在OnClick事件中出現NullPointerException

Question

您好我對android開發非常陌生，我正在創建一個有4個圖像按鈕的活動，並且我首先嚐試使用一個圖像按鈕來鏈接到一個新的活動，但在我甚至能夠鏈接之前該頁面，似乎我的OnClick事件給我錯誤。

從我的logcat我明白，我有一個空指針異常，在第30行拋出：imageButton1.setOnClickListener(new View.OnClickListener() {

我懷疑它可能會像這導致我的findViewById ImageButtons（不同的ID）我的佈局元素（）返回null ，但嘗試，因爲我可能仍然無法找到可能導致它的錯誤。因爲我還在學習，請原諒我的理解。真的很感謝任何幫助，謝謝！

RecipesFragment.java

package com.example.sgrecipe; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageButton; 
import android.content.Intent; 

public class RecipesFragment extends Fragment { 

ImageButton imageButton1; 
ImageButton imageButton2; 
ImageButton imageButton3; 
ImageButton imageButton4; 
Intent intent; 


@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) { 

    View rootView = inflater.inflate(R.layout.activity_recipes_fragment, container, false); 
    intent = new Intent(getActivity(), FavouriteFragment.class); 
    final ImageButton imageButton1 = (ImageButton) findViewById(R.id.imageButton1); 

    imageButton1.setOnClickListener(new View.OnClickListener() { //<--error here 
      public void onClick(View v) { 
      //  startActivity(intent); 
      } 
     }); 

    return rootView; 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_recipes_fragment); 

    addListenerOnButton(); 

} 

private void setContentView(int activityRecipesFragment) { 
    // TODO Auto-generated method stub 

} 

public void addListenerOnButton() { 

    imageButton1 = (ImageButton) findViewById(R.id.imageButton1); 
    imageButton2 = (ImageButton) findViewById(R.id.imageButton2); 
    imageButton3 = (ImageButton) findViewById(R.id.imageButton3); 
    imageButton4 = (ImageButton) findViewById(R.id.imageButton4); 
    } 

private ImageButton findViewById(int imagebuttonselector) { 
    // TODO Auto-generated method stub 
    return null; 
}; 
} 

activity_recipes_fragment.xml

<?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"> 

<TableLayout 
android:id="@+id/tableLayout1" 
android:layout_width="match_parent" 
android:layout_height="match_parent" > 

<TableRow 
    android:id="@+id/tableRow1" 
    android:layout_width="fill_parent" 
    android:layout_height="0dp" 
    android:layout_weight="1" > 

<ImageButton 
    android:id="@+id/imageButton1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_weight="1" 
    android:background="@drawable/chinese_button" /> 

<ImageButton 
    android:id="@+id/imageButton2" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_weight="1" 
    android:background="@drawable/malay_button" /> 
</TableRow> 

<TableRow 
    android:id="@+id/tableRow1" 
    android:layout_width="fill_parent" 
    android:layout_height="0dp" 
    android:layout_weight="1" > 

<ImageButton 
    android:id="@+id/imageButton3" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_weight="1" 
    android:background="@drawable/indian_button" /> 

<ImageButton 
    android:id="@+id/imageButton4" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_weight="1" 
    android:background="@drawable/others_button" /> 
</TableRow> 

</TableLayout> 
</LinearLayout> 

Answer 1

使用rootView從activity_recipes_fragment佈局訪問視圖：

final ImageButton imageButton1 = (ImageButton) 
         rootView.findViewById(R.id.imageButton1);