java - 找不到符号方法 getcontext

Question

我是 android/java 编程新手，并且遇到错误，提示符号 getContext 无法解析。该系统以Activity启动，有两个fragment。第一个是显示 Rest Api 的按钮。请帮忙

InstansiActivity.java:

package com.example.instansi;


import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;


import com.example.instansi.adapter.InstansiAdapter;
import com.example.instansi.model.DaftarInstansiItem;

import java.util.ArrayList;

public class InstansiActivity extends AppCompatActivity {
    private InstansiAdapter instansiAdapter;
    private RecyclerView rvInstansi;
    private com.example.instansi.viewmodel.InstansiViewModel instansiViewModel;

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

        instansiAdapter= new InstansiAdapter(getContext());
        instansiAdapter.notifyDataSetChanged();

        rvInstansi= view.findViewById(R.id.finstansi_rv);
        rvInstansi.setLayoutManager(new GridLayoutManager(getContext(),1));

        instansiViewModel= new ViewModelProvider(this).get(com.example.instansi.viewmodel.InstansiViewModel.class);
        instansiViewModel.setInstansi();
        instansiViewModel.getInstansi().observe(this, getInstansi_);

        rvInstansi.setAdapter(instansiAdapter);
    }


    private Observer<ArrayList<DaftarInstansiItem>> getInstansi_ = new Observer<ArrayList<DaftarInstansiItem>>() {
        @Override
        public void onChanged(ArrayList<DaftarInstansiItem> daftarInstansiItems) {
            if (daftarInstansiItems != null) {
                instansiAdapter.setData(daftarInstansiItems);
            }
        }
    };
}

Answer 1

获取 Activity 上下文的简单方法是放置this。

在您的 Activity 中，要获取 Activity 上下文，请使用 this，要获取 applicationContext()，请使用 getApplicationContext()

activity context 和 application context 之间最区别是: Application context 与应用程序的生命周期相关联，而Activity context与Activity的生命周期相关联。