android开发之自定义ViewGroup实现竖向引导界面

一般进入APP都有欢迎界面，基本都是水平滚动的，今天和大家分享一个垂直滚动的例子，但是该项目只能跑在Android 3.0及以上的移动设备上。

1、先来看看效果把：

2、核心代码–自定义ViewGroup

/** * Created by Zane on 2015/3/11. */public class VerticalLinearLayout extends ViewGroup{    /**     * 屏幕的高度     */    private int mScreenHeight;    /**     * 手指按下时的getScrollY     */    private int mScrollStart;    /**     * 手指抬起时的getScrollY     */    private int mScrollEnd;    /**     * 记录移动时的Y     */    private int mLastY;    /**     * 滚动的辅助类     */    private Scroller mScroller;    /**     * 是否正在滚动     */    private boolean isScrolling;    /**     * 加速度检测     */    private VelocityTracker mVelocityTracker;    /**     * 记录当前页     */    private int currentPage = 0;    private OnPageChangeListener mOnPageChangeListener;    public VerticalLinearLayout(Context context, AttributeSet attrs)    {        super(context, attrs);        /**         * 获得屏幕的高度         */        WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);        DisplayMetrics outMetrics = new DisplayMetrics();        wm.getDefaultDisplay().getMetrics(outMetrics);        mScreenHeight = outMetrics.heightPixels;        // 初始化        mScroller = new Scroller(context);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)    {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int count = getChildCount();        for (int i = 0; i < count; ++i)        {            View childView = getChildAt(i);            measureChild(childView, widthMeasureSpec,mScreenHeight);        }    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b)    {        if (changed)        {            int childCount = getChildCount();            // 设置主布局的高度            MarginLayoutParams lp = (MarginLayoutParams) getLayoutParams();            lp.height = mScreenHeight * childCount;            setLayoutParams(lp);            for (int i = 0; i < childCount; i++)            {                View child = getChildAt(i);                if (child.getVisibility() != View.GONE)                {                    child.layout(l, i * mScreenHeight, r, (i+1) * mScreenHeight);// 调用每个自布局的layout                }            }        }    }    @Override    public boolean onTouchEvent(MotionEvent event)    {        // 如果当前正在滚动，调用父类的onTouchEvent        if (isScrolling)            return super.onTouchEvent(event);        int action = event.getAction();        int y = (int) event.getY();        obtainVelocity(event);        switch (action)        {            case MotionEvent.ACTION_DOWN:                mScrollStart = getScrollY();                mLastY = y;                break;            case MotionEvent.ACTION_MOVE:                if (!mScroller.isFinished())                {                    mScroller.abortAnimation();                }                int dy = mLastY - y;                // 边界值检查                int scrollY = getScrollY();                // 已经到达顶端，下拉多少，就往上滚动多少                if (dy < 0 && scrollY + dy < 0)                {                    dy = -scrollY;                }                // 已经到达底部，上拉多少，就往下滚动多少                if (dy > 0 && scrollY + dy > getHeight() - mScreenHeight)                {                    dy = getHeight() - mScreenHeight - scrollY;                }                scrollBy(0, dy);                mLastY = y;                break;            case MotionEvent.ACTION_UP:                mScrollEnd = getScrollY();                int dScrollY = mScrollEnd - mScrollStart;                if (wantScrollToNext())// 往上滑动                {                    if (shouldScrollToNext())                    {                        mScroller.startScroll(0, getScrollY(), 0, mScreenHeight - dScrollY);                    } else                    {                        mScroller.startScroll(0, getScrollY(), 0, -dScrollY);                    }                }                if (wantScrollToPre())// 往下滑动                {                    if (shouldScrollToPre())                    {                        mScroller.startScroll(0, getScrollY(), 0, -mScreenHeight - dScrollY);                    } else                    {                        mScroller.startScroll(0, getScrollY(), 0, -dScrollY);                    }                }                isScrolling = true;                postInvalidate();                recycleVelocity();                break;        }        return true;    }    /**     * 根据滚动距离判断是否能够滚动到下一页     *     * @return     */    private boolean shouldScrollToNext()    {        return mScrollEnd - mScrollStart > mScreenHeight / 2 || Math.abs(getVelocity()) > 600;    }    /**     * 根据用户滑动，判断用户的意图是否是滚动到下一页     *     * @return     */    private boolean wantScrollToNext()    {        return mScrollEnd > mScrollStart;    }    /**     * 根据滚动距离判断是否能够滚动到上一页     *     * @return     */    private boolean shouldScrollToPre()    {        return -mScrollEnd + mScrollStart > mScreenHeight / 2 || Math.abs(getVelocity()) > 600;    }    /**     * 根据用户滑动，判断用户的意图是否是滚动到上一页     *     * @return     */    private boolean wantScrollToPre()    {        return mScrollEnd < mScrollStart;    }    @Override    public void computeScroll()    {        super.computeScroll();        if (mScroller.computeScrollOffset())        {            scrollTo(0, mScroller.getCurrY());            postInvalidate();        } else        {            int position = getScrollY() / mScreenHeight;            Log.e("xxx", position + "," + currentPage);            if (position != currentPage)            {                if (mOnPageChangeListener != null)                {                    currentPage = position;                    mOnPageChangeListener.onPageChange(currentPage);                }            }            isScrolling = false;        }    }    /**     * 获取y方向的加速度     *     * @return     */    private int getVelocity()    {        mVelocityTracker.computeCurrentVelocity(1000);        return (int) mVelocityTracker.getYVelocity();    }    /**     * 释放资源     */    private void recycleVelocity()    {        if (mVelocityTracker != null)        {            mVelocityTracker.recycle();            mVelocityTracker = null;        }    }    /**     * 初始化加速度检测器     *     * @param event     */    private void obtainVelocity(MotionEvent event)    {        if (mVelocityTracker == null)        {            mVelocityTracker = VelocityTracker.obtain();        }        mVelocityTracker.addMovement(event);    }    /**     * 设置回调接口     *     * @param onPageChangeListener     */    public void setOnPageChangeListener(OnPageChangeListener onPageChangeListener)    {        mOnPageChangeListener = onPageChangeListener;    }    /**     * 回调接口     *     * @author zhy     *     */    public interface OnPageChangeListener    {        void onPageChange(int currentPage);    }}

3、再来一个布局文件：

<com.zanelove.VerticalLinearLayoutDemo.VerticalLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"        android:id="@+id/id_main_ly"        android:layout_width="match_parent"        android:layout_height="fill_parent"        android:orientation="vertical"        android:background="#fff" >    <RelativeLayout            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:background="@drawable/guide_1"/>    <RelativeLayout            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:background="@drawable/guide_2"/>    <RelativeLayout            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:background="@drawable/guide_3"/>    <RelativeLayout            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:background="@drawable/guide_4"/></com.zanelove.VerticalLinearLayoutDemo.VerticalLinearLayout>

4、最终逻辑代码–MyActivity

public class MyActivity extends Activity {    private VerticalLinearLayout mVertical_LL;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        mVertical_LL = (VerticalLinearLayout) findViewById(R.id.id_main_ly);        mVertical_LL.setOnPageChangeListener(new VerticalLinearLayout.OnPageChangeListener() {            @Override            public void onPageChange(int currentPage) {                Toast.makeText(MyActivity.this,"第"+currentPage+"页",Toast.LENGTH_SHORT).show();            }        });    }}

在此希望大家，跟我一起解决两个问题：
1、解决版本兼容问题，使得2.3及以上的版本都能运行成功！
2、仔细的大神们也许看出来了，那就是图片显示超出了屏幕范围，一部分图片最下边看不到，如何解决？

望大家积极进言献策！谢谢！

免责声明：转载http://blog.csdn.net/lmj623565791/article/details/23692439

示例代码戳Here