一、简介

实现效果图如下：

屏幕快照 2018-07-30 下午3.35.03.png

类似美团主页的底部菜单栏，禁止横向滑动，可以点击tab切换fragment。

采用的框架为Material Design中的tabLayout+ViewPager实现Fragment的切换

二、布局/资源文件

在xml中定义一个tab背景选中和没选中时采用不同的图片，以及不同的字体颜色

2.1 tab的ImageButton背景选择器

selector_home_tab.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/ic_home_red" android:state_selected="true" />
    <item android:drawable="@drawable/ic_home_gray" android:state_selected="false" />
</selector>

selector_surround.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/ic_surround_gray" android:state_selected="false" />
    <item android:drawable="@drawable/ic_surround_red" android:state_selected="true" />
</selector>

其余三个标签类似

2.2 tab中文字颜色背景选择器

selector_tab_text.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="@color/colorRed" android:state_selected="true"/>
    <item android:color="@color/colorDefaultText" android:state_selected="false"/>
</selector>

2.3 tab item的布局文件

tab_item.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingTop="5dp">
    <LinearLayout
        android:layout_width="@dimen/tab_width"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <ImageButton
            android:id="@+id/tab_btn"
            android:layout_width="match_parent"
            android:layout_height="@dimen/image_button_height"
            android:background="@drawable/ic_find_gray"
            android:clickable="false"/>

        <TextView
            android:layout_width="match_parent"
            android:layout_height="@dimen/tab_text_height"
            android:text="发现"
            android:textColor="@drawable/selector_tab_text"
            android:textAlignment="center"
            android:id="@+id/tab_text"/>
    </LinearLayout>

</LinearLayout>

2.4 Fragment布局文件

这次demo没有写好几种Fragment，而是用同一种Fragment。

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="fragment"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:id="@+id/frag_text"/>
</android.support.constraint.ConstraintLayout>

2.5 MainActivity布局文件

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.meituan.huangdanyang.practise.CustomViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="450dp"
        android:orientation="vertical" />

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/colorBoarder"
        app:layout_constraintBottom_toTopOf="@+id/menu" />

    <android.support.design.widget.TabLayout
        android:layout_width="match_parent"
        android:layout_height="@dimen/tab_layout_height"
        android:id="@+id/menu"
        app:layout_constraintBottom_toBottomOf="parent"
        app:tabIndicatorHeight="0dp"/>
</android.support.constraint.ConstraintLayout>

三、java文件

3.1 HomeFragment.java

package com.meituan.huangdanyang.practise;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class HomeFragment extends BaseFragment {

    private final static String ARG_PARAM1 = "text";
    private String text;

    public HomeFragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param text Parameter text.
     * @return A new instance of fragment HomeFragment.
     */

    public static HomeFragment newInstance(String text) {
        HomeFragment fragment = new HomeFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, text);
        fragment.setArguments(args);

        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            text = getArguments().getString(ARG_PARAM1);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_home, container, false);
        TextView textView = view.findViewById(R.id.frag_text);
        textView.setText(text);
        return view;
    }

}

使用newInstance方法创造对象，类似建造者模式，可以构造出不同的对象，给对象中塞入参数。

3.2 ViewPager适配器

HomeFragmentPagerAdapter.java:

package com.meituan.huangdanyang.practise;

import android.content.Context;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;

public class HomeFragmentPagerAdapter extends FragmentPagerAdapter {
    private int[] tabViewId = {R.drawable.selector_home_tab, R.drawable.selector_surround_tab,
            R.drawable.selector_find_tab, R.drawable.selector_order_tab, R.drawable
            .selector_my_tab};
    private String[] tabName = {"首页", "附近", "发现", "订单", "我的"};
    private Context context;

    public HomeFragmentPagerAdapter(FragmentManager fm,Context context) {
        super(fm);
        this.context = context;
    }

    @Override
    public Fragment getItem(int position) {
        HomeFragment homeFragment = HomeFragment.newInstance(tabName[position]);
        homeFragment.TAG = tabName[position];
        return homeFragment;
    }

    @Override
    public int getCount() {
        return Math.min(tabViewId.length,tabName.length);
    }

    public View getTabView(int pos) {
        View view = LayoutInflater.from(context).inflate(R.layout.tab_item,null);
        TextView textView = view.findViewById(R.id.tab_text);
        textView.setText(tabName[pos]);
        ImageButton imageButton = view.findViewById(R.id.tab_btn);
        imageButton.setBackground(context.getDrawable(tabViewId[pos]));
        return view;
    }
}

3.3 MainActivity.java

package com.meituan.huangdanyang.practise;

import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.ImageButton;
import android.widget.LinearLayout;

import com.meituan.huangdanyang.practise.BaseActivity;

import java.util.List;

public class MainActivity extends BaseActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        CustomViewPager viewPager = findViewById(R.id.view_pager);
        TabLayout tabLayout = findViewById(R.id.menu);
        HomeFragmentPagerAdapter adapter = new HomeFragmentPagerAdapter(getSupportFragmentManager(),
                this);
        viewPager.setAdapter(adapter);
        tabLayout.setupWithViewPager(viewPager);
        tabLayout.setTabMode(TabLayout.MODE_FIXED);
        for (int i = 0;i < tabLayout.getTabCount();i++){
            TabLayout.Tab tab = tabLayout.getTabAt(i);
            if (tab != null) {
                //设置标签应当对应的view
                tab.setCustomView(adapter.getTabView(i));
            }
        }
    }

    @Override
    protected String getName() {
        return "MainActivity";
    }

}

3.4 禁止横向滑动

写一个CustomViewPager继承自ViewPager类，在布局中使用。

package com.meituan.huangdanyang.practise;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;

public class CustomViewPager extends ViewPager {
    private boolean canScroll = false;

    public CustomViewPager(@NonNull Context context) {
        super(context);
    }

    public CustomViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        return canScroll && super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        return canScroll && super.onTouchEvent(ev);
    }
}

CustomViewPager中重写了ViewPager的的事件拦截和触摸事件的方法，不能scroll时，事件拦截器和触摸事件直接返回false，不会调用原本的事件拦截和触摸事件中的实现，返回false意味着这个事件没有分发完毕，还会继续向下分发。