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

[转]http://lipeng88213.iteye.com/blog/1073463

ScrollLayout.java

Java代码

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

Java代码

    <?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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