Android Development Example: Children's Calculator

package com.example.childrencalculator;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends Activity {

  private Button button0;
  private Button button1;
  private Button button2;
  private Button button3;
  private Button button4;
  private Button button5;
  private Button button6;
  private Button button7;
  private Button button8;
  private Button button9;
  private Button buttonClear;
  private Button buttonDivide;
  private Button buttonMultiply;
  private Button buttonAdd;
  private Button buttonSubtract;
  private TextView numberTextView;
  private TextView smileyTextView;
  public int currentAmount=0;
  public int buttonClicked =0;

  @Override
  protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    numberTextView = (TextView) findViewById(R.id.numberTextView);
    smileyTextView = (TextView) findViewById(R.id.smileyTextView);
    buttonClear = (Button) findViewById(R.id.clearButton);
    button0 = (Button) findViewById(R.id.zeroButton);
    button1 = (Button) findViewById(R.id.oneButton);
    button2 = (Button) findViewById(R.id.twoButton);
    button3 = (Button) findViewById(R.id.threeButton);
    button4 = (Button) findViewById(R.id.fourButton);
    button5 = (Button) findViewById(R.id.fiveButton);
    button6 = (Button) findViewById(R.id.sixButton);
    button7 = (Button) findViewById(R.id.sevenButton);
    button8 = (Button) findViewById(R.id.eightButton);
    button9 = (Button) findViewById(R.id.nineButton);
    buttonDivide = (Button) findViewById(R.id.divideButton);
    buttonMultiply = (Button) findViewById(R.id.multiplyButton);
    buttonAdd = (Button) findViewById(R.id.plusButton);
    buttonSubtract = (Button) findViewById(R.id.minusButton);

    buttonClear = (Button) findViewById(R.id.clearButton);

    //Write the event handler here:
    buttonClear.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("");
        smileyTextView.setText("");
        currentAmount = 0;
        buttonClicked = 0;

      }

    });

    button1 = (Button) findViewById(R.id.oneButton);

    //Write the event handler here:
    button1.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("1");
        buttonClicked = 1;

      }

    });

    button2 = (Button) findViewById(R.id.twoButton);

    //Write the event handler here:
    button2.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("2");
        buttonClicked = 2;
      }

    });

    button3 = (Button) findViewById(R.id.threeButton);

    //Write the event handler here:
    button3.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("3");
        buttonClicked = 3;

      }

    });

    button4 = (Button) findViewById(R.id.fourButton);
    //Write the event handler here:
    button4.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("4");
        buttonClicked = 4;

      }

    });

    button5 = (Button) findViewById(R.id.fiveButton);
    //Write the event handler here:
    button5.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("5");
        buttonClicked = 5;

      }

    });

    button6 = (Button) findViewById(R.id.sixButton);
    //Write the event handler here:
    button6.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("6");
        buttonClicked = 6;

      }

    });

    button7 = (Button) findViewById(R.id.sevenButton);
    //Write the event handler here:
    button7.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("7");
        buttonClicked = 7;

      }

    });

    button8 = (Button) findViewById(R.id.eightButton);
    //Write the event handler here:
    button8.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("8");
        buttonClicked = 8;

      }

    });

    button9 = (Button) findViewById(R.id.nineButton);
    //Write the event handler here:
    button9.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("9");
        buttonClicked = 9;

      }

    });

    button0 = (Button) findViewById(R.id.zeroButton);
    //Write the event handler here:
    button0.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText("0");
        buttonClicked = 0;

      }

    });

    buttonDivide = (Button) findViewById(R.id.divideButton);
    //Write the event handler here:
    buttonDivide.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        if (buttonClicked != 0) {

          numberTextView.setText(Integer.toString(Calculator.divideInput(currentAmount, buttonClicked)));
          currentAmount = Calculator.divideInput(currentAmount, buttonClicked);
          smileyTextView.setText(Faces.determineFace(currentAmount));

        }

      }

    });

    buttonMultiply = (Button) findViewById(R.id.multiplyButton);
    //Write the event handler here:
    buttonMultiply.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText(Integer.toString(Calculator.multiplyInput(currentAmount, buttonClicked)));
        currentAmount = Calculator.multiplyInput(currentAmount, buttonClicked);
        smileyTextView.setText(Faces.determineFace(currentAmount));

      }

    });

    buttonAdd = (Button) findViewById(R.id.plusButton);
    //Write the event handler here:
    buttonAdd.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {

        numberTextView.setText(Integer.toString(Calculator.addInput(currentAmount, buttonClicked)));
        currentAmount = Calculator.addInput(currentAmount, buttonClicked);
        smileyTextView.setText(Faces.determineFace(currentAmount));

      }

    });

    buttonSubtract = (Button) findViewById(R.id.minusButton);
    //Write the event handler here:
    buttonSubtract.setOnClickListener(new View.OnClickListener() {

      @Override
      public void onClick(View v) {
        numberTextView.setText(Integer.toString(Calculator.subtractInput(currentAmount, buttonClicked)));
        currentAmount = Calculator.subtractInput(currentAmount, buttonClicked);
        smileyTextView.setText(Faces.determineFace(currentAmount));

      }

    });

  }

}