学习日志18

底部导航栏+ViewPager滑动切换页面

1.view简介

一个页面切换的组件,我们可以往里面填充多个View,然后我们可以通过触摸屏幕左右滑动 切换不同的View。
2.案例演示
在project视图中写入几个Java类,与上一个博客使用的方法相同就不显示了。
学习日志18_第1张图片

2.1在activity_mian.xml文件中写入

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="net.nell.fragmentdemo.MainActivity">

    <RelativeLayout
        android:id="@+id/ly_top_bar"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:background="@color/bg_topbar">

        <TextView
            android:id="@+id/txt_topbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_centerInParent="true"
            android:gravity="center"
            android:text="提醒"
            android:textColor="@color/text_topbar"
            android:textSize="18sp" />

        <View
            android:layout_width="match_parent"
            android:layout_height="2px"
            android:layout_alignParentBottom="true"
            android:background="@color/div_white" />

    </RelativeLayout>


    <RadioGroup
        android:id="@+id/rg_tab_bar"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:layout_alignParentBottom="true"
        android:background="@color/bg_white"
        android:orientation="horizontal">

        <RadioButton
            android:id="@+id/rb_channel"
            style="@style/tab_menu_item"
            android:drawableTop="@drawable/tab_menu_channel"
            android:text="@string/tab_menu_alert" />

        <RadioButton
            android:id="@+id/rb_message"
            style="@style/tab_menu_item"
            android:drawableTop="@drawable/tab_menu_message"
            android:text="@string/tab_menu_profile" />

        <RadioButton
            android:id="@+id/rb_better"
            style="@style/tab_menu_item"
            android:drawableTop="@drawable/tab_menu_better"
            android:text="@string/tab_menu_pay" />

        <RadioButton
            android:id="@+id/rb_setting"
            style="@style/tab_menu_item"
            android:drawableTop="@drawable/tab_menu_setting"
            android:text="@string/tab_menu_setting" />

    </RadioGroup>

    <View
        android:id="@+id/div_tab_bar"
        android:layout_width="match_parent"
        android:layout_height="2px"
        android:layout_above="@id/rg_tab_bar"
        android:background="@color/div_white" />

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/vpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/div_tab_bar"
        android:layout_below="@id/ly_top_bar" />


</RelativeLayout>


2.2创建一个新的类写入代码



import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.view.ViewGroup;


public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
     

    private final int PAGER_COUNT = 4;
    private MyFragment1 myFragment1 = null;
    private MyFragment2 myFragment2 = null;
    private MyFragment3 myFragment3 = null;
    private MyFragment4 myFragment4 = null;


    public MyFragmentPagerAdapter(FragmentManager fm) {
     
        super(fm);
        myFragment1 = new MyFragment1();
        myFragment2 = new MyFragment2();
        myFragment3 = new MyFragment3();
        myFragment4 = new MyFragment4();
    }


    @Override
    public int getCount() {
     
        return PAGER_COUNT;
    }

    @Override
    public Object instantiateItem(ViewGroup vg, int position) {
     
        return super.instantiateItem(vg, position);
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
     
        System.out.println("position Destory" + position);
        super.destroyItem(container, position, object);
    }

    @Override
    public Fragment getItem(int position) {
     
        Fragment fragment = null;
        switch (position) {
     
            case MainActivity.PAGE_ONE:
                fragment = myFragment1;
                break;
            case MainActivity.PAGE_TWO:
                fragment = myFragment2;
                break;
            case MainActivity.PAGE_THREE:
                fragment = myFragment3;
                break;
            case MainActivity.PAGE_FOUR:
                fragment = myFragment4;
                break;
        }
        return fragment;
    }


}



2.3在主方法中写入代码


import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;



public class MainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener,
        ViewPager.OnPageChangeListener {
     

    //UI Objects
    private TextView txt_topbar;
    private RadioGroup rg_tab_bar;
    private RadioButton rb_channel;
    private RadioButton rb_message;
    private RadioButton rb_better;
    private RadioButton rb_setting;
    private ViewPager vpager;

    private MyFragmentPagerAdapter mAdapter;

    //几个代表页面的常量
    public static final int PAGE_ONE = 0;
    public static final int PAGE_TWO = 1;
    public static final int PAGE_THREE = 2;
    public static final int PAGE_FOUR = 3;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
     
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager());
        bindViews();
        rb_channel.setChecked(true);
    }

    private void bindViews() {
     
        txt_topbar = (TextView) findViewById(R.id.txt_topbar);
        rg_tab_bar = (RadioGroup) findViewById(R.id.rg_tab_bar);
        rb_channel = (RadioButton) findViewById(R.id.rb_channel);
        rb_message = (RadioButton) findViewById(R.id.rb_message);
        rb_better = (RadioButton) findViewById(R.id.rb_better);
        rb_setting = (RadioButton) findViewById(R.id.rb_setting);
        rg_tab_bar.setOnCheckedChangeListener(this);

        vpager = (ViewPager) findViewById(R.id.vpager);
        vpager.setAdapter(mAdapter);
        vpager.setCurrentItem(0);
        vpager.addOnPageChangeListener(this);
    }

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
     
        switch (checkedId) {
     
            case R.id.rb_channel:
                vpager.setCurrentItem(PAGE_ONE);
                break;
            case R.id.rb_message:
                vpager.setCurrentItem(PAGE_TWO);
                break;
            case R.id.rb_better:
                vpager.setCurrentItem(PAGE_THREE);
                break;
            case R.id.rb_setting:
                vpager.setCurrentItem(PAGE_FOUR);
                break;
        }
    }


    //重写ViewPager页面切换的处理方法
    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
     
    }

    @Override
    public void onPageSelected(int position) {
     
    }

    @Override
    public void onPageScrollStateChanged(int state) {
     
        //state的状态有三个,0表示什么都没做,1正在滑动,2滑动完毕
        if (state == 2) {
     
            switch (vpager.getCurrentItem()) {
     
                case PAGE_ONE:
                    rb_channel.setChecked(true);
                    break;
                case PAGE_TWO:
                    rb_message.setChecked(true);
                    break;
                case PAGE_THREE:
                    rb_better.setChecked(true);
                    break;
                case PAGE_FOUR:
                    rb_setting.setChecked(true);
                    break;
            }
        }
    }
}


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