2011.06.08——— android 1.6 launcher研究之launcher的左右滑动

2011.06.08——— android 1.6 launcher研究之launcher的左右滑动
参考：http://blog.csdn.net/assassin4824/archive/2011/05/30/6454923.aspx
http://blog.sina.com.cn/s/blog_4d142b550100s1sx.html
http://blog.csdn.net/xiaoxiaobian3310903/archive/2011/05/24/6443250.aspx
http://www.ibm.com/developerworks/cn/opensource/os-cn-android-anmt2/

ScrollLayout.java

package com.lp;  import android.content.Context;  import android.graphics.Canvas;  import android.util.AttributeSet;  import android.util.Log;  import android.view.MotionEvent;  import android.view.VelocityTracker;  import android.view.View;  import android.view.ViewConfiguration;  import android.view.ViewGroup;  import android.widget.Scroller;  /**  * 仿Launcher中的WorkSapce，可以左右滑动切换屏幕的类  */  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;      public ScrollLayout(Context context, AttributeSet attrs) {          this(context, attrs, 0);          // TODO Auto-generated constructor stub      }      public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {          super(context, attrs, defStyle);          // TODO Auto-generated constructor stub          mScroller = new Scroller(context);          //默认显示第一屏        mCurScreen = mDefaultScreen;          mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();      }      @Override      protected void onLayout(boolean changed, int l, int t, int r, int b) {          // TODO Auto-generated method stub          if (changed) {              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;                      //很明显 0 - 320 | 320 - 640 | 640 - 960 ...（假设屏幕宽320）                }              }          }      }      @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);            //x坐标 y坐标        //移动到第几屏        scrollTo(mCurScreen * width, 0);               }              /**      * According to the position of current layout      * scroll to the destination page.     * 判断滑动的位置      * 如果大于当前屏中间的位置 则换屏     * 否则 仍然是这个屏      * getScrollX x方向的偏移量     */         public void snapToDestination() {          final int screenWidth = getWidth();          //判断        final int destScreen = (getScrollX()+ screenWidth/2)/screenWidth;          snapToScreen(destScreen);      }            public void snapToScreen(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();             //开始滚动            //x，y，x方向移动量，y方向移动量，滚动持续时间，负数往左滚            mScroller.startScroll(getScrollX(), 0,                       delta, 0, Math.abs(delta)*2);              mCurScreen = whichScreen;              invalidate();       // Redraw the layout          }      }            public void setToScreen(int whichScreen) {          whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1));          mCurScreen = whichScreen;          scrollTo(whichScreen*getWidth(), 0);      }            public int getCurScreen() {          return mCurScreen;      }      //只有当前LAYOUT中的某个CHILD导致SCROLL发生滚动，才会致使自己的COMPUTESCROLL被调用    @Override      public void computeScroll() {          // TODO Auto-generated method stub          Log.e(TAG,"computeScroll");        //如果返回true，表示动画还没有结束        //因为前面startScroll，所以只有在startScroll完成时 才会为false        if (mScroller.computeScrollOffset()) {              Log.e(TAG, mScroller.getCurrX()+"======"+mScroller.getCurrY());            //产生了动画效果 每次滚动一点            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());             postInvalidate();          }      }      @Override      public boolean onTouchEvent(MotionEvent event) {          // TODO Auto-generated method stub          Log.e(TAG,"onTouchEvent start");        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! "+mScroller.isFinished());              //如果屏幕的滚动动画没有结束 你就按下了 就结束动画            if (!mScroller.isFinished()){                  mScroller.abortAnimation();              }              mLastMotionX = x;              break;                        case MotionEvent.ACTION_MOVE:              Log.e(TAG, "event move!");             //取得偏移量            int deltaX = (int)(mLastMotionX - x);             Log.e(TAG,"detaX: "+deltaX);            mLastMotionX = x;              //x方向的偏移量 y方向的偏移量            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 {                     //一般都掉用这个                snapToDestination();                 }                 if (mVelocityTracker != null) {                     mVelocityTracker.recycle();                     mVelocityTracker = null;                 }                 // }                 mTouchState = TOUCH_STATE_REST;                 break;          case MotionEvent.ACTION_CANCEL:              mTouchState = TOUCH_STATE_REST;              break;          }                    return true;      }      //这个感觉没什么作用 不管true还是false 都是会执行onTouchEvent的 因为子view里面onTouchEvent返回false了    @Override      public boolean onInterceptTouchEvent(MotionEvent ev) {          // TODO Auto-generated method stub          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:              Log.e(TAG,"onInterceptTouchEvent move");            final int xDiff = (int)Math.abs(mLastMotionX-x);              if (xDiff>mTouchSlop) {                  mTouchState = TOUCH_STATE_SCROLLING;                                }              break;                        case MotionEvent.ACTION_DOWN:              Log.e(TAG,"onInterceptTouchEvent down");            mLastMotionX = x;              mLastMotionY = y;              Log.e(TAG,mScroller.isFinished()+"");            mTouchState = mScroller.isFinished()? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;              break;                        case MotionEvent.ACTION_CANCEL:          case MotionEvent.ACTION_UP:              Log.e(TAG,"onInterceptTouchEvent up or cancel");            mTouchState = TOUCH_STATE_REST;              break;          }          Log.e(TAG,mTouchState+"===="+TOUCH_STATE_REST);        return mTouchState != TOUCH_STATE_REST;      }        }

main.xml

<?xml version="1.0" encoding="utf-8"?>  <com.lp.ScrollLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/ScrollLayoutTest"    android:layout_width="fill_parent"    android:layout_height="fill_parent">  <LinearLayout    android:background="#FF00"    android:layout_width="fill_parent"    android:layout_height="fill_parent"></LinearLayout>      <FrameLayout    android:background="#F0F0"    android:layout_width="fill_parent"    android:layout_height="fill_parent"></FrameLayout>      <FrameLayout    android:background="#F00F"    android:layout_width="fill_parent"    android:layout_height="fill_parent">    </FrameLayout>      <LinearLayout    android:background="#FF00"    android:layout_width="fill_parent"    android:layout_height="fill_parent">    <Button      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="Button1" />    </LinearLayout>  <LinearLayout    android:layout_width="wrap_content"    android:layout_height="wrap_content">    <Button      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="Button2" />    </LinearLayout>  </com.lp.ScrollLayout>

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