Question

我正在开发一个将标签布局作为图像的应用程序。

我想将MVVM架构与数据绑定库一起使用，但我是这个框架的新手。

我可以通过使用ViewPager作为此示例的常规设置选项卡布局而不使用MVVM来执行此操作。

没有MVVM和数据绑定的常规选项卡布局：

activity_main.xml中：

<android.support.design.widget.CoordinatorLayout 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.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabMode="fixed"
        app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"  />

MainActivity.java：

public class MainActivity extends AppCompatActivity {

private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    viewPager = (ViewPager) findViewById(R.id.viewpager);
    setupViewPager(viewPager);

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);
}

private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new OneFragment(), "ONE");
    adapter.addFragment(new TwoFragment(), "TWO");
    adapter.addFragment(new ThreeFragment(), "THREE");
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

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

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

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

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

}

MVVM中的标签布局：

将MVVM与数据绑定库一起使用时，我们必须使用选项卡布局视图的视图模型。

我不知道如何在XML和视图模型中设置标签布局。如何使用数据绑定库

处理诸如“点击布局的一个选项卡”之类的事件

是否有任何使用带有数据绑定库的MVVM中的Tab布局的样本？

感谢您的帮助。

Answer 1

MainActivity -

public class MainActivity extends Activity 
{
    @Override
    protected void onCreate(@Nullable final Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        App.get(this).component().inject(this);
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setHandler(this);
        binding.setManager(getSupportFragmentManager());
    }

    @BindingAdapter({"bind:handler"})
    public static void bindViewPagerAdapter(final ViewPager view, final MainActivity activity)
    {
        final MainActionsAdapter adapter = new MainActionsAdapter(view.getContext(), activity.getSupportFragmentManager());
        view.setAdapter(adapter);
    }

    @BindingAdapter({"bind:pager"})
    public static void bindViewPagerTabs(final TabLayout view, final ViewPager pagerView)
    {
        view.setupWithViewPager(pagerView, true);
    }

}

xml -

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:fresco="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <import type="android.view.View" />

        <variable
            name="handler"
            type="com.ui.main.MainActivity" />

        <variable
            name="manager"
            type="android.support.v4.app.FragmentManager" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:animateLayoutChanges="true"
            app:title="@string/app_name"
            app:titleMarginStart="8dp" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:pager="@{(pager)}">
        </android.support.design.widget.TabLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:handler="@{handler}" />

    </LinearLayout>

</layout>

适配器 -

public class MainSectionsAdapter extends FragmentPagerAdapter
{
    private static final int CONTACTS = 0;
    private static final int CALLS = 1;
    private static final int CHATS = 2;

    private static final int[] TABS = new int[]{CONTACTS, CHATS};

    private Context mContext;

    public MainSectionsAdapter(final Context context, final FragmentManager fm)
    {
        super(fm);
        mContext = context.getApplicationContext();
    }

    @Override
    public Fragment getItem(int position)
    {
        switch (TABS[position])
        {
            case CONTACTS:
                return ContactsFragment.newInstance();
            case CALLS:
                return CallsFragment.newInstance();
            case CHATS:
                return ChatsFragment.newInstance();
        }
        return null;
    }

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

    @Override
    public CharSequence getPageTitle(int position)
    {
        switch (TABS[position])
        {
            case CONTACTS:
                return mContext.getResources().getString(R.string.contacts);
            case CALLS:
                return mContext.getResources().getString(R.string.calls);
            case CHATS:
                return mContext.getResources().getString(R.string.chats);
        }
        return null;
    }
}

Answer 2

以下是setUpWithViewpager使用databinding：

的解决方案

public class BindingUtil
{
    @BindingAdapter({ "setUpWithViewpager" })
    public static void setUpWithViewpager(final TabLayout tabLayout, ViewPager viewPager)
    {
        viewPager.addOnAdapterChangeListener(new ViewPager.OnAdapterChangeListener()
        {
            @Override
            public void onAdapterChanged(@NonNull ViewPager viewPager, @Nullable PagerAdapter oldAdapter, @Nullable PagerAdapter newAdapter)
            {
                if (oldAdapter == null && (newAdapter == null || newAdapter.getCount() == 0))
                {
                    // this function will helpful when 
                    // we don't create viewpager immediately 
                    // when view created (this mean we create
                    // will pager after a period time)
                    return;
                }
                tabLayout.setupWithViewPager(viewPager);
            }
        });
    }
}

<强> XML

<android.support.design.widget.TabLayout
     ... 
     app:setUpWithViewpager="@{ viewPager }"
/>

<android.support.v4.view.ViewPager
     ...
     android:id="@+id/viewPager"
     app:adapter="@{viewModel.pagerAdapter}"
/>

<强>视图模型

public class MainViewModel extends BaseObservable
{

    @Bindable
    public PagerAdapter getPagerAdapter()
    {
        return adapter;
    }

    private void createViewPagerAdapter()
    {
        ...
        notifyPropertyChanged(BR.pagerAdapter);
    }
}

full demo project here

希望有所帮助

Answer 3

我不确定这是不是最近才引入的，但是对于Android支持版本27.1.1，您甚至不需要自定义数据绑定适配器，只需使用：

<android.support.design.widget.TabLayout
                android:id="@+id/tl_1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:setupWithViewPager="@{viewPager}"
                app:tabSelectedTextColor="@android:color/white"
                app:tabTextColor="@color/v5_grey_55"
                />


        <android.support.v4.view.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:addOnPageChangeListener="@{vm.pageChangeListener}"
            app:setAdapter="@{vm.pageAdapter}"
            app:setCurrentItem="@{vm.pageChangeListener.currentPosition}"
            />

请注意，viewPager中的app:setupWithViewPager="@{viewPager}"变量指向android:id="@+id/viewPager"。这样就完成了对ViewPager的引用（就像我知道的魔术一样！）！

Answer 4

如 Phan Van Linh's answer 所示，它对我有用，但是当我们在括号中提供 viewPager 的 ID 作为对 tabLayout 的引用时，它显示绑定错误。

我通过简单地提供不带括号的 ID 解决了这个问题，并在驼峰式大小写中提供了 ViewPager 的 ID。

在MVVM体系结构中使用Tab布局和数据绑定库

4 个答案: