How do I use Intent.putExtra dynamically?

Question

I have 2 Activities which are ( MainActivity , LoadIntentActivity ). I know how to putExtra() from MainActivity and receive the value in LoadIntentActivity with getIntent().getExtra() . However, I want to start LoadIntentActivity with 2 method: 1 is with the putExtra() and the other is without putExtra() . But the LoadIntentActivity already have a getIntent().getExtra() that will result NullPointerException if i trying to start LoadIntentActivity without putExtra() .

This is my code:

activity_main.xml :

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 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"
        android:orientation="vertical"
        tools:context=".MainActivity">
    
        <Button
            android:id="@+id/btnGotoIA"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Go to IntentActivity"/>
        <ListView
            android:id="@+id/lvList"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    
    
    </LinearLayout>

**MainActivity.java** :

    public class MainActivity extends AppCompatActivity {
    
        Button btnGotoIA;
        ListView lvList;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            btnGotoIA = findViewById(R.id.btnGotoIA);
            lvList = findViewById(R.id.lvList);
    
            String[] items = {"1", "4", "53", "3", "99"};
    
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);
            lvList.setAdapter(adapter);
    
            btnGotoIA.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent intent = new Intent(MainActivity.this, LoadIntentActivity.class);
                    startActivity(intent);
                }
            });
    
            lvList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                    Intent intent = new Intent(MainActivity.this, LoadIntentActivity.class);
                    intent.putExtra("text", adapter.getItem(i));
                    startActivity(intent);
                }
            });
        }
    }

**activity_load_intent.xml** :

    <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout 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=".LoadIntentActivity">
    
        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

LoadIntentActivity.java :

    public class LoadIntentActivity extends AppCompatActivity {
    
        TextView textView;
        Bundle bundle = getIntent().getExtras();
        String text = bundle.getString("text");
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_load_intent);
            textView = findViewById(R.id.textView);
            // if i start this Activity without putExtra the TextView should be empty
            textView.setText(text);
        }
    }

Answer 1

If you want to handle the case of a missing bundle, just check if it (and the string extracted from it) is null before using it.

public class LoadIntentActivity extends AppCompatActivity {

    private TextView textView;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_load_intent);
        textView = findViewById(R.id.textView);
        
        Bundle bundle = getIntent().getExtras();
        if( bundle != null ) {
            String bText = bundle.getString("text");
            if( bText != null ) {
                textView.setText(bText);
            }
        }
    }
}

Alternately, if you need to save the text as a class member still you could do something like this:

public class LoadIntentActivity extends AppCompatActivity {

    private TextView textView;
    private String text = "";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_load_intent);
        textView = findViewById(R.id.textView);
        
        Bundle bundle = getIntent().getExtras();
        if( bundle != null ) {
            String bText = bundle.getString("text");
            if( bText != null ) {
                text = bText;
            }
        }

        textView.setText(text);
    }
}

You could also save a similar class member boolean to indicate whether the activity had been started with a bundle or not (in case it affects the actions taken later in the activity).