Java Android Studio获取adView.loadAd（adRequest）错误上的空指针异常错误。并在android棒棒糖设备上崩溃

我一直在尝试将AdMob横幅广告代码添加到我的应用程序中。当我尝试这样做时，我在adView.loadAd（adRequest）上得到空指针异常错误

另一个错误是我的应用程序在android棒棒糖操作系统上崩溃。如何修复此问题。帮我个忙。我是android新手

这是我的布局xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay">

            <include android:layout_width="match_parent" android:layout_height="wrap_content" layout="@layout/ab"/>

        </androidx.appcompat.widget.Toolbar>

    </com.google.android.material.appbar.AppBarLayout>

    <include layout="@layout/content_main_f" />

    <com.google.android.gms.ads.AdView
        xmlns:ads="http://schemas.android.com/apk/res-auto"
        android:id="@+id/adView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_alignParentBottom="true"
        android:layout_gravity="bottom"
        ads:adSize="SMART_BANNER"
        ads:adUnitId="@string/banner_ad" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

另一个活动代码（意图）

公共课堂数学活动{
私人间质；
//在适配器中设置字符串值
私有最终字符串[]n=新字符串[]{“基本代数”、“索引”、“向量加减”、“数学属性”，
“百分比公式”、“单利和复利”、“计量”、“二进制数”、“概率公式”，
“摄氏公式”、“角度公式”、“反导数”、“微积分公式”、“三角公式”、“恒等式和三角形”}；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity\u数学）；
ActionBar ActionBar=getSupportActionBar（）；
actionBar.setHomeButtonEnabled（真）；
actionBar.setDisplayHomeAsUpEnabled（true）；
//使用id调用最终列表
//呼叫列表视图
ListView ListView=findViewById（R.id.list\u数学）；
//谷歌广告补充道
AdView AdView=this.findviewbyd（R.id.AdView）；
AdRequest AdRequest=新建AdRequest.Builder（）.build（）；
adView.loadAd（adRequest）；
Minterstitalad=新的间隙（本）；
minterstitalad.setAdUnitId（getString（R.string.inst_ad））；
minterstitalad.loadAd（新的addRequest.Builder（）.build（））；
/*
*将数学类中的适配器设置为“显示列表字符串”
* */
setAdapter（新的ArrayAdapter（this，R.layout.list\u basic\u learn，R.id.item\u name\u basiclist，this.n））；
//启用文本可点击
listView.setClickable（真）；
//将侦听器设置为数学布局
setOnItemClickListener（新的AdapterView.OnItemClickListener（）{
@凌驾
public void onItemClick（AdapterView父对象、视图、整型位置、长id）{
//将数据传输到所有数学子类
开关（位置）{
案例0：
数学.this.startActivity（新意图（数学.this，BasicAlgebra.class））；
打破
案例1：
数学.this.startActivity（新意图（数学.this.index.class））；
打破
案例2：
数学.this.startActivity（新意图（math.this，VectorAdditionMath.class））；
打破
案例3：
数学.this.startActivity（新意图（数学.this，数学属性.class））；
打破
案例4：
数学.this.startActivity（新意图（数学.this，百分比公式.class））；
打破
案例5：
数学.this.startActivity（新意图（数学.this，SimpleandCompoundInterest.class））；
打破
案例6：
数学.this.startActivity（新意图（数学.this.measurement.class））；
打破
案例7：
数学.this.startActivity（新意图（数学.this，二进制数.class））；
打破
案例8：
数学.this.startActivity（新意图（数学.this，概率公式.class））；
打破
案例9：
数学.this.startActivity（新意图（数学.this，CelsiusFormula.class））；
打破
案例10：
数学.this.startActivity（新意图（数学.this.AngleFormula.class））；
打破
案例11：
数学.this.startActivity（新意图（数学.this，反派生类））；
打破
案例12：
数学.this.startActivity（新意图（数学.this，CalculusFormula.class））；
打破
案例13：
数学.this.startActivity（新意图（数学.this，三角公式类））；
打破
案例14：
数学.this.startActivity（新意图（数学.this.identies.class））；
打破
违约：
}
}
});
}
//回去的时候把班毁了
public void onBackPressed（）{
super.onBackPressed（）；
if（minterstitalad.isload（））{
minterstitalad.show（）；
}否则{
Log.d（“标签”，“间隙尚未加载”）；
}
完成（）；
}
}

---

有人能帮我解决这个问题吗？谢谢。

您可以尝试以下链接，

AdRequest AdRequest=新建AdRequest.Builder（）.build（）； mAdView.loadAd（adRequest）//要添加的示例

---

谢谢。

你可能没有读我的帖子。我已经做到了。但是不起作用！根据检查代码时应首先检查ad.isLoaded是否已加载，如果已加载，则可以使用ad.show（）或其他所需工具！请张贴日志。这是我的日志。。。有人帮我吗？尽管如此，我还是在我的代码中添加了堆栈！！

public class MainActivity extends AppCompatActivity {

    public InterstitialAd mInterstitialAd;
    private ShareActionProvider mProvider;
    private long mLong;
    private Toast mToast;
    private AdView adView;

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

        //Toolbar
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        //Maths Text View
        TextView mathsView = findViewById(R.id.maths);
        //Set Maths onClickListener
        mathsView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // Step 2.2: Start the new activity
                Intent mathsIntent = new Intent(MainActivity.this, Maths.class);
                startActivity(mathsIntent);
            }
        });

        //Physics Text View
        TextView physicsView = findViewById(R.id.physics);
        //Set Physics onClickListener
        physicsView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // Step 2.2: Start the new activity
                Intent physicsIntent = new Intent(MainActivity.this, Physics.class);
                startActivity(physicsIntent);
            }
        });

        //Chemistry Text View
        TextView chemistryView = findViewById(R.id.chemistry);
        //Set Chemistry onClickListener
        chemistryView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent chemistryIntent = new Intent(MainActivity.this, Chemistry.class);
                startActivity(chemistryIntent);
            }
        });

        //Extra Text View
        TextView extraView = findViewById(R.id.extra);
        //Set Extra onClickListener
        extraView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent extraIntent = new Intent(MainActivity.this, Extra.class);
                startActivity(extraIntent);

            }
        });

        //Premium Version
        Button pre = findViewById(R.id.btn_premium);
        pre.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final String appPackageName = "xxxxxxxxxxxxx"; // package name of the app
                try {
                    startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("market://details?id=" + appPackageName)));
                } catch (ActivityNotFoundException e) {
                    startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=" + appPackageName)));
                }
            }
        });

        //Ads Initialize
        MobileAds.initialize(this, new OnInitializationCompleteListener() {
            @Override
            public void onInitializationComplete(InitializationStatus initializationStatus) {
            }
        });

        //Google Banner Ads added
        adView = this.findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        adView.loadAd(adRequest);

        //Google InterstitialAd Ads added
        mInterstitialAd = new InterstitialAd(this);
        mInterstitialAd.setAdUnitId(getString(R.string.inst_ad));
        mInterstitialAd.loadAd(new AdRequest.Builder().build());

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);

        //share the app
        MenuItem menuItem = menu.findItem(R.id.action_share);
        mProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(menuItem);
        setShareActionIntent("https://play.google.com/store/apps/details?id=");
        return super.onCreateOptionsMenu(menu);
    }


    private void setShareActionIntent(String text) {
        Intent intent = new Intent(Intent.ACTION_SEND);
        intent.setType("text/plain");
        String str2 = text + getPackageName();
        intent.putExtra(Intent.EXTRA_SUBJECT, "All In One Formula");
        intent.putExtra(Intent.EXTRA_TEXT, str2);
        mProvider.setShareIntent(intent);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        //noinspection SimplifiableIfStatement
        if (id == R.id.rate_us) {
            try {
                startActivity(new Intent(Intent.ACTION_VIEW,
                        Uri.parse("market://details?id=" + this.getPackageName())));
            } catch (ActivityNotFoundException e) {
                e.printStackTrace();
                startActivity(new Intent(Intent.ACTION_VIEW,
                        Uri.parse("http://play.google.com/store/apps/details?id=" + this.getPackageName())));
            }
            return true;
        } else if (id == R.id.about_us) {
            Intent extraIntent = new Intent(MainActivity.this, AboutUs.class);
            startActivity(extraIntent);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (adView != null) {
            adView.resume();
        }
    }

    @Override
    protected void onPause() {
        if (adView != null) {
            adView.pause();
        }
        super.onPause();
    }

    /**
     * Called before the activity is destroyed
     */
    @Override
    public void onDestroy() {
        if (adView != null) {
            adView.destroy();
        }
        super.onDestroy();
    }

    //Double press to exit!
    @Override
    public void onBackPressed() {
        long currentTime = System.currentTimeMillis();
        if (currentTime - mLong > 5000) {
            mToast = Toast.makeText(getBaseContext(), getString(R.string.back_pressed), Toast.LENGTH_LONG);
            mToast.show();
            mLong = currentTime;
        } else {
            if (mToast != null) mToast.cancel();
            super.onBackPressed();
        }
    }

}

public class Maths extends AppCompatActivity {

    private InterstitialAd mInterstitialAd;
    //Set String value in adapter
    private final String[] n = new String[]{"Basic Algebra", "Indices", "Vector Addition and Subtraction", "Mathematical Properties",
            "Percentage Formulas", "Simple and Compound Interest", "Mensuration", "Binary Numbers", "Probability Formulas",
            "Celsius Formulas", "Angle Formulas", "Antiderivative", "Calculus Formulas", "Trigonometry Formulas", "Identities and Triangle"};

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

        ActionBar actionBar = getSupportActionBar();
        actionBar.setHomeButtonEnabled(true);
        actionBar.setDisplayHomeAsUpEnabled(true);


        //Call final list with id
        //Call List View
        ListView listView = findViewById(R.id.list_maths);

        //Google Ads added
        AdView adView = this.findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        adView.loadAd(adRequest);

        mInterstitialAd = new InterstitialAd(this);
        mInterstitialAd.setAdUnitId(getString(R.string.inst_ad));
        mInterstitialAd.loadAd(new AdRequest.Builder().build());

        /*
         * Set the adapter In Maths class to showing list String
         * */
        listView.setAdapter(new ArrayAdapter<>(this, R.layout.list_basic_learn, R.id.item_name_basiclist, this.n));
        //Enable Text clickable
        listView.setClickable(true);
        //Set OnItemClickListener to Maths layout
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                //Transfer the data to all Maths sub class
                switch (position) {
                    case 0:
                        Maths.this.startActivity(new Intent(Maths.this, BasicAlgebra.class));
                        break;
                    case 1:
                        Maths.this.startActivity(new Intent(Maths.this, Indices.class));
                        break;
                    case 2:
                        Maths.this.startActivity(new Intent(Maths.this, VectorAdditionMath.class));
                        break;
                    case 3:
                        Maths.this.startActivity(new Intent(Maths.this, MathematicalProperties.class));
                        break;
                    case 4:
                        Maths.this.startActivity(new Intent(Maths.this, PercentageFormula.class));
                        break;
                    case 5:
                        Maths.this.startActivity(new Intent(Maths.this, SimpleandCompoundInterest.class));
                        break;
                    case 6:
                        Maths.this.startActivity(new Intent(Maths.this, Mensuration.class));
                        break;
                    case 7:
                        Maths.this.startActivity(new Intent(Maths.this, BinaryNumbers.class));
                        break;
                    case 8:
                        Maths.this.startActivity(new Intent(Maths.this, ProbabilityFormulas.class));
                        break;
                    case 9:
                        Maths.this.startActivity(new Intent(Maths.this, CelsiusFormula.class));
                        break;
                    case 10:
                        Maths.this.startActivity(new Intent(Maths.this, AngleFormula.class));
                        break;
                    case 11:
                        Maths.this.startActivity(new Intent(Maths.this, Antiderivative.class));
                        break;
                    case 12:
                        Maths.this.startActivity(new Intent(Maths.this, CalculusFormula.class));
                        break;
                    case 13:
                        Maths.this.startActivity(new Intent(Maths.this, TrigonometryFormula.class));
                        break;
                    case 14:
                        Maths.this.startActivity(new Intent(Maths.this, Identities.class));
                        break;
                    default:
                }
            }
        });
    }

    //Destroy the class when going back
    public void onBackPressed() {
        super.onBackPressed();
        if (mInterstitialAd.isLoaded()) {
            mInterstitialAd.show();
        } else {
            Log.d("TAG", "The interstitial wasn't loaded yet.");
        }
        finish();
    }

}