上一篇android通讯录实例（一）地址：http://blog.csdn.net/specialshoot/article/details/50651080

这一此我们把UI上最重要的部分IndexableListView说明，这个项目可以在github上找到。https://github.com/woozzu/IndexableListView

源码下载下来我们发现核心代码有两片，IndexableListView和IndexScroller这两个文件。其中IndexScroller是右侧字母滚动条的代码，IndexableListView是继承自ListView将滚动条整合到ListView的代码。

IndexScroller

IndexScroller.java源代码：

/* * Copyright 2011 woozzu * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *     http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.woozzu.android.widget;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.RectF;import android.os.Handler;import android.os.Message;import android.os.SystemClock;import android.view.MotionEvent;import android.widget.Adapter;import android.widget.ListView;import android.widget.SectionIndexer;public class IndexScroller {    private float mIndexbarWidth;//索引条宽度    private float mIndexbarMargin; //索引条外边距    private float mPreviewPadding; //索引条内边距    private float mDensity; //颜色密度(用于控制颜色透明度)    private float mScaledDensity;  //缩放密度    private float mAlphaRate;//透明度    private int mState = STATE_HIDDEN;  //索引条状态，默认为隐藏    private int mListViewWidth; //listview宽度    private int mListViewHeight;//listview高度    private int mCurrentSection = -1;  //当前索引    private boolean mIsIndexing = false;//是否正在索引    private ListView mListView = null;//listview实例    private SectionIndexer mIndexer = null;//列表适配器    private String[] mSections = null;//存放索引字符的数组    private RectF mIndexbarRect;//索引条背景图形    //索引条状态    private static final int STATE_HIDDEN = 0;  //隐藏    private static final int STATE_SHOWING = 1; //正在显示    private static final int STATE_SHOWN = 2;   //已显示    private static final int STATE_HIDING = 3;  //正在隐藏    public IndexScroller(Context context, ListView lv) {        mDensity = context.getResources().getDisplayMetrics().density;//获取密度值        mScaledDensity = context.getResources().getDisplayMetrics().scaledDensity;//获得缩放密度值        mListView = lv;//listview实例        setAdapter(mListView.getAdapter()); //设置适配器        mIndexbarWidth = 20 * mDensity;        mIndexbarMargin = 10 * mDensity;        mPreviewPadding = 5 * mDensity;    }    public void draw(Canvas canvas) {        if (mState == STATE_HIDDEN)            return;        // mAlphaRate determines the rate of opacity        Paint indexbarPaint = new Paint();//用于显示当前滑动到字母的背景画笔(屏幕中间大字)        indexbarPaint.setColor(Color.BLACK);        indexbarPaint.setAlpha((int) (64 * mAlphaRate));        indexbarPaint.setAntiAlias(true);//抗锯齿        canvas.drawRoundRect(mIndexbarRect, 5 * mDensity, 5 * mDensity, indexbarPaint);        if (mSections != null && mSections.length > 0) {            // Preview is shown when mCurrentSection is set            if (mCurrentSection >= 0) {                Paint previewPaint = new Paint();   //预览图中背景画笔(右侧滚动条)                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();   //预览图中文字画笔(滚动条上的文字)                previewTextPaint.setColor(Color.WHITE);                previewTextPaint.setAntiAlias(true);                previewTextPaint.setTextSize(50 * mScaledDensity);                float previewTextWidth = previewTextPaint.measureText(mSections[mCurrentSection]);//字符宽度                float previewSize = 2 * mPreviewPadding + previewTextPaint.descent() - previewTextPaint.ascent();//背景宽度/高度                RectF previewRect = new RectF((mListViewWidth - previewSize) / 2                        , (mListViewHeight - previewSize) / 2                        , (mListViewWidth - previewSize) / 2 + previewSize                        , (mListViewHeight - previewSize) / 2 + previewSize);                canvas.drawRoundRect(previewRect, 5 * mDensity, 5 * mDensity, previewPaint);                canvas.drawText(mSections[mCurrentSection], previewRect.left + (previewSize - previewTextWidth) / 2 - 1                        , previewRect.top + mPreviewPadding - previewTextPaint.ascent() + 1, previewTextPaint);            }            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;//索引条中每个字符空间的高度            float paddingTop = (sectionHeight - (indexPaint.descent() - indexPaint.ascent())) / 2;//索引条中每个字符的上下边距,indexPaint.descent() - indexPaint.ascent()得到的是字符的高度            for (int i = 0; i < mSections.length; i++) {                //索引条中各个字符的左右边距,其中indexPaint.measureText(mSections[i])为字符的宽度                float paddingLeft = (mIndexbarWidth - indexPaint.measureText(mSections[i])) / 2;                canvas.drawText(mSections[i], mIndexbarRect.left + paddingLeft                        , mIndexbarRect.top + mIndexbarMargin + sectionHeight * i + paddingTop - indexPaint.ascent(), indexPaint);            }        }    }    /**     * 索引条的触摸事件     *     * @param ev     * @return     */    public boolean onTouchEvent(MotionEvent ev) {        switch (ev.getAction()) {            case MotionEvent.ACTION_DOWN:                // If down event occurs inside index bar region, start indexing                // 索引条可见,且按下事件发生在索引条范围内                if (mState != STATE_HIDDEN && contains(ev.getX(), ev.getY())) {                    setState(STATE_SHOWN);  //索引条设置为显示状态                    // It demonstrates that the motion event started from index bar                    mIsIndexing = true; //正在索引                    // Determine which section the point is in, and move the list to that section                    mCurrentSection = getSectionByPoint(ev.getY());//获取当前点击的索引条中字符的位置                    mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));//列表定位到指定位置                    return true;                }                break;            case MotionEvent.ACTION_MOVE:                if (mIsIndexing) {                    // If this event moves inside index bar                    // 在索引条上滑动                    if (contains(ev.getX(), ev.getY())) {                        // Determine which section the point is in, and move the list to that section                        mCurrentSection = getSectionByPoint(ev.getY());// 获取当前手指触摸点对应的索引条中字符的位置                        mListView.setSelection(mIndexer.getPositionForSection(mCurrentSection));// 列表定位到指定位置                    }                    return true;                }                break;            case MotionEvent.ACTION_UP:                if (mIsIndexing) {                    mIsIndexing = false;// 设置mIsIndexing为false,表示正在索引取消                    mCurrentSection = -1;// 将当前索引字符位置设置为-1,隐藏预览图                }                if (mState == STATE_SHOWN)                    setState(STATE_HIDING);// 渐退索引条                break;        }        return false;    }    /**     * 索引条位置重定位     *     * @param w     * @param h     * @param oldw     * @param oldh     */    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);    }    /**     * 显示索引条     */    public void show() {        if (mState == STATE_HIDDEN)            setState(STATE_SHOWING);        else if (mState == STATE_HIDING)            setState(STATE_HIDING);    }    /**     * 隐藏索引条     */    public void hide() {        if (mState == STATE_SHOWN)            setState(STATE_HIDING);    }    /**     * 设置监听器     *     * @param adapter     */    public void setAdapter(Adapter adapter) {        if (adapter instanceof SectionIndexer) {            mIndexer = (SectionIndexer) adapter;            mSections = (String[]) mIndexer.getSections();        }    }    /**     * 设置索引条状态     *     * @param state     */    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;        }    }    /**     * 判断该点是否在索引条范围内,包括索引条右边距     *     * @param x     * @param y     * @return     */    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());    }    /**     * 根据手指触摸位置返回对应索引字符位置     *     * @param y     * @return     */    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:                    // 开始渐进显示索引条                    // 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:                    // 取消渐进效果                    // If no action, hide automatically                    setState(STATE_HIDING);                    break;                case STATE_HIDING:                    // 3秒后开始渐退                    // Fade out effect                    mAlphaRate -= mAlphaRate * 0.2;                    if (mAlphaRate < 0.1) {                        mAlphaRate = 0;                        setState(STATE_HIDDEN);                    }                    mListView.invalidate();                    fade(10);                    break;            }        }    };}

整个文件的变量及方法说明如注释所示。

IndexableListView

IndexableListView.java代码：

/* * Copyright 2011 woozzu * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *     http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.woozzu.android.widget;import android.content.Context;import android.graphics.Canvas;import android.util.AttributeSet;import android.view.GestureDetector;import android.view.MotionEvent;import android.widget.ListAdapter;import android.widget.ListView;public class IndexableListView extends ListView {    private boolean mIsFastScrollEnabled = false;//快速滚动设置    private IndexScroller mScroller = null;//索引条实例    private GestureDetector mGestureDetector = null;    //手势监听    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) {        mIsFastScrollEnabled = enabled;        if (mIsFastScrollEnabled) {            if (mScroller == null)                mScroller = new IndexScroller(getContext(), this);  //设置快速滚动,初始化索引条        } else {            //否则隐藏索引条            if (mScroller != null) {                mScroller.hide();                mScroller = null;            }        }    }    @Override    public void draw(Canvas canvas) {        super.draw(canvas);        // Overlay index bar        if (mScroller != null)            mScroller.draw(canvas); //绘制索引条(在索引条不为null时)    }    /**     * 触摸事件     *     * @param ev     * @return     */    @Override    public boolean onTouchEvent(MotionEvent ev) {        // Intercept ListView's touch event        if (mScroller != null && mScroller.onTouchEvent(ev)) {            //若1.索引条类不为null 2.索引条可见且触摸事件发生在索引条范围内,则if语句中为true,onTouchEvent不再向下执行            return true;        }        if (mGestureDetector == null) {            //若索引条不可见或触摸事件不是发生在索引条范围内            mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {                @Override                public boolean onFling(MotionEvent e1, MotionEvent e2,                                       float velocityX, float velocityY) {                    // If fling happens, index bar shows                    if (mScroller != null)                        mScroller.show();   //显示索引条                    return super.onFling(e1, e2, velocityX, velocityY);                }            });        }        mGestureDetector.onTouchEvent(ev);        return super.onTouchEvent(ev);    }    /**     * 拦截触摸事件     *     * @param ev     * @return     */    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        if (mScroller.contains(ev.getX(), ev.getY()))            return true;        return super.onInterceptTouchEvent(ev);    }    /**     * 设置adapter     *     * @param adapter     */    @Override    public void setAdapter(ListAdapter adapter) {        super.setAdapter(adapter);        if (mScroller != null)            mScroller.setAdapter(adapter);    }    /**     * View大小改变时触发     *     * @param w     * @param h     * @param oldw     * @param oldh     */    @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);    }}

IndexableListView解释同样见注释。

onInterceptTouchEvent及onTouchEvent的详细用法可以见http://blog.csdn.net/lvxiangan/article/details/9309927

1、onInterceptTouchEvent()是用于处理事件（类似于预处理，当然也可以不处理）并改变事件的传递方向，也就是决定是否允许Touch事件继续向下（子控件）传递，一但返回True（代表事件在当前的viewGroup中会被处理），则向下传递之路被截断（所有子控件将没有机会参与Touch事件），同时把事件传递给当前的控件的onTouchEvent()处理；返回false，则把事件交给子控件的onInterceptTouchEvent()

2、onTouchEvent()用于处理事件，返回值决定当前控件是否消费（consume）了这个事件，也就是说在当前控件在处理完Touch事件后，是否还允许Touch事件继续向上（父控件）传递，一但返回True，则父控件不用操心自己来处理Touch事件。返回true，则向上传递给父控件（注：可能你会觉得是否消费了有关系吗，反正我已经针对事件编写了处理代码？答案是有区别！比如ACTION_MOVE或者ACTION_UP发生的前提是一定曾经发生了ACTION_DOWN，如果你没有消费ACTION_DOWN，那么系统会认为ACTION_DOWN没有发生过，所以ACTION_MOVE或者ACTION_UP就不能被捕获。）

对于此控件

首先如果捕获到手势，进入IndexableListView的onInterceptTouchEvent，若手势滑动到右边控制条，则进入IndexableListView的onTouchEvent事件中。如果此时索引条可见，则返回true不再向下执行，mScroll.onTouchEvent就可以执行IndexScroller中的动作了
如果此时滚动条不可见或触摸事件不是发生在索引条范围内，则将索引条显示出来

以上就是IndexableListView的代码分析，下篇将会讲解获取手机通讯录信息的相关知识。

android通讯录实例（二）

IndexScroller

IndexableListView

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