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分类: Java

2014-11-30 15:37:22

对于Launcher的桌面滑动大家应该都比较熟悉了,最好的体验应该是可以随着手指的滑动而显示不同位置的桌面,

比一般用ViewFlinger+动画所实现的手势切换页面感觉良好多了~~~~

分析了一下Launcher中的WorkSpace,里面有太多的代码我们用不上了(拖拽,长按,,,),把里面的冗余代码去掉得到实现滑动切换屏幕所必需的。。。。

新建一个ScrollLayout类,继承自ViewGroup。

重写onMeasure和onLayout两个方法:

其中onMeasure方法中,得到ScrollLayout的布局方式(一般使用FILL_PARENT),然后再枚举其中所有的子view,设置它们的布局(FILL_PARENT),这样在ScrollLayout之中的每一个子view即为充满屏幕可以滑动显示的其中一页。

在onLayout方法中,横向画出每一个子view,这样所得到的view的高与屏幕高一致,宽度为getChildCount()-1个屏幕宽度的view。

添加一个Scroller来平滑过渡各个页面之间的切换

重写onInterceptTouchEvent和onTouchEvent来响应手指按下划动时所需要捕获的消息,例如划动的速度,划动的距离等。再配合使用scrollBy (int x, int y)方法得到慢速滑动小距离的时候,所需要显示的内容。最后当手指起来时,根据划动的速度与跨度来判断是向左滑动一页还是向右滑动一页,确保每次用户操作结束之后显示的都是整体的一个子view.

ScrollLayout源码:

点击(此处)折叠或打开

  1. package com.yao_guet.test;
  2. import Android.content.Context;
  3. import android.graphics.Canvas;
  4. import android.util.AttributeSet;
  5. import android.util.Log;
  6. import android.view.MotionEvent;
  7. import android.view.VelocityTracker;
  8. import android.view.View;
  9. import android.view.ViewConfiguration;
  10. import android.view.ViewGroup;
  11. import android.widget.Scroller;
  12. /**
  13.  * 仿Launcher中的WorkSapce,可以左右滑动切换屏幕的类
  14.  * @author Yao.GUET
  15.  * blog: http://blog.csdn.NET/Yao_GUET
  16.  * date: 2011-05-04
  17.  */
  18. public class ScrollLayout extends ViewGroup {
  19.     private static final String TAG = "ScrollLayout";
  20.     private Scroller mScroller;
  21.     private VelocityTracker mVelocityTracker;
  22.         
  23.     private int mCurScreen;
  24.     private int mDefaultScreen = 0;
  25.         
  26.     private static final int TOUCH_STATE_REST = 0;
  27.     private static final int TOUCH_STATE_SCROLLING = 1;
  28.         
  29.     private static final int SNAP_VELOCITY = 600;
  30.         
  31.     private int mTouchState = TOUCH_STATE_REST;
  32.     private int mTouchSlop;
  33.     private float mLastMotionX;
  34.     private float mLastMotionY;
  35.     public ScrollLayout(Context context, AttributeSet attrs) {
  36.         this(context, attrs, 0);
  37.         // TODO Auto-generated constructor stub
  38.     }
  39.     public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
  40.         super(context, attrs, defStyle);
  41.         // TODO Auto-generated constructor stub
  42.         mScroller = new Scroller(context);
  43.             
  44.         mCurScreen = mDefaultScreen;
  45.         mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
  46.     }
  47.     @Override
  48.     protected void onLayout(boolean changed, int l, int t, int r, int b) {
  49.         // TODO Auto-generated method stub
  50.         if (changed) {
  51.             int childLeft = 0;
  52.             final int childCount = getChildCount();
  53.                 
  54.             for (int i=0; i<childCount; i++) {
  55.                 final View childView = getChildAt(i);
  56.                 if (childView.getVisibility() != View.GONE) {
  57.                     final int childWidth = childView.getMeasuredWidth();
  58.                     childView.layout(childLeft, 0,
  59.                             childLeft+childWidth, childView.getMeasuredHeight());
  60.                     childLeft += childWidth;
  61.                 }
  62.             }
  63.         }
  64.     }
  65.     @Override
  66.     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  67.         Log.e(TAG, "onMeasure");
  68.         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  69.       
  70.         final int width = MeasureSpec.getSize(widthMeasureSpec);
  71.         final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
  72.         if (widthMode != MeasureSpec.EXACTLY) {
  73.             throw new IllegalStateException("ScrollLayout only canmCurScreen run at EXACTLY mode!");
  74.         }
  75.       
  76.         final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
  77.         if (heightMode != MeasureSpec.EXACTLY) {
  78.             throw new IllegalStateException("ScrollLayout only can run at EXACTLY mode!");
  79.         }
  80.       
  81.         // The children are given the same width and height as the scrollLayout
  82.         final int count = getChildCount();
  83.         for (int i = 0; i < count; i++) {
  84.             getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
  85.         }
  86.         // Log.e(TAG, "moving to screen "+mCurScreen);
  87.         scrollTo(mCurScreen * width, 0);
  88.     }
  89.         
  90.     /**
  91.      * According to the position of current layout
  92.      * scroll to the destination page.
  93.      */
  94.     public void snapToDestination() {
  95.         final int screenWidth = getWidth();
  96.         final int destScreen = (getScrollX()+ screenWidth/2)/screenWidth;
  97.         snapToScreen(destScreen);
  98.     }
  99.         
  100.     public void snapToScreen(int whichScreen) {
  101.         // get the valid layout page
  102.         whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));
  103.         if (getScrollX() != (whichScreen*getWidth())) {
  104.                 
  105.             final int delta = whichScreen*getWidth()-getScrollX();
  106.             mScroller.startScroll(getScrollX(), 0,
  107.                     delta, 0, Math.abs(delta)*2);
  108.             mCurScreen = whichScreen;
  109.             invalidate(); // Redraw the layout
  110.         }
  111.     }
  112.         
  113.     public void setToScreen(int whichScreen) {
  114.         whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));
  115.         mCurScreen = whichScreen;
  116.         scrollTo(whichScreen*getWidth(), 0);
  117.     }
  118.         
  119.     public int getCurScreen() {
  120.         return mCurScreen;
  121.     }
  122.         
  123.     @Override
  124.     public void computeScroll() {
  125.         // TODO Auto-generated method stub
  126.         if (mScroller.computeScrollOffset()) {
  127.             scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
  128.             postInvalidate();
  129.         }
  130.     }
  131.     @Override
  132.     public boolean onTouchEvent(MotionEvent event) {
  133.         // TODO Auto-generated method stub
  134.             
  135.         if (mVelocityTracker == null) {
  136.             mVelocityTracker = VelocityTracker.obtain();
  137.         }
  138.         mVelocityTracker.addMovement(event);
  139.             
  140.         final int action = event.getAction();
  141.         final float x = event.getX();
  142.         final float y = event.getY();
  143.             
  144.         switch (action) {
  145.         case MotionEvent.ACTION_DOWN:
  146.             Log.e(TAG, "event down!");
  147.             if (!mScroller.isFinished()){
  148.                 mScroller.abortAnimation();
  149.             }
  150.             mLastMotionX = x;
  151.             break;
  152.                 
  153.         case MotionEvent.ACTION_MOVE:
  154.             int deltaX = (int)(mLastMotionX - x);
  155.             mLastMotionX = x;
  156.                 
  157.             scrollBy(deltaX, 0);
  158.             break;
  159.                 
  160.         case MotionEvent.ACTION_UP:
  161.             Log.e(TAG, "event : up");
  162.             // if (mTouchState == TOUCH_STATE_SCROLLING) {
  163.             final VelocityTracker velocityTracker = mVelocityTracker;
  164.             velocityTracker.computeCurrentVelocity(1000);
  165.             int velocityX = (int) velocityTracker.getXVelocity();
  166.             Log.e(TAG, "velocityX:"+velocityX);
  167.                 
  168.             if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
  169.                 // Fling enough to move left
  170.                 Log.e(TAG, "snap left");
  171.                 snapToScreen(mCurScreen - 1);
  172.             } else if (velocityX < -SNAP_VELOCITY
  173.                     && mCurScreen < getChildCount() - 1) {
  174.                 // Fling enough to move right
  175.                 Log.e(TAG, "snap right");
  176.                 snapToScreen(mCurScreen + 1);
  177.             } else {
  178.                 snapToDestination();
  179.             }
  180.             if (mVelocityTracker != null) {
  181.                 mVelocityTracker.recycle();
  182.                 mVelocityTracker = null;
  183.             }
  184.             // }
  185.             mTouchState = TOUCH_STATE_REST;
  186.             break;
  187.         case MotionEvent.ACTION_CANCEL:
  188.             mTouchState = TOUCH_STATE_REST;
  189.             break;
  190.         }
  191.             
  192.         return true;
  193.     }
  194.     @Override
  195.     public boolean onInterceptTouchEvent(MotionEvent ev) {
  196.         // TODO Auto-generated method stub
  197.         Log.e(TAG, "onInterceptTouchEvent-slop:"+mTouchSlop);
  198.             
  199.         final int action = ev.getAction();
  200.         if ((action == MotionEvent.ACTION_MOVE) &&
  201.                 (mTouchState != TOUCH_STATE_REST)) {
  202.             return true;
  203.         }
  204.             
  205.         final float x = ev.getX();
  206.         final float y = ev.getY();
  207.             
  208.         switch (action) {
  209.         case MotionEvent.ACTION_MOVE:
  210.             final int xDiff = (int)Math.abs(mLastMotionX-x);
  211.             if (xDiff>mTouchSlop) {
  212.                 mTouchState = TOUCH_STATE_SCROLLING;
  213.                     
  214.             }
  215.             break;
  216.                 
  217.         case MotionEvent.ACTION_DOWN:
  218.             mLastMotionX = x;
  219.             mLastMotionY = y;
  220.             mTouchState = mScroller.isFinished()? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
  221.             break;
  222.                 
  223.         case MotionEvent.ACTION_CANCEL:
  224.         case MotionEvent.ACTION_UP:
  225.             mTouchState = TOUCH_STATE_REST;
  226.             break;
  227.         }
  228.             
  229.         return mTouchState != TOUCH_STATE_REST;
  230.     }
  231.         
  232. }

测试程序布局:

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  1. <?xml version="1.0" encoding="utf-8"?>
  2. <com.yao_guet.test.ScrollLayout
  3.   xmlns:android="http://schemas.android.com/apk/res/android"
  4.   android:id="@+id/ScrollLayoutTest"
  5.   android:layout_width="fill_parent"
  6.   android:layout_height="fill_parent">
  7. <LinearLayout
  8.   android:background="#FF00"
  9.   android:layout_width="fill_parent"
  10.   android:layout_height="fill_parent"></LinearLayout>
  11.       
  12. <FrameLayout
  13.   android:background="#F0F0"
  14.   android:layout_width="fill_parent"
  15.   android:layout_height="fill_parent"></FrameLayout>
  16.       
  17. <FrameLayout
  18.   android:background="#F00F"
  19.   android:layout_width="fill_parent"
  20.   android:layout_height="fill_parent">
  21.   </FrameLayout>
  22.       
  23. <LinearLayout
  24.   android:background="#FF00"
  25.   android:layout_width="fill_parent"
  26.   android:layout_height="fill_parent">
  27.   <Button
  28.     android:layout_width="wrap_content"
  29.     android:layout_height="wrap_content"
  30.     android:text="Button1" />
  31.   </LinearLayout>
  32. <LinearLayout
  33.   android:layout_width="wrap_content"
  34.   android:layout_height="wrap_content">
  35.   <Button
  36.     android:layout_width="wrap_content"
  37.     android:layout_height="wrap_content"
  38.     android:text="Button2" />
  39.   </LinearLayout>
  40. </com.yao_guet.test.ScrollLayout>


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