將項目遷移到gradle後的空指針異常

-3

將我的項目遷移到gradle後出現以下錯誤。我不確定爲什麼會發生這種情況，並且在遷移之前這種情況正在發生。我試圖將文件複製到一個全新的項目，這些項目是從頭開始構建的，現在我遇到了這些問題。將項目遷移到gradle後的空指針異常

Process: com.hospital.headling.hospital, PID: 5243 
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hospital.headling.hospital/com.hospital.headling.hospital.ListViewActivity}: java.lang.NullPointerException: Attempinvoke virtual method 'void com.hospital.headling.hospital.util.ExpandableHeightGridView.setAdapter(android.widget.ListAdapter)' 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 'void com.hospital.headling.hospital.util.ExpandableHeightGridView.setAdapter(android.widget.ListAdapter)' on a null object reference 
at com.hospital.headling.hospital.ListViewActivity.setAdapters(ListViewActivity.java:127) 
at com.hospital.headling.hospital.ListViewActivity.onCreate(ListViewActivity.java:61) 
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$H.handleMessage(ActivityThread.java:1477)  
atandroid.os.Handler.dispatchMessage(Handler.java:102)  
at android.os.Looper.loop(Looper.java:154)  
at android.app.ActivityThread.main(ActivityThread.java:6119)  
at java.lang.reflect.Method.invoke(Native Method)  
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

ListViewActivity.java

package com.hospital.headling.hospital; 

    import android.annotation.SuppressLint; 
    import android.app.Activity; 
    import android.content.Intent; 
    import android.os.Bundle; 
    import android.view.View; 
    import android.widget.AdapterView; 
    import android.widget.ArrayAdapter; 
    import android.widget.ListView; 

    import com.hospital.headling.hospital.adapter.CustomAdapter; 
    import com.hospital.headling.hospital.util.ExpandableHeightGridView; 

    import org.apache.commons.lang3.ArrayUtils; 

    import java.util.ArrayList; 

    public class ListViewActivity extends Activity { 

     private ExpandableHeightGridView gridView; 
     private ListView listView; 


     //drawables array for gridview 
     private static final int[] osImage = { R.drawable.cardiac, R.drawable.ortho, 
       R.drawable.neuro, R.drawable.cancer, R.drawable.doctors, R.drawable.services, 
       R.drawable.visit, R.drawable.careers, R.drawable.bills, R.drawable.email, R.drawable.about }; 

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

      ArrayList<String> menu_links = new ArrayList<>(); 
      menu_links.add("Cardiac"); 
      menu_links.add("Orthopedic"); 
      menu_links.add("Neurosciences"); 
      menu_links.add("Cancer"); 
      menu_links.add("Find A Doctor"); 
      menu_links.add("Medical Services"); 
      menu_links.add("Patients and Visitors"); 
      menu_links.add("Careers"); 
      menu_links.add("Pay Your Bill"); 
    // Find a reference to the {@link ListView} in the layout 
      ListView companiesListView = (ListView) findViewById(R.id.list); 

    // Create a new {@link ArrayAdapter} of the menu_links 
      ArrayAdapter<String> adapter = new ArrayAdapter<String>(
        this, android.R.layout.simple_list_item_1, menu_links); 


    // Set the adapter on the {@link ListView} 
    // so the list can be populated in the user interface 
      companiesListView.setAdapter(adapter); 


      ///end of stuff 


      setAdapters(); 

      //start 
      companiesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
       public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
        switch (position) { 
       /* case 0: Intent Cardiac = new Intent(this, Cardiac.class); 
         startActivity(Cardiac); 
         break; 
        case 1: Intent Orthopedic = new Intent(this, Orthopedic.class); 
         startActivity(newActivity); 
         break; 
        case 2: Intent Neurosciences = new Intent(this, Neurosciences.class); 
         startActivity(newActivity); 
         break; 
        case 3: Intent Cancer = new Intent(this, Cancer.class); 
         startActivity(FindADoctor); 
         break; 
        case 4: Intent newActivity = new Intent(this, reservetickets.class); 
         startActivity(newActivity); 
         break; 
        case 4: Intent newActivity = new Intent(this, reservetickets.class); 
         startActivity(newActivity); 
         break; 
        case 4: Intent newActivity = new Intent(this, reservetickets.class); 
         startActivity(newActivity); 
         break; 
        case 4: Intent newActivity = new Intent(this, reservetickets.class); 
         startActivity(newActivity); 
         break; */ 
         case 9: 
          Intent ContactForm = new Intent(ListViewActivity.this, com.hospital.headling.hospital.ContactForm.class); 
          startActivity(ContactForm); 
          break; 
        } 
       } 
      }); 
      //finish 

     } 

     /** 
     * set footer for listview (it's a gridview) 
     */ 
     @SuppressLint("InflateParams") 
     private void addGridViewAsListViewFooter() { 
      View footer = (View) getLayoutInflater().inflate(R.layout.layout_gridview, null); 
      listView.addFooterView(footer); 

      gridView = (ExpandableHeightGridView) footer.findViewById(R.id.gridview); 

      // set expand to show all gridview rows 
      gridView.setExpanded(true); 
     } 


     /** 
     * set adapters for list view and gridview 
     */ 
     private void setAdapters() { 
      // convert int array to Integer array by apache common lang library 
      Integer[] osImageList = ArrayUtils.toObject(osImage); 

      // set gridview adapter 
      CustomAdapter gridViewAdapter = new CustomAdapter(this, R.layout.item_grid, R.id.image, osImageList); 

      gridView.setAdapter(gridViewAdapter); 

     } 
    }

ExampleHeightGridView.java

package com.hospital.headling.hospital.util; 

import android.content.Context; 
import android.util.AttributeSet; 
import android.view.ViewGroup; 
import android.widget.GridView; 

public class ExpandableHeightGridView extends GridView { 

    boolean expanded = false; 

    public ExpandableHeightGridView(Context context) { 
     super(context); 
    } 

    public ExpandableHeightGridView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
    } 

    public ExpandableHeightGridView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
    } 

    public boolean isExpanded() { 
     return expanded; 
    } 

    @Override 
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
     if (isExpanded()) { 
      // Calculate entire height by providing a very large height hint. 
      // MEASURED_SIZE_MASK represents the largest height possible. 
      int expandSpec = MeasureSpec.makeMeasureSpec(MEASURED_SIZE_MASK, MeasureSpec.AT_MOST); 
      super.onMeasure(widthMeasureSpec, expandSpec); 

      ViewGroup.LayoutParams params = getLayoutParams(); 
      params.height = getMeasuredHeight(); 
     } else { 
      super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
     } 
    } 

    public void setExpanded(boolean expanded) { 
     this.expanded = expanded; 
    } 
}

layout_gridview.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 



    <com.healinghospital.healinghospital.util.ExpandableHeightGridView 
     android:id="@+id/gridview" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:gravity="center" 
     android:horizontalSpacing="10dp" 
     android:verticalSpacing="10dp" 
     android:numColumns="6" 
     android:stretchMode="columnWidth"/> 

    <!--<TextView 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_marginTop="10dp" 
     android:background="#000099" 
     android:text="@string/corporation" 
     android:textColor="@android:color/white" /> --> 

    <TextView 
     android:id="@+id/list" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_marginTop="10dp" 
     android:background="#000099" 
     android:textColor="@android:color/white" /> 


</LinearLayout>

activity_mail.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical"> 

    <ListView 
     android:id="@+id/list" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content"/> 

</LinearLayout>

CustomAdapter.java

package com.hospital.headling.hospital.adapter; 
import android.app.Activity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.ImageView; 

import com.hospital.headling.hospital.R; 

public class CustomAdapter extends ArrayAdapter<Integer> { 

    private Activity activity; 

    public CustomAdapter(Activity activity, int resource, int textViewResourceId, Integer[] osimage) { 
     super(activity, resource, textViewResourceId, osimage); 
     this.activity = activity; 
    } 



    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     ViewHolder holder = null; 

     // inflate layout from xml 
     LayoutInflater inflater = (LayoutInflater) activity 
      .getSystemService(Activity.LAYOUT_INFLATER_SERVICE); 

     // If holder not exist then locate all view from UI file. 
     if (convertView == null) { 
      // inflate UI from XML file 
      convertView = inflater.inflate(R.layout.item_grid, parent, false); 
      // get all UI view 
      holder = new ViewHolder(convertView); 
      // set tag for holder 
      convertView.setTag(holder); 
     } else { 
      // if holder created, get tag from view 
      holder = (ViewHolder) convertView.getTag(); 
     } 

     holder.image.setImageResource(getItem(position)); 

     return convertView; 
    } 

    private class ViewHolder { 
     private ImageView image; 

     public ViewHolder(View v) { 
      image = (ImageView)v.findViewById(R.id.image); 
     } 
    } 
}

來源

2017-04-08 SwimJim

下一次，請不要事後所有的前初始化XML和Java代碼在你的問題（它需要很多時間來閱讀所有內容）。您應該通過第一條logcat消息瞭解問題： null對象引用 –

上的java.lang.NullPointerException：Attempinvoke虛方法'void com.hospital.headling.hospital.util.ExpandableHeightGridView.setAdapter（android.widget.ListAdapter）' Gradle在你自己的代碼中不會導致NullPointerExceptions，只是你知道的。 –

@HonorLT XML和一些Java代碼是必要的（因爲ID可能會從XML中丟失，這會導致它爲空）。然而，一個[mcve]（關鍵字最小），將是不錯的 –

你永遠不會調用其初始化ExpandableHeightGridView方法addGridViewAsListViewFooter()。

gridView = (ExpandableHeightGridView) footer.findViewById(R.id.gridview);

因此，在這一行：

gridView.setAdapter(gridViewAdapter);

這裏gridView從未初始化，所以它提供了NullPointerException

調用setAdapter()

來源

2017-04-08 18:50:40 rafsanahmad007

將項目遷移到gradle後的空指針異常

回答

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