我无法从 Activity 调用 Fragment 方法

Question

我有一个活动。当我单击按钮时，我想在 Fragment 中运行该方法。但它不起作用。我尝试了很多方法，但我无法让它工作。

我的活动；

public class MyActivity extends Activity {

Button button;

TabLayout tabLayout;

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.myactivity_main);

    tabLayout = (TabLayout) findViewById(R.id.tab_layout);

    tabLayout.addTab(tabLayout.newTab().setText("First"));

    tabLayout.addTab(tabLayout.newTab().setText("Second"));

    viewPager= (CustomViewPager) findViewById(R.id.pager);

    final PagerAdapter adapter = new MyFragmentAdapter(getSupportFragmentManager(),tabLayout.getTabCount());

    viewPager.setAdapter(adapter);

    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {

        @Override

        public void onTabSelected(TabLayout.Tab tab) {

            viewPager.setCurrentItem(tab.getPosition());

            }

            @Override

            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override

            public void onTabReselected(TabLayout.Tab tab) {

            }

    });        

    button = (Button)findViewById(R.id.button);

    button .setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            MyFragment firstfragment = (MyFragment ) getFragmentManager().findFragmentByTag(“tab1”); 

            firstfragment.MyMethod();

        }

    });

    }

}

我的片段适配器

import android.support.v4.app.Fragment;

import android.support.v4.app.FragmentManager;

import android.support.v4.app.FragmentPagerAdapter;

import com.webviewapp.Fragment.PromotionFragment;

import com.webviewapp.Fragment.WebFragment;

public class MyFragmentAdapter extends FragmentPagerAdapter {

int tabCount;

public MyFragmentAdapter(FragmentManager fm, int numberOfTabs) {

    super(fm);

    this.tabCount = numberOfTabs;

}

Answer 1

如果你想从 FirstFragment 调用一个方法FirstFragment firstFragment = (FirstFragment) getSupportFragmentManager().getFragments().get(0);firstFragment.MyMethod();如果你想从 SecondFragment 调用一个方法SecondFragment secondFragment = (SecondFragment) getSupportFragmentManager().getFragments().get(1);secondFragment.MyMethod();索引 0 或 1 基于getItem您的适配器方法中的位置。@Overridepublic Fragment getItem(int position) {    switch (position) {        case 0:            FirstFragment tab1 = new FirstFragment();            return tab1;        case 1:            SecondFragment tab2 = new SecondFragment();            return tab2;        default:            return null;    }}那就试试吧。