android TabLayout实现京东详情效果

Google在2015的IO大会上，给我们带来了更加详细的Material Design设计规范，同时，也给我们带来了全新的Android Design Support Library，在这个support库里面，Google给我们提供了更加规范的MD设计风格的控件。最重要的是，Android Design Support Library的兼容性更广，直接可以向下兼容到Android 2.2。

这两天需要做一个仿京东详情的页面，上面的Tab切换，以前都是自己写Viewpager+fragment，或者Indicator的深度定制，一直想尝试一下TabLayout，于是就有了下面的坑。



然后下面是我简单的实现效果（个人觉得很坑，还不如自己自定义的导航器）



添加引用库

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:24.2.0'
compile 'com.android.support:design:24.2.0'
compile 'com.android.support:recyclerview-v7:24.2.0'
compile 'com.android.support:cardview-v7:24.2.0'
}

Toolbar与TabLayout

我们来看一下实现的布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/c12"
android:gravity="center_vertical"
android:minHeight="45dp"
android:orientation="horizontal"
android:paddingLeft="15dp"
android:paddingRight="15dp">

<ImageView
android:id="@+id/back"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/back_icon" />

<LinearLayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:orientation="horizontal">

<android.support.design.widget.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:tabTextAppearance="@style/TabLayoutTextStyle"
app:tabGravity="center"
app:tabMode="fixed"
app:tabTextColor="@color/c7"
app:tabSelectedTextColor="@color/c8"/>

</LinearLayout>

<ImageView
android:id="@+id/toolbar_more"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:background="@drawable/more_icon" />
</LinearLayout>

<View style="@style/horizontal_line" />

<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" />

<View style="@style/horizontal_line" />

<LinearLayout
android:layout_width="match_parent"
android:layout_height="48dp"
android:background="@color/c12"
android:orientation="horizontal">

<LinearLayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1">

<TextView
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
android:text="收藏"
android:textSize="10sp" />

<View style="@style/vertical_line" />

<TextView
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:gravity="center"
android:text="购物车"
android:textSize="10sp" />
</LinearLayout>

<LinearLayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1.5"
android:background="@color/c8"
android:gravity="center">

<TextView
style="@style/style_c12_s16"
android:gravity="center"
android:text="加入购物车" />
</LinearLayout>
</LinearLayout>
</LinearLayout>

[/code]
这布局文件最关键的一点就是android.support.design.widget.TabLayout 标签中的app:tabMode=”scrollable”，他设置tab的模式为“可滑动的”。
其他的用法和Indicator的用法差不多，都需要设置适配器，然后通过数据实现页面的适配。直接上代码Adapter

public class ProductDetailPagerAdapter extends FragmentPagerAdapter {

private List<Fragment> mFragments=null;
private List<String> mTitles=null;

public ProductDetailPagerAdapter(FragmentManager fm, List<Fragment> mFragments,List<String> mTitles) {
super(fm);
this.mFragments =mFragments;
this.mTitles=mTitles;
}

public ProductDetailPagerAdapter(FragmentManager fm, Fragment... fragments) {
super(fm);
this.mFragments = Arrays.asList(fragments);
}

@Override
public Fragment getItem(int position) {
return mFragments.get(position);
}

@Override
public int getCount() {
return mFragments.size();
}

@Override
public CharSequence getPageTitle(int position) {
return mTitles.get(position);
}
}

主页面的相关逻辑，这里的Fragment就是简单的Fragment。

public class ProductDetailsActivity extends BaseActivity {

@BindView(R.id.viewPager)
ViewPager viewPager;
@BindView(R.id.toolbar_more)
ImageView toolbarMore;
@BindView(R.id.tabLayout)
TabLayout tabLayout;

private List<Fragment> mFragments;
private String[] titles = new String[]{"商品", "详情"};
private ProductDetailPagerAdapter productPagerAdapter = null;
private MorePopupWindow popupWindow = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_product_details);
ButterKnife.bind(this);
init();
}

private void init() {
initViewPager();
}

private void initViewPager() {
mFragments = new ArrayList<>();
mFragments.add(new ProductFragment());
mFragments.add(new ProductDetailFragment());

productPagerAdapter = new ProductDetailPagerAdapter(getSupportFragmentManager(), mFragments, Arrays.asList(titles));
viewPager.setOffscreenPageLimit(2);
viewPager.setAdapter(productPagerAdapter);
viewPager.setCurrentItem(1);
tabLayout.setupWithViewPager(viewPager);
}

@OnClick(R.id.back)
public void backClick() {
finish();
}

@OnClick(R.id.toolbar_more)
public void moreClick() {

}

private AdapterView.OnItemClickListener onItemClickListener = new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
popupWindow.dismiss();
}
};

public static void open(Context context) {
Intent intent = new Intent(context, ProductDetailsActivity.class);
context.startActivity(intent);
}
}

[/code]上面的代码都比较简单不做过多的解释，在使用TabLayout的时候需要注意一点：tabmode有两个属性值：MODE_FIXED:Fixed tabs display all tabs concurrently and are best used with content that benefits from quick pivots between tabs.
MODE_SCROLLABLE:Scrollable tabs display a subset of tabs at any given moment, and can contain longer tab labels and a larger number of tabs.
MODE_SCROLLABLE适合很多tabs的情况,是可以滚动的，如果你要实现京东的那种挤在一起的效果就需要MODE_FIXED了。
为了更好的满足开发需要，TabLayout实现了自定义TabLayout的样式，然后通过引入

app:tabTextAppearance=""

自定义icon添加到tab

当前的TabLayout没有方法让我们去添加icon，我们可以使用SpannableString结合ImageSpan来实现

private int[] imageResId = {
R.drawable.ic_one,
R.drawable.ic_two,
R.drawable.ic_three
};

// ...

@Override
public CharSequence getPageTitle(int position) {
// Generate title based on item position
// return tabTitles[position];
Drawable image = context.getResources().getDrawable(imageResId[position]);
image.setBounds(0, 0, image.getIntrinsicWidth(), image.getIntrinsicHeight());
SpannableString sb = new SpannableString(" ");
ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BOTTOM);
sb.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
return sb;
}

运行，发现没有显示，这是因为TabLayout创建的tab默认设置textAllCaps属性为true，这阻止了ImageSpan被渲染出来，可以通过下面的样式文件定义来改变：

<style name="MyCustomTabLayout" parent="Widget.Design.TabLayout">
<item name="tabTextAppearance">@style/MyCustomTextAppearance</item>
</style>

<style name="MyCustomTextAppearance" parent="TextAppearance.Design.Tab">
<item name="textAllCaps">false</item>
</style>

然后在getPageTitle方法中设置上有标题的tab

@Override
public CharSequence getPageTitle(int position) {
// Generate title based on item position
Drawable image = context.getResources().getDrawable(imageResId[position]);
image.setBounds(0, 0, image.getIntrinsicWidth(), image.getIntrinsicHeight());
// Replace blank spaces with image icon
SpannableString sb = new SpannableString("   " + tabTitles[position]);
ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BOTTOM);
sb.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
return sb;
}

TabLayout还支持自定义View，通过getTabView来设置，这里就不讲怎么实现了，有兴趣的可以自行研究。


部分代码：https://github.com/xiangzhihong/jingdongApp