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