应用luncher实现类似iphone平滑滑动效果

使用luncher实现类似iphone平滑滑动效果

import android.content.Context;   
import android.util.Log;   
import android.content.res.TypedArray;   
import android.util.AttributeSet;   
import android.view.MotionEvent;   
import android.view.VelocityTracker;   
import android.view.View;   
import android.view.ViewGroup;   
import android.view.ViewConfiguration;   
import android.widget.Scroller;   
  
public class DragableSpace extends ViewGroup {   
    private Scroller mScroller;   
    private VelocityTracker mVelocityTracker;   
  
    private int mScrollX = 0;   
    private int mCurrentScreen = 0;   
  
    private float mLastMotionX;   
  
    private static final String LOG_TAG = "DragableSpace";   
  
    private static final int SNAP_VELOCITY = 1000;   
  
    private final static int TOUCH_STATE_REST = 0;   
    private final static int TOUCH_STATE_SCROLLING = 1;   
  
    private int mTouchState = TOUCH_STATE_REST;   
  
    private int mTouchSlop = 0;   
  
    public DragableSpace(Context context) {   
        super(context);   
        mScroller = new Scroller(context);   
  
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();   
  
        this.setLayoutParams(new ViewGroup.LayoutParams(   
                    ViewGroup.LayoutParams.WRAP_CONTENT,   
                    ViewGroup.LayoutParams.FILL_PARENT));   
    }   
  
    public DragableSpace(Context context, AttributeSet attrs) {   
        super(context, attrs);   
        mScroller = new Scroller(context);   
  
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();   
  
        this.setLayoutParams(new ViewGroup.LayoutParams(   
                    ViewGroup.LayoutParams.WRAP_CONTENT ,   
                    ViewGroup.LayoutParams.FILL_PARENT));   
  
        TypedArray a=getContext().obtainStyledAttributes(attrs,R.styleable.DragableSpace);   
        mCurrentScreen = a.getInteger(R.styleable.DragableSpace_default_screen, 0);   
    }   
  
    @Override  
    public boolean onInterceptTouchEvent(MotionEvent ev) {   
          
  
          
        final int action = ev.getAction();   
        if ((action == MotionEvent.ACTION_MOVE)   
                && (mTouchState != TOUCH_STATE_REST)) {   
            return true;   
                }   
  
        final float x = ev.getX();   
  
        switch (action) {   
            case MotionEvent.ACTION_MOVE:   
                  
  
                  
                final int xDiff = (int) Math.abs(x - mLastMotionX);   
  
                boolean xMoved = xDiff > mTouchSlop;   
  
                if (xMoved) {   
                    // Scroll if the user moved far enough along the X axis   
                    mTouchState = TOUCH_STATE_SCROLLING;   
                }   
                break;   
  
            case MotionEvent.ACTION_DOWN:   
                // Remember location of down touch   
                mLastMotionX = x;   
  
                  
                mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;   
                break;   
  
            case MotionEvent.ACTION_CANCEL:   
            case MotionEvent.ACTION_UP:   
                // Release the drag   
                mTouchState = TOUCH_STATE_REST;   
                break;   
        }   
  
          
        return mTouchState != TOUCH_STATE_REST;   
    }   
  
    @Override  
    public boolean onTouchEvent(MotionEvent event) {   
  
        if (mVelocityTracker == null) {   
            mVelocityTracker = VelocityTracker.obtain();   
        }   
        mVelocityTracker.addMovement(event);   
  
        final int action = event.getAction();   
        final float x = event.getX();   
  
        switch (action) {   
            case MotionEvent.ACTION_DOWN:   
                Log.i(LOG_TAG, "event : down");   
                  
                if (!mScroller.isFinished()) {   
                    mScroller.abortAnimation();   
                }   
  
                // Remember where the motion event started   
                mLastMotionX = x;   
                break;   
            case MotionEvent.ACTION_MOVE:   
                // Log.i(LOG_TAG,"event : move");   
                // if (mTouchState == TOUCH_STATE_SCROLLING) {   
                // Scroll to follow the motion event   
                final int deltaX = (int) (mLastMotionX - x);   
                mLastMotionX = x;   
  
                //Log.i(LOG_TAG, "event : move, deltaX " + deltaX + ", mScrollX " + mScrollX);   
  
                if (deltaX < 0) {   
                    if (mScrollX > 0) {   
                        scrollBy(Math.max(-mScrollX, deltaX), 0);   
                    }   
                } else if (deltaX > 0) {   
                    final int availableToScroll = getChildAt(getChildCount() - 1)   
                        .getRight()   
                        - mScrollX - getWidth();   
                    if (availableToScroll > 0) {   
                        scrollBy(Math.min(availableToScroll, deltaX), 0);   
                    }   
                }   
                // }   
                break;   
            case MotionEvent.ACTION_UP:   
                Log.i(LOG_TAG, "event : up");   
                // if (mTouchState == TOUCH_STATE_SCROLLING) {   
                final VelocityTracker velocityTracker = mVelocityTracker;   
                velocityTracker.computeCurrentVelocity(1000);   
                int velocityX = (int) velocityTracker.getXVelocity();   
  
                if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {   
                    // Fling hard enough to move left   
                    snapToScreen(mCurrentScreen - 1);   
                } else if (velocityX < -SNAP_VELOCITY   
                        && mCurrentScreen < getChildCount() - 1) {   
                    // Fling hard enough to move right   
                    snapToScreen(mCurrentScreen + 1);   
                } else {   
                    snapToDestination();   
                }   
  
                if (mVelocityTracker != null) {   
                    mVelocityTracker.recycle();   
                    mVelocityTracker = null;   
                }   
                // }   
                mTouchState = TOUCH_STATE_REST;   
                break;   
            case MotionEvent.ACTION_CANCEL:   
                Log.i(LOG_TAG, "event : cancel");   
                mTouchState = TOUCH_STATE_REST;   
        }   
        mScrollX = this.getScrollX();   
  
        return true;   
    }   
  
    private void snapToDestination() {   
        final int screenWidth = getWidth();   
        final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;   
        Log.i(LOG_TAG, "from des");   
        snapToScreen(whichScreen);   
    }   
  
    public void snapToScreen(int whichScreen) {            
        Log.i(LOG_TAG, "snap To Screen " + whichScreen);   
        mCurrentScreen = whichScreen;   
        final int newX = whichScreen * getWidth();   
        final int delta = newX - mScrollX;   
        mScroller.startScroll(mScrollX, 0, delta, 0, Math.abs(delta) * 2);                
        invalidate();   
    }   
  
    public void setToScreen(int whichScreen) {   
        Log.i(LOG_TAG, "set To Screen " + whichScreen);   
        mCurrentScreen = whichScreen;   
        final int newX = whichScreen * getWidth();   
        mScroller.startScroll(newX, 0, 0, 0, 10);                
        invalidate();   
    }   
  
    @Override  
    protected void onLayout(boolean changed, int l, int t, int r, int b) {   
        int childLeft = 0;   
  
        final int count = getChildCount();   
        for (int i = 0; i < count; i++) {   
            final View child = getChildAt(i);   
            if (child.getVisibility() != View.GONE) {   
                final int childWidth = child.getMeasuredWidth();   
                child.layout(childLeft, 0, childLeft + childWidth, child   
                        .getMeasuredHeight());   
                childLeft += childWidth;   
            }   
        }   
  
    }   
  
    @Override  
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {   
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);   
  
        final int width = MeasureSpec.getSize(widthMeasureSpec);   
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);   
        if (widthMode != MeasureSpec.EXACTLY) {   
            throw new IllegalStateException("error mode.");   
        }   
  
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);   
        if (heightMode != MeasureSpec.EXACTLY) {   
            throw new IllegalStateException("error mode.");   
        }   
  
        // The children are given the same width and height as the workspace   
        final int count = getChildCount();   
        for (int i = 0; i < count; i++) {   
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);   
        }   
        Log.i(LOG_TAG, "moving to screen "+mCurrentScreen);   
        scrollTo(mCurrentScreen * width, 0);         
    }     
  
    @Override  
    public void computeScroll() {   
        if (mScroller.computeScrollOffset()) {   
            mScrollX = mScroller.getCurrX();   
            scrollTo(mScrollX, 0);   
            postInvalidate();   
        }   
    }   
} 

<?xml version="1.0" encoding="utf-8"?>   
<com.matthieu.launcher.DragableSpace xmlns:app="http://schemas.android.com/apk/res/com.matthieu.launcher"  
    xmlns:android="http://schemas.android.com/apk/res/android"  
android:id="@+id/space"  
android:layout_width="fill_parent"  
android:layout_height="fill_parent"  
app:default_screen="1"  
>   
<include android:id="@+id/left"  layout="@layout/left_screen" />   
<include android:id="@+id/center"  layout="@layout/initial_screen" />   
<include android:id="@+id/right"  layout="@layout/right_screen" />   
</com.matthieu.launcher.DragableSpace> 

values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
 <declare-styleable name="DragableSpace"> 
  <attr name="default_screen" format="integer"/> 
 </declare-styleable> 
</resources>

http://blog.sina.com.cn/s/blog_4d142b550100s1th.html

另一篇：
提取Launcher中的WorkSapce，可以左右滑动切换屏幕页面的类
http://blog.csdn.net/Yao_GUET/archive/2011/05/04/6393962.aspx

Android中使用GridView分页显示系统所安装的应用，支持拖动与手势滑动
http://blog.csdn.net/Yao_GUET/archive/2011/05/05/6397197.aspx

多抽屉效果 （类似最早QQ使用的效果）
http://blog.csdn.net/feng88724/archive/2011/02/24/6206388.aspx