如何加载AdMob间隙广告只有一个活动？

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;

public class MainActivity extends AppCompatActivity {
    private AdView mAdView;

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

        // 在布局文件中添加AdView视图，或者在代码中动态创建并添加到布局中
        mAdView = findViewById(R.id.adView);

        // 设置广告单元ID
        AdRequest adRequest = new AdRequest.Builder()
                .addTestDevice(AdRequest.DEVICE_ID_EMULATOR)
                .build();
        mAdView.loadAd(adRequest);
    }

    @Override
    protected void onResume() {
        super.onResume();
        mAdView.resume();
    }

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