package com.wise.extend;
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.ViewGroup;
import android.widget.Scroller;
public class MyScrollLayout extends ViewGroup{
private static final String TAG = "ScrollLayout";
private VelocityTracker mVelocityTracker; // 用于判断甩动手势
private static final int SNAP_VELOCITY = 600; //滑动速度
private Scroller mScroller; // 滑动控制器
private int mCurScreen; //当前所在屏幕
private int mDefaultScreen = 0;
private float mLastMotionX;
private OnViewChangeListener mOnViewChangeListener;
public MyScrollLayout(Context context) {
super(context);
init(context);
}
public MyScrollLayout(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public MyScrollLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
private void init(Context context){
Log.d(TAG, "init");
mCurScreen = mDefaultScreen;
mScroller = new Scroller(context);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
Log.d(TAG, "onLayout="+changed);
if (changed) {
int childLeft = 0;
final int childCount = getChildCount();
for (int i=0; i<childCount; i++) {
final View childView = getChildAt(i);
final int childWidth = childView.getMeasuredWidth();
childView.layout(childLeft, 0,
childLeft+childWidth, childView.getMeasuredHeight());
childLeft += childWidth;
}
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
final int count = getChildCount();
for (int i = 0; i < count; i++) {
getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
}
scrollTo(0, 0);
Log.d(TAG, "-------------count="+count);
}
/**
* 滑动速度过慢的话调用这个方法判断是否滑动了半个屏幕
* 并计算出当前显示那个屏幕
*/
public void snapToDestination() {
final int screenWidth = getWidth();
final int destScreen = (getScrollX()+ screenWidth/2)/screenWidth; //算出对应的屏幕
//Log.d(TAG, "screenWidth="+screenWidth+",getScrollX()="+getScrollX()+",destScreen="+destScreen);
snapToScreen(destScreen);
}
/**
* 跳转到对应的屏幕
* @param whichScreen
*/
public void snapToScreen(int whichScreen) {
// get the valid layout page
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount()-1)); //防止输入不再范围内的数字
if (getScrollX() != (whichScreen*getWidth())) {
final int delta = whichScreen*getWidth()-getScrollX(); //还有多少没有显示
mScroller.startScroll(getScrollX(), 0,delta, 0, Math.abs(delta)*2); //Math.abs(delta)*2滚动delta距离
mCurScreen = whichScreen; //当前显示的屏幕
invalidate(); // Redraw the layout
if (mOnViewChangeListener != null){
mOnViewChangeListener.OnViewChange(mCurScreen);
//mOnViewChangeListener.doit(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
final int action = event.getAction();
final float x = event.getX();
final float y = event.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
mVelocityTracker.addMovement(event);
}
if (!mScroller.isFinished()){
mScroller.abortAnimation();
}
mLastMotionX = x;
//Log.d(TAG, "mLastMotionX="+mLastMotionX);
break;
case MotionEvent.ACTION_MOVE:
int deltaX = (int)(mLastMotionX - x);//计算横向移动距离
//Log.d(TAG, "deltaX="+deltaX+",mLastMotionX="+mLastMotionX+",x="+x);
if (IsCanMove(deltaX)){
if (mVelocityTracker != null){
mVelocityTracker.addMovement(event);
}
mLastMotionX = x;
//Log.d(TAG, "deltaX="+deltaX);
scrollBy(deltaX, 0); //画面跟随指尖
}
break;
case MotionEvent.ACTION_UP:
int velocityX = 0;
if (mVelocityTracker != null){
mVelocityTracker.addMovement(event);
mVelocityTracker.computeCurrentVelocity(1000);
velocityX = (int) mVelocityTracker.getXVelocity();//计算x方向的速度
//Log.d(TAG, "velocityX="+velocityX + ",mCurScreen=" + mCurScreen);
}
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 {
//Log.e(TAG, "到底翻不翻");
snapToDestination();
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
break;
}
return true;
}
/**
* 排除第一页像左划，最后一页像右划
* @param deltaX
* @return
*/
private boolean IsCanMove(int deltaX){
//Log.d(TAG, "getScrollX() = "+getScrollX() + ",deltaX = "+ deltaX);
if (getScrollX() <= 0 && deltaX < 0 ){
return false;
}
if (getScrollX() >= (getChildCount() - 1) * getWidth() && deltaX > 0){
return false;
}
return true;
}
public void SetOnViewChangeListener(OnViewChangeListener listener){
mOnViewChangeListener = listener;
}
public void showWhatSp(){
System.out.println("showWhatSp()");
}
}