Android 自定义控件实现ListView索引

实现listview 的索引 中间的预览文本因为截图水平有限没有截出来。。

源代码下载地址：

实现该方法需要重写lisetview 控件。实现步骤如下
1. 新建一个数组 用于存放右侧的a-z 的26个字母 然后写自定义空间IndexLisetview
2.IndexLisetview继承Lisetview 然后重写setFastScrollEnabled 、 draw、onTouchEvent、setAdapter、onSizeChanged 等方法。
3.在IndexScroller类实现绘制索引条和绘制预览文本的方法。并实现索引条的显示和隐藏的方法。
4.因为索引匹配，所以需要一个字符串匹配的算法。

部分代码如下
1.定义IndexLisetview

public class IndexableListView extends ListView {

    private boolean mIsFastScrollEnabled = false;
    private IndexScroller mScroller = null;//負責繪製索引條
    private GestureDetector mGestureDetector = null;

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

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

    public IndexableListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public boolean isFastScrollEnabled() {
        return mIsFastScrollEnabled;
    }

    @Override
    public void setFastScrollEnabled(boolean enabled) {//如果允许快速滚动的话
        mIsFastScrollEnabled = enabled;
        if (mIsFastScrollEnabled) {
            if (mScroller == null)
                //创建IndexScroller对象
                mScroller = new IndexScroller(getContext(), this);
        } else {
            if (mScroller != null) {
                mScroller.hide();
                mScroller = null;
            }
        }
    }

    @Override
    public void draw(Canvas canvas) {   //用于绘制右侧的索引条
        super.draw(canvas);//绘制listview 原来的东西

        //绘制右侧的索引条
        if (mScroller != null)
            mScroller.draw(canvas);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        //如果mscroller自己处理触摸事件，该方法返回true
        if (mScroller != null && mScroller.onTouchEvent(ev))
            return true;

        if (mGestureDetector == null) {
            //使用手势处理触摸事件
            mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {

                @Override
                public boolean onFling(MotionEvent e1, MotionEvent e2,
                        float velocityX, float velocityY) {
                    //直接显示右侧的索引条
                    if (mScroller != null)
                        mScroller.show();
                    return super.onFling(e1, e2, velocityX, velocityY);
                }

            });
        }
        mGestureDetector.onTouchEvent(ev);

        return super.onTouchEvent(ev);
    }

    @Override
    public void setAdapter(ListAdapter adapter) {
        super.setAdapter(adapter);
        if (mScroller != null)
            mScroller.setAdapter(adapter);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if (mScroller != null)
            mScroller.onSizeChanged(w, h, oldw, oldh);
    }
}

2.绘制索引条和预览文本

public class IndexScroller {

    private float mIndexbarWidth;//索引條寬度
    private float mIndexbarMargin;//索引條距離右邊距離
    private float mPreviewPadding;//中心現實的預覽文版距離四周的長度
    private float mDensity;//当前的屏幕密度和标准的屏幕密度(160)的商 dp sp会随字体变化而变化 
    private float mScaledDensity;//当前的屏幕密度和标准的屏幕密度(160)的商（设置字体尺寸）
    private float mAlphaRate;//透明度（用于显示和隐藏索引条）0-1之间
    private int mState = STATE_HIDDEN;//索引条的状态
    private int mListViewWidth;
    private int mListViewHeight;
    private int mCurrentSection = -1;
    private boolean mIsIndexing = false;
    private ListView mListView = null;
    private SectionIndexer mIndexer = null;
    private String[] mSections = null;
    private RectF mIndexbarRect;//索引的区域
    //索引的四个状态
    private static final int STATE_HIDDEN = 0;//隐藏
    private static final int STATE_SHOWING = 1;
    private static final int STATE_SHOWN = 2;
    private static final int STATE_HIDING = 3;
public IndexScroller(Context context, ListView lv) {
          //獲得屏幕密度的比值
        mDensity = context.getResources().getDisplayMetrics().density;
        mScaledDensity = context.getResources().getDisplayMetrics().scaledDensity;
        mListView = lv;
        setAdapter(mListView.getAdapter());
          //根據屏幕密度技術索引條的寬度（單位像素）索引條會跟隨屏幕密度變化
        mIndexbarWidth = 20 * mDensity;
        mIndexbarMargin = 10 * mDensity;
        mPreviewPadding = 5 * mDensity;
    }
      //繪製索引條和預覽文本
    public void draw(Canvas canvas) {
         //绘制索引条，包括索引条的背景和文版；
          //绘制预览文版和背景
        if (mState == STATE_HIDDEN)
            //如果索引条隐藏不进行绘制
            return;

        //设置索引背景的绘制属性
        Paint indexbarPaint = new Paint();
        indexbarPaint.setColor(Color.BLACK);
        indexbarPaint.setAlpha((int) (64 * mAlphaRate));
        indexbarPaint.setAntiAlias(true);
          //绘制索引条(4个交都是圆角举行)
        canvas.drawRoundRect(mIndexbarRect, 5 * mDensity, 5 * mDensity, indexbarPaint);
        //绘制sections
        if (mSections != null && mSections.length > 0) {
            //绘制预览文本和背景
            if (mCurrentSection >= 0) {
                Paint previewPaint = new Paint();
                previewPaint.setColor(Color.BLACK);
                previewPaint.setAlpha(96);
                previewPaint.setAntiAlias(true);
                previewPaint.setShadowLayer(3, 0, 0, Color.argb(64, 0, 0, 0));

                Paint previewTextPaint = new Paint();
                previewTextPaint.setColor(Color.WHITE);
                previewTextPaint.setAntiAlias(true);
                previewTextPaint.setTextSize(50 * mScaledDensity);

                float previewTextWidth = previewTextPaint.measureText(mSections[mCurrentSection]);
                  // 下端descent 正值， 上端ascent 负值
                float previewSize = 2 * mPreviewPadding + previewTextPaint.descent() - previewTextPaint.ascent();
                 //预览文本背景区域 矩形 左 上 右 底
                RectF previewRect = new RectF((mListViewWidth - previewSize) / 2
                        , (mListViewHeight - previewSize) / 2
                        , (mListViewWidth - previewSize) / 2 + previewSize
                        , (mListViewHeight - previewSize) / 2 + previewSize);
                 //绘制背景
                canvas.drawRoundRect(previewRect, 5 * mDensity, 5 * mDensity, previewPaint);
                 //绘制预览文本
                canvas.drawText(mSections[mCurrentSection], previewRect.left + (previewSize - previewTextWidth) / 2 - 1
                        , previewRect.top + mPreviewPadding - previewTextPaint.ascent() + 1, previewTextPaint);
            }
              //绘制索引条的文本
            Paint indexPaint = new Paint();
            indexPaint.setColor(Color.WHITE);
            indexPaint.setAlpha((int) (255 * mAlphaRate));
            indexPaint.setAntiAlias(true);
            indexPaint.setTextSize(12 * mScaledDensity);

            float sectionHeight = (mIndexbarRect.height() - 2 * mIndexbarMargin) / mSections.length;
            float paddingTop = (sectionHeight - (indexPaint.descent() - indexPaint.ascent())) / 2;
            for (int i = 0; i < mSections.length; i++) {
                float paddingLeft = (mIndexbarWidth - indexPaint.measureText(mSections[i])) / 2;
                //绘制索引条上的文字
                canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft
                        , mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - indexPaint.ascent(), indexPaint);
            }
        }
    }

    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // If down event occurs inside index bar region, start indexing
            if (mState != STATE_HIDDEN && contains(ev.getX(), ev.getY())) {
                setState(STATE_SHOWN);

                // It demonstrates that the motion event started from index bar
                mIsIndexing = true;
                // Determine which section the point is in, and move the list to that section
                mCurrentSection = getSectionByPoint(ev.getY());
                mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
                return true;
            }
            break;
        case MotionEvent.ACTION_MOVE:
            if (mIsIndexing) {
                // If this event moves inside index bar
                if (contains(ev.getX(), ev.getY())) {
                    // Determine which section the point is in, and move the list to that section
                    mCurrentSection = getSectionByPoint(ev.getY());
                    mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));
                }
                return true;
            }
            break;
        case MotionEvent.ACTION_UP:
            if (mIsIndexing) {
                mIsIndexing = false;
                mCurrentSection = -1;
            }
            if (mState == STATE_SHOWN)
                setState(STATE_HIDING);
            break;
        }
        return false;
    }

    public void onSizeChanged(int w, int h, int oldw, int oldh) {
        mListViewWidth = w;
        mListViewHeight = h;
        mIndexbarRect = new RectF(w - mIndexbarMargin - mIndexbarWidth
                , mIndexbarMargin
                , w - mIndexbarMargin
                , h - mIndexbarMargin);
    }

    public void show() {
        if (mState == STATE_HIDDEN)
            setState(STATE_SHOWING);
        else if (mState == STATE_HIDING)
            setState(STATE_HIDING);
    }

    public void hide() {
        if (mState == STATE_SHOWN)
            setState(STATE_HIDING);
    }

    public void setAdapter(Adapter adapter) {
        if (adapter instanceof SectionIndexer) {
            mIndexer = (SectionIndexer) adapter;
            mSections = (String[]) mIndexer.getSections();
        }
    }

    private void setState(int state) {
        if (state < STATE_HIDDEN || state > STATE_HIDING)
            return;

        mState = state;
        switch (mState) {
        case STATE_HIDDEN:
            // Cancel any fade effect
            mHandler.removeMessages(0);
            break;
        case STATE_SHOWING:
            // Start to fade in
            mAlphaRate = 0;
            fade(0);
            break;
        case STATE_SHOWN:
            // Cancel any fade effect
            mHandler.removeMessages(0);
            break;
        case STATE_HIDING:
            // Start to fade out after three seconds
            mAlphaRate = 1;
            fade(3000);
            break;
        }
    }

    public boolean contains(float x, float y) {
        // Determine if the point is in index bar region, which includes the right margin of the bar
        return (x >= mIndexbarRect.left && y >= mIndexbarRect.top && y <= mIndexbarRect.top + mIndexbarRect.height());
    }

    private int getSectionByPoint(float y) {
        if (mSections == null || mSections.length == 0)
            return 0;
        if (y < mIndexbarRect.top + mIndexbarMargin)
            return 0;
        if (y >= mIndexbarRect.top + mIndexbarRect.height() - mIndexbarMargin)
            return mSections.length - 1;
        return (int) ((y - mIndexbarRect.top - mIndexbarMargin) / ((mIndexbarRect.height() - 2 * mIndexbarMargin) / mSections.length));
    }

    private void fade(long delay) {
        mHandler.removeMessages(0);
        mHandler.sendEmptyMessageAtTime(0, SystemClock.uptimeMillis() + delay);
    }

    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

            switch (mState) {
            case STATE_SHOWING:
                // Fade in effect
                mAlphaRate += (1 - mAlphaRate) * 0.2;
                if (mAlphaRate > 0.9) {
                    mAlphaRate = 1;
                    setState(STATE_SHOWN);
                }

                mListView.invalidate();
                fade(10);
                break;
            case STATE_SHOWN:
                // If no action, hide automatically
                setState(STATE_HIDING);
                break;
            case STATE_HIDING:
                // Fade out effect
                mAlphaRate -= mAlphaRate * 0.2;
                if (mAlphaRate < 0.1) {
                    mAlphaRate = 0;
                    setState(STATE_HIDDEN);
                }

                mListView.invalidate();
                fade(10);
                break;
            }
        }

    };
}

3.实现A-z字母数组是适配和字符串匹配算法的调用

private class ContentAdapter extends ArrayAdapter<String> implements SectionIndexer {

        private String mSections = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        public ContentAdapter(Context context, int textViewResourceId,
                List<String> objects) {
            super(context, textViewResourceId, objects);
        }

        @Override
        public int getPositionForSection(int section) {
            // 根据Section来获得位置Position

            //Y没有对应的items就往前查X直到查到对应的为止
            for (int i = section; i >= 0; i--) {
                for (int j = 0; j < getCount(); j++) {
                    if (i == 0) {
                        //查询数字
                        for (int k = 0; k <= 9; k++) {
                            if (StringMatcher.match(String.valueOf(getItem(j).charAt(0)), String.valueOf(k)))
                                return j;
                        }
                    } else {//查询字母
                        if (StringMatcher.match(String.valueOf(getItem(j).charAt(0)), String.valueOf(mSections.charAt(i))))
                            return j;
                    }
                }
            }
            return 0;
        }

        @Override
        public int getSectionForPosition(int position) {
            // 根据Position来获得位置Section
            return 0;
        }

        @Override
        public Object[] getSections() {
            // 存储数组元素 列表右侧的ABCD
            String[] sections = new String[mSections.length()];
            //将每个section作为但的数组袁术放到sections中
            for (int i = 0; i < mSections.length(); i++)
                //从section中获得每一个字符
                sections[i] = String.valueOf(mSections.charAt(i));
            return sections;
        }
    }
}