Android Studio 在 adView.loadAd(adRequest) 错误时出现空指针异常错误。并在安卓棒棒糖设备上崩溃

Question

我一直在尝试将 AdMob 横幅广告代码添加到我的应用中。当我尝试这样做时，我在 adView.loadAd(adRequest) 上收到 Null Pointer Exception 错误。

另一个错误是我的应用在 android lollipop os 上崩溃。如何解决这个问题。帮帮我。我是安卓新手。

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>

这是我的主要活动.java

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();
        }
    }

}

另一个活动代码（Intent）

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();
    }

}

有人可以帮我解决这个问题吗？谢谢。

Answer 1

你可以试试下面的链接， https://developers.google.com/admob/android/quick-start

AdRequest adRequest = new AdRequest.Builder().build(); mAdView.loadAd(adRequest);//添加 AdRequest 的示例。

谢谢。