android null對象引用，儘管存在

-1

我有一個MainActivity，它基本上有一個framelayout，它有不同的片段坐在它取決於用戶在做什麼。android null對象引用，儘管存在

activity_main.xml中

<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:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:orientation="vertical" tools:context=".MainActivity"> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:background="#27b" 
     android:layout_weight=".04"> 
     <FrameLayout 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:id="@+id/activity_main_framelayout"> 
     </FrameLayout> 
    </LinearLayout> 
    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_weight=".9" 
     android:orientation="horizontal"> 
     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:background="#1B5F96" 
      android:layout_weight=".9" 
      android:id="@+id/activity_main_status_title" 
      android:text="@string/activity_main_status_title" 
      tools:ignore="NestedWeights" /> 
     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:background="#AD3333" 
      android:layout_weight=".15" 
      android:id="@+id/activity_main_status_value" 
      android:text="@string/activity_main_status_value"/> 
    </LinearLayout> 
</LinearLayout>

問題開始與接口方法void WillYouAccept(final String caller)

@Override 
    public void WillYouAccept(final String caller) { 
     Connection f = new Connection(); 
     ShiftView(f); 

     runOnUiThread(new Runnable() { 
      @Override 
      public void run() { 
       Connection b = (Connection) getFragmentManager().findFragmentById(R.layout.connection_display); 
       b.updateInitiator(caller); 
      } 
     }); 
    }

線b.updateInitiator(caller);即啓動空對象引用錯誤。 ShiftView已經基本上將碎片交換到framelayout中，並且迄今爲止運行良好。

@Override 
    public void ShiftView(Object obj) { 
     FragmentTransaction ft = getFragmentManager().beginTransaction(); 
     ft.replace(R.id.activity_main_framelayout, (Fragment) obj); 
     ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN); 
     ft.addToBackStack(null); 
     ft.commit(); 
    }

基本上在connection_display.xml一個TextView（Connection.java）需要從在MainActivity更新，並以某種方式initiator = (TextView) view.findViewById(R.id.textView_connection_display_initiator_ID);爲空時，它被與來自MainActivity交互。

Connection.java

package ""; 

import android.app.Activity; 
import android.app.Fragment; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.TextView; 

public class Connection extends Fragment { 
    MiddleMan mCallBack; 

    Button accept; 
    Button deny; 
    TextView initiator; 

    @Override 
    public void onAttach(Activity activity) { 
     super.onAttach(activity); 
     try { 
      mCallBack = (MiddleMan) activity; 
     } catch (ClassCastException e) { 
      throw new ClassCastException(activity.toString() + " must implement ReqestConnect"); 
     } 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.connection_display, container, false); 
     mCallBack.DisplayHome(); 
     initiator = (TextView) view.findViewById(R.id.textView_connection_display_initiator_ID); 
     accept = (Button) view.findViewById(R.id.button_connection_display_ACCEPT); 
     accept.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       buttonAccept(); 
      } 
     }); 
     deny = (Button) view.findViewById(R.id.button_connection_display_DENY); 
     deny.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       buttonDeny(); 
      } 
     }); 
     return view; 
    } 

    private void buttonAccept() { 
     System.out.println("Accept Button Pressed"); 
    } 

    private void buttonDeny() { 
     System.out.println("Deny Button Pressed"); 
    } 

    public void updateInitiator(final String s) { 
     initiator.setText(s); 
    } 
}

connection_display.xml

<?xml version="1.0" encoding="utf-8"?> 
<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"> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:textAppearance="?android:attr/textAppearanceLarge" 
     android:text="@string/textView_connection_display_title" 
     android:id="@+id/textView_connection_display_title" /> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:orientation="horizontal" 
     android:layout_marginTop="45dp" 
     android:layout_weight=".004"> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginLeft="65dp" 
      android:textAppearance="?android:attr/textAppearanceMedium" 
      android:text="@string/textView_connection_display_ID_label" 
      android:id="@+id/textView_connection_display_ID_label" /> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:textAppearance="?android:attr/textAppearanceMedium" 
      android:id="@+id/textView_connection_display_initiator_ID" 
      android:text="@string/textView_connection_display_initiator_ID" /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:orientation="horizontal" 
     android:layout_weight=".004"> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginLeft="15dp" 
      android:textAppearance="?android:attr/textAppearanceSmall" 
      android:text="@string/textView_connection_display_exp" 
      android:id="@+id/textView_connection_display_exp" /> 

    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:orientation="horizontal" 
     android:layout_weight=".04"> 

     <Button 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginLeft="100dp" 
      android:text="@string/button_connection_display_ACCEPT" 
      android:id="@+id/button_connection_display_ACCEPT" 
      tools:ignore="ButtonStyle" /> 

     <Button 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="@string/button_connection_display_DENY" 
      android:id="@+id/button_connection_display_DENY" 
      tools:ignore="ButtonStyle" /> 

    </LinearLayout> 

</LinearLayout>

來源

2015-09-06 Never Nor

來自'findViewById（）'調用的NPE通常是請求的視圖不存在的結果，因爲您正在搜索的視圖的子視圖不存在。請確保您嘗試獲取的視圖的視圖已添加到父級，如果它在一個片段中，請改用'fragment.findViewById（）'。 – ygesher

b體的絕對調高爲空，但該位上方一直找到了片段，所以我解決了這個問題：

@Override 
    public void WillYouAccept(final String caller) { 
     final Connection f = new Connection(); 
     ShiftView(f); 
     runOnUiThread(new Runnable() { 
      @Override 
      public void run() { 
       f.updateInitiator(caller); 
      } 
     }); 
    }

來源

2015-09-06 20:51:37

android null對象引用，儘管存在

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