空点异常和java.lang.String

时间：2017-11-10 13:03:10

标签： android exception nullpointerexception

嘿伙计们，我正在尝试从ExhibitAdapter.java中获取数据 但是由于零点异常我的ExhibitDetailActivity.java没有运行我已经在SuperHero.java中声明了所有方法，并且在SuperHero.java类中已经声明了变量的java.lang.String错误消息。我会解决这个问题。 

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.abhilasha.marvelsfacts.R;
import com.example.abhilasha.marvelsfacts.models.SuperHero;
import com.squareup.picasso.Picasso;



 public class ExhibitDetailActivity extends AppCompatActivity {
  public static final String EXTRA_SUPERHERO="extra_superhero";
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_exhibit_detail);
    Toolbar toolbar=(Toolbar)findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);



             getSupportActionBar().setDisplayHomeAsUpEnabled(true);



    SuperHero superHero=getIntent().getExtras().getParcelable("EXTRA_SUPERHERO");
    TextView description=(TextView)findViewById(R.id.description);
    ImageView image=(ImageView)findViewById(R.id.image);



        description.setText(superHero.getDescription());//getDescription has 
      an null point error


    Picasso.with(this).load(superHero.getImage()).into(image);

}

}

这是我的ExhibitAdapter.java文件

    import android.content.Context;
    import android.support.annotation.LayoutRes;
     import android.support.annotation.NonNull;
     import android.view.LayoutInflater;
    import android.view.View;
   import android.view.ViewGroup;
     import android.widget.ArrayAdapter;
                 import android.widget.ImageView;
               import android.widget.TextView;

          import com.example.abhilasha.marvelsfacts.R;
           import com.example.abhilasha.marvelsfacts.models.SuperHero;
           import com.squareup.picasso.Picasso;



        public class ExhibitsAdapter extends ArrayAdapter<SuperHero> {
          public ExhibitsAdapter(@NonNull Context context, @LayoutRes int 
        resource) {
           super(context, resource);
        }



     @NonNull
      @Override
      public View getView(int position, View convertView, @NonNull ViewGroup 
        parent) {
       ViewHolder holder;
       if( convertView == null ) {
        holder = new ViewHolder();
        convertView = LayoutInflater.from( getContext() ).inflate( 
         R.layout.view_exhibit_list_item, parent, false );

        holder.name = (TextView) convertView.findViewById( R.id.name );
        holder.thumbnail = (ImageView) convertView.findViewById( 
        R.id.thumbnail );

        convertView.setTag( holder );
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.name.setText( getItem(position).getName() );//here too getName() 
   has null point exception


    Picasso.with(getContext()).load( getItem( position ).getThumbnail() 
    ).into( holder.thumbnail );// getThumbnail() too has null point 
exception

    return convertView;
}

private class  ViewHolder {
    ImageView thumbnail;
    TextView name;
}

}

这是我的SuperHero.java类

      import android.os.Parcel;
      import android.os.Parcelable;


  public  class  SuperHero implements Parcelable {
   private  String name;
   private String description;
   private String thumbnail;
   private String image;

public SuperHero() {


   }

      public SuperHero( String name, String description, String thumbnail, 
    String image ) {
    this.name = name;
    this.description = description;
    this.thumbnail = thumbnail;
    this.image = image;
}

public SuperHero( Parcel source ) {
    name = source.readString();
    description = source.readString();
    thumbnail = source.readString();
    image = source.readString();
}

public String getImage() {

    return image;
}
public void setImage(String image) {

    this.image = image;
}

public String getThumbnail() {
    return thumbnail;
}

public void setThumbnail(String thumbnail) {
    this.thumbnail = thumbnail;

}

public String getDescription() {

    return description;
}

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



public String getName() {

    return name;
}

public void setName(String name) {
    this.name = name;

}

@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
    applyDefaultValues();

    dest.writeString( name );
    dest.writeString( description );
    dest.writeString( thumbnail );
    dest.writeString( image );
}

private void applyDefaultValues() {
    if( name == null )
        name = "";
    if( description == null )
        description = "";
    if( thumbnail == null )
        thumbnail = "";
    if( image == null )
        image = "";
}

public static Creator<SuperHero> CREATOR = new Creator<SuperHero>() {

    @Override
    public SuperHero createFromParcel(Parcel source) {
        return new SuperHero( source );
    }

    @Override
    public SuperHero[] newArray(int size) {
        return new SuperHero[size];
       }
    };
}

我得到的错误如下           11-10 18：25：44.527 10738-10738 / com.example.abhilasha.marvelsfacts           E / AndroidRuntime：FATAL EXCEPTION：main 

      Process: com.example.abhilasha.marvelsfacts, PID: 10738

      java.lang.RuntimeException: Unable to start activity 
     ComponentInfo{com.example.abhilasha.marvelsfacts/
     com.example.abhilasha.marvelsfacts.activities.ExhibitDetailActivity}:
     java.lang.NullPointerException: Attempt to invoke virtual method 
     'java.lang.String 
      com.example.abhilasha.marvelsfacts.models.SuperHero.getDescription()' 
     on a null object reference                                                                             
       at
       android.app.ActivityThread.
    performLaunchActivity(ActivityThread.java:2665)

      at android.app.ActivityThread.handleLaunchActivity
  (ActivityThread.java:2726)

    at android.app.ActivityThread.-wrap12(ActivityThread.java)

     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)

    at android.os.Handler.dispatchMessage(Handler.java:102)

    at android.os.Looper.loop(Looper.java:154)

     at android.app.ActivityThread.main(ActivityThread.java:6119)

    at java.lang.reflect.Method.invoke(Native Method)                                                                                         
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run
   (ZygoteInit.java:886)

  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

     Caused by: java.lang.NullPointerException: Attempt to invoke virtual 
        method 'java.lang.String 
        com.example.abhilasha.marvelsfacts.models
   .SuperHero.getDescription()' on a null object reference
                                                                                    at com.example.abhilasha.marvelsfacts.activities.ExhibitDetailActivity.onCreate(ExhibitDetailActivity.java:37)
                                                                                    at android.app.Activity.performCreate(Activity.java:6679)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                                                                                    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:154) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:6119) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

.... 我无法得到究竟是什么异常以及如何解决方法异常任何建议请帮助... !!!!!!

这是activity_exhibit_detail.xml文件

         <?xml version="1.0" encoding="utf-8"?>
      <LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical" android:layout_width="match_parent"
          android:layout_height="match_parent">

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:background="?attr/colorPrimary"
    android:minHeight="?android:attr/actionBarSize" />

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <ImageView
            android:id="@+id/image"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:scaleType="fitCenter" />


        <TextView
            android:id="@+id/description"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textColor="@android:color/background_dark"/>

    </LinearLayout>
   </ScrollView>

这是我调用ExhibitDetailActivity.java的活动 ExhibitFragment.java 

          import android.content.Intent;
         import android.os.Bundle;
        import android.support.annotation.Nullable;
         import android.support.v4.app.ListFragment;
          import android.util.Log;
               import android.view.View;
         import android.widget.ListView;

               import com.example.abhilasha.marvelsfacts.R;
                    import 

  com.example.abhilasha.marvelsfacts.activities.ExhibitDetailActivity;
           import 
          com.example.abhilasha.marvelsfacts.adapter.ExhibitsAdapter;
          import com.example.abhilasha.marvelsfacts.models.SuperHero;
           import 
          com.example.abhilasha.marvelsfacts.utils.SuperHeroApiInterface;
          import java.util.List;

          import retrofit.Callback;
          import retrofit.RestAdapter;
          import retrofit.RetrofitError;
          import retrofit.client.Response;


          public class ExhibitsListFragment extends ListFragment {
            private ExhibitsAdapter mExhibitsAdaptern;

        public static ExhibitsListFragment getInstance() {
        ExhibitsListFragment fragment = new ExhibitsListFragment();
        return fragment;
       }

         @Override
         public void onActivityCreated(@Nullable Bundle savedInstanceState) 
        {
    super.onActivityCreated(savedInstanceState);
    setListShown(false);
    mExhibitsAdaptern=new ExhibitsAdapter(getActivity(),0);

    RestAdapter restAdapter = new RestAdapter.Builder()
            .setEndpoint( getString( R.string.super_hero ) )
            .build();

        SuperHeroApiInterface superHeroApiInterface = 
          restAdapter.create(SuperHeroApiInterface.class );

          superHeroApiInterface.getStreams( new Callback<List<SuperHero>>() 
           {
        @Override
        public void success(List<SuperHero> superheroes, Response response) 
             {
            if( superheroes == null || superheroes.isEmpty() )
                return;


            for( SuperHero superHero : superheroes ) {
                mExhibitsAdaptern.add(superHero);
            }
            mExhibitsAdaptern.notifyDataSetChanged();
            setListAdapter(mExhibitsAdaptern);
            setListShown(true);
        }

        @Override
        public void failure(RetrofitError error) {
            Log.e( "Zoo", "Retrofit error " + error.getMessage() );
        }
       });
       }

     @Override
     public void onListItemClick(ListView l, View v, int position, long id) 
     {
    super.onListItemClick(l, v, position, id);

    Intent intent = new Intent( getActivity(), ExhibitDetailActivity.class 
    );
    intent.putExtra( ExhibitDetailActivity.EXTRA_SUPERHERO, 
    mExhibitsAdaptern.getItem( position ) );

    startActivity( intent );
    } 
}

2 个答案:

答案 0 :(得分：0)

我认为问题不是getDescription（）方法，而是 superhero 对象。 您刚刚声明了该对象，这意味着它不包含任何内容（null或垃圾）。 我认为如果为超级英雄对象分配内存，您的问题就会得到解决。 试试这个：

SuperHero superHero = new SuperHero();

答案 1 :(得分：-2)

更改此

SuperHero superHero=getIntent().getExtras().getParcelable("EXTRA_SUPERHERO");

到此：

SuperHero superHero=getIntent().getExtras().getParcelable(EXTRA_SUPERHERO);

您的密钥不同，这就是为什么superHero为空。希望它有所帮助：）

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