indexChanged(word);
                }

                break;
            case MotionEvent.ACTION_UP:
                lastIndex = -1;
                break;
            default:
                break;
        }

        //自行处理触摸事件，不向上传递
        return true;
    }

    /**
     * 当前的索引位置是否和上一个相等
     *
     * @return
     */
    private boolean isSameIndex(int currIndex) {
        return lastIndex == currIndex;
    }

    private IndexChangedListener mIndexChangedListener;

    public void setIndexChangedListener(IndexChangedListener indexChangedListener) {
        mIndexChangedListener = indexChangedListener;
    }

    public interface IndexChangedListener {
        void indexChanged(String word);
    }

在处理onTouch事件时，改变画笔的设置，画出不同的图案。

在onTouch中调用

    //重新调用onDraw
    invalidate();

在onDraw中增加下面的逻辑：
画每个元素之前先设置不同的画笔。    

    if (i == lastIndex) {               //正在touch的位置 需要更加人性化的交互
    paint.setTextSize(60);
    paint.setColor(Color.GRAY);
    } else {
    paint.setTextSize(40);
    paint.setColor(Color.WHITE);
    }

当前Activity接受到QuickIndexBar的变化事件后，调用showIndexLabel方法，通过handler完成延迟操作。

    private Handler mHandler = new Handler();

    private void showIndexLabel(String word) {
    mLabel.setVisibility(View.VISIBLE);
    mLabel.setText(word);

    mHandler.removeCallbacksAndMessages(null); //移除所有消息队列
    mHandler.postDelayed(new Runnable() {      //发送延时消息
        @Override
        public void run() {
            mLabel.setVisibility(View.GONE);
        }
    }, DEFAULT_DELAY);
    }