App is crashing

Question

I am learning android. Every time I run the app it is crashing. I can't seem to find any error. Help needed.

Here is the main code.

MainActivity.java

package com.example.arnab.myfirstapplication;

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

public class MainActivity extends Activity implements View.OnClickListener {

    Button btnAdd = (Button)findViewById(R.id.btnAdd);
    EditText num1 = (EditText)findViewById(R.id.num1);
    EditText num2 = (EditText)findViewById(R.id.num2);
    TextView result = (TextView)findViewById(R.id.result);

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

        btnAdd.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if(v == btnAdd){
            int n1 = Integer.parseInt(num1.getText().toString());
            int n2 = Integer.parseInt(num2.getText().toString());
            int sum = n1 + n2;
            result.setText(Integer.toString(sum));
        }
    }

    @Override
    public void onPointerCaptureChanged(boolean hasCapture) {

    }
}

Please help is very much appreciated. I am stuck at this stage. No matter what I do, the app crashes.

Update I did not know that it is not possible to use findViewById before setcontentview . at that time my logic was not clear. Sorry about this.

You cannot use `findViewById` before you have set the content view. So move your subview initializations into the `onCreate` method. — Henry, Dec 31 '17 at 16:38

score 2 · Accepted Answer · answered Dec 31 '17 at 16:48

2

You cannot call findViewById or any other method outside method block.

btnAdd = (Button)findViewById(R.id.btnAdd);
num1 = (EditText)findViewById(R.id.num1);
num2 = (EditText)findViewById(R.id.num2);
result = (TextView)findViewById(R.id.result);

add these code after setContentViewin onCreate and remove all initialization from top.

answered Dec 31 '17 at 16:48

Suraj Vaishnav

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Thanks for the help. – Arnab Feb 22 '18 at 17:27

score 1 · Answer 2 · answered Dec 31 '17 at 16:49

Try this

 package com.example.arnab.myfirstapplication;

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

 public class MainActivity extends Activity implements View.OnClickListener 
 {



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

Button btnAdd = (Button)findViewById(R.id.btnAdd);
EditText num1 = (EditText)findViewById(R.id.num1);
EditText num2 = (EditText)findViewById(R.id.num2);
TextView result = (TextView)findViewById(R.id.result);

    btnAdd.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    if(v == btnAdd){
        int n1 = Integer.parseInt(num1.getText().toString());
        int n2 = Integer.parseInt(num2.getText().toString());
        int sum = n1 + n2;
        result.setText(Integer.toString(sum));
    }
}

@Override
public void onPointerCaptureChanged(boolean hasCapture) {

}
}

Thanks for the answer. @Syed Hamza Hassan – Arnab Mar 02 '18 at 12:58 — Arnab, Mar 02 '18 at 12:58

App is crashing

2 Answers2