Trouble starting new layout after button click

Question

I am trying to make a fairly simple calculator app for getting familiar with android. My goal is to load a new interface with trig, logarithmic functions, etc. upon clicking the mode button on the xml layout file. I included activity in the manifest as well but it failed when I ran the project. What can I do so that it works?

Here is the main activity class:

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class Calculator extends Activity implements OnClickListener{
public String str = "";
Character task = 'q';
double num, numtemp;
EditText showResult;
Button mode;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.display);
    showResult = (EditText) findViewById(R.id.result_id);
    mode = (Button) findViewById(R.id.bMode);
    mode.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    if(v.getId() == R.id.bMode)
    {
        Intent i = new Intent("zero.paradox.valvemachine.SWITCHNODE");
        startActivity(i);
    }
}

public void btn1Clicked(View v) {
    insert(1);
}

public void btn2Clicked(View v) {
    insert(2);
}

public void btn3Clicked(View v) {
    insert(3);
}

public void btn4Clicked(View v) {
    insert(4);
}

public void btn5Clicked(View v) {
    insert(5);
}

public void btn6Clicked(View v) {
    insert(6);
}

public void btn7Clicked(View v) {
    insert(7);
}

public void btn8Clicked(View v) {
    insert(8);
}

public void btn9Clicked(View v) {
    insert(9);
}

public void btn0Clicked(View v){
    insert(0);
}

public void btnplusClicked(View v) {
    perform();
    task = '+';
}

public void btnminusClicked(View v) {
    perform();
    task = '-';
}

public void btndivideClicked(View v) {
    perform();
    task = '/';
}

public void btnmultiClicked(View v) {
    perform();
    task = '*';
}

public void btnequalClicked(View v) {
    calculate();
}

public void btnclearClicked(View v) {
    reset();
}

private void reset() {
    // TODO Auto-generated method stub
    str = "";
    task = 'q';
    num = 0;
    numtemp = 0;
    showResult.setText("");
}

private void insert(int j) {
    // TODO Auto-generated method stub
    str = str + Integer.toString(j);
    num = Integer.valueOf(str).intValue();
    showResult.setText(str);

}

private void perform() {
    // TODO Auto-generated method stub
    str = "";
    numtemp = num;
}

private void calculate() {
    // TODO Auto-generated method stub
    if (task == '+')
        num = numtemp + num;
    else if (task == '-')
        num = numtemp - num;
    else if (task == '/')
        num = numtemp / num;
    else if (task == '*')
        num = numtemp * num;
    showResult.setText("" + num);
    }

}

And the code for the new mode:

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class SwitchMode extends Activity implements OnClickListener{

Button mode2;
EditText showResult2;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.display2);
    showResult2 = (EditText) findViewById(R.id.edtNode);
    mode2 = (Button) findViewById(R.id.bMode);
    mode2.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    if(v.getId() == R.id.mode)
    {
        Intent i = new Intent("org.calculator.MAINACTIVITY");
        startActivity(i);
    }
}

}

This is not working for me.. is there anything I can do to fix it?

Answer 1

In order to starting another activity you have to create a Intent intent = new Intent() and indicate to this intent the activity you want to start with setClass(Context packageContext, Class<?> cls) method.

There are different ways to construct a intent, read the documentation. Everything is here :

• Reference: http://developer.android.com/reference/android/content/Intent.html
• Training : http://developer.android.com/training/basics/firstapp/starting-activity.html

This is a part of your code after a clean up, try this :

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.EditText;

    public class Calculator extends Activity implements OnClickListener{

        private static EditText mShowResult;
        private static Button mMode;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.display);

            mMode = (Button) findViewById(R.id.bMode);
            mShowResult = (EditText) findViewById(R.id.result_id);

            if (mMode != null) {
                mMode.setOnClickListener(this);
            }
        }

        @Override
        public void onClick(View view) {
            if(view == mMode) {
                Intent intent = new Intent();
                intent.setClass(this, SwitchMode.class);
                startActivity(intent);
            }
        }
    }

Answer 2

The simplest solution is to use a different constructor for your Intents:

Change

Intent i = new Intent("zero.paradox.valvemachine.SWITCHNODE");

to

Intent i = new Intent(getContext(), SwitchMode.class);

Also, you misspelled your class name (switch* N *ode instead of switch* M *ode), which is probably why you are having the problem, as the constructor you are using should also work, I just prefer to use strongly typed class names over a String.