Text View Null: void android.widget.Textview.setText(java.lang.Charsequence)' on a null Object Reference

Question

I’m taking a data from an API on a fragment to change the txt of Activity. But when I call the function that makes this change the setText gives NullPointerException. If I call the same function on the screen activity works, but if I call anywhere from fragment he makes a mistake.

Scanactivity.java

import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
public class ScanActivity extends BaseActivity {

    private TextView txtResultado;
    private TextView txtInfo;
    private TextView txtHorario;
    private TextView txtData;
    private TextView txtUrl;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scan);
        setupToolbar();

        txtResultado    = findViewById(R.id.txt_result);
        txtInfo         = findViewById(R.id.txt_info);
        txtHorario      = findViewById(R.id.txt_horario);
        txtData         = findViewById(R.id.txt_data);
        txtUrl         = findViewById(R.id.txt_url);

        setResult("teste 001", "teste URL");


    }

    public void setResult(String result, String fullURL){
        Log.i("RESULTADO", result);
        txtResultado.setText(result);
        txtUrl.setText(fullURL);


    }


}

Leitorfragment.java

import android.app.Fragment;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.Nullable;
import android.support.annotation.RequiresApi;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.google.zxing.Result;
import com.site.qrcode_demo.MySingleton;
import com.site.qrcode_demo.ScanActivity;
import com.site.qrcode_demo.R;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;

import me.dm7.barcodescanner.zxing.ZXingScannerView;


public class LeitorFragment extends Fragment implements ZXingScannerView.ResultHandler {

    private static final String FLASH_STATE = "FLASH_STATE";
    private static final String AUTO_FOCUS_STATE = "AUTO_FOCUS_STATE";
    private static final String SELECTED_FORMATS = "SELECTED_FORMATS";
    private static final String CAMERA_ID = "CAMERA_ID";
    private ZXingScannerView mScannerView;
    private boolean mFlash;
    private boolean mAutoFocus;
    private ArrayList<Integer> mSelectedIndices;
    private int mCameraId = -1;

    ScanActivity scanActivity;
    String url = "https://httpbin.org/get";
    private RequestQueue queue;
    private String data;

    Context context;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle state) {
        mScannerView = new ZXingScannerView(getActivity());
        if (state != null) {
            mFlash = state.getBoolean(FLASH_STATE, false);
            mAutoFocus = state.getBoolean(AUTO_FOCUS_STATE, true);
            mSelectedIndices = state.getIntegerArrayList(SELECTED_FORMATS);
            mCameraId = state.getInt(CAMERA_ID, -1);
        } else {
            mFlash = false;
            mAutoFocus = true;
            mSelectedIndices = null;
            mCameraId = -1;
        }
        return mScannerView;
    }


    @Override
    public void onCreate(Bundle state) {
        super.onCreate(state);
        setHasOptionsMenu(true);
        context = getActivity();
    }

    @Override
    public void onResume() {
        super.onResume();
        mScannerView.setResultHandler(this);
        mScannerView.startCamera();

    }

    @Override
    public void handleResult(Result result) {
        conection(result.getText());
        Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mScannerView.resumeCameraPreview(LeitorFragment.this);
            }
        }, 1000);
    }


    @Override
    public void onPause() {
        super.onPause();
        mScannerView.startCamera();
    }


    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        inflater.inflate(R.menu.menu_scan, menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle presses on the action bar items
        switch (item.getItemId()) {
            case R.id.menu_flash:
                mFlash = !mFlash;
                if (mFlash) {
                    item.setIcon(R.drawable.ic_flash_on);
                } else {
                    item.setIcon(R.drawable.ic_flash_off);
                }
                mScannerView.setFlash(mFlash);
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }


    public void conection(final String result) {
        //Log.i("RESPOSTA:", resposta);
        final String fullURL = url+"/"+result;
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(url, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        try {
                            data = response.getString("url");
                            Log.i("DATA", data);
                            scanActivity = new ScanActivity();
                            scanActivity.setResult(data, fullURL);
                            //resposta = data;
                        } catch (JSONException e) {
                            Log.i("ERRO 1:", "Deu Erro no try");
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        error.printStackTrace();
                        queue.stop();
                    }
                });
        MySingleton.getInstance(context).addRequestque(jsonObjectRequest);

    }


}

activity_scan.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.site.qrcode_demo.ScanActivity">

    <fragment android:name="com.site.qrcode_demo.Fragments.LeitorFragment"
        android:id="@+id/scanner_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_gravity="top"
        android:minHeight="?attr/actionBarSize"
        android:background="@color/actionbar_opacity"
        app:theme="@style/TransparentToolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/txt_result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top|right"
        android:layout_marginTop="80dp"
        android:text="1250,50"
        android:textAlignment="center"
        android:textSize="30dp"
        android:layout_marginHorizontal="@dimen/margin"
        android:textColor="@android:color/white" />

    <TextView
        android:id="@+id/txt_info"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top|right"
        android:layout_marginRight="16dp"
        android:layout_marginTop="120dp"
        android:text="Informações adicionais"
        android:textAlignment="center"
        android:layout_marginHorizontal="@dimen/margin"
        android:textColor="@android:color/white" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center|bottom"
        android:layout_marginBottom="100dp"
        android:gravity="center"
        android:layout_marginHorizontal="@dimen/margin">
    <TextView
        android:id="@+id/txt_sensor"
        android:text="Sensor x366"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:textColor="#ffffff"
        android:layout_height="wrap_content"
        android:textAlignment="center"
        android:textSize="25dp"/>
        <LinearLayout
            android:layout_weight="1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:gravity="center">
            <TextView
                android:id="@+id/txt_horario"
                android:text="09:04"
                android:layout_width="wrap_content"
                android:layout_height="0dp"
                android:layout_weight="1"
                android:textColor="#ffffff"
                android:textAlignment="center"
                android:textSize="35dp"/>
            <TextView
                android:id="@+id/txt_data"
                android:text="06/04/2018"
                android:layout_width="wrap_content"
                android:layout_weight="1"
                android:layout_height="0dp"
                android:textColor="#ffffff"
                android:textAlignment="center"
                android:textSize="20dp"/>
        </LinearLayout>

    </LinearLayout>

    <TextView
        android:id="@+id/txt_url"
        android:layout_gravity="center|bottom"
        android:text="htto://URL.com/teste"
        android:layout_width="wrap_content"
        android:textColor="#ffffff"
        android:layout_height="wrap_content"
        android:layout_marginBottom="50dp"/>

    <TextView
        android:layout_gravity="center|bottom"
        android:text="Place a barcode in the viewfinder rectangle to scan it."
        android:layout_width="wrap_content"
        android:textColor="#ffffff"
        android:layout_height="wrap_content"/>

</FrameLayout>

PS: Before it was working this way. I don’t know what was the change I made to happen this problem

Answer 1

Bro you did not say if Textview is in Activity or in the Textview view, anyway the error is in the edittext statement, when you declare so: txtResultado= findViewById(R.id.txt_result); it subunderstands that edittext belongs to the current Activity, so if it is in the Fragment view you declare it No Fragment informing that it belongs to view, thus: txtResultado = mScannerView.findViewById(R.id.txt_result);, if you do not have Voce declares informing Activity, thus: txtResultado = getActivity().findViewById(R.id.txt_result);. Got it? you need to inform where is the edittext to be identified.

Answer 2

Resolution:

Leitorfragment.java

    @Override
public void onResume() {
    super.onResume();
    mScannerView.setResultHandler(this);
    mScannerView.startCamera();

    txtResult   = getActivity().findViewById(R.id.txt_result);
    txtInfo     = getActivity().findViewById(R.id.txt_info);
    txtSensor   = getActivity().findViewById(R.id.txt_sensor);
    txtHorario  = getActivity().findViewById(R.id.txt_horario);
    txtData     = getActivity().findViewById(R.id.txt_data);
    txtUrl  = getActivity().findViewById(R.id.txt_url);

}

If I put the code in onCreate it gave null object. Then the solution was to capture Textview by onResume