Example logic for tipping application

tippers

package com.example.tippers;

import java.math.BigDecimal;
import java.text.NumberFormat;
import android.os.Bundle;
import android.app.Activity;
import android.content.SharedPreferences;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnSeekBarChangeListener {
  
	public static final String PREFS_NAME = "MyPrefsFile";
	private TextView percentage_amount;
	private SeekBar percentage_value;
	private TextView people_amount;
	private SeekBar people_value;
	private TextView bill_amount;
	private TextView your_tip;
	private TextView total_bill_value;
	private TextView per_person;
	private Button percentage_minus;
	private Button percentage_plus;
	private Button people_minus;
	private Button people_plus;
	private CheckBox cash_checkbox;
	private SharedPreferences preferences;
	private static final int max_people = 24;
	
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		// Load preferences
		preferences = getSharedPreferences(PREFS_NAME, 0);
		
		// Set variables as application references
		percentage_amount = (TextView) findViewById(R.id.percentage_value);
		percentage_value = (SeekBar) findViewById(R.id.percentage_seekbar); 
		people_amount = (TextView) findViewById(R.id.people_value);
		people_value = (SeekBar) findViewById(R.id.people_seekbar);
		bill_amount = (TextView) findViewById(R.id.bill_amount);
		your_tip = (TextView) findViewById(R.id.your_tip_value);
		total_bill_value = (TextView) findViewById(R.id.total_bill_value);
		per_person = (TextView) findViewById(R.id.per_person_value);
		cash_checkbox = (CheckBox) findViewById(R.id.cash_checkbox);
		
		people_plus = (Button) findViewById(R.id.people_plus);
		people_minus = (Button) findViewById(R.id.people_minus);
		percentage_plus = (Button) findViewById(R.id.percentage_plus);
		percentage_minus = (Button) findViewById(R.id.percentage_minus);
		
		// Set SeekBar Listeners and max values
		percentage_value.setMax(100);
		percentage_value.setProgress(Integer.parseInt(percentage_amount.getText().toString()));
		percentage_value.setOnSeekBarChangeListener(this);
		
		people_value.setMax(max_people);
		people_value.setProgress(Integer.parseInt(people_amount.getText().toString()));
		people_value.setOnSeekBarChangeListener(this);
		
		
		// Listeners for plus and minus buttons
		people_plus.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	// When clicked get the current value and convert to integer
            	int old_amount = Integer.parseInt(people_amount.getText().toString());
            	
            	// Increment by 1 as this is the plus listener
            	int new_amount = old_amount + 1;
            	
            	// Ensure the value stays within bounds
            	if (new_amount > max_people) {
            		new_amount = max_people;
            	}
            	
            	// Update the amount text field with this new value
            	people_amount.setText(Integer.toString(new_amount));
            	// Update the SeekBar to represent this new value
            	people_value.setProgress(new_amount);
            }
        });
		
		people_minus.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	int old_amount = Integer.parseInt(people_amount.getText().toString());
            	int new_amount = old_amount - 1;
            	
            	if (new_amount < 1) {
            		new_amount = 1;
            	}
            	
            	people_amount.setText(Integer.toString(new_amount));
            	people_value.setProgress(new_amount);
            }
        });
		
		// Listeners for percentage plus and minus buttons, editing the values and SeekBar as appropriate		
		percentage_plus.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	int old_amount = Integer.parseInt(percentage_amount.getText().toString());
            	int new_amount = old_amount + 1;
            	
            	if (new_amount > 100) {
            		new_amount = 100;
            	}
            	
            	percentage_amount.setText(Integer.toString(new_amount));
            	percentage_value.setProgress(new_amount);
            }
        });
		
		percentage_minus.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	int old_amount = Integer.parseInt(percentage_amount.getText().toString());
            	int new_amount = old_amount - 1;
            	
            	if (new_amount <= 0) {
            		new_amount = 1;
            	}
            	
            	percentage_amount.setText(Integer.toString(new_amount));
            	percentage_value.setProgress(new_amount);
            }
        });
		
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present
		getMenuInflater().inflate(R.menu.activity_main, menu);
		return true;
	}
	
	protected void onResume() {
		super.onResume();
		
		// Access the shared preferences 
		preferences = getSharedPreferences(PREFS_NAME, 0);

		// Find stored value
		int percent = preferences.getInt("percent", 15);
		
		// Update fields with these values or defaults
		percentage_amount.setText(Integer.toString(percent));
		percentage_value.setProgress(percent);
		}
	
	@Override
	protected void onPause() {
		super.onPause();
		
		// Grab the current percent
		int percent = Integer.parseInt(percentage_amount.getText().toString());
		
		// Access the shared preferences
	    SharedPreferences.Editor editor = preferences.edit();
	    
	    // Update preferences with newest value
	    editor.putInt("percent", percent);

	    // Commit this edit
	    editor.commit();
	}
	
	// Method called from the XML 'Reset' and 'Calculate' buttons via onClick
	public void onClick(View view) {
		// Determine which button was pressed
		switch(view.getId()) {
		case R.id.calculate:
			// Call the Calculation method with the boolean for if it's cash or not
			calculation(view, (cash_checkbox.isChecked()));
			return;
		case R.id.reset:
			// Call Reset method which planks out all the fields back to their default setting
			reset(view);
			return;
		}
	}
		
	public void calculation(View view, boolean cash) {
			int input_percentage = 0;
			float input_bill = 0;
			
			// Quick value access to check the values are valid
			try {
				input_percentage = Integer.parseInt(percentage_amount.getText().toString());
			} catch (NumberFormatException e) {
				Toast toast = Toast.makeText(this, "Input Percent invalid",  Toast.LENGTH_SHORT);
				toast.show();
			}
			
			try {
				input_bill = Float.parseFloat(bill_amount.getText().toString());
			} catch (NumberFormatException e) {
				Toast toast = Toast.makeText(this, "Input Bill invalid",  Toast.LENGTH_SHORT);
				toast.show();
			}
			
			// Check the values sent for calculation fall within bounds
			if (input_bill > 0.00) {
				if (input_percentage > 0 && input_percentage <= 100) {
					// Create BigDecimal variables
					BigDecimal one_hundred = new BigDecimal("100");
					BigDecimal twenty = new BigDecimal("20");
					BigDecimal percentage = new BigDecimal(percentage_amount.getText().toString());
					BigDecimal bill = new BigDecimal(bill_amount.getText().toString());	
					BigDecimal people = new BigDecimal(people_amount.getText().toString());
					BigDecimal individual_tip_output = null;
					BigDecimal bill_divided = null;
					
					
					// Find out the total tip for all people
					BigDecimal tip = bill.divide(one_hundred, 2, 2); 
					tip = tip.multiply(percentage);
					
					// Find out the tip for each person
					individual_tip_output = tip.divide(people, 2, 2);
					
					// Find out the how much of the bill each person has to pay
					bill_divided = bill.divide(people, 2, 0);

					// Calculate the exact per person cost (unrounded)
					BigDecimal pp = individual_tip_output.add(bill_divided);
					
					if (cash) {
						BigDecimal xpp = null;
						BigDecimal difference = null;
						
						// 5p Rounding
						if (pp.doubleValue() < 1.00) {
							
							// Round this to nearest 0.05
							xpp = new BigDecimal(pp.multiply(twenty)
		                            								.add(new BigDecimal("0.5"))
		                            								.toBigInteger()).divide(twenty);
							
							if (xpp == new BigDecimal("0.00")) {
								xpp = new BigDecimal("0.05");
							}
							
							if (xpp.doubleValue() > pp.doubleValue()) {
								// Rounded up
								difference = xpp.subtract(pp);
								individual_tip_output = individual_tip_output.add(difference);
							} else {
								// Rounded down
								// Tip can't be rounded down to exactly 0.00
								if (individual_tip_output.doubleValue() == 0.00) {
									BigDecimal force_up = new BigDecimal("0.05");
									individual_tip_output = individual_tip_output.add(force_up);
									xpp = xpp.add(force_up);
								}
								// If the rounding falls into negative range, force it to re-round up
								if (individual_tip_output.doubleValue() < 0.00) {
									xpp = pp.setScale(2, BigDecimal.ROUND_UP);
									difference = xpp.subtract(pp);
									individual_tip_output = individual_tip_output.add(difference);
								}
							}
							pp = xpp;
						}
						
						// £1 Rounding
						if (pp.doubleValue() > 1.00 && pp.doubleValue() < 100.00) {
							xpp = pp.setScale(0, BigDecimal.ROUND_HALF_UP);
							
							if (xpp.doubleValue() > pp.doubleValue()) {
								// Rounded up
								difference = xpp.subtract(pp);
								individual_tip_output = individual_tip_output.add(difference);
							} else {
								// Rounded down
								difference = pp.subtract(xpp);
								individual_tip_output = individual_tip_output.subtract(difference);
								// Tip can't be rounded to exactly 0.00
								if (individual_tip_output.doubleValue() == 0.00) {
									BigDecimal force_up = new BigDecimal("0.05");
									individual_tip_output = individual_tip_output.add(force_up);
									xpp = xpp.add(force_up);
								}
								// If the rounding falls into negative range, force it to re-round up
								if (individual_tip_output.doubleValue() < 0.00) {
									xpp = pp.setScale(0, BigDecimal.ROUND_UP);
									difference = xpp.subtract(pp);
									individual_tip_output = individual_tip_output.add(difference);
								}
							}
							
							pp = xpp;
						}
						
						// £5 Rounding
						if (pp.doubleValue() > 100.00 && pp.intValue() % 5 != 0) {							
							BigDecimal one = new BigDecimal("1");
							BigDecimal two = new BigDecimal("2");
							xpp = pp.setScale(0, BigDecimal.ROUND_HALF_UP);
							
							double mod = (xpp.doubleValue() % 5);
							if (mod == 1) {
								// Round down
								xpp = xpp.subtract(one);
								individual_tip_output = individual_tip_output.subtract(one);
							} else if (mod == 2) {
								// Round down
								xpp = xpp.subtract(two);
								individual_tip_output = individual_tip_output.subtract(two);
							} else if (mod == 3) {
								// Round up
								xpp = xpp.add(two);
								individual_tip_output = individual_tip_output.add(two);
							} else if (mod == 4) {
								// Round up
								xpp = xpp.add(one);
								individual_tip_output = individual_tip_output.add(one);
							}
							
							pp = xpp;
						}
					}
					// Add up the total tip and the total bill to find the total payable for everyone
					BigDecimal total_bill = pp.multiply(people);
					
					// Set these new values WITH LOCATION to determine correct currency to use	
					your_tip.setText(String.valueOf(NumberFormat.getCurrencyInstance().format(individual_tip_output)));
					total_bill_value.setText(String.valueOf(NumberFormat.getCurrencyInstance().format(total_bill)));
					per_person.setText(String.valueOf(NumberFormat.getCurrencyInstance().format(pp)));
				} else {
					// Handle error or do nothing
					Toast toast = Toast.makeText(this, "Percentage to high or low",  Toast.LENGTH_SHORT);
					toast.show();
				}
			} else {
				// Handle error or do nothing
				Toast toast = Toast.makeText(this, "Please enter a Bill above 0",  Toast.LENGTH_SHORT);
				toast.show();
			}			
	}
	
	public void reset(View view) {
		// Reset all values to blank and default, including preferences
		bill_amount.setText(String.valueOf(""));
		
		// Access the shared preferences if the app is being reopened from 
		preferences = getSharedPreferences(PREFS_NAME, 0);

		int percent = preferences.getInt("percent", 15);
		percentage_amount.setText(Integer.toString(percent));
		
		percentage_value.setProgress(percent);
		// Default value set to 4 people
		people_value.setProgress(4);
		
		cash_checkbox.setChecked(false);
		people_amount.setText("4");
		your_tip.setText("0.00");
		total_bill_value.setText("0.00");
		per_person.setText("0.00");
		
		Toast toast = Toast.makeText(this, "Reset Complete",  Toast.LENGTH_SHORT);
		toast.show();
	}	

	@Override
	public void onProgressChanged(SeekBar arg0, int progress, boolean arg2) {
		if (arg0.equals(percentage_value))
	    {
			// Enforce percentage in bounds as range includes 0
			if (progress < 1) progress = 1;
			// Set new value for percent
			percentage_amount.setText(Integer.toString(progress));
	    }
	    else if (arg0.equals(people_value))
	    {
	    	// Enforce people in bounds as range includes 0
	    	if (progress < 1) progress = 1;
	    	// Set new value for people
	    	people_amount.setText(Integer.toString(progress));
	    }
		return;
	}

	@Override
	public void onStartTrackingTouch(SeekBar arg0) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void onStopTrackingTouch(SeekBar arg0) {
		// TODO Auto-generated method stub
		
	}

}