每次我运行它时，android应用程序都会意外崩溃

Question

[这是我的 MainActivity.java 文件][1]

package com.example.socialmediaintegration;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;
import com.facebook.AccessToken;
import com.facebook.AccessTokenTracker;
import com.facebook.CallbackManager;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.GraphRequest;
import com.facebook.GraphResponse;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.Arrays;


import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import de.hdodenhof.circleimageview.CircleImageView;

公共类 MainActivity 扩展 AppCompatActivity {

private LoginButton loginButton;
private CircleImageView circleImageView;
private TextView txtName, txtEmail;

private CallbackManager callbackManager;

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

   // private static final String EMAIL = "email";

    loginButton =  findViewById(R.id.login_button);
    circleImageView = findViewById(R.id.profile_pic);
    txtName = findViewById(R.id.profile_name);
    txtEmail = findViewById(R.id.profile_email);

    callbackManager = CallbackManager.Factory.create();
    loginButton.setPermissions(Arrays.asList("email", "public_profile"));
    checkLoginStatus();


    loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {

        }

        @Override
        public void onCancel() {

        }

        @Override
        public void onError(FacebookException error) {

        }
    });

}

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    callbackManager.onActivityResult(requestCode, resultCode, data);
    super.onActivityResult(requestCode, resultCode, data);
}

AccessTokenTracker tokenTracker = new AccessTokenTracker() {
    @Override
    protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken, AccessToken currentAccessToken) {

        if (currentAccessToken == null)
        {
            txtName.setText("");
            txtEmail.setText("");
            circleImageView.setImageResource(0);
            Toast.makeText(MainActivity.this, "User Logged out", Toast.LENGTH_LONG).show();
        }
        else {
            loadUserProfile(currentAccessToken);
        }
    }
};

private void loadUserProfile(AccessToken newAccessToken){
    GraphRequest request = GraphRequest.newMeRequest(newAccessToken, new GraphRequest.GraphJSONObjectCallback() {
        @Override
        public void onCompleted(JSONObject object, GraphResponse response) {
            try {
                String first_name = object.getString("first_name");
                String last_name = object.getString("last_name");
                String email = object.getString("email");
                String id = object.getString("id");

                String image_url =  "http://graph.facebook.com/"+id+"/picture?type=normal";

                txtEmail.setText(email);
                txtName.setText(first_name + " " + last_name);
                RequestOptions requestOptions = new RequestOptions();
                requestOptions.dontAnimate();

                Glide.with( MainActivity.this).load(image_url).into(circleImageView);

            } catch (JSONException e){
                e.printStackTrace();
            }


        }
    });

    Bundle parameters = new Bundle();
    parameters.putString("fields", "first_name, last_name, email_id");
    request.setParameters(parameters);
    request.executeAsync();
}

private void checkLoginStatus(){

    if (AccessToken.getCurrentAccessToken()!=null)
    {
        loadUserProfile(AccessToken.getCurrentAccessToken());
    }
}

}

这是我在 Logcat 中显示的错误-->>

2020-10-12 12:01:23.621 19597-19602/com.example.socialmediaintegration I/zygote：将代码缓存容量增加到 256KB 2020-10-12 12:01:27.373 19597-19623/com.example.socialmediaintegration E/GraphResponse: {HttpStatus: 400, errorCode: 100, subErrorCode: 33, errorType: GraphMethodException, errorMessage: 不支持获取请求。 ID 为“980066249173751”的对象不存在，由于缺少权限而无法加载，或者不支持此操作。请阅读https://developers.facebook.com/docs/graph-api} 的 Graph API 文档 2020-10-12 12:01:32.329 19597-19623/com.example.socialmediaintegration E/GraphResponse: {HttpStatus: 400, errorCode: 100, subErrorCode: -1, errorType: OAuthException, errorMessage: (#100) 尝试访问不存在的节点类型（用户）上的字段（email_id）} 2020-10-12 12:01:32.329 19597-19597/com.example.socialmediaintegration D/AndroidRuntime：关闭 VM 2020-10-12 12:01:32.332 19597-19597/com.example.socialmediaintegration E/AndroidRuntime: 致命例外: main 进程：com.example.socialmediaintegration，PID：19597 java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“java.lang.String org.json.JSONObject.getString(java.lang.String)” 在 com.example.socialmediaintegration.MainActivity$3.onCompleted(MainActivity.java:102) 在 com.facebook.GraphRequest$1.onCompleted(GraphRequest.java:317) 在 com.facebook.GraphRequest$5.run(GraphRequest.java:1398) 在 android.os.Handler.handleCallback(Handler.java:790) 在 android.os.Handler.dispatchMessage(Handler.java:99) 在 android.os.Looper.loop(Looper.java:164) 在 android.app.ActivityThread.main(ActivityThread.java:6626) 在 java.lang.reflect.Method.invoke（本机方法） 在 com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:811)

Answer 1

在这个错误行中

Attempt to invoke virtual method 'java.lang.String 
org.json.JSONObject.getString(java.lang.String)' on a null object reference

据说你的JSONObject实例为null，抛出NullPointerException

在从 JSONObject 读取数据之前，您需要先检查请求是否成功

检查处理错误部分

https://developers.facebook.com/docs/android/graph