android 开源控件收集讲解 （scrollLayout）

一.扯淡
一直以来都是在索取，而没有贡献，所以希望能够也写点东西做点总结。希望对大家有帮助，自己也是一个学习总结的过程.坚持坚持坚持。

今天给加大推荐一个好东西--ScrollLayout（滑动），他其实是一个左右滑动屏幕的控件，同样来自oschina的项目.可能大家之前都用viewpage.或者说现在还有actionbar,

之所以推荐他，就是因为他真的是封装的非常好.完全可以实现很友好的交互界面.

二.详细

因为也是拿别人的东西讲，所以我也不好去评论.但是我在做项目的时候就用上了.而且我觉得特别友好.用好了绝对是利器。

 1.怎么用 --xml中使用，代码如下

  其中：net.oschina.app.widget.ScrollLayout是包名加类名，其实java很多新手特别是学生不知道面向对象是什么意思，我想说类的概念，面向对象的概念只有你拿着代码去看

，去理解，完全可以理解这些。

 <net.oschina.app.widget.ScrollLayout   
      android:id="@+id/main_scrolllayout"    
      android:layout_width="fill_parent"    
      android:layout_height="fill_parent"
         android:layout_weight="1">   

  2.类的封装

 ----------------------在这里你只需要新建一个包名，然后把这个类放进去。之后就是跟使用android本身的组件是一样的了.很多人可能写了这么久的代码也都没有尝试过自定义过东西。我虽然这里也不敢说厉害.但是也还算是写过.大家如果懒直接拿过去用就是了.但是我建议还是在项目不紧张的时候仔细看看别人的代码，别人这么写的原因是什么.之后肯定又是一大提升.什么时候自己自定义个。一定成就感十足.加油吧.大家可以看到他是继承的ViewGroup.然后重写了里面的方法.仔细看看他是怎么实现的.我怕我写的不够好，就不说了。仔细看看代码应该就能够明白.

/**
 * 左右滑动切换屏幕控件
 * @author Yao.GUET date: 2011-05-04
 * @modify liux (http://my.oschina.net/liux)
 */
public class ScrollLayout extends ViewGroup {
    private static final String TAG = "ScrollLayout";
    private Scroller mScroller;
    private VelocityTracker mVelocityTracker;
    private int mCurScreen;
    private int mDefaultScreen = 0;
    private static final int TOUCH_STATE_REST = 0;
    private static final int TOUCH_STATE_SCROLLING = 1;
    private static final int SNAP_VELOCITY = 600;
    private int mTouchState = TOUCH_STATE_REST;
    private int mTouchSlop;
    private float mLastMotionX;
    private float mLastMotionY;
    private OnViewChangeListener mOnViewChangeListener;

    /**
     * 设置是否可左右滑动
     * @author liux
     */
    private boolean isScroll = true;
    public void setIsScroll(boolean b) {
        this.isScroll = b;
    }
    
    public ScrollLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScroller = new Scroller(context);
        mCurScreen = mDefaultScreen;
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int childLeft = 0;
        final int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View childView = getChildAt(i);
            if (childView.getVisibility() != View.GONE) {
                final int childWidth = childView.getMeasuredWidth();
                childView.layout(childLeft, 0, childLeft + childWidth,
                        childView.getMeasuredHeight());
                childLeft += childWidth;
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //Log.e(TAG, "onMeasure");
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException(
                    "ScrollLayout only canmCurScreen run at EXACTLY mode!");
        }
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException(
                    "ScrollLayout only can run at EXACTLY mode!");
        }

        // The children are given the same width and height as the scrollLayout
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }
        // Log.e(TAG, "moving to screen "+mCurScreen);
        scrollTo(mCurScreen * width, 0);
    }

    /**
     * According to the position of current layout scroll to the destination
     * page.
     */
    public void snapToDestination() {
        final int screenWidth = getWidth();
        final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
        snapToScreen(destScreen);
    }

    public void snapToScreen(int whichScreen) {
        //是否可滑动
        if(!isScroll) {
            this.setToScreen(whichScreen);
            return;
        }
        
        scrollToScreen(whichScreen);
    }

    public void scrollToScreen(int whichScreen) {        
        // get the valid layout page
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        if (getScrollX() != (whichScreen * getWidth())) {
            final int delta = whichScreen * getWidth() - getScrollX();
            mScroller.startScroll(getScrollX(), 0, delta, 0,
                    Math.abs(delta) * 1);//持续滚动时间 以毫秒为单位
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout
            
            if (mOnViewChangeListener != null)
            {
                mOnViewChangeListener.OnViewChange(mCurScreen);
            }
        }
    }
    
    public void setToScreen(int whichScreen) {
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        mCurScreen = whichScreen;
        scrollTo(whichScreen * getWidth(), 0);
        
        if (mOnViewChangeListener != null)
        {
            mOnViewChangeListener.OnViewChange(mCurScreen);
        }
    }

    public int getCurScreen() {
        return mCurScreen;
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //是否可滑动
        if(!isScroll) {
            return false;
        }
        
        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(event);
        final int action = event.getAction();
        final float x = event.getX();
        final float y = event.getY();
        switch (action) {
        case MotionEvent.ACTION_DOWN:
            //Log.e(TAG, "event down!");
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }
            mLastMotionX = x;
            
            //---------------New Code----------------------
            mLastMotionY = y;
            //---------------------------------------------
            
            break;
        case MotionEvent.ACTION_MOVE:
            int deltaX = (int) (mLastMotionX - x);
            
            //---------------New Code----------------------
            int deltaY = (int) (mLastMotionY - y);
            if(Math.abs(deltaX) < 200 && Math.abs(deltaY) > 10)
                break;
            mLastMotionY = y;
            //-------------------------------------
            
            mLastMotionX = x;
            scrollBy(deltaX, 0);
            break;
        case MotionEvent.ACTION_UP:
            //Log.e(TAG, "event : up");
            // if (mTouchState == TOUCH_STATE_SCROLLING) {
            final VelocityTracker velocityTracker = mVelocityTracker;
            velocityTracker.computeCurrentVelocity(1000);
            int velocityX = (int) velocityTracker.getXVelocity();
            //Log.e(TAG, "velocityX:" + velocityX);
            if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
                // Fling enough to move left
                //Log.e(TAG, "snap left");
                snapToScreen(mCurScreen - 1);
            } else if (velocityX < -SNAP_VELOCITY
                    && mCurScreen < getChildCount() - 1) {
                // Fling enough to move right
                //Log.e(TAG, "snap right");
                snapToScreen(mCurScreen + 1);
            } else {
                snapToDestination();
            }
            if (mVelocityTracker != null) {
                mVelocityTracker.recycle();
                mVelocityTracker = null;
            }
            // }
            mTouchState = TOUCH_STATE_REST;
            break;
        case MotionEvent.ACTION_CANCEL:
            mTouchState = TOUCH_STATE_REST;
            break;
        }
        return true;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        //Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop);
        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE)
                && (mTouchState != TOUCH_STATE_REST)) {
            return true;
        }
        final float x = ev.getX();
        final float y = ev.getY();
        switch (action) {
        case MotionEvent.ACTION_MOVE:
            final int xDiff = (int) Math.abs(mLastMotionX - x);
            if (xDiff > mTouchSlop) {
                mTouchState = TOUCH_STATE_SCROLLING;
            }
            break;
        case MotionEvent.ACTION_DOWN:
            mLastMotionX = x;
            mLastMotionY = y;
            mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
                    : TOUCH_STATE_SCROLLING;
            break;
        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            mTouchState = TOUCH_STATE_REST;
            break;
        }
        return mTouchState != TOUCH_STATE_REST;
    }
    
    /**
     * 设置屏幕切换监听器
     * @param listener
     */
    public void SetOnViewChangeListener(OnViewChangeListener listener)
    {
        mOnViewChangeListener = listener;
    }

    /**
     * 屏幕切换监听器
     * @author liux
     */
    public interface OnViewChangeListener {
        public void OnViewChange(int view);
    }
}

 3.方法

   在这个类里面我们可以看到几个方法。看看我们怎么用他们，如下面的这个方法，就是要滑动到那个页面。这个碉堡了.效果真的不错.大家可以试试.

  

public void snapToScreen(int whichScreen) {
        //是否可滑动
        if(!isScroll) {
            this.setToScreen(whichScreen);
            return;
        }
        
        scrollToScreen(whichScreen);
    }

    public void scrollToScreen(int whichScreen) {        
        // get the valid layout page
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        if (getScrollX() != (whichScreen * getWidth())) {
            final int delta = whichScreen * getWidth() - getScrollX();
            mScroller.startScroll(getScrollX(), 0, delta, 0,
                    Math.abs(delta) * 1);//持续滚动时间 以毫秒为单位
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout
            
            if (mOnViewChangeListener != null)
            {
                mOnViewChangeListener.OnViewChange(mCurScreen);
            }
        }
    }

三.总结

          今天跟大家讲了这个组件。也说了使用的方法，可能还是不够详细。所以我还是希望大家去下载源码好好研究。我这也算是一种学习。大家有任何问题可以跟我交流.

我不是大牛。但是我希望我能够坚持.-----

最后附上osa的源码下载地址.有什么使用上的问题大家可以随时交流--------

http://www.oschina.net/app