是否可以从其他类别的主要活动中访问插页式广告？

Question

希望您一切都好。我想在单击按钮上显示插页式广告，但是我为插页式广告建立了一个单独的类，并在此类中创建了一种方法。它访问插页广告类的方法并显示广告，但是当我单击按钮时，它给我插页广告类中的错误。我在这一小错误上停留了一天，但我无法解决。我希望你们能给我更好的答复。

SplashScreen

package com.deitel.adsmobapp;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.InterstitialAd;
import com.google.android.gms.ads.MobileAds;
import com.google.android.gms.ads.NativeExpressAdView;

public class SplashScreen extends AppCompatActivity {
    private AdView mAdview;
    Button btn_move;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash_screen);
        btn_move=findViewById(R.id.btn_move);
        btn_move.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Interstitial interstitial=new Interstitial();
                interstitial.prepareAd();
                Intent i=new Intent(SplashScreen.this,MainActivity.class);
                startActivity(i);
            }
        });
        /*Banner Ads*/
        MobileAds.initialize(this,"ca-app-pub-3940256099942544~3347511713");
        mAdview=findViewById(R.id.adView);
        AdRequest adRequest=new AdRequest.Builder().build();
        mAdview.loadAd(adRequest);

    }

    @Override
    protected void onPause() {
        super.onPause();
        finish();
    }
}

Interstiatil类

package com.deitel.adsmobapp;

import android.app.Activity;
import android.app.Application;
import android.util.Log;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.InterstitialAd;

public class Interstitial extends Application {
    private InterstitialAd interstitialAd;

    @Override
    public void onCreate() {
        super.onCreate();

        SplashScreen splashScreen=new SplashScreen();
        interstitialAd = new InterstitialAd(splashScreen);
        interstitialAd.setAdUnitId("ca-app-pub-3940256099942544/1033173712");
        AdRequest adRequest=new AdRequest.Builder().build();
        interstitialAd.loadAd(adRequest);
        prepareAd();
    }
    public void prepareAd() {

        if (interstitialAd.isLoaded())
        {
            interstitialAd.show();
        }
        else
            {
                Log.d("tag","Ads is not loaded");
            }

    }
}

错误

01-06 17:05:51.907 7044-7044/com.deitel.adsmobapp E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.NullPointerException
        at com.deitel.adsmobapp.Interstitial.prepareAd(Interstitial.java:26)
        at com.deitel.adsmobapp.SplashScreen$1.onClick(SplashScreen.java:31)
        at android.view.View.performClick(View.java:4084)
        at android.view.View$PerformClick.run(View.java:16966)

        at android.os.Handler.dispatchMessage(Handler.java:92)

Answer 1

错误是Interstiatil类im方法prepareAd（）的第26行中的NPE。interstitialAd为null，因为它是在创建活动时调用的onCreate（）中初始化的。您应该将类​​更改为从Activity继承，而不是从Application继承。并且不要在onClick方法中调用prepareAd（）。

public class Interstitial extends Activity