code

 

package com.android.multitheme;

import android.content.Context;
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.view.animation.Interpolator;
import android.widget.Scroller;
//AllAppsScrollLayout
/**
 * アプリリストのGridView
 */
public class AppListLayout extends ViewGroup {

 private static final String TAG = "AppListLayout";
 private Scroller mScroller;
 private VelocityTracker mVelocityTracker;
 private static final int SNAP_VELOCITY = 600;
 private int mTouchSlop;

 private int mCurScreen;
 private int mDefaultScreen = 0;

 private static final int TOUCH_STATE_REST = 0;
 private static final int TOUCH_STATE_SCROLLING = 1;
 private int mTouchState = TOUCH_STATE_REST;

 private float mLastMotionX;
 private float mLastMotionY;
 
 public AppListLayout(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
  // TODO Auto-generated constructor stub
 }

 public AppListLayout(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  // TODO Auto-generated constructor stub
  mScroller = new Scroller(context);
  mCurScreen = mDefaultScreen;
  mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  final int width = MeasureSpec.getSize(widthMeasureSpec);
  if (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY) {
   throw new IllegalStateException(
     "AppListLayout only canmCurScreen run at EXACTLY mode!");
  }
  if (MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY) {
   throw new IllegalStateException(
     "AppListLayout only can run at EXACTLY mode!");
  }
  final int count = getChildCount();
  for (int i = 0; i < count; i++) {
   getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
  }
  scrollTo(mCurScreen * width, 0);
 }

 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
  // TODO Auto-generated method stub
  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;
   }
  }
 }

 public void snapToDestination() {
  final int screenWidth = getWidth();
  final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
  snapToScreen(destScreen);
 }

 public void snapToScreen(int whichScreen) {
  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) * 2);
   mCurScreen = whichScreen;
   
   invalidate();
  }
 }

 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;
 }

 @Override
 public void computeScroll() {
  // TODO Auto-generated method stub
  if (mScroller.computeScrollOffset()) {
   scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
   postInvalidate();
  }
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  // TODO Auto-generated method stub
  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;
   break;

  case MotionEvent.ACTION_MOVE:
   int deltaX = (int) (mLastMotionX - x);
   mLastMotionX = x;
   scrollBy(deltaX, 0);
   break;

  case MotionEvent.ACTION_UP:
   final VelocityTracker velocityTracker = mVelocityTracker;
   velocityTracker.computeCurrentVelocity(1000);
   int velocityX = (int) velocityTracker.getXVelocity();
   if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
    snapToScreen(mCurScreen - 1);
   } else if (velocityX < -SNAP_VELOCITY
     && mCurScreen < getChildCount() - 1) {
    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) {
  // TODO Auto-generated method stub
  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;
 }
}