java - 在Android中向ArrayList添加项目时出错

Question

错误:-

 cannot resolve symbol add
 cannot resolve symbol setAdapter

我已经导入了ArrayList和ListView

当我运行该应用程序时，它显示您的文件有错误，因此无法运行它。

package com.example.listviewdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    ListView myListView = (ListView)findViewById(R.id.myListView);
    ArrayList<String> myFamily = new ArrayList<String>();
    myFamily.add("Neha");
    myFamily.add("Ishaan");

    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myFamily);
    myListView.setAdapter(arrayAdapter);

}

Answer 1

您的代码位于 oncreate 之外，并且没有从任何地方调用。就这样做。

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    ListView myListView = (ListView)findViewById(R.id.myListView);
    ArrayList<String> myFamily = new ArrayList<String>();
    myFamily.add("Neha");
    myFamily.add("Ishaan");

    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myFamily);
    myListView.setAdapter(arrayAdapter);
}