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在在这里问这个问题之前，我已经做了很多谷歌搜索。

我已将 NativeExpressAdView 集成到我的 Recyclerview 中，如此处在此google 示例中所述，它也运行良好。但问题是，在这个示例项目中，他们从零位置添加 NativeExpressAdView，但不想在零位置添加 NativeExpressAdView。

我也可以在随机位置添加，但是当我们必须从代码中为 NativeExpressAdView 设置广告大小时就会出现问题。

在MainActivity的方法中访问的 CardviewsetUpAndLoadNativeExpressAds将为 Null，如果不在第零位添加视图，则会给出 NPE。

这是我修改后的代码片段

/**
     * Adds Native Express ads to the items list.
     */
    private void addNativeExpressAds() {

        // Loop through the items array and place a new Native Express ad in every ith position in
        // the items List.
        for (int i = 7; i <= mRecyclerViewItems.size(); i += ITEMS_PER_AD) {
            final NativeExpressAdView adView = new NativeExpressAdView(MainActivity.this);
            mRecyclerViewItems.add(i, adView);
        }
    }

    /**
     * Sets up and loads the Native Express ads.
     */
    private void setUpAndLoadNativeExpressAds() {
        // Use a Runnable to ensure that the RecyclerView has been laid out before setting the
        // ad size for the Native Express ad. This allows us to set the Native Express ad's
        // width to match the full width of the RecyclerView.
        mRecyclerView.post(new Runnable() {
            @Override
            public void run() {
                final float scale = MainActivity.this.getResources().getDisplayMetrics().density;
                // Set the ad size and ad unit ID for each Native Express ad in the items list.
                for (int i = 7; i <= mRecyclerViewItems.size(); i += ITEMS_PER_AD) {
                    final NativeExpressAdView adView =
                            (NativeExpressAdView) mRecyclerViewItems.get(i);
                    final CardView cardView = (CardView) findViewById(R.id.ad_card_view);
                    final int adWidth = cardView.getWidth() - cardView.getPaddingLeft()
                            - cardView.getPaddingRight(); //Here cardView will be Null (so NPE).
                    AdSize adSize = new AdSize((int) (adWidth / scale), NATIVE_EXPRESS_AD_HEIGHT);
                    adView.setAdSize(adSize);
                    adView.setAdUnitId(AD_UNIT_ID);
                }

                // Load the first Native Express ad in the items list.
                loadNativeExpressAd(7); //Not added code for this method as nothing is modified in that.
            }
        });
    }

即使我在从 repo 中提取示例项目代码后实施相同的更改，也会出现此问题。

这是我的 logcat 崩溃

    FATAL EXCEPTION: main
java.lang.NullPointerException                                                                                                                           at com.google.android.gms.example.nativeexpressrecyclerviewexample.MainActivity$1.run(MainActivity.java:106)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)

这是某种错误还是我做错了什么。

4

1 回答 1

0

只需再添加一个条件

if (i!=0){}

在两个 for 循环
更新中：

  */
private void addNativeExpressAds() {

    // Loop through the items array and place a new Native Express ad in every ith position in
    // the items List.
    for (int i = 0; i <= mRecyclerViewItems.size(); i += ITEMS_PER_AD) {
if(i!=0){
        final NativeExpressAdView adView = new NativeExpressAdView(MainActivity.this);
        mRecyclerViewItems.add(i, adView);
    }}
}

/**
 * Sets up and loads the Native Express ads.
 */
private void setUpAndLoadNativeExpressAds() {
    // Use a Runnable to ensure that the RecyclerView has been laid out before setting the
    // ad size for the Native Express ad. This allows us to set the Native Express ad's
    // width to match the full width of the RecyclerView.
    mRecyclerView.post(new Runnable() {
        @Override
        public void run() {
            final float scale = MainActivity.this.getResources().getDisplayMetrics().density;
            // Set the ad size and ad unit ID for each Native Express ad in the items list.
            for (int i = 0; i <= mRecyclerViewItems.size(); i += ITEMS_PER_AD) {
if(i!=0){
                final NativeExpressAdView adView =
                        (NativeExpressAdView) mRecyclerViewItems.get(i);
                final CardView cardView = (CardView) findViewById(R.id.ad_card_view);
                final int adWidth = cardView.getWidth() - cardView.getPaddingLeft()
                        - cardView.getPaddingRight(); //Here cardView will be Null (so NPE).
                AdSize adSize = new AdSize((int) (adWidth / scale), NATIVE_EXPRESS_AD_HEIGHT);
                adView.setAdSize(adSize);
                adView.setAdUnitId(AD_UNIT_ID);
            }}

            // Load the first Native Express ad in the items list.
            loadNativeExpressAd(ITEMS_PER_AD); //Not added code for this method as nothing is modified in that.
        }
    });
}
于 2017-09-02T05:40:26.317 回答