java.lang.NullPointerException: On Button Click Listener

Question

Whenever The Custom Dialog is opened the app crashes throwing the following error

ive checked for duplicate initialization but could not find anything

In MainActivity.java

public class MainActivity extends AppCompatActivity {

    PieChart pieChart;
    ImageView edit;
    Dialog editDialog;

    EditText edit_cal,edit_carb,edit_prot,edit_fats;
    String cal,carb,prot,fats;
    Button save;

    public static final String SHARED_PREFS = "sharedPrefs";
    public static final String CAL = "text";
    public static final String CARB = "text";
    public static final String PROT = "text";
    public static final String FATS = "text";

    TextView tcal,tcarb,tprot,tfats;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit=findViewById(R.id.edit);
        pieChart=findViewById(R.id.pie);
        tcal=findViewById(R.id.tcal);
        tcarb=findViewById(R.id.tcarb);
        tprot=findViewById(R.id.tprot);
        tfats=findViewById(R.id.tfats);
        saveData();
        loadData();
        updateViews();


        edit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                custom_Dialog();
            }
        });

    }

    private void custom_Dialog() {
        editDialog=new Dialog(MainActivity.this);
        editDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        editDialog.setCancelable(true);
        editDialog.setContentView(R.layout.edit_nutrient);
        editDialog.show();

        edit_cal=findViewById(R.id.edit_cal);
        edit_carb=findViewById(R.id.edit_carb);
        edit_prot=findViewById(R.id.edit_prot);
        edit_fats=findViewById(R.id.edit_fats);

        save=findViewById(R.id.savebtn);


        save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                cal=edit_cal.getText().toString();
                carb=edit_carb.getText().toString();
                prot=edit_prot.getText().toString();
                fats=edit_fats.getText().toString();

                if(isValid(cal,carb,prot,fats))
                {
                    saveData();
                    loadData();
                    updateViews();
                    editDialog.dismiss();

                }
                else
                {
                   Toast.makeText(MainActivity.this,"Please fill your diet plan correctly",Toast.LENGTH_SHORT).show();
                }



            }
        });


    }

In edit_nutrient.xml

    <Button
        android:id="@+id/savebtn"
        android:layout_width="296dp"
        android:layout_height="48dp"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="340dp"
        android:background="@drawable/button_default_2"
        android:fontFamily="sans-serif-medium"
        android:letterSpacing="-0.03"
        android:text="Save"
        android:textColor="#ffffff"
        android:textSize="13sp"
        android:textStyle="normal"


        />

android.widget.Button.setOnClickListener(android.view.View$OnClickListener)'
on a null object reference
        at com.example.android.chartvisual.MainActivity.custom_Dialog(MainActivity.java:122)
        at com.example.android.chartvisual.MainActivity.access$000(MainActivity.java:29)
        at com.example.android.chartvisual.MainActivity$1.onClick(MainActivity.java:101)
        at android.view.View.performClick(View.java:6319)
        at android.view.View$PerformClick.run(View.java:24955)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:192)
        at android.app.ActivityThread.main(ActivityThread.java:6701)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:826)

Ben P. · Accepted Answer · 2019-10-28 17:02:17Z

1

Here, you set the content view of your dialog:

editDialog.setContentView(R.layout.edit_nutrient);

However, in these lines, you are searching for views inside of your Activity, not your dialog:

edit_cal=findViewById(R.id.edit_cal);
edit_carb=findViewById(R.id.edit_carb);
edit_prot=findViewById(R.id.edit_prot);
edit_fats=findViewById(R.id.edit_fats);

save=findViewById(R.id.savebtn);

You need to use the findViewById() method of your dialog to search within it:

edit_cal=editDialog.findViewById(R.id.edit_cal);
edit_carb=editDialog.findViewById(R.id.edit_carb);
edit_prot=editDialog.findViewById(R.id.edit_prot);
edit_fats=editDialog.findViewById(R.id.edit_fats);

save=editDialog.findViewById(R.id.savebtn);

answered Oct 28, 2019 at 17:02

Ben P.

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Md. Asaduzzaman · Accepted Answer · 2019-10-28 17:05:41Z

0

You have to create View from layout and then pass it to create dialog. Also use view instance to get child elements. Check below:

private void custom_Dialog() {
    View view = LayoutInflater.from(this).inflate(R.layout.edit_nutrient, null, false);

    editDialog=new Dialog(MainActivity.this);
    editDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
    editDialog.setCancelable(true);
    editDialog.setContentView(view);
    editDialog.show();

    edit_cal = view.findViewById(R.id.edit_cal);
    edit_carb = view.findViewById(R.id.edit_carb);
    edit_prot = view.findViewById(R.id.edit_prot);
    edit_fats = view.findViewById(R.id.edit_fats);

    save = view.findViewById(R.id.savebtn);


    save.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            cal=edit_cal.getText().toString();
            carb=edit_carb.getText().toString();
            prot=edit_prot.getText().toString();
            fats=edit_fats.getText().toString();

            if(isValid(cal,carb,prot,fats))
            {
                saveData();
                loadData();
                updateViews();
                editDialog.dismiss();

            }
            else
            {
               Toast.makeText(MainActivity.this,"Please fill your diet plan correctly",Toast.LENGTH_SHORT).show();
            }
        }
    });
}

edited Oct 28, 2019 at 17:05

answered Oct 28, 2019 at 17:00

Md. Asaduzzaman

15.5k2 gold badges36 silver badges48 bronze badges

2 Comments

Ben P. Over a year ago

Manually inflating the view is reasonable, but this will suffer from the original problem: vanilla findViewById() searches within the Activity's view hierarchy. You could use view.findViewById() in your solution.

Ben P. Over a year ago

When the save button is clicked, edit_cal.getText() will be invoked and throw NPE because it is not found.

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