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Null object reference if configuration changes

由 回眸只為那壹抹淺笑 提交于 2019-12-07 15:36:16

问题


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

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

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}

objects return this error are called chart , progress_layout .

edited

most of class "related code snippet" cause full class 1000 line cannot post it

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
    }

manifest

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

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 file

    <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 in advance!


回答1:


Hi @Error, I will try with One Simple Demo in which i am able to get the Object of Progressbar and Linear Layout when Screen orientation changed. Here i have described simple example as follows:

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);
}
}

And the Layout file as below:

<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>

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



来源：https://stackoverflow.com/questions/33048409/null-object-reference-if-configuration-changes

标签
android
orientation
android-linearlayout
android-view
onconfigurationchanged
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