EnergyGroup.java

package com.wise.customView;

import com.wise.extend.OnViewChangeListener;
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.widget.Scroller;
/**
 * 我的车况滑滑动控件
 * @author honesty
 */
public class EnergyGroup extends ViewGroup{
    //private static final String TAG = "EnergyGroup";
    private VelocityTracker velocityTracker;//判断手势
    private static final int SNAP_VELOCITY = 600;  //滑动速度
    private int TOUCH_SLOP; //判断移动的阀值
    private int mCurScreen = 0;  //当前所在屏幕   
    private float downMotionX; //按下x坐标
    OnViewChangeListener mOnViewChangeListener;
    Scroller scroller;
    Context mContext;
    public EnergyGroup(Context context){
        super(context);
        init(context);
    }
    public EnergyGroup(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }
    private void init(Context context){
        scroller = new Scroller(context);
        mContext = context;
        TOUCH_SLOP = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int count = getChildCount();
        for(int i = 0 ; i < count; i++){
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);//设置每个view的大小
        }
        scrollTo(0, 0);//Scroller定位
    }
    @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 childView = getChildAt(i);
            final int width = childView.getMeasuredWidth();
            childView.layout(childLeft, 0, childLeft+width, childView.getMeasuredHeight());
            childLeft += width;
        }
    }
    private float mLastMotionY;
    private final static int TOUCH_STATE_REST = 0;  
    private final static int TOUCH_STATE_SCROLLING = 1; 
    private int mTouchState = TOUCH_STATE_REST;  
    
    boolean isSliding = false;
    float moveXOfFirst;
    float x;
    /**
     * false子控件获取焦点
     * true父控件获取焦点
     */
    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        downMotionX = event.getX(0);
        moveXOfFirst = event.getX(0);
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if(velocityTracker == null){
                velocityTracker = VelocityTracker.obtain();
                velocityTracker.addMovement(event);
            }
            x = moveXOfFirst;
            isSliding = false;
            break;

        case MotionEvent.ACTION_MOVE:
            if(Math.abs(moveXOfFirst-x) > TOUCH_SLOP) {  
                //移动超过阈值，则表示移动了  
                isSliding = true;
            }
            break;
        case MotionEvent.ACTION_UP:
            break;
        }
        return isSliding;
    }
    
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if(velocityTracker == null){
                velocityTracker = VelocityTracker.obtain();
                velocityTracker.addMovement(event);
            }
            if(!scroller.isFinished()){ //解决在松开手滚动时，按下无效
                scroller.abortAnimation();
            }
            downMotionX = x;
            break;
        case MotionEvent.ACTION_MOVE:
            int deltaX = (int)(downMotionX - x);
            downMotionX = x;
            scrollBy(deltaX, 0);//画面跟随指尖
            if (velocityTracker != null){
                velocityTracker.addMovement(event); 
             }
            break;
        case MotionEvent.ACTION_UP:
            int velocityX = 0;
            if(velocityTracker != null){
                velocityTracker.addMovement(event);
                velocityTracker.computeCurrentVelocity(1000);
                velocityX = (int)velocityTracker.getXVelocity();//计算x方向速度
            }
            if(velocityX > SNAP_VELOCITY && mCurScreen > 0){ //速度快且不是第一屏
                snapToScreen(mCurScreen - 1);
            }else if(velocityX < -SNAP_VELOCITY && mCurScreen < getChildCount() - 1){//速度快且不是最后一屏
                snapToScreen(mCurScreen + 1);
            }else{
                snapToDestination(); //判断是否翻转
            }
            break;
        case MotionEvent.ACTION_CANCEL:
            break;
        }
        return true;
    }
    /**
     * 跳转到那个屏幕
     * @param whichScreen
     */
    public void snapToScreen(int whichScreen){
        if(whichScreen > (getChildCount() -1)){
            addView();
        }
        whichScreen = Math.max(0, Math.min(whichScreen, (getChildCount() - 1)));//防止输入不再范围内的数字
        if(getScrollX() != getWidth() * whichScreen){//时候需要移动
            int delta = whichScreen*getWidth()-getScrollX();  //还有多少没有显示
            scroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta)*2);//滚动完剩下的距离
            mCurScreen = whichScreen;
            invalidate();
            if(mOnViewChangeListener != null){
                mOnViewChangeListener.OnViewChange(whichScreen);
            }
        }
    }
    /**
     * 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
     */
    private void snapToDestination(){
        int screenWidth = getWidth();
        int destScreen = (getScrollX() + screenWidth/2)/screenWidth;
        snapToScreen(destScreen);
    }
    
    @Override
    public void computeScroll() {//需要，不然松手后不会滑动
        if (scroller.computeScrollOffset()) {    
            scrollTo(scroller.getCurrX(), scroller.getCurrY());  
            postInvalidate();    
        }
    }
    public void setOnViewChangeListener(OnViewChangeListener onViewChangeListener){
        mOnViewChangeListener = onViewChangeListener;
    }
    public void addView(){
        if(mOnViewChangeListener != null){
            mOnViewChangeListener.OnLastView();
        }
    }
}