一个通过继承ViewGroup，应用Scroller实现的手动拖拽滚屏及自动滚屏的自定义UI控件

package com.android.launcher2; import android.content.Context; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.widget.Scroller; public class AllAppScroller extends ViewGroup { private boolean mFirstLayout = true; private float finalx = 0; private boolean isPortrait = false; private int screenWidth = 1280; private Scroller mScroller; public void setScreenWidth(int screenWidth) { this.screenWidth = screenWidth; } public AllAppScroller(Context context) { super(context); initScroller(); } public AllAppScroller(Context context, AttributeSet attrs) { super(context, attrs); initScroller(); } private void initScroller() { // TODO Auto-generated method stub mScroller = new Scroller(getContext()); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); final int width = isPortrait ? 300 : 383; // The children are given the same width and height as the workspace final int count = getChildCount(); for (int i = 0; i < count; i++) { if (isPortrait) getChildAt(i).measure(300, 363); else getChildAt(i).measure(383, 280); } if (mFirstLayout) { // if (isPortrait) // scrollTo((count * width - screenWidth) / 2, 0); // else scrollTo((count * width - screenWidth) / 2 + 1280, 0); // updateWallpaperOffset(width * (getChildCount() - 1)); mFirstLayout = false; } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int childLeft = 1280; final int count = getChildCount(); for (int i = 0; i < count; i++) { final View child = getChildAt(i); if (child.getVisibility() != View.GONE) { final int childWidth = isPortrait ? 300 : 383; child.layout(childLeft, 0, childLeft + childWidth, child .getMeasuredHeight()); childLeft += childWidth; } } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { int action = ev.getAction(); switch (action) { case MotionEvent.ACTION_DOWN: finalx = ev.getX(); return false; case MotionEvent.ACTION_MOVE: return true; case MotionEvent.ACTION_UP: return false; default: return false; } } @Override public boolean onTouchEvent(MotionEvent event) { int action = event.getAction(); float x = event.getX(); switch (action) { case MotionEvent.ACTION_DOWN: break; case MotionEvent.ACTION_MOVE: final int deltaX = (int) (finalx - x); finalx = x; final int mScrollX = this.getScrollX(); if (deltaX < 0) { if (mScrollX > 0) { scrollBy(Math.max(-mScrollX, deltaX), 0); } } else if (deltaX > 0) { final int availableToScroll = (getChildAt(getChildCount() - 1) .getRight() - mScrollX - screenWidth + 1280); if (availableToScroll > 0) { scrollBy(Math.min(availableToScroll, deltaX), 0); } } break; case MotionEvent.ACTION_UP: int whichone = (getScrollX() - 1280 + 640 + 383) / 383; whichone = whichone > 0 ? whichone : 1; whichone = whichone <= getChildCount() ? whichone : getChildCount(); int dx = 1280 + whichone * 383 - 191 - getScrollX() - 640; mScroller.startScroll(getScrollX(), 0, dx, 0, Math.abs(dx)); invalidate(); break; default: break; } return true; } public void setOrientation(boolean isPortrait) { this.isPortrait = isPortrait; } //隐藏方法，复写以实现使用scroller自动滚动 public void computeScroll() { if (mScroller.computeScrollOffset()) { mScrollX = mScroller.getCurrX(); mScrollY = mScroller.getCurrY(); // updateWallpaperOffset(); postInvalidate(); } } }