【GT-安卓应用开发之好友快速索引】

前言：众所周知，目前大多数的社交软件好友列表都是按照一定的规则排序的，我个人比较喜欢根据全拼的首字母进行排序，这样可以方便我们查找。

        今天，分享一个利用侧边字符索引栏进行检索的方法：

        Step1，好友列表排序

        我们假定已经获得了好友列表，只不过从后台获取的数据是乱序的，需要我们手动对其进行排序

        在定义User的时候需要定义一个首字母，可以利用pinyin4j实现，具体代码如下：

if (name != null&&!name.equals("")) {
    pinyin = Cn2Spell.getPinYin(name); // 根据姓名获取拼音
} else {
    pinyin = Cn2Spell.getPinYin(hxId);
}
firstLetter = pinyin.substring(0, 1).toUpperCase(); // 获取拼音首字母并转成大写
if (!firstLetter.matches("[A-Z]")) { // 如果不在A-Z中则默认为“#”
    firstLetter = "#";
}

       定义比较规则如下：

@Override
public int compareTo(User another) {
    if (firstLetter.equals("#") && !another.getFirstLetter().equals("#")) {
        return 1;
    } else if (!firstLetter.equals("#") && another.getFirstLetter().equals("#")) {
        return -1;
    } else {
        return pinyin.compareToIgnoreCase(another.getPinyin());
    }
}

       Step2，数据渲染

       好友列表排序之后，需要利用适配器将其渲染至ListView，具体代码比较简单，这里就不贴出来了

       Step3，定义索引栏

       定义一个SideBar类继承TextView，并重新处理事件逻辑和重写绘制方法，整个类的代码如下：

public class SideBar extends TextView {
    private String[] letters = new String[]{"A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z", "#"};
    private Paint textPaint;
    private Paint bigTextPaint;
    private Paint scaleTextPaint;

    private Canvas canvas;
    private int itemH;
    private int w;
    private int h;
    /**
     * 普通情况下字体大小
     */
    float singleTextH;
    /**
     * 缩放离原始的宽度
     */
    private float scaleWidth;
    /**
     * 滑动的Y
     */
    private float eventY = 0;
    /**
     * 缩放的倍数
     */
    private int scaleSize = 1;
    /**
     * 缩放个数item，即开口大小
     */
    private int scaleItemCount = 6;
    private ISideBarSelectCallBack callBack;

    public SideBar(Context context) {
        this(context, null);
    }

    public SideBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

    private void init(AttributeSet attrs) {
        if (attrs != null) {
            TypedArray ta = getContext().obtainStyledAttributes(attrs, R.styleable.SideBar);
            scaleSize = ta.getInteger(R.styleable.SideBar_scaleSize, 1);
            scaleItemCount = ta.getInteger(R.styleable.SideBar_scaleItemCount, 6);
            scaleWidth = ta.getDimensionPixelSize(R.styleable.SideBar_scaleWidth, dp(100));
            ta.recycle();
        }
        textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        textPaint.setColor(getCurrentTextColor());
        textPaint.setTextSize(getTextSize());
        textPaint.setTextAlign(Paint.Align.CENTER);
        bigTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        bigTextPaint.setColor(getCurrentTextColor());
        bigTextPaint.setTextSize(getTextSize() * (scaleSize + 3));
        bigTextPaint.setTextAlign(Paint.Align.CENTER);
        scaleTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        scaleTextPaint.setColor(getCurrentTextColor());
        scaleTextPaint.setTextSize(getTextSize() * (scaleSize + 1));
        scaleTextPaint.setTextAlign(Paint.Align.CENTER);
    }

    public void setDataResource(String[] data) {
        letters = data;
        invalidate();
    }

    public void setOnStrSelectCallBack(ISideBarSelectCallBack callBack) {
        this.callBack = callBack;
    }

    /**
     * 设置字体缩放比例
     *
     * @param scale
     */
    public void setScaleSize(int scale) {
        scaleSize = scale;
        invalidate();
    }

    /**
     * 设置缩放字体的个数，即开口大小
     *
     * @param scaleItemCount
     */
    public void setScaleItemCount(int scaleItemCount) {
        this.scaleItemCount = scaleItemCount;
        invalidate();
    }

    private int dp(int px) {
        final float scale = getContext().getResources().getDisplayMetrics().density;
        return (int) (px * scale + 0.5f);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                if (event.getX() > (w - getPaddingRight() - singleTextH - 10)) {
                    eventY = event.getY();
                    invalidate();
                    return true;
                } else {
                    eventY = 0;
                    invalidate();
                    break;
                }
            case MotionEvent.ACTION_CANCEL:
                eventY = 0;
                invalidate();
                return true;
            case MotionEvent.ACTION_UP:
                if (event.getX() > (w - getPaddingRight() - singleTextH - 10)) {
                    eventY = 0;
                    invalidate();
                    return true;
                } else
                    break;
        }
        return super.onTouchEvent(event);
    }


    @Override
    protected void onDraw(Canvas canvas) {
        this.canvas = canvas;
        DrawView(eventY);
    }

    private void DrawView(float y) {
        int currentSelectIndex = -1;
        if (y != 0) {
            for (int i = 0; i < letters.length; i++) {
                float currentItemY = itemH * i;
                float nextItemY = itemH * (i + 1);
                if (y >= currentItemY && y < nextItemY) {
                    currentSelectIndex = i;
                    if (callBack != null) {
                        callBack.onSelectStr(currentSelectIndex, letters[i]);
                    }
                    //画大的字母
                    Paint.FontMetrics fontMetrics = bigTextPaint.getFontMetrics();
                    float bigTextSize = fontMetrics.descent - fontMetrics.ascent;
                    canvas.drawText(letters[i], w - getPaddingRight() - scaleWidth - bigTextSize, singleTextH + itemH * i, bigTextPaint);
                }
            }
        }
        drawLetters(y, currentSelectIndex);
    }

    private void drawLetters(float y, int index) {
        //第一次进来没有缩放情况，默认画原图
        if (index == -1) {
            w = getMeasuredWidth();
            h = getMeasuredHeight();
            itemH = h / letters.length;
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            singleTextH = fontMetrics.descent - fontMetrics.ascent;
            for (int i = 0; i < letters.length; i++) {
                canvas.drawText(letters[i], w - getPaddingRight(), singleTextH + itemH * i, textPaint);
            }
            //触摸的时候画缩放图
        } else {
            //遍历所有字母
            for (int i = 0; i < letters.length; i++) {
                //要画的字母的起始Y坐标
                float currentItemToDrawY = singleTextH + itemH * i;
                float centerItemToDrawY;
                if (index < i)
                    centerItemToDrawY = singleTextH + itemH * (index + scaleItemCount);
                else
                    centerItemToDrawY = singleTextH + itemH * (index - scaleItemCount);
                float delta = 1 - Math.abs((y - currentItemToDrawY) / (centerItemToDrawY - currentItemToDrawY));
                float maxRightX = w - getPaddingRight();
                //如果大于0，表明在y坐标上方
                scaleTextPaint.setTextSize(getTextSize() + getTextSize() * delta);
                float drawX = maxRightX - scaleWidth * delta;
                //超出边界直接花在边界上
                if (drawX > maxRightX)
                    canvas.drawText(letters[i], maxRightX, singleTextH + itemH * i, textPaint);
                else
                    canvas.drawText(letters[i], drawX, singleTextH + itemH * i, scaleTextPaint);
            }
        }
    }

    public interface ISideBarSelectCallBack {
        void onSelectStr(int index, String selectStr);
    }

}

        Step4，事件处理

        代码如下：

sideBar.setOnStrSelectCallBack(new SideBar.ISideBarSelectCallBack() {
    @Override
    public void onSelectStr(int index, String selectStr) {
        for (int i = 0; i < userList.size(); i++) {
            if (selectStr.equalsIgnoreCase(userList.get(i).getFirstLetter())) {
                ltLv.setSelection(i); // 选择到首字母出现的位置
                return;
            }
        }
    }
});