从活动中调用选项卡式片段方法 [英] Call Tabbed Fragment method from Activity

问题描述

我有一个活动，其中包含三个片段.这些片段通过PagerAdapter使用操作栏选项卡.我想做的是从主要活动中访问活动选项卡式片段中的方法.我已经尝试了下面的代码，但是这只是将片段返回为null，所以我想它在选项卡中找不到它！

I have one activity that comprises of three fragments. The fragments use the actionbar tabs using a PagerAdapter. What I want to do is access a method in the active tabbed fragment from the main activity. I have tried the below code but this just returns the fragment as null, so I guess it cant find it within the tabs!

 NPListFragment articleFrag = (NPListFragment) getSupportFragmentManager().findFragmentByTag("NP");
    articleFrag.refreshT();

PagerAdapter:

PagerAdapter:

public class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int i) {
    switch (i) {
        case 0:
            return new NPListFragment();
        case 1:
            return new PListFragment();
        case 2:
            return new FavouritesFragment();
    }
    return null;
}

@Override
public int getCount() {
    return 3;
}

}有人可以建议吗?我已经花了大约6个小时来解决这个问题，但是我并没有取得任何进展.

} Can anyone advise? I have spent about 6 hours on this, i'm just not making any progress resolving this.

推荐答案

您应该做的是:每个片段仅创建一次，然后将其用于对getItem方法的所有调用.

What you should do is : create only once each fragment and then give it for all calls to the getItem method.

例如:

public class AppSectionsPagerAdapter extends FragmentPagerAdapter {

Fragment one, two, three;

public AppSectionsPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int i) {
    switch (i) {
        case 0:
            if(one == null)
                one = new NPListFragment();
            return one;
        case 1:
            if(two == null)
                two= new PListFragment();
            return two;
        case 2:
            if(three == null)
                three= new FavouritesFragment();
            return three;
    }
    return null;
}

@Override
public int getCount() {
    return 3;
}

} 

现在，即使您在活动中，也可以呼叫 getItem

Now, even you in your activity you can call getItem

如果要调用特定方法，只需要将其转换为真实的片段类.

You'll just need to cast it to the real fragment class if you want to call a specific method.

int pos = viewpager.getCurrentItem();    
Fragment activeFragment = adapter.getItem(pos);
if(pos == 0)
    ((NPListFragment)activeFragment).refreshT();
...

这篇关于从活动中调用选项卡式片段方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！