Question

我在带有API19的S4 mini上使用我的APP时出现NullPointerException错误。在带有API 23的S7上，一切正常。为什么我在较旧的API上出现此错误？

这是错误：

致命的例外：主要过程：com.example.entwicklung1.designtestapp，PID：32571 显示java.lang.NullPointerException 在 com.example.entwicklung1.designtestapp.NewsAdapter.getItemCount（NewsAdapter.java:64）在 android.support.v7.widget.RecyclerView.dispatchLayoutStep1（RecyclerView.java:3170）在 android.support.v7.widget.RecyclerView.onMeasure（RecyclerView.java:2782）在android.view.View.measure（View.java:17331）在android.widget.RelativeLayout.measureChild（RelativeLayout.java:689）在android.widget.RelativeLayout.onMeasure（RelativeLayout.java:473）在android.view.View.measure（View.java:17331）在 android.support.v4.widget.DrawerLayout.onMeasure（DrawerLayout.java:1079）在android.view.View.measure（View.java:17331）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5376）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在 android.support.v7.widget.ContentFrameLayout.onMeasure（ContentFrameLayout.java:135）在android.view.View.measure（View.java:17331）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5376）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1410）在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）在android.view.View.measure（View.java:17331）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5376）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在android.view.View.measure（View.java:17331）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5376）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1410）在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）在android.view.View.measure（View.java:17331）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5376）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在 com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2548）在android.view.View.measure（View.java:17331）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2279）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1393）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1592）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1251）在 android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6540）在 android.view.Choreographer $ CallbackRecord.run（Choreographer.java:813）在android.view.Choreographer.doCallbacks（Choreographer.java:613）在android.view.Choreographer.doFrame（Choreographer.java:583）在 android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:799）在android.os.Handler.handleCallback（Handler.java:733）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:146）在android.app.ActivityThread.main（ActivityThread.java:5593） at java.lang.reflect.Method.invokeNative（Native Method）在java.lang.reflect.Method.invoke（Method.java:515）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1283）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1099）在dalvik.system.NativeStart.main（本地方法）

我知道有很多关于NullPointerException的问题，但还没有解决我的问题。

以下是第一行显示的代码：

@Override
        public int getItemCount() {   return feedItems.size();    }


    And the FeedItem.class:

        public class FeedItem {
        String titel;
        String link;
        String description;
        String pubDate;
        String imgsrc;
        String category;
        String summary;

        public String getSummary() {     return summary;    }

        public void setSummary(String summary) {
            this.summary = summary;
        }

        public String getCategory() {     return category;    }

        public void setCategory(String category) {  this.category = category;  }

        public String getDescription() {
            return description;
        }

        public void setDescription(String description) {
            this.description = description;
        }

        public String getImgsrc() {
            return imgsrc;
        }

        public void setImgsrc(String imgsrc) {
            this.imgsrc = imgsrc;
        }

        public String getLink() {
            return link;
        }

        public void setLink(String link) {
            this.link = link;
        }

        public String getPubDate() {
            return pubDate;
        }

        public void setPubDate(String pubDate) {
            this.pubDate = pubDate;
        }

        public String getTitel() {
            return titel;
        }

        public void setTitel(String titel) {
            this.titel = titel;
        }
    }

Answer 1

您可以检查arraylist何时为空或未设置适配器。

if(!list.isEmpty())
{
 CustomAdapter adapter=new CustomAdapter();
}

或者

@Override
 public int getItemCount() {
     return (list == null) ? 0 : list.size();
 }

希望这会对你有所帮助。

API 19上的NullPointerException而不是API 23

1 个答案: