android studio 30天学习笔记-day 18-viewPager

viewPager是页面区块内容的切换，可通过滑动的方式进行页面的切换。

dependencies

    implementation "androidx.viewpager2:viewpager2:1.0.0"

先创建3个fragment(我取名为:BindFragment1,BindFragment2,BindFragment3)

activity_main4.xml

<LinearLayout 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=".SqlLiteTest.MainActivity4"
    android:orientation="vertical">
        <com.google.android.material.tabs.TabLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/tablayout"
            app:tabRippleColor="@color/colorAccent"
            app:tabIndicatorColor="@color/colorPrimary">

        </com.google.android.material.tabs.TabLayout>

    <androidx.viewpager.widget.ViewPager
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/viewpager"/>
</LinearLayout>

BindFragmentAdapter

public class BindFragmentAdapter extends FragmentPagerAdapter {
    //宣告阵列
    private  Fragment[] mFragments;
    private String[] titles;
    
    //初始化
    public BindFragmentAdapter(@NonNull FragmentManager fm,String[] titles,Fragment[] mFragments) {
        super(fm);
        this.mFragments=mFragments;
        this.titles=titles;
    }


    @NonNull
    @Override
    public Fragment getItem(int position) { //取分页的内容
        return mFragments[position];
    }

    @Override
    public int getCount() {  //分页数量
        return mFragments.length;
    }

    @Override
    public CharSequence getPageTitle(int position) { //取tab的名称
        return titles[position];
    }
}

MainActivity4

public class MainActivity4 extends AppCompatActivity {
    
    private BindFragment1 bindFragment1 =new BindFragment1();
    private BindFragment2 bindFragment2 =new BindFragment2();
    private BindFragment3 bindFragment3 =new BindFragment3();
    
    private Fragment[] fragments=new Fragment[3];
    private TabLayout tab;
    private String[] titles=new String[3];
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main4);
        init();
    }

    private void init() {
        final ViewPager viewPager=(ViewPager)findViewById(R.id.viewpager);
        tab=(TabLayout)findViewById(R.id.tablayout);
        
        //将要显示的tab name放入titles
        titles[0]="第一页";
        titles[1]="第二页";
        titles[2]="第三页";
        
        for (String title:titles) {
            tab.addTab(tab.newTab().setText(title));
        }
        //将要显示的fragment放入fragments阵列
        fragments[0]=bindFragment1;
        fragments[1]=bindFragment2;
        fragments[2]=bindFragment3;
        //将titles跟fragments传给BindFragmentAdapter
        BindFragmentAdapter adapter = new BindFragmentAdapter(getSupportFragmentManager(), titles,fragments);
        //将BindFragmentAdapter与viewPager绑定
        viewPager.setAdapter(adapter);
        
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tab));//viewpager换页时，tablayout也跟着换页。
        
        tab.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());//点击tabitem，viewpager跟着换页；没加这行点击tabItem，fragment不会做换页。
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });
    }
}