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Android Build an Interactive Story App (Retired) Intents and Multiple Activities Introducing String Resources

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

FATAL EXCEPTION

Dear community,

My plan is to type a text into a TextView and display this text in a different activity´s TextView.

I get this nasty error:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.nexuskiller.interactivestory/com.example.nexuskiller.interactivestory.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference

This is my code:

MainActivity

package com.example.nexuskiller.interactivestory;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {

    TextView mTextView = (TextView) findViewById(R.id.textView);
    Button mButton = (Button) findViewById(R.id.button);
    private String mText = " ";

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

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mText = mTextView.getText().toString();
                callNewActivity(mText);
            }
        });
    }

    public void callNewActivity(String text) {
        Intent intent = new Intent(MainActivity.this, secondActivity.class);
        intent.putExtra(getString(R.string.name), text);
        startActivity(intent);
    }
}

secondActivity

package com.example.nexuskiller.interactivestory;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class secondActivity extends Activity {
    public static final String TAG = secondActivity.class.getSimpleName();
    TextView secondTW = (TextView) findViewById(R.id.secondEditText);
    String stringFromTW = " ";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        Intent intent = getIntent();

        stringFromTW = intent.getStringExtra(getString(R.string.name));
        secondTW.setText(stringFromTW);
    }
}

Any help is highly appreciated :)

Grigorij

1 Answer

Kourosh Raeen
Kourosh Raeen
23,733 Points

Hi Grigorij - The calls to findViewById need to be inside onCreate() and after the call to setContentView(), so your first activity should look like this:

package com.example.nexuskiller.interactivestory;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {

    private TextView mTextView;
    private Button mButton;
    private String mText = " ";

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

        mTextView = (TextView) findViewById(R.id.textView);
        mButton = (Button) findViewById(R.id.button);

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mText = mTextView.getText().toString();
                callNewActivity(mText);
            }
        });
    }

    public void callNewActivity(String text) {
        Intent intent = new Intent(MainActivity.this, secondActivity.class);
        intent.putExtra(getString(R.string.name), text);
        startActivity(intent);
    }
}
Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hi Kourosh,

thank you sooo much. You saved my head from turning into a giant black hole :smiley:

Grigorij