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ViewPager

一.效果

1.点击底部，Viewpager切换 2.滑动ViewPager，底部也变化 3.Selector选择器的使用

二.思路：1个ViewPager+4个Fragment+1个FragmentPagerAdapter

1.容器：ViewPager

2.数据：ArrayList<Fragment 3.适配器：FragmentPagerAdapter

重写的方法：

(1)getItem() 返回指定下标对于的Fragment

(2)getCount() 得到当前数据源的总数量

四.代码

（1）4个Fragment省略不写

（2）布局activity_main.xml:ViewPager+小圆点+开始体验+右上角倒计时

(3)Java代码：MainActivity.java

/** * 1.viewpager * 2.List
   
     * 3.FragmentPagerAdapter * 4.RadioGroup设置点击事件 * */public class MainActivity extends AppCompatActivity {
       //视图    private ViewPager vp;    private RadioGroup rg;    private RadioButton rb1,rb2,rb3,rb4;    //数据    private ArrayList
    
      fragmentArrayList=new ArrayList<>();    //适配器    private MyFragmentPagerAdpater myFragmentPagerAdpater;    @Override    protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);        //TODO 去除Bar        supportRequestWindowFeature(Window.FEATURE_NO_TITLE);//这句话一定要放到中间        setContentView(R.layout.activity_main);        initview();        initdata();        initadpater();        initlistener();    }    private void initlistener() {
           //点击顶部的时候，切换ViewPager        rg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
               @Override            public void onCheckedChanged(RadioGroup group, int checkedId) {
                   //checkedId代表的是选中的rb的id                if(rb1.getId()==checkedId){
                       vp.setCurrentItem(0);                }else if(rb2.getId()==checkedId){
                       vp.setCurrentItem(1);                }else if(rb3.getId()==checkedId){
                       vp.setCurrentItem(2);                }else if(rb4.getId()==checkedId){
                       vp.setCurrentItem(3);                }                                            }        });        //滑动ViewPager的时候切换底部        vp.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
               @Override            public void onPageScrolled(int i, float v, int i1) {
               }            @Override            public void onPageSelected(int i) {
                   if(i==0){
                       rb1.setChecked(true);                }else  if(i==1){
                       rb2.setChecked(true);                }else  if(i==2){
                       rb3.setChecked(true);                }else  if(i==3){
                       rb4.setChecked(true);                }            }            @Override            public void onPageScrollStateChanged(int i) {
               }        });    }    private void initadpater() {
           myFragmentPagerAdpater=new MyFragmentPagerAdpater(getSupportFragmentManager(),fragmentArrayList);        vp.setAdapter(myFragmentPagerAdpater);    }    private void initdata() {
           fragmentArrayList.add(new Fragment1());        fragmentArrayList.add(new Fragment2());        fragmentArrayList.add(new Fragment3());        fragmentArrayList.add(new Fragment4());    }    private void initview() {
           vp=findViewById(R.id.vp);        rg=findViewById(R.id.rg);        rb1=findViewById(R.id.rb1);        rb2=findViewById(R.id.rb2);        rb3=findViewById(R.id.rb3);        rb4=findViewById(R.id.rb4);    }}
    
   

（4）适配器代码：

public class MyFragmentPagerAdpater extends FragmentPagerAdapter {
       private ArrayList
   
     list;    public MyFragmentPagerAdpater(FragmentManager fm, ArrayList
    
      list) {
           super(fm);        this.list=list;    }    @Override    public Fragment getItem(int i) {
           return list.get(i);    }    @Override    public int getCount() {
           return list.size();    }}
    
   

源代码：

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