Andoird自定义ViewGroup实现竖向引导界面

拼搏现实的明天。 2022-07-24 06:16 193阅读 0赞

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。  
先来看看效果把：

![20140414173155640][]

首先是布局文件：

<com.example.verticallinearlayout.VerticalLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
        xmlns:tools="http://schemas.android.com/tools"  
        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/w02" >  
    
            <Button  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:text="hello" />  
        </RelativeLayout>  
    
        <RelativeLayout  
            android:layout_width="fill_parent"  
            android:layout_height="fill_parent"  
            android:background="@drawable/w03" >  
    
            <Button  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:layout_centerInParent="true"  
                android:background="#fff"  
                android:text="hello" />  
        </RelativeLayout>  
    
        <RelativeLayout  
            android:layout_width="fill_parent"  
            android:layout_height="fill_parent"  
            android:background="@drawable/w04" >  
    
            <Button  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:layout_centerInParent="true"  
                android:text="hello" />  
        </RelativeLayout>  
    
        <RelativeLayout  
            android:layout_width="fill_parent"  
            android:layout_height="fill_parent"  
            android:background="@drawable/w05" >  
    
            <Button  
                android:layout_width="wrap_content"  
                android:layout_height="wrap_content"  
                android:layout_centerInParent="true"  
                android:text="hello" />  
        </RelativeLayout>  
    
    </com.example.verticallinearlayout.VerticalLinearLayout>

### 自定义的Layout了 ###

package com.example.verticallinearlayout;
    
    import android.content.Context;
    import android.util.AttributeSet;
    import android.util.DisplayMetrics;
    import android.util.Log;
    import android.view.MotionEvent;
    import android.view.VelocityTracker;
    import android.view.View;
    import android.view.ViewGroup;
    import android.view.WindowManager;
    import android.widget.Scroller;
    
    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, heightMeasureSpec);
            }
        }
    
        @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;
                    Log.i("test", "已经到达顶端，下拉多少，就往上滚动多少scrollY="+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;
                    Log.i("test", "已经到达顶端，下拉多少，就往上滚动多少scrollY=="+scrollY);
                }
                Log.i("test", "dy="+dy+",scrollY"+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);
        }
    }

释还是相当详细的，我简单描述一下，Action\_down时获得当前的scrollY,然后Action\_move时，根据移动的距离不断scrollby就行了，当前处理了一下边界判断，在Action\_up中再次获得scrollY，两个的scrollY进行对比，然后根据移动的距离与方向决定最后的动作

### MainActivity ###

package com.example.verticallinearlayout;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.widget.Toast;
    
    import com.example.verticallinearlayout.VerticalLinearLayout.OnPageChangeListener;
    
    public class MainActivity extends Activity
    {
        
        private VerticalLinearLayout mMianLayout;
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mMianLayout = (VerticalLinearLayout) findViewById(R.id.id_main_ly);
            mMianLayout.setOnPageChangeListener(new OnPageChangeListener()
            {
                @Override
                public void onPageChange(int currentPage)
                {
    //              mMianLayout.getChildAt(currentPage);
                    Toast.makeText(MainActivity.this, "第"+(currentPage+1)+"页", Toast.LENGTH_SHORT).show();
                }
            });
        }
    
    }

为了提供可扩展性，还是定义了回调接口，完全可以把这个当成一个垂直的ViewPager使用。  
总结下：  
Scroller这个辅助类还是相当好用的，原理我简单说一下：每次滚动时，让Scroller进行滚动，然后调用postInvalidate方法，这个方法会引发调用onDraw方法，onDraw方法中会去调用computeScroll方法，然后我们在computScroll中判断，Scroller的滚动是否结束，没有的话，把当前的View滚动到现在Scroller的位置，然后继续调用postInvalidate，这样一个循环的过程。  
画张图方便大家理解，ps:没找到什么好的画图工具，那rose随便画了，莫计较。

![Center][]

### 源码 ###

[源码点击此处下载][Link 1]

### 完成 ###

[20140414173155640]: /images/20220722/933ebdcfc6da452bacdf73b14b47373b.png
[Center]: /images/20220722/3f992c2be33942f6b3024f99dd7e7dc0.png
[Link 1]: http://download.csdn.net/detail/lmj623565791/7192253