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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
Posted by 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
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
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