1、android.support.design.widget.BottomNavigationView 是android原生的一个底部导航框架
区别于gitthub上start数量很多的com.roughike:bottom-bar:2.3.1'(github地址:点击打开链接):
①android原生的bottomNavigationView初始代码很少也很简单,掌握起来也很快。
②在不使用ViewPager实现联动的情况下,bottomNavigationView使用起来还是很简单,容易上手的。(如有与ViewPager联动的需求,建议使用bottombar)
2、bottomNavigationView + Fragment的实现方式过程:
一、新建项目以BottomNavigationView为初始化模板,默认代码如下:
①activity_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:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.zxp.text.MainActivity"> <TextView android:id="@+id/message" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="@dimen/activity_horizontal_margin" android:layout_marginStart="@dimen/activity_horizontal_margin" android:layout_marginTop="@dimen/activity_vertical_margin" android:text="@string/title_home" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintTop_toTopOf="parent" /> <android.support.design.widget.BottomNavigationView android:id="@+id/navigation" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginEnd="0dp" android:layout_marginStart="0dp" android:background="?android:attr/windowBackground" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:menu="@menu/navigation" /> </android.support.constraint.ConstraintLayout>
最初的xml代码中仅有两个基本控件,一个是tab切换的时候显示的textView,还有一个就是BottomNavigationView,其中决定tab底部按钮的显示的,就是menu文件夹下的navigation.xml文件。
②navigation.xml
<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/navigation_home" android:icon="@drawable/ic_home_black_24dp" android:title="@string/title_home" /> <item android:id="@+id/navigation_dashboard" android:icon="@drawable/ic_dashboard_black_24dp" android:title="@string/title_dashboard" /> <item android:id="@+id/navigation_notifications" android:icon="@drawable/ic_notifications_black_24dp" android:title="@string/title_notifications" /> </menu>
③MainActivity.java
import android.os.Bundle; import android.support.annotation.NonNull; import android.support.design.widget.BottomNavigationView; import android.support.v7.app.AppCompatActivity; import android.view.MenuItem; import android.widget.TextView; public class MainActivity extends AppCompatActivity { private TextView mTextMessage; private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() { @Override public boolean onNavigationItemSelected(@NonNull MenuItem item) { switch (item.getItemId()) { case R.id.navigation_home: mTextMessage.setText(R.string.title_home); return true; case R.id.navigation_dashboard: mTextMessage.setText(R.string.title_dashboard); return true; case R.id.navigation_notifications: mTextMessage.setText(R.string.title_notifications); return true; } return false; } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextMessage = (TextView) findViewById(R.id.message); BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation); navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener); } }
显然,点击tab切换页面的逻辑是发生在OnNavigationItemSelectedListener这个回调中,当然,我们的实际需求肯定不是为了切换显示一个TextView,那也太没有意义了,接下来就是怎么把Fragment中替换到原来的TextView中。
二、添加Fragment
1、新建几个Fragment,切换嘛,没有几个Fragment怎么切换。新建Fragment1、Fragment2、Fragment3等。
2、
import android.os.Bundle; import android.support.annotation.NonNull; import android.support.design.widget.BottomNavigationView; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.app.FragmentTransaction; import android.view.MenuItem; public class MainActivity extends FragmentActivity { private Fragment1 fragment1; //Fragment1对象 private Fragment2 fragment2; //Fragment2对象 private Fragment[] fragments; //Fragment数组 private int lastShowFragment = 0; //表示最后一个显示的Fragment private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() { @Override public boolean onNavigationItemSelected(@NonNull MenuItem item) { switch (item.getItemId()) { case R.id.navigation_home: if (lastShowFragment != 0) { switchFrament(lastShowFragment, 0); lastShowFragment = 0; } return true; case R.id.navigation_dashboard: if (lastShowFragment != 1) { switchFrament(lastShowFragment, 1); lastShowFragment = 1; } return true; } return false; } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation); navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener); initFragments(); } /** * 切换Fragment * * @param lastIndex 上个显示Fragment的索引 * @param index 需要显示的Fragment的索引 */ public void switchFrament(int lastIndex, int index) { FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); transaction.hide(fragments[lastIndex]); if (!fragments[index].isAdded()) { transaction.add(R.id.container, fragments[index]); } transaction.show(fragments[index]).commitAllowingStateLoss(); }
private void initFragments() { fragment1 = new PstationFragment(); fragment2 = new UserInfoFragment(); fragments = new Fragment[]{fragment1, fragment2}; lastShowFragment = 0; getSupportFragmentManager() .beginTransaction() .add(R.id.container, fragment1) .show(fragment1) .commit(); } }