java - 无法在 public void 函数中使用 findViewById 方法

Question

我在android中使用 fragment ，我在这个 fragment 中有一个名为CustomersFragment的 fragment ，我在onCreateView上使用这个方法时使用findViewById方法没问题，但是当我在 public void 函数中使用时出现错误，这是底部的我的 fragment 代码

package com.androiddeft.navigationdrawer.fragments;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.androiddeft.navigationdrawer.MyListAdapter;
import com.androiddeft.navigationdrawer.R;
import com.androiddeft.navigationdrawer.Employee;
import com.androiddeft.navigationdrawer.DatabaseHelper;
import com.androiddeft.navigationdrawer.constants.NavigationDrawerConstants;

import java.util.List;


public class CustomersFragment extends Fragment {

    private Button btnSubmit;
    private Button btnCancel;
    private ListView listView;
    private MyListAdapter adapter;
    private EditText edtSearch, edtName, edtPhone, edtAddress;
    private int seletcedEmployeeId;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setTitle(NavigationDrawerConstants.TAG_CUSTOMERS);
    }

    @Override
    public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
        // Create the view from XML layout.
        final View view = inflater.inflate(R.layout.fragment_customers, null);
        // Perform additional configuration on layout components here.
        Button btnAdd = (Button) view.findViewById(R.id.btn_add);
        Button btnShowSearch = (Button) view.findViewById(R.id.btn_search);
        Button btnCloseSearch = (Button) view.findViewById(R.id.btn_close_search);
        Button btnDoSearch = (Button) view.findViewById(R.id.btn_do_search);
        btnCancel = (Button) view.findViewById(R.id.btn_cancel);
        btnSubmit = (Button) view.findViewById(R.id.btn_submit);

        edtSearch = (EditText) view.findViewById(R.id.edt_search);
        edtName = (EditText) view.findViewById(R.id.edt_employee_name);
        edtPhone = (EditText) view.findViewById(R.id.edt_employee_phone);
        edtAddress = (EditText) view.findViewById(R.id.edt_employee_address);

        btnAdd.setOnClickListener(onAddClicked);
        btnShowSearch.setOnClickListener(onShowSearchClicked);
        btnCloseSearch.setOnClickListener(onCloseSearchClicked);
        btnDoSearch.setOnClickListener(onDoSearchClicked);
        btnCancel.setOnClickListener(onCancelbuttonClicked);

        listView = (ListView) view.findViewById(R.id.listView);
        refreshList();
        return view;
    }
    private void refreshList() {
        List<Employee> employees = new DatabaseHelper(this).getListOfEmployees();
        adapter = new MyListAdapter(this, employees);
        listView.setAdapter(adapter);
    }

    public void editEmployee(Employee employee) {
        findViewById(R.id.lin_add_search).setVisibility(View.GONE);
        findViewById(R.id.add_edit_employee).setVisibility(View.VISIBLE);
        btnSubmit.setOnClickListener(onEditEmployeeSubmit);
        edtName.setText(employee.getName());
        edtPhone.setText(employee.getPhone());
        edtAddress.setText(employee.getAddress());
        seletcedEmployeeId = employee.getId();
    }

    private View.OnClickListener onAddClicked = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            findViewById(R.id.lin_add_search).setVisibility(View.GONE);
            findViewById(R.id.add_edit_employee).setVisibility(View.VISIBLE);
            btnSubmit.setOnClickListener(onNewEmployeeSubmit);
        }
    };

    private View.OnClickListener onShowSearchClicked = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            findViewById(R.id.lin_add_search).setVisibility(View.GONE);
            findViewById(R.id.search_bar).setVisibility(View.VISIBLE);
        }
    };

    private View.OnClickListener onCloseSearchClicked = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            findViewById(R.id.lin_add_search).setVisibility(View.VISIBLE);
            findViewById(R.id.search_bar).setVisibility(View.GONE);
            edtSearch.setText("");
            refreshList();
        }
    };

    private View.OnClickListener onDoSearchClicked = new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            String input = edtSearch.getText().toString();
            if (input.length() == 0) {
                Toast.makeText(getActivity(), "لطفا قسمتی از نام کارمند را بنویسید", Toast.LENGTH_SHORT).show();
                return;
            }

            List<Employee> employees = new DatabaseHelper(getActivity()).searchByName(input);
            adapter = new MyListAdapter(getActivity(), employees);
            listView.setAdapter(adapter);
            Toast.makeText(getActivity(), employees.size() + " کارمند پیدا شد", Toast.LENGTH_SHORT).show();
        }
    };

    private View.OnClickListener onCancelbuttonClicked = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            edtName.setText("");
            edtPhone.setText("");
            edtAddress.setText("");
            findViewById(R.id.lin_add_search).setVisibility(View.VISIBLE);
            findViewById(R.id.add_edit_employee).setVisibility(View.GONE);
        }
    };

    private View.OnClickListener onNewEmployeeSubmit = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (edtName.getText().length() == 0 || edtPhone.getText().length() == 0 || edtAddress.getText().length() == 0) {
                Toast.makeText(getActivity(), "لطفا اطلاعات را وارد کنید", Toast.LENGTH_SHORT).show();
                return;
            }
            Employee employee = new Employee();
            employee.setName(edtName.getText().toString());
            employee.setPhone(edtPhone.getText().toString());
            employee.setAddress(edtAddress.getText().toString());
            new DatabaseHelper(getActivity()).addNewEmployee(employee);
            refreshList();
            btnCancel.performClick();
        }
    };

    private View.OnClickListener onEditEmployeeSubmit = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (edtName.getText().length() == 0 || edtPhone.getText().length() == 0 || edtAddress.getText().length() == 0) {
                Toast.makeText(getActivity(), "لطفا اطلاعات را وارد کنید", Toast.LENGTH_SHORT).show();
                return;
            }
            Employee employee = new Employee();
            employee.setId(seletcedEmployeeId);
            employee.setName(edtName.getText().toString());
            employee.setPhone(edtPhone.getText().toString());
            employee.setAddress(edtAddress.getText().toString());
            new DatabaseHelper(getActivity()).editEmployee(employee);
            refreshList();
            btnCancel.performClick();
        }
    };
}

Answer 1

Android 开发人员通常使用两种名为 findViewById() 的方法。其中之一是 Activity 类的一部分，通常按如下方式调用:

public void myMethod() {
    View myView = findViewById(R.id.myView);
}

另一个是View类的一部分，通常像这样调用:

public void myMethod(View root) {
    View myView = root.findViewById(R.id.myView);
}

但是，Fragment 类中没有 findViewById() 方法，因此您必须使用 View 方法。您已经在 onCreateView() 中执行此操作:

@Override
public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
    final View view = inflater.inflate(R.layout.fragment_customers, null);
    Button btnAdd = (Button) view.findViewById(R.id.btn_add);
                             ^^^^^^^^^^^^^^^^^

但是，稍后你会得到这个:

public void editEmployee(Employee employee) {
    findViewById(R.id.lin_add_search).setVisibility(View.GONE);
    ^^^^^^^^^^^^

同样，Fragment 类没有 findViewById() 方法，因此无法编译。通常解决方法是调用 getView().findViewById()。 getView() 方法返回的 View 实例与您从 onCreateView() 返回的 View 实例相同，因此它可以正常工作。

类似这样的事情:

public void editEmployee(Employee employee) {
    getView().findViewById(R.id.lin_add_search).setVisibility(View.GONE);