无法解决在FragmentManager中的super()方法错误。

huangapple
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英文:

Cannot resolve method super() error in fragmentmanager Android

问题

我不是Java程序员，但我在尝试构建一个应用程序的同时也在学习Java编程。我试图添加两个片段，一个是登录片段，另一个是注册片段，但在使用超类构造函数时，我遇到了"cannot resolve"错误。有人能指出我做错了什么吗？

我知道"super"用于访问父类构造函数，而在我的情况下父类构造函数不是空的。

以下是MainActivity的代码：

  1. public class MainActivity extends FragmentActivity {
  3.     @Override
  4.     protected void onCreate(Bundle savedInstanceState) {
  5.         super.onCreate(savedInstanceState);
  6.         setContentView(R.layout.activity_main);
  8.         ViewPager2 viewPager = findViewById(R.id.viewPager);
  10.         AuthenticationPagerAdapter pagerAdapter = new AuthenticationPagerAdapter(getSupportFragmentManager());
  11.         pagerAdapter.addFragment(new fragment_login());
  12.         pagerAdapter.addFragment(new fragment_register());
  13.         viewPager.setAdapter(pagerAdapter);
  14.     }
  16.     public static class AuthenticationPagerAdapter extends FragmentStateAdapter {
  17.         private ArrayList<Fragment> fragmentList = new ArrayList<>();
  19.         public AuthenticationPagerAdapter(FragmentManager fragmentActivity) {
  20.             super(fragmentActivity);
  21.         }
  23.         public Fragment getItem(int i) {
  24.             return fragmentList.get(i);
  25.         }
  27.         public int getCount() {
  28.             return fragmentList.size();
  29.         }
  31.         void addFragment(Fragment fragment) {
  32.             fragmentList.add(fragment);
  33.         }
  35.         @NonNull
  36.         @Override
  37.         public Fragment createFragment(int position) {
  38.             return null;
  39.         }
  41.         @Override
  42.         public int getItemCount() {
  43.             return 0;
  44.         }
  45.     }
  46. }
英文:

I am not a Java coder but trying to build an app while trying to learn Java along the way.
I am trying to add 2 fragments one is the login fragment and one is the register fragment but while using super constructor I am facing cannot resolve error.
Could anyone suggest what I am doing wrong?

I get that super is used for accessing the parent class constructor which in my case is not empty.

Following is the MainActivity code:

  1. public class MainActivity extends FragmentActivity
  2. {
  4.     @Override
  5.     protected void onCreate(Bundle savedInstanceState)
  6.     {
  7.         super.onCreate(savedInstanceState);
  8.         setContentView(R.layout.activity_main);
  10.         ViewPager2 viewPager = findViewById(R.id.viewPager);
  12.         AuthenticationPagerAdapter pagerAdapter = new AuthenticationPagerAdapter(getSupportFragmentManager());
  13.         pagerAdapter.addFragment(new fragment_login());
  14.         pagerAdapter.addFragment(new fragment_register());
  15.         viewPager.setAdapter(pagerAdapter);
  16.     }
  18.     public static class AuthenticationPagerAdapter extends FragmentStateAdapter
  19.     {
  20.         private ArrayList&lt;Fragment&gt; fragmentList = new ArrayList&lt;&gt;();
  22.         public AuthenticationPagerAdapter(FragmentManager fragmentActivity)
  23.         {
  24.             super(fragmentActivity);
  25.         }
  27.         public Fragment getItem(int i)
  28.         {
  29.             return fragmentList.get(i);
  30.         }
  32.         public int getCount()
  33.         {
  34.             return fragmentList.size();
  35.         }
  37.         void addFragment(Fragment fragment) {
  38.             fragmentList.add(fragment);
  39.         }
  41.         @NonNull
  42.         @Override
  43.         public Fragment createFragment(int position)
  44.         {
  45.             return null;
  46.         }
  48.         @Override
  49.         public int getItemCount()
  50.         {
  51.             return 0;
  52.         }
  53.     }
  54. }

答案1

得分: 0

我认为对于 fragmentActivity 参数，使用 super() 是不可能的。您应该从更高级的构造函数向 super() 方法发送一个值。顺便说一下，我看不到 MainActivity 类的构造函数。您想从哪个类中获取值？

英文:

I think it's impossible using super() for fragmentActivity parameter. You should send a values to super() method from higher situated constructor. By the way I can't see a constructor for MainActivity class. From which one class you want get a values?

答案2

得分: 0

使用super()在构造函数中，你试图调用父类的构造函数。

在这种情况下，FragmentStateAdapter 有3个构造函数：

  1. FragmentStateAdapter(FragmentActivity fragmentActivity)
  2. FragmentStateAdapter(Fragment fragment)
  3. FragmentStateAdapter(FragmentManager fragmentManager，Lifecycle lifecycle)

在你的情况下：

  1. public AuthenticationPagerAdapter(FragmentManager fragmentActivity)

而 super(FragmentManager); 不匹配 任何超类构造函数。

你可以使用类似这样的代码：

  1. public AuthenticationPagerAdapter(FragmentActivity fragmentActivity) {
  2.         super(fragmentActivity);
  3.     }
  5. public AuthenticationPagerAdapter(FragmentManager fragmentManager, Lifecycle lifecycle) {
  6.         super(fragmentManager, lifecycle);
  7.     }
英文:

Using the super() in a constructor you are trying to call the constructor of the parent class.

In this case the FragmentStateAdapter has 3 constructors:

  1. FragmentStateAdapter(FragmentActivity fragmentActivity)
  2. FragmentStateAdapter(Fragment fragment)
  3. FragmentStateAdapter(FragmentManager fragmentManager, Lifecycle lifecycle)

In your case you have:

  1. public AuthenticationPagerAdapter(FragmentManager fragmentActivity)

and super(FragmentManager); doesn't match any super constructor.

You can use something like:

  1. public AuthenticationPagerAdapter(FragmentActivity fragmentActivity) {
  2.         super(fragmentActivity);
  3.     }
  5. public AuthenticationPagerAdapter(FragmentManager fragmentManager,Lifecycle lifecycle) {
  6.         super(fragmentManager, lifecycle);
  7.     }

huangapple
  • 本文由 发表于 2020年8月30日 23:37:04
  • 转载请务必保留本文链接：https://go.coder-hub.com/63659135.html
  • android
  • android-fragment-manager
  • constructor
  • java
  • super
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