错误的第一个论证类型

Question

这是我的导入样本

import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;

这就是我使用Fragment

的地方

private void SetUpViewPager(ViewPager viewpager) {
    /*Creating a tab adapter*/
    TabAdapter adapter = new TabAdapter(getSupportFragmentManager());
    adapter.AddFragment(new Fragment1(),"Activity");
    adapter.AddFragment(new Fragment2(),"Friends");
    adapter.AddFragment(new Fragment3(),"Inbox");

    /*Set the adapter to the view pager property*/
    viewpager.setAdapter(adapter);
}

我收到错误的第一个参数发现Fragment1 Required Fragment2

这是适配器类 我不确定问题出在哪里 在代码中   下面         私有类TabAdapter扩展了FragmentPagerAdapter {

    private ArrayList<Fragment> Fragments;
    ArrayList<String> FragmentNames;

    /*Constructor*/
    TabAdapter(FragmentManager fm) {
        super(fm);
        Fragments = new ArrayList<>();
        FragmentNames = new ArrayList<>();
    }

    /*Helper method which adds a fragment which in turn adds a tab*/
    void AddFragment(Fragment1 fragment, String name) {
        Fragments.add(fragment);
        FragmentNames.add(name);
    }

    /*Get the current item of the tab its on*/
    @Override
    public Fragment getItem(int position) {
        return Fragments.get(position);
    }

    /*Returns the number of fragments that are in this adapter*/
    @Override
    public int getCount() {
        return Fragments.size();//Check on This
    }

    @Override
    public CharSequence getPageTitle(int position)
    {
        return FragmentNames.get(position);
    }
}

Answer 1

AddFragment（）期待 Fragment1 作为第一个参数。所以错误是显而易见的。

/*Helper method which adds a fragment which in turn adds a tab*/
void AddFragment(Fragment1 fragment, String name) {
    Fragments.add(fragment);
    FragmentNames.add(name);
}

如果你想让你的方法接受多个类，那么你有两个选择。

1. 将AddFragment()接受Fragment作为第一个参数

   addFragment(Fragment fragment, String name)

2. 声明一个接口并使您的类符合该接口，并将该接口用作参数。

FragmentInterface.java

public interface FragmentInterface{
    // You can declare common functionalities here
}

Fragment1.java

public class Fragment1 extends Fragment implements FragmentInterface {
    // Class implementation
}

TabAdapter.java

/*Helper method which adds a fragment which in turn adds a tab*/
void AddFragment(FragmentInterface fragment, String name) {
    Fragments.add(fragment);
    FragmentNames.add(name);
}