如果配置發生變化，則返回空對象引用

如果只有LinearLayout對象發生配置更改，則會獲得空對象引用。如果配置發生變化，則返回空對象引用

景觀模式我必須setVisiblity = View.GONE所有視圖除了一個視圖

肖像模式我必須setVisibility = View.VISIBLE所有的觀點：

if (Activity started in portrait mode then turned into landscape) 
{it work fine} 
else {it get null object reference only for linearLayout objects}

對象返回該錯誤被稱爲chart，progress_layout 。

編輯

最一流的「相關的代碼片斷」引起滿級的1000線不能將它張貼

public class Cardio extends ActionBarActivity implements InsertDialogue.Insert, saveDialogue.Save, HistoryDialogue.History, AdapterView.OnItemSelectedListener { 
    float Float; 
    int Day = 0; 
    Database database; 
    int i; 
    int num; 
    static Spinner spinner; 
    static int pos; 
    Progress p; 
    SubActionButton goalSubButton; 
    boolean gool = false; 
    YAxis leftAxis ; 
    LineChart Running_LineChart ; 
    int intent ; 
    FloatingActionMenu x ; 
    FloatingActionButton actionButton ; 
    String orientation ; 
    LinearLayout historyText ; 
    ArrayList<Entry> Running_ArrayEntry ; 
    int First_entries ; 
    LinearLayout chart ; 
    LinearLayout progress_layout ; 
    boolean HistoryTextAfterRotation ; 



    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     historyText = (LinearLayout) findViewById(R.id.historyLayoutText); 
     chart = (LinearLayout) findViewById(R.id.chartid); 
     progress_layout = (LinearLayout) findViewById(R.id.group); 
     Running_LineChart = (LineChart) findViewById(R.id.chart); 
     Log.e("oncreate","oncreate"); 
     getWindow().getDecorView().setSystemUiVisibility(
       View.SYSTEM_UI_FLAG_LAYOUT_STABLE 
         | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN); 
     database = new Database(this); 
     Bundle extras = getIntent().getExtras(); 
     intent = extras.getInt("activity"); 
     p = new Progress(); 
     orientation = getRotation(); 
     if(savedInstanceState == null) { 
      getSupportFragmentManager().beginTransaction() 
        .add(R.id.group, p) 
        .commit(); 
     } 
     else 
     { 
      String ftagment = savedInstanceState.getString("frag"); 
      getSupportFragmentManager().beginTransaction() 
        .add(p,ftagment) 
        .commit(); 
     } 
     addPlus(); 
     switch (orientation) { 
      case "l": 
       actionButton.setVisibility(View.GONE); 
       break; 
      case "p" : 
       actionButton.setVisibility(View.VISIBLE); 
       break; 
     } 
    } 

    @Override 
    public void onConfigurationChanged(Configuration newConfig) { 
     orientation = getRotation() ; 
     setGoalSubButton_Visiblity(); 
     if(newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) { 
      if(actionButton!=null&&actionButton.getVisibility()!=View.GONE) { 
       actionButton.setVisibility(View.GONE); 
      } 
      if(spinner!=null&&spinner.getVisibility()!=View.GONE) { 
       spinner.setVisibility(View.GONE); 
      } 
     // p.setUserVisibleHint(false); 


      if(progress_layout!=null&&progress_layout.getVisibility()!=View.GONE) { 
       progress_layout.setVisibility(View.GONE); 
      } 

      if(chart!=null&&chart.getVisibility()!=View.GONE) { 
       chart.getLayoutParams().height = LinearLayout.LayoutParams.MATCH_PARENT; 
      } 
      if(historyText!=null&&historyText.getVisibility()!=View.GONE) { 
       historyText.setVisibility(View.GONE); 
      } 
      if(Running_LineChart!=null&&Running_LineChart.getVisibility()!=View.GONE) { 
       Running_LineChart.animateY(1300); 
      } 
      // Changes the height and width to the specified *pixels* 
      // chart = (LinearLayout) findViewById(R.id.chartid); 
      // chart.getLayoutParams().height = LayoutParams.MATCH_PARENT; 
      // setContentView(R.layout.activity_main_land); 
      // Toast.makeText(this,"chnge orientation",Toast.LENGTH_SHORT).show(); 
     } 
     else if(newConfig.orientation ==Configuration.ORIENTATION_PORTRAIT) { 
      actionButton.setVisibility(View.VISIBLE); 
      spinner.setVisibility(View.VISIBLE); 
      p.setUserVisibleHint(false); 
      Log.e("BEFORE LOG","BEFOR PROGRESS LAYOUT "); 
      progress_layout.setVisibility(View.VISIBLE); 
      chart.getLayoutParams().height =0; 
      if(HistoryTextAfterRotation&&historyText.getVisibility()!=View.VISIBLE) { 
       historyText.setVisibility(View.VISIBLE);} 
      Running_LineChart.animateY(1300); 
      x.close(true); 
     } 
     super.onConfigurationChanged(newConfig); 


    } 
     public String getRotation(){ 
     final int rotation = ((WindowManager) this.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getOrientation(); 
     switch (rotation) { 
      case Surface.ROTATION_0: 
       return "p"; 
      case Surface.ROTATION_90: 
       return "l"; 
      case Surface.ROTATION_180: 
       return "p"; 
      default: 
       return "l"; 
     } 

    } 



    public void setGoalSubButton_Visiblity() { 
     orientation = getRotation() ; 
     switch (orientation) { 
     case "p": { 
      if (getIdsFromGoalLimitsTables()) { 
       x.close(true); 
       actionButton.removeAllViews(); 
       actionButton.detach(); 
       Log.e("mohab", "gool must be visible "); 
       addPlus(); 
       p.setGoal_unset(); 
      } else { 
       x.close(true); 
       actionButton.removeAllViews(); 
       actionButton.detach(); 
       Log.e("mohab", "gool must be invisible"); 
       addPlus(); 
       p.setGoal(getgoalFromDatabase()); 
      } 
      } 
     } 
     updateProgress(); 
     addEntries(0, 0, true,false,0); 

    } 



    @Override 
    protected void onSaveInstanceState(Bundle savedInstanceState) { 
     if (p != null) { 
      savedInstanceState.putString("frag", 
        p.getTag()); 
     } 
     super.onSaveInstanceState(savedInstanceState); 
    } 



    @Override 
    protected void onResume() { 
     super.onResume(); 
     setSpinner(); 
     setGoalSubButton_Visiblity(); 
     // addEntries(0, 0, true, false, 0); // cause its added in setGoal event 
    }

清單

<activity 
     android:name=".Cardio.Cardio" 
     android:configChanges="orientation|screenSize" 
     > 
    </activity>

logcat的

10-10 07:05:42.721: E/AndroidRuntime(4115): FATAL EXCEPTION: main 
10-10 07:05:42.721: E/AndroidRuntime(4115): Process: developer.mohab.gymee, PID: 4115 
10-10 07:05:42.721: E/AndroidRuntime(4115): java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.LinearLayout.setVisibility(int)' on a null object reference 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at developer.mohab.gymee.Cardio.Cardio.onConfigurationChanged(Cardio.java:154) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.app.ActivityThread.performConfigurationChanged(ActivityThread.java:4150) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.app.ActivityThread.handleConfigurationChanged(ActivityThread.java:4225) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1461) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.os.Handler.dispatchMessage(Handler.java:102) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.os.Looper.loop(Looper.java:211) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at android.app.ActivityThread.main(ActivityThread.java:5389) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at java.lang.reflect.Method.invoke(Native Method) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at java.lang.reflect.Method.invoke(Method.java:372) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020) 
10-10 07:05:42.721: E/AndroidRuntime(4115):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)

xml文件

<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:weightSum="5" 
    android:orientation="vertical" 
    tools:context=".MainActivity" 
    android:id="@+id/layout" 
    android:background="@android:color/white"> 




    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:layout_weight="3" 
     android:orientation="vertical" 
     android:id="@+id/chartid" 
     android:background="@color/gridBack"> 
    <com.github.mikephil.charting.charts.LineChart 
     android:id="@+id/chart" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_marginTop="25dp" 
     /> 
    </LinearLayout> 

    <LinearLayout 
     android:layout_width="match_parent" 
     android:gravity="center" 
     android:layout_height="wrap_content" 
     android:orientation="vertical" 
     android:id="@+id/historyLayoutText"> 
     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:gravity="center" 
      android:textColor="@color/start" 
      android:textSize="23dp" 
      android:layout_marginTop="5dp" 
      android:text="History" /> 
    </LinearLayout> 



    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:id="@+id/linearLayout2" 
     android:layout_weight="2" 
     android:gravity="right" 
     android:orientation="horizontal" 

     > 
     <LinearLayout 
      android:id="@+id/group" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:orientation="vertical" 
      android:layout_weight="1" 
      > 
     </LinearLayout> 

     <Spinner 
      android:layout_width="130dp" 
      android:layout_height="50dp" 
      android:layout_marginTop="10dp" 
      android:id="@+id/spinner" 

      /> 


    </LinearLayout> 




</LinearLayout>

thanx提前！

來源

2015-10-09 Error

請發佈錯誤信息 – Elltz

null對象引用progress_layout和chart onConfigurationChanged事件...我將更新問題 – Error

更新...如果我評論此行「progress_layout.setVisibility（View.VISIBLE）;」我錯誤返回，而我越來越layoutorrams在圖表對象.. – Error

嗨@錯誤，我會嘗試一個簡單的演示，其中我可以在屏幕方向更改時獲取進度條對象和線性佈局。在這裏我所描述的簡單示例如下：

public class MainActivity extends Activity { 

float Float; 
int Day = 0; 
TextView tview; 
int i; 
int num; 
static Spinner spinner; 
static int pos; 
boolean gool = false; 

int intent; 

String orientation; 
LinearLayout historyText; 

int First_entries; 
LinearLayout chart; 
LinearLayout progress_layout; 
boolean HistoryTextAfterRotation; 

@SuppressLint("NewApi") 
@Override 
protected void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    historyText = (LinearLayout) findViewById(R.id.historyLayoutText); 
    chart = (LinearLayout) findViewById(R.id.chartid); 
    progress_layout = (LinearLayout) findViewById(R.id.group); 
    tview = (TextView) findViewById(R.id.chart); 
    getWindow().getDecorView().setSystemUiVisibility(
      View.SYSTEM_UI_FLAG_LAYOUT_STABLE 
        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN); 

    if (getScreenOrientation() == 1) { 
     chart.setVisibility(View.VISIBLE); 
    } else { 
     chart.setVisibility(View.GONE); 
    } 
} 

public int getScreenOrientation() { 
    Display getOrient = getWindowManager().getDefaultDisplay(); 
    int orientation = Configuration.ORIENTATION_UNDEFINED; 
    if (getOrient.getWidth() == getOrient.getHeight()) { 
     orientation = Configuration.ORIENTATION_SQUARE; 
    } else { 
     if (getOrient.getWidth() < getOrient.getHeight()) { 
      orientation = Configuration.ORIENTATION_PORTRAIT; 
     } else { 
      orientation = Configuration.ORIENTATION_LANDSCAPE; 
     } 
    } 
    return orientation; 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 
    return true; 
} 

@Override 
public void onConfigurationChanged(Configuration _newConfig) { 
    // TODO Auto-generated method stub 
    if (_newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) { 
     chart.setVisibility(View.GONE); 
    } 

    if (_newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) { 
     chart.setVisibility(View.VISIBLE); 
    } 
    super.onConfigurationChanged(_newConfig); 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 
}

，如下列版式文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
android:id="@+id/layout" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:background="@android:color/white" 
android:orientation="vertical" 
android:weightSum="5" 
tools:context=".MainActivity" > 

<LinearLayout 
    android:id="@+id/chartid" 
    android:layout_width="match_parent" 
    android:layout_height="0dp" 
    android:layout_weight="3" 
    android:background="@android:color/black" 
    android:orientation="vertical" > 

    <TextView 
     android:id="@+id/chart" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_marginTop="25dp" /> 
</LinearLayout> 

<LinearLayout 
    android:id="@+id/historyLayoutText" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:gravity="center" 
    android:orientation="vertical" > 

    <TextView 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_marginTop="5dp" 
     android:gravity="center" 
     android:text="History" 
     android:textColor="@android:color/white" 
     android:textSize="23dp" /> 
</LinearLayout> 

<LinearLayout 
    android:id="@+id/linearLayout2" 
    android:layout_width="match_parent" 
    android:layout_height="0dp" 
    android:layout_weight="2" 
    android:gravity="right" 
    android:orientation="horizontal" > 

    <LinearLayout 
     android:id="@+id/group" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:orientation="vertical" > 
    </LinearLayout> 

    <Spinner 
     android:id="@+id/spinner" 
     android:layout_width="130dp" 
     android:layout_height="50dp" 
     android:layout_marginTop="10dp" /> 
</LinearLayout> 

</LinearLayout>

請檢查出來當我能夠用這個代碼做，讓我知道如果你有任何疑問。

來源

2015-10-10 06:35:12

thanx你的時間..仍然得到相同的錯誤...錯誤必須與其他東西我會分享全班代碼 – Error

讓我知道一旦你分享代碼。 –

現在我會更新問題 – Error

如果配置發生變化，則返回空對象引用

回答

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