如果配置更改空对象引用 [英] Null object reference if configuration changes

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本文介绍了如果配置更改空对象引用的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我得到空对象引用如果仅的LinearLayout 对象配置更改。

I get null object reference if configuration changes for only LinearLayout objects.

景观模式我必须 setVisiblity = View.GONE 所有视图除了一个视图

landscape mode I have to setVisiblity = View.GONE for all views except one view

纵向模式我必须 setVisibility = View.VISIBLE 所有视图：

portrait mode I have to setVisibility = View.VISIBLE for all views: 

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

对象返回该错误被称为图， progress_layout 。

编辑

大多数类的相关code片段引起满级的1000系列不能将它张贴 

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
    }

清单 

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

的logcat 

    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！

thanx in advance!

推荐答案

嗨@Error，我会尽量在这我能够当屏幕方向改变为获得进度和线性布局的对象中一个简单的演示。在这里，我所描述的简单例子如下： 

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);
}
}

且布局文件，如下： 

<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>

请检查出来当我能够做到这个code，让我知道如果您有任何疑问。

Please Check it out As I am able to do with this code and let me know If you have any doubts.

这篇关于如果配置更改空对象引用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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