Android 仿腾讯应用宝 之 Toolbar +Scroolview +tab滑动悬停效果

先说下最近做应用市场，想要的效果如下：

1、上面actionbar使用的toolbar最新的工具条来代替acionbar.

2、toolbar下面有一个 app详情

3、app详情下面有一个滑动tab ，tab下是viewpage ，viewpage里面嵌套的是2个Fragment，一个是Scrollview,一个是ListView。

要实现，监听Scrollview或者ListView滚动事件，来推挤tab向上移动，并且悬停在Toolbar下面。

具体效果如图：

代码不多解释，直接下载demo自行运行demo哈。稍后放源码。

声明：本代码基于其他开源项目，修改而来。

package com.github.ksoichiro.android.observablescrollview.samples;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import com.example.toolbar.R;
import com.github.ksoichiro.android.observablescrollview.ObservableScrollView;
import com.github.ksoichiro.android.observablescrollview.ObservableScrollViewCallbacks;
import com.github.ksoichiro.android.observablescrollview.ScrollState;
import com.github.ksoichiro.android.observablescrollview.ScrollUtils;
import com.google.samples.apps.iosched.ui.widget.SlidingTabLayout;
import com.nineoldandroids.view.ViewHelper;
import com.nineoldandroids.view.ViewPropertyAnimator;
public class ViewPagerTabScrollViewActivity extends ActionBarActivity implements ObservableScrollViewCallbacks {

    private View mHeaderView;
    private View appinfo;
    private int mBaseTranslationY;
    private ViewPager mPager;
    private NavigationAdapter mPagerAdapter;
    private Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_viewpagertab);
        toolbar=(Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        mHeaderView = findViewById(R.id.header);
        ViewCompat.setElevation(mHeaderView, getResources().getDimension(R.dimen.toolbar_elevation));
        appinfo = findViewById(R.id.apptitleview);
        mPagerAdapter = new NavigationAdapter(getSupportFragmentManager());
        mPager = (ViewPager) findViewById(R.id.pager);
        mPager.setAdapter(mPagerAdapter);

        SlidingTabLayout slidingTabLayout = (SlidingTabLayout) findViewById(R.id.sliding_tabs);
        slidingTabLayout.setCustomTabView(R.layout.tab_indicator, android.R.id.text1);
        slidingTabLayout.setSelectedIndicatorColors(getResources().getColor(R.color.accent));
        slidingTabLayout.setDistributeEvenly(true);
        slidingTabLayout.setViewPager(mPager);

        // When the page is selected, other fragments' scrollY should be adjusted
        // according to the toolbar status(shown/hidden)
        slidingTabLayout.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int i, float v, int i2) {
            }

            @Override
            public void onPageSelected(int i) {
                propagateToolbarState(toolbarIsShown());
            }

            @Override
            public void onPageScrollStateChanged(int i) {
            }
        });

        propagateToolbarState(toolbarIsShown());
    }

    @Override
    public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
    	//判断如果是拖动
        if (dragging) {
            int toolbarHeight = appinfo.getHeight();
            float currentHeaderTranslationY = ViewHelper.getTranslationY(mHeaderView);
            if (firstScroll) {
                if (-toolbarHeight < currentHeaderTranslationY) {
                    mBaseTranslationY = scrollY;
                }
            }
            float headerTranslationY = ScrollUtils.getFloat(-(scrollY - mBaseTranslationY), -toolbarHeight, 0);
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewHelper.setTranslationY(mHeaderView, headerTranslationY);
        }else{
        	if(!firstScroll){
        		int toolbarHeight = appinfo.getHeight();
        		float headerTranslationY = ScrollUtils.getFloat(-(scrollY - mBaseTranslationY), -toolbarHeight, 0);
                ViewPropertyAnimator.animate(mHeaderView).cancel();
                ViewHelper.setTranslationY(mHeaderView, headerTranslationY);
        	}

        }
    }

    @Override
    public void onDownMotionEvent() {
    }

    @Override
    public void onUpOrCancelMotionEvent(ScrollState scrollState) {
        mBaseTranslationY = 0;

        Fragment fragment = getCurrentFragment();
        if (fragment == null) {
            return;
        }
        View view = fragment.getView();
        if (view == null) {
            return;
        }

        int toolbarHeight = appinfo.getHeight();
        final ObservableScrollView scrollView = (ObservableScrollView) view.findViewById(R.id.scroll);
        if (scrollView == null) {
            return;
        }
        int scrollY = scrollView.getCurrentScrollY();
        if (scrollState == ScrollState.DOWN) {//按下
        	//判断滑动到顶部的时候，开始显示 toolbar 不是顶部的  隐藏toolbar

        	if(scrollView.getScrollY()<=toolbarHeight){
        		showToolbar();
        	}else{
                hideToolbar();
        	}

        } else if (scrollState == ScrollState.UP) {//抬起
            if (toolbarHeight <= scrollY) {
                hideToolbar();
            } else {
                showToolbar();
            }
        } else {
        	//
            // Even if onScrollChanged occurs without scrollY changing, toolbar should be adjusted
            if (toolbarIsShown() || toolbarIsHidden()) {
                // Toolbar is completely moved, so just keep its state
                // and propagate it to other pages
                propagateToolbarState(toolbarIsShown());
            } else {
                // Toolbar is moving but doesn't know which to move:
                // you can change this to hideToolbar()
                showToolbar();
            }
        }
    }

    private Fragment getCurrentFragment() {
        return mPagerAdapter.getItemAt(mPager.getCurrentItem());
    }

    private void propagateToolbarState(boolean isShown) {
        int toolbarHeight = appinfo.getHeight();
        //设置scrollY尚未创建的片段
        // Set scrollY for the fragments that are not created yet
        mPagerAdapter.setScrollY(isShown ? 0 : toolbarHeight);
        //设置活动scrollY碎片

        // Set scrollY for the active fragments
        for (int i = 0; i < mPagerAdapter.getCount(); i++) {
            // Skip current item
            if (i == mPager.getCurrentItem()) {
                continue;
            }

            // Skip destroyed or not created item
            Fragment f = mPagerAdapter.getItemAt(i);
            if (f == null) {
                continue;
            }

            ObservableScrollView scrollView = (ObservableScrollView) f.getView().findViewById(R.id.scroll);
            if (isShown) {
                // Scroll up
                if (0 < scrollView.getCurrentScrollY()) {//滚动到 顶部
                    scrollView.scrollTo(0, 0);
                }
            } else {
                // Scroll down (to hide padding)//滚动到底部
                if (scrollView.getCurrentScrollY() < toolbarHeight) {
                    scrollView.scrollTo(0, toolbarHeight);
                }
            }
        }
    }

    private boolean toolbarIsShown() {
        return ViewHelper.getTranslationY(mHeaderView) == 0;
    }
    private boolean toolbarIsHidden() {
        return ViewHelper.getTranslationY(mHeaderView) == -appinfo.getHeight();
    }

    private void showToolbar() {
        float headerTranslationY = ViewHelper.getTranslationY(mHeaderView);
        if (headerTranslationY != 0) {
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewPropertyAnimator.animate(mHeaderView).translationY(0).setDuration(200).start();
        }
        propagateToolbarState(true);
    }

    private void hideToolbar() {
        float headerTranslationY = ViewHelper.getTranslationY(mHeaderView);
        int toolbarHeight = appinfo.getHeight();
        if (headerTranslationY != -toolbarHeight) {
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewPropertyAnimator.animate(mHeaderView).translationY(-toolbarHeight).setDuration(200).start();
        }
        propagateToolbarState(false);
    }

    private static class NavigationAdapter extends CacheFragmentStatePagerAdapter {

        private static final String[] TITLES = new String[]{"Applepie", "Butter Cookie"};

        private int mScrollY;

        public NavigationAdapter(FragmentManager fm) {
            super(fm);
        }

        public void setScrollY(int scrollY) {
            mScrollY = scrollY;
        }

        @Override
        protected Fragment createItem(int position) {
            Fragment f = new ViewPagerTabScrollViewFragment();
            if (0 <= mScrollY) {
                Bundle args = new Bundle();
                args.putInt(ViewPagerTabScrollViewFragment.ARG_SCROLL_Y, mScrollY);
                f.setArguments(args);
            }
            return f;
        }

        @Override
        public int getCount() {
            return TITLES.length;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return TITLES[position];
        }
    }
}