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Android淘宝电影日期滚动栏的实现
2015-06-12 11:06:13         来源:钟钟的专栏  
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最近又有大片上映了,前几天刚看完《末日崩塌》,《侏罗纪世界》又来了,对于大片迷来说是一种福利,所以这几天手机上装了各种电影票团购软件,没办法,同样的电影同样的电影院同样的座位,但是不同的团购软件,价格就不一样。ok,言归正传

在淘宝电影上面有这样一个功能,日期可以滑动,并且选中的是在正中间,效果如下:
这里写图片描述

看完了,那么问题来了。这个功能怎么实现呢?

我们先来分析一下:
把功能拆分一下来看,如果不能滚动,是不是很好实现?其实就是一个 tab 栏,我在前面的 blog 中Android 快速实现 ViewPager 滑动页卡切换(可用作整个 app上导航) 中就实现了此功能,然后在此功能的基础上加上滚动功能即可,具体的实现原理是通过水平滚动控件 HorizontalScrollView把 tab 栏包含起来,然后通过 tab 的选中item 来控制HorizontalScrollView的滚动。<喎"https://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">vcD4NCjxwPrT6wuvKtc/Wo7o8L3A+DQo8cD4xoaLKtc/WINfUtqjS5SB0YWKjrNXiwO++zbK7z7i9ssHLo6y4+seww+bEx8aqIGJsb2cgvLi69dK70fmjrNaxvdPM+bT6wuvBy6OssrvH5bP+tcTH67+0x7DD5rXEIGJsb2c8L3A+DQo8cHJlIGNsYXNzPQ=="brush:java;"> package toolbar.scrollstripview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.util.TypedValue; import android.view.View; import android.widget.LinearLayout; import android.widget.TextView; /** * Created by moon.zhong on 2015/5/25. */ public class SlidingTabView extends LinearLayout { private static final float DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS = 0.5f; private static final byte DEFAULT_BOTTOM_BORDER_COLOR_ALPHA = 0x26; private static final int SELECTED_INDICATOR_THICKNESS_DIPS = 3; private static final int DEFAULT_SELECTED_INDICATOR_COLOR = 0xFF33B5E5; private static final int DEFAULT_DIVIDER_THICKNESS_DIPS = 1; private static final byte DEFAULT_DIVIDER_COLOR_ALPHA = 0x20; private static final float DEFAULT_DIVIDER_HEIGHT = 0.5f; private final float mBottomBorderThickness; private final Paint mBottomBorderPaint; private final int mSelectedIndicatorThickness; private final Paint mSelectedIndicatorPaint; private final Paint mDividerPaint; private final float mDividerHeight; private int mSelectedPosition; private float mSelectionOffset; public SlidingTabView(Context context) { this(context, null); } public SlidingTabView(Context context, AttributeSet attrs) { super(context, attrs); setWillNotDraw(false); final float density = getResources().getDisplayMetrics().density; TypedValue outValue = new TypedValue(); getContext().getTheme().resolveAttribute(android.R.attr.colorForeground, outValue, true); final int themeForegroundColor = outValue.data; mBottomBorderThickness = (int) (DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS * density); mBottomBorderPaint = new Paint(); mBottomBorderPaint.setColor(getResources().getColor(R.color.color_line)); mSelectedIndicatorThickness = (int) (SELECTED_INDICATOR_THICKNESS_DIPS * density); mSelectedIndicatorPaint = new Paint(); mSelectedIndicatorPaint.setColor(0xffff1322); mDividerHeight = DEFAULT_DIVIDER_HEIGHT; mDividerPaint = new Paint(); mDividerPaint.setStrokeWidth((int) (DEFAULT_DIVIDER_THICKNESS_DIPS * density)); mDividerPaint.setColor(getResources().getColor(R.color.color_line)); } void viewPagerChange(int position, float offset){ this.mSelectedPosition = position ; this.mSelectionOffset = offset ; if (offset == 0){ for (int i = 0; i < getChildCount(); i++) { TextView child = (TextView) getChildAt(i); child.setTextColor(0xff666666); } TextView selectedTitle = (TextView) getChildAt(mSelectedPosition); selectedTitle.setTextColor(0xffff1322); } invalidate(); } @Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); final int height = getHeight(); final int childCount = getChildCount(); final int piderHeightPx = (int) (Math.min(Math.max(0f, mDividerHeight), 1f) * height); if (childCount > 0) { TextView selectedTitle = (TextView) getChildAt(mSelectedPosition); int left = selectedTitle.getLeft(); int right = selectedTitle.getRight(); selectedTitle.setTextColor(blendColors(0xff666666,0xffff1322,mSelectionOffset)); if (mSelectionOffset > 0f && mSelectedPosition < (getChildCount() - 1)) { TextView nextTitle = (TextView) getChildAt(mSelectedPosition + 1); left = (int) (mSelectionOffset * nextTitle.getLeft() + (1.0f - mSelectionOffset) * left); right = (int) (mSelectionOffset * nextTitle.getRight() + (1.0f - mSelectionOffset) * right); nextTitle.setTextColor(blendColors(0xffff1322,0xff666666,mSelectionOffset)); } canvas.drawRect(left, height - mSelectedIndicatorThickness, right, height, mSelectedIndicatorPaint); } canvas.drawRect(0, height - mBottomBorderThickness, getWidth(), height, mBottomBorderPaint); int separatorTop = (height - piderHeightPx) / 2; for (int i = 0; i < childCount - 1; i++) { View child = getChildAt(i); canvas.drawLine(child.getRight(), separatorTop, child.getRight(), separatorTop + piderHeightPx, mDividerPaint); } } private static int blendColors(int color1, int color2, float ratio) { final float inverseRation = 1f - ratio; float r = (Color.red(color1) * ratio) + (Color.red(color2) * inverseRation); float g = (Color.green(color1) * ratio) + (Color.green(color2) * inverseRation); float b = (Color.blue(color1) * ratio) + (Color.blue(color2) * inverseRation); return Color.rgb((int) r, (int) g, (int) b); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); } }

2、自定义HorizontalScrollView
这个自定义类的功能,主要是填充 tab 的数据,通过选中的 item 来滚动HorizontalScrollView
填充数据:

    private void populateTabStrip() {
        final PagerAdapter adapter = mViewPager.getAdapter();
        final OnClickListener tabClickListener = new TabClickListener();
/**/
        /*通过 viewPager 的 item 来确定tab 的个数*/

        for (int i = 0; i < adapter.getCount(); i++) {
            View tabView = null;
            TextView tabTitleView = null;

            if (mTabViewLayoutId != 0) {
                // If there is a custom tab view layout id set, try and inflate it
                tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip,
                        false);
                tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
            }

            if (tabView == null) {
                /*创建textView*/
                tabView = createDefaultTabView(getContext());
            }

            if (tabTitleView == null && TextView.class.isInstance(tabView)) {
                tabTitleView = (TextView) tabView;
            }

            tabTitleView.setText(adapter.getPageTitle(i));
            tabView.setOnClickListener(tabClickListener);
            tabView.setBackgroundResource(R.drawable.item_selector_bg);
            /*把 textView 放入到自定义的 tab 栏中*/
            mTabStrip.addView(tabView);
        }
    }

滚动 ScrollView

    /**
     * 这个方法是关键
     * 滚动 scrollview
     * @param tabIndex
     * @param positionOffset
     */
    private void scrollToTab(int tabIndex, int positionOffset) {
        final int tabStripChildCount = mTabStrip.getChildCount();
        if (tabStripChildCount == 0 || tabIndex < 0 || tabIndex >= tabStripChildCount) {
            return;
        }

        /*获取当前选中的 item*/
        View selectedChild = mTabStrip.getChildAt(tabIndex);
        if (selectedChild != null) {
            /*获取当前 item 的偏移量*/
            int targetScrollX = selectedChild.getLeft() + positionOffset;
            /*item 的宽度*/
            int width = selectedChild.getWidth();
            /*item 距离正中间的偏移量*/
            mTitleOffset = (int) ((mWidth-width)/2.0f);

            if (tabIndex > 0 || positionOffset > 0) {
                /*计算出正在的偏移量*/
                targetScrollX -= mTitleOffset;
            }
            Log.v(zgy,==================mWidth=======+mWidth) ;
            /*这个时候偏移的量就是屏幕的正中间*/
            scrollTo(targetScrollX, 0);
        }
    }

具体的调用当然就是 在 ViewPager 的OnPageChangeListener中。
完整类的代码如下:

package toolbar.scrollstripview;

import android.app.Activity;
import android.content.Context;
import android.os.Build;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.HorizontalScrollView;
import android.widget.TextView;

/**
 * Created by moon.zhong.
 */
public class SlidingTabLayout extends HorizontalScrollView {
    private static final int TITLE_OFFSET_DIPS = 24;
    private static final int TAB_VIEW_PADDING_DIPS_TB = 15;
    private static final int TAB_VIEW_PADDING_DIPS = 16;
    private static final int TAB_VIEW_TEXT_SIZE_SP = 14;
    private int mTitleOffset;

    private int mTabViewLayoutId;
    private int mTabViewTextViewId;

    private ViewPager mViewPager;
    private final SlidingTabView mTabStrip;

    private int mWidth ;
    public SlidingTabLayout(Context context) {
        this(context, null);
    }

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

    public SlidingTabLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        setHorizontalScrollBarEnabled(false);

        setFillViewport(true);

        mTitleOffset = (int) (TITLE_OFFSET_DIPS * getResources().getDisplayMetrics().density);

        mTabStrip = new SlidingTabView(context);
        addView(mTabStrip, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
        DisplayMetrics displayMetrics = new DisplayMetrics() ;
        ((Activity) context).getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
        mWidth = (int) (displayMetrics.widthPixels) ;
    }
    public void setViewPager(ViewPager viewPager) {
        mTabStrip.removeAllViews();

        mViewPager = viewPager;
        if (viewPager != null) {
            viewPager.addOnPageChangeListener(new InternalViewPagerListener());
            populateTabStrip();
        }
    }
    private void populateTabStrip() {
        final PagerAdapter adapter = mViewPager.getAdapter();
        final OnClickListener tabClickListener = new TabClickListener();
/**/
        /*通过 viewPager 的 item 来确定tab 的个数*/

        for (int i = 0; i < adapter.getCount(); i++) {
            View tabView = null;
            TextView tabTitleView = null;

            if (mTabViewLayoutId != 0) {
                // If there is a custom tab view layout id set, try and inflate it
                tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip,
                        false);
                tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
            }

            if (tabView == null) {
                /*创建textView*/
                tabView = createDefaultTabView(getContext());
            }

            if (tabTitleView == null && TextView.class.isInstance(tabView)) {
                tabTitleView = (TextView) tabView;
            }

            tabTitleView.setText(adapter.getPageTitle(i));
            tabView.setOnClickListener(tabClickListener);
            tabView.setBackgroundResource(R.drawable.item_selector_bg);
            /*把 textView 放入到自定义的 tab 栏中*/
            mTabStrip.addView(tabView);
        }
    }
    /*这里就是创建 textView,没什么可讲的*/
    protected TextView createDefaultTabView(Context context) {
        TextView textView = new TextView(context);
        textView.setGravity(Gravity.CENTER);
        textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, TAB_VIEW_TEXT_SIZE_SP);;

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {

            TypedValue outValue = new TypedValue();
            getContext().getTheme().resolveAttribute(android.R.attr.selectableItemBackground,
                    outValue, true);
            textView.setBackgroundResource(outValue.resourceId);
        }

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
            textView.setAllCaps(true);
        }

        int paddingTB = (int) (TAB_VIEW_PADDING_DIPS_TB * getResources().getDisplayMetrics().density);
        textView.setPadding(0, paddingTB, 0, paddingTB);
        textView.setTextColor(0xff666666);
        int width = (int) (100 * getResources().getDisplayMetrics().density);
        ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(width, ViewGroup.LayoutParams.WRAP_CONTENT) ;
        textView.setLayoutParams(params);
        return textView;
    }

    /**
     * 这个方法是关键
     * 滚动 scrollview
     * @param tabIndex
     * @param positionOffset
     */
    private void scrollToTab(int tabIndex, int positionOffset) {
        final int tabStripChildCount = mTabStrip.getChildCount();
        if (tabStripChildCount == 0 || tabIndex < 0 || tabIndex >= tabStripChildCount) {
            return;
        }

        /*获取当前选中的 item*/
        View selectedChild = mTabStrip.getChildAt(tabIndex);
        if (selectedChild != null) {
            /*获取当前 item 的偏移量*/
            int targetScrollX = selectedChild.getLeft() + positionOffset;
            /*item 的宽度*/
            int width = selectedChild.getWidth();
            /*item 距离正中间的偏移量*/
            mTitleOffset = (int) ((mWidth-width)/2.0f);

            if (tabIndex > 0 || positionOffset > 0) {
                /*计算出正在的偏移量*/
                targetScrollX -= mTitleOffset;
            }
            Log.v(zgy,==================mWidth=======+mWidth) ;
            /*这个时候偏移的量就是屏幕的正中间*/
            scrollTo(targetScrollX, 0);
        }
    }


    private class InternalViewPagerListener implements ViewPager.OnPageChangeListener {
        private int mScrollState;

        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            int tabStripChildCount = mTabStrip.getChildCount();
            if ((tabStripChildCount == 0) || (position < 0) || (position >= tabStripChildCount)) {
                return;
            }

            mTabStrip.viewPagerChange(position, positionOffset);

            View selectedTitle = mTabStrip.getChildAt(position);
            int extraOffset = (selectedTitle != null)
                    ? (int) (positionOffset * selectedTitle.getWidth())
                    : 0;
            scrollToTab(position, extraOffset);


        }

        @Override
        public void onPageScrollStateChanged(int state) {
            mScrollState = state;

        }

        @Override
        public void onPageSelected(int position) {
            if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
                mTabStrip.viewPagerChange(position, 0f);
                scrollToTab(position, 0);
            }

        }

    }
    private class TabClickListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            for (int i = 0; i < mTabStrip.getChildCount(); i++) {
                if (v == mTabStrip.getChildAt(i)) {
                    mViewPager.setCurrentItem(i);
                    return;
                }
            }
        }
    }
}

代码引用



    
    

运行效果:
这里写图片描述

总结:
1、对前面Android 快速实现 ViewPager 滑动页卡切换(可用作整个 app上导航) blog 的运用;
2、scrollTo(targetScrollX, 0);方法的灵活运用,targetScrollX如果小于0,获取targetScrollX大于 view 的宽度的时候这个方法都不会起作用,看源码可知:

    public void scrollTo(int x, int y) {
        // we rely on the fact the View.scrollBy calls scrollTo.
        if (getChildCount() > 0) {
            View child = getChildAt(0);
            x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth());
            y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight());
            if (x != mScrollX || y != mScrollY) {
                super.scrollTo(x, y);
            }
        }
    }

对 x、y 做了相应的截取操作

 

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