LAB4_WeatherActivity_java.md

Weatherctivity.java

package com.example.labs;

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

public class WeatherActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener, OnClickListener {

    // Declare variables
    private RadioButton btnFah;
    private RadioButton btnCel;
    private RadioButton btnKel ;
    private EditText txtInputTemp;
    private TextView lblOutputDegF;
    private TextView lblOutputDegC;
    private TextView lblOutputDegK;
    private Button btnConvert;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_weather);
        
        // Initialize the RadioGroup and set a listener for checked state changes
        RadioGroup tempGroup = (RadioGroup) findViewById(R.id.tempGroup);
        tempGroup.setOnCheckedChangeListener(this);

        // Initialize the convert button and set a click listener
        btnConvert = (Button) findViewById(R.id.btnConvert);
        btnConvert.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // Get Resources for radio buttons, text boxes, and labels
        btnFah = (RadioButton) findViewById(R.id.btnDegF);
        btnCel = (RadioButton) findViewById(R.id.btnDegC);
        btnKel = (RadioButton) findViewById(R.id.btnDegK);
        txtInputTemp = (EditText) findViewById(R.id.txtInputTemp);
        lblOutputDegF = (TextView) findViewById(R.id.lblOutputF);
        lblOutputDegC = (TextView) findViewById(R.id.lblOutputC);
        lblOutputDegK = (TextView) findViewById(R.id.lblOutputK);

        // Convert the input temperature to double
        double temp = Double.parseDouble(String.valueOf(txtInputTemp.getText()));
        double answer = 0;

        // If the user chose Fahrenheit, convert to Celsius and Kelvin and display in those text boxes
        if (btnFah.isChecked()) {
            lblOutputDegF.setText(temp + " degrees F");
            lblOutputDegC.setText((Math.round((temp - 32) * 5 / 9 * 100.0) / 100.0) + " degrees C");
            lblOutputDegK.setText((Math.round((temp + 459.67) * 5 / 9 * 100.0) / 100.0) + " degrees K");
        }

        // If the user chose Celsius, convert to Fahrenheit and Kelvin and display in those text boxes
        if (btnCel.isChecked()) {
            lblOutputDegF.setText((Math.round(((temp * 9) / 5 + 32) * 100.0) / 100.0) + " degrees F");
            lblOutputDegC.setText(temp + " degrees C");
            lblOutputDegK.setText((Math.round((temp + 273.15) * 100.0) / 100.0) + " degrees K");
        }

        // If the user chose Kelvin, convert to Fahrenheit and Celsius and display in those text boxes
        if (btnKel.isChecked()) {
            lblOutputDegF.setText((Math.round((temp * 9 / 5 - 459.67) * 100.0) / 100.0) + " degrees F");
            lblOutputDegC.setText((Math.round((temp - 273.15) * 100.0) / 100.0) + " degrees C");
            lblOutputDegK.setText(temp + " degrees K");
        }
    }

    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        // Display the chosen temperature unit in a label
        TextView lblOutput = (TextView) findViewById(R.id.lblOutput);
        switch (checkedId) {
            case R.id.btnDegF:
                lblOutput.setText("You chose Fahrenheit");
                break;
            case R.id.btnDegC:
                lblOutput.setText("You chose Celsius");
                break;
            case R.id.btnDegK:
                lblOutput.setText("You chose Kelvin");
                break;
        }
    }

    // @Override
    // public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    // switch(item.getItemId()) {
    // case R.id.mnuMain:
    // startActivity(new Intent(getApplicationContext(), MainMenuActivity.class));
    // return true;
    // case R.id.mnuExit:
    // finish();
    // default:
    // return super.onOptionsItemSelected(item);
    // }
    // }
}

Detailed Comments Explanation

Imports:

The import statements bring in necessary classes from the Android SDK and AndroidX libraries. These include:

• AppCompatActivity for the activity class.
• Bundle for saving the state.
• View for UI interactions.
• Button for the button component.
• EditText for input text fields.
• RadioButton for radio button components.
• RadioGroup for grouping radio buttons.
• TextView for displaying text.
• OnClickListener for handling click events.

Class Declaration:

WeatherActivity extends AppCompatActivity to inherit functionality for an Android activity. It also implements RadioGroup.OnCheckedChangeListener to handle changes in the radio button group and View.OnClickListener to handle button click events.

onCreate Method:

onCreate is called when the activity is created. It initializes the activity.

• super.onCreate(savedInstanceState) calls the superclass's method to perform default setup.
• setContentView(R.layout.activity_weather) sets the user interface layout for this activity.
• RadioGroup tempGroup = (RadioGroup) findViewById(R.id.tempGroup) finds the RadioGroup defined in the XML layout.
• tempGroup.setOnCheckedChangeListener(this) sets the current instance as the listener for changes in the checked state of the radio buttons in the group.
• Button btnConvert = (Button) findViewById(R.id.btnConvert) finds the Button defined in the XML layout.
• btnConvert.setOnClickListener(this) sets the current instance as the click listener for the Button.

onClick Method:

This method is called when the Button is clicked.

• btnFah = (RadioButton) findViewById(R.id.btnDegF) finds the RadioButton for Fahrenheit.
• btnCel = (RadioButton) findViewById(R.id.btnDegC) finds the RadioButton for Celsius.
• btnKel = (RadioButton) findViewById(R.id.btnDegK) finds the RadioButton for Kelvin.
• txtInputTemp = (EditText) findViewById(R.id.txtInputTemp) finds the EditText for inputting the temperature.
• lblOutputDegF = (TextView) findViewById(R.id.lblOutputF) finds the TextView for displaying Fahrenheit.
• lblOutputDegC = (TextView) findViewById(R.id.lblOutputC) finds the TextView for displaying Celsius.
• lblOutputDegK = (TextView) findViewById(R.id.lblOutputK) finds the TextView for displaying Kelvin.
• double temp = Double.parseDouble(String.valueOf(txtInputTemp.getText())) converts the input temperature to a double.

The if statements check which radio button is selected and perform the corresponding conversions. The converted values are then displayed in the respective TextViews.

onCheckedChanged Method:

This method is called when the checked state of a radio button in the RadioGroup changes.

• TextView lblOutput = (TextView) findViewById(R.id.lblOutput) finds the TextView defined in the XML layout where the result will be displayed.
• The switch statement checks which radio button was selected using checkedId and updates the TextView accordingly.

Summary:

This code sets up an Android activity with a RadioGroup containing three radio buttons and a Button to convert temperatures. When the user selects one of the radio buttons, the text of a TextView is updated to reflect the user's choice. When the user clicks the Button, the input temperature is converted to the other two scales. The @Override annotations indicate that onCreate, onClick, and onCheckedChanged methods are overriding methods from their respective parent classes or interfaces.