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