Android ListView在Fragment中的使用示例详解

?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
    <data>
        <variable
            name="viewModel"
            type="com.example.simplenotebook.ui.functionpage.regist.RegistViewModel" />
    </data>
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".ui.functionpage.regist.RegistFragment">
        <!--学习练习-->
        <ListView
            android:id="@+id/lv"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </FrameLayout>
</layout>

<?xml version="1.0" encoding="utf-8"?>
<layout 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">
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="20dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="20dp"
            android:background="@color/white"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:roundPercent="0.2">
            <TextView
                android:id="@+id/tv"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginLeft="15dp"
                android:gravity="center_vertical"
                android:textColor="#3D3D3D"
                android:textSize="14sp" />
        </androidx.constraintlayout.widget.ConstraintLayout>
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

public class UserBean {
    private String name;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

public class RegistFragment extends Fragment {
    private RegistViewModel viewModel;
    private FragmentRegistBinding binding;
    private ListView myListView;
    @Override
    public void onStart() {
        super.onStart();
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        viewModel = new ViewModelProvider(this).get(RegistViewModel.class);
    }
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if (binding == null) {
            binding = FragmentRegistBinding.inflate(inflater,container,false);
            binding.setViewModel(viewModel);//一定要在xml的<data>中申明好才可以setViewModel
            binding.setLifecycleOwner(this);
            myListView = binding.lv;
            myListView.setAdapter(new myAdapter(viewModel.userList,getContext()));
            myListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                    Log.d("TAG", "onItemClick: "+i);
                }
            });
        }
        View rootView = binding.getRoot();
        return rootView;
    }
    /**
     * 给ListView设置适配器
     */
    public class myAdapter extends BaseAdapter{
        private List<UserBean> list;
        private Context context;//下面把数据显示到平台上会有用到这个参数
        public myAdapter(List<UserBean> list, Context context) {//创建构造方法
            this.list = list;
            this.context = context;
        }
        @Override
        public int getCount() {//listView能够显示多少数据，，一般是list有多少数据就会显示多少数据
            return list.size();
        }
        @Override
        public Object getItem(int i) {
            return null;
        }
        @Override
        public long getItemId(int i) {
            return i;
        }
        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {//把数据显示到界面上
            //1.拿到布局文件,为了方式view不停创建我们需要做一个判断，当view为空的时候再去创建
            ViewHoder viewHoder;
            if (view == null) {
                //每次都要去找这个控件比较耗时，如何解决呢？我们需要创建一个viewHoder
               viewHoder = new ViewHoder();
                view = LayoutInflater.from(context).inflate(R.layout.item_home,viewGroup,false);
                viewHoder.textView = view.findViewById(R.id.tv);
                view.setTag(viewHoder);
            }else {
                viewHoder = (ViewHoder) view.getTag();
            }
            //2.拿到textView，把值传给textView
//            TextView textView = view.findViewById(R.id.tv);
            viewHoder.textView.setText(list.get(i).getName());
            Log.i("TAG", "getView: "+i);
            //3.把view返回出去
            return view;
        }
    }
    private final class ViewHoder{
        TextView textView;
    }
}

 
public class RegistViewModel extends ViewModel {
    public List<UserBean> userList = new ArrayList<>();
    public void setData(){
        for (int i = 0; i < 100; i++) {
            UserBean ub = new UserBean();
            ub.setName("流沔"+i);
            userList.add(ub);
        }
    }
}