TabLayout.java

package org.kymjs.music.ui.widget;

import org.kymjs.kjframe.utils.KJLoger;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

/**
 * 底部TAB导航屏幕控件
 * 
 * @author kymjs
 * 
 */
public class TabLayout extends ViewGroup {
    private final Scroller mScroller;
    private VelocityTracker mVelocityTracker;
    private int mCurScreen;
    private final int mDefaultScreen = 0;
    private static final int TOUCH_STATE_REST = 0;
    private static final int TOUCH_STATE_SCROLLING = 1;
    private static final int SNAP_VELOCITY = 600;
    private int mTouchState = TOUCH_STATE_REST;
    private final int mTouchSlop;
    private float mLastMotionX;
    private float mLastMotionY;
    private OnViewChangeListener mOnViewChangeListener;

    /**
     * 设置是否可左右滑动
     */
    private boolean isScroll = true;

    public void setScroll(boolean scroll) {
        this.isScroll = scroll;
    }

    public TabLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TabLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScroller = new Scroller(context);
        mCurScreen = mDefaultScreen;
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    /**
     * 对该控件里面的子控件定位
     */
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        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;
            }
        }
    }

    @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(
                    "ScrollLayout only canmCurScreen run at EXACTLY mode!");
        }
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        // 由于与底部升起的抽屉效果冲突，Main.java中必须改为FrameLayout.LayoutParams.WRAP_CONTENT，所以这里的异常检测去除
        // if (heightMode != MeasureSpec.EXACTLY) {
        // throw new IllegalStateException(
        // "ScrollLayout only can run at EXACTLY mode!");
        // }

        // The children are given the same width and height as the scrollLayout
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }
        scrollTo(mCurScreen * width, 0);
    }

    /**
     * 根据当前的布局滚动位置到目标页
     */
    public void snapToDestination() {
        final int screenWidth = getWidth();
        final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
        snapToScreen(destScreen);
    }

    public void snapToScreen(int whichScreen) {
        // 是否可滑动
        if (!isScroll) {
            this.setToScreen(whichScreen);
            return;
        }
        scrollToScreen(whichScreen);
    }

    public void scrollToScreen(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) * 1);// 持续滚动时间 以毫秒为单位
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout

            if (mOnViewChangeListener != null) {
                mOnViewChangeListener.OnViewChange(mCurScreen);
            }
        }
    }

    public void setToScreen(int whichScreen) {
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        mCurScreen = whichScreen;
        scrollTo(whichScreen * getWidth(), 0);

        if (mOnViewChangeListener != null) {
            mOnViewChangeListener.OnViewChange(mCurScreen);
        }
    }

    public int getCurScreen() {
        return mCurScreen;
    }

    @Override
    public void computeScroll() {
        int currentX = mScroller.getCurrX();
        if (mScroller.computeScrollOffset()) {
            scrollTo(currentX, mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (!isScroll) {
            return false;
        }
        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:
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }
            mLastMotionX = x;
            mLastMotionY = y;
            break;
        case MotionEvent.ACTION_MOVE:
            int deltaX = (int) (mLastMotionX - x);
            int deltaY = (int) (mLastMotionY - y);
            if (Math.abs(deltaX) < 200 && Math.abs(deltaY) > 10)
                break;
            mLastMotionY = y;
            mLastMotionX = x;
            scrollBy(deltaX, 0);
            KJLoger.debug(getClass() + "-----  " + deltaX + "-------"
                    + getWidth() * (getChildCount() - 1));
            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) {
        if (!isScroll) {
            return false;
        }
        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;

    }

    /**
     * 设置屏幕切换监听器
     * 
     * @param listener
     */
    public void SetOnViewChangeListener(OnViewChangeListener listener) {
        mOnViewChangeListener = listener;
    }

    /**
     * 屏幕切换监听器
     * 
     * @author liux
     */
    public interface OnViewChangeListener {
        public void OnViewChange(int view);
    }
}