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