Android Studio: Cara Membuat Android Apps 8
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In this tutorial we take it to the next level. In the last video we designed the interface for our Android conversion app. This time we will create the whole backend and finish the app.
The goal of this tutorial is to show you how to make an entire app in one video. We’ll cover use case descriptions, activity diagrams, class diagrams, flexible ways to solve our conversion problem, dynamically changing classes and much more. If you don’t understand everything don’t worry about it. This tutorial is all about seeing it all so you’ll grasp what is coming next.
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Here is the entire package for download Android Conversion App.
Note : In the video I set up the emulator to lvl 20, change to 19 in your build.gradle file and try 19.1.0 as I show below. I was trying to do too many things and that was a mistake.
UML Diagrams
Click the image below a few times to view it full screen
Android UML Diagrams
Use Case Description
SIMPLE ACTIONS
1. The user enters a number they want converted into an EditText
2. They change the spinner to the unit of measure to convert from
3. The other conversion types all show their measurement version of that unit amount
1. Create the layout in activity_main.xml
a. Use relative layout for for label "Convert From", Edittext and Spinner
b. Use GridLayout for bottom that contains 2 columns and 6 rows
c. Make gridlayout a blue color
d. Use the units teaspoons, tablespoons, cup, ounces, pints, quarts, gallons, pounds, milliliter, liter, milligram kilograms
2. Setup MainActivity
a. Create Spinner, EditText, TextViews
b. In onCreate
I. add items to the spinner
i. Create an ArrayAdapter using String array resource (Make strings.xml)
ii. Define the layout to use with the Spinner
iii. Connect the Adapter to the Spinner
II. Add a listener to the Spinner
i. Use setOnItemSelectedListener for Spinner
ii. NOTE : Maybe check if I am going to use a base class for unit conversion
III. Get the value in the EditText
IV. Initialize the TextViews
c. End onCreate ---------------------
3. Define a Quantity Class ----------
a. Quantity class contains a value and Unit enum
b. Define an enum for each unit type
c. Get the conversion for each unit type from teaspoon which is the base unit
d. Receive the number of teaspoons for the starting unit
e. To convert to the base unit teaspoons divide by the base unit
f. To convert to another unit other then teaspoons multiply by the base unit
g. Constructor receives the value and the unit
h. Create a toString that prints out the value and unit type to 4 decimals
4. Finish MainActivity
a. Item changed in the Spinner
I. Check if I'm converting from teaspoons?
i. If I am check if I'm updating tsps or not
- I Have Decided to Model this in an Activity Diagram *
Code From the Video
/src/build.gradle
apply plugin: 'android'
android {
compileSdkVersion 19
buildToolsVersion "19.1.0"
defaultConfig {
minSdkVersion 14
targetSdkVersion 19
versionCode 1
versionName "1.0"
}
buildTypes {
release {
runProguard false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:19.+'
}
Quantity.java
package com.newthinktank.derekbanas.conversion;
import java.text.DecimalFormat;
public class Quantity {
// Each object will have both a value and a unit of measure
final double value;
final Unit unit;
// Enum types use a constant key to represent a value
// They allow use to easily define how to convert all the other types
// of measurements to convert from teaspoon to anything. Then to make
// any conversion we convert from the starting type to teaspoon and then
// to the final required type.
public static enum Unit {
tsp(1.0d), tbs(0.3333d), cup(0.0208d), oz(0.1666d),
pint(0.0104d), quart(0.0052d), gallon(0.0013), pound(0.0125d),
ml(4.9289d), liter(0.0049d), mg(5687.5d), kg(0.0057d);
// We define that tsp will be the base unit of measure that we will
// convert to and then convert from.
final static Unit baseUnit = tsp;
// Will hold the number of tsp the original unit converts to
final double byBaseUnit;
// Receives the number of tsps the starting unit equals
private Unit(double inTsp) {
this.byBaseUnit = inTsp;
}
// Converts any other unit value to the number of tsps
public double toBaseUnit(double value) {
return value / byBaseUnit;
}
// We convert to another unit by using the teaspoon conversion percent
// defined in the enum
public double fromBaseUnit(double value) {
return value * byBaseUnit;
}
}
// The constructor that receives the value and unit of measure
public Quantity(double value, Unit unit) {
super();
this.value = value;
this.unit = unit;
}
// Converts from tsp to the desired unit type
public Quantity to(Unit newUnit) {
Unit oldUnit = this.unit;
return new Quantity(newUnit.fromBaseUnit(oldUnit.toBaseUnit(value)),
newUnit);
}
// Prints out to screen the unit amount and unit type
@Override
public String toString() {
DecimalFormat df = new DecimalFormat("#.0000");
return df.format(value) + " " + unit.name();
}
}
MainActivity.java
package com.newthinktank.derekbanas.conversion;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
private Spinner unitTypeSpinner;
private EditText amountTextView;
TextView teaspoonTextView, tablespoonTextView, cupTextView, ounceTextView,
pintTextView, quartTextView, gallonTextView, poundTextView,
milliliterTextView, literTextView, milligramTextView, kilogramTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Fills the spinner with the unit options
addItemsToUnitTypeSpinner();
// Add listener to the Spinner
addListenerToUnitTypeSpinner();
// Get a reference to the edit text view to retrieve the amount of the unit type
amountTextView = (EditText) findViewById(R.id.amount_text_view);
initializeTextViews();
}
public void initializeTextViews(){
teaspoonTextView = (TextView) findViewById(R.id.tsp_text_view);
tablespoonTextView = (TextView) findViewById(R.id.tbs_text_view);
cupTextView = (TextView) findViewById(R.id.cup_text_view);
ounceTextView = (TextView) findViewById(R.id.oz_text_view);
pintTextView = (TextView) findViewById(R.id.pint_text_view);
quartTextView = (TextView) findViewById(R.id.quart_text_view);
gallonTextView = (TextView) findViewById(R.id.gallon_text_view);
poundTextView = (TextView) findViewById(R.id.pound_text_view);
milliliterTextView = (TextView) findViewById(R.id.ml_text_view);
literTextView = (TextView) findViewById(R.id.liter_text_view);
milligramTextView = (TextView) findViewById(R.id.mg_text_view);
kilogramTextView = (TextView) findViewById(R.id.kg_text_view);
}
public void addItemsToUnitTypeSpinner(){
// Get a reference to the spinner
unitTypeSpinner = (Spinner) findViewById(R.id.unit_type_spinner);
// Create an ArrayAdapter using the string array and a default spinner layout
ArrayAdapter<CharSequence> unitTypeSpinnerAdapter = ArrayAdapter.createFromResource(this,
R.array.conversion_types, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
unitTypeSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// Apply the adapter to the spinner
unitTypeSpinner.setAdapter(unitTypeSpinnerAdapter);
}
public void addListenerToUnitTypeSpinner() {
unitTypeSpinner = (Spinner) findViewById(R.id.unit_type_spinner);
unitTypeSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View arg1, int pos, long arg3)
{
// Get the item selected in the Spinner
String itemSelectedInSpinner = parent.getItemAtPosition(pos).toString();
// Verify if I'm converting from teaspoon so that I use the right
// conversion algorithm
checkIfConvertingFromTsp(itemSelectedInSpinner);
}
public void onNothingSelected(AdapterView<?> arg0)
{
// TODO maybe add something here later
}
});
}
public void checkIfConvertingFromTsp(String currentUnit){
if(currentUnit.equals("teaspoon")){
updateUnitTypesUsingTsp(Quantity.Unit.tsp);
} else {
if(currentUnit.equals("tablespoon")){
updateUnitTypesUsingOther(Quantity.Unit.tbs);
} else if(currentUnit.equals("cup")){
updateUnitTypesUsingOther(Quantity.Unit.cup);
} else if(currentUnit.equals("ounce")){
updateUnitTypesUsingOther(Quantity.Unit.oz);
} else if(currentUnit.equals("pint")){
updateUnitTypesUsingOther(Quantity.Unit.pint);
} else if(currentUnit.equals("quart")){
updateUnitTypesUsingOther(Quantity.Unit.quart);
} else if(currentUnit.equals("gallon")){
updateUnitTypesUsingOther(Quantity.Unit.gallon);
} else if(currentUnit.equals("pound")){
updateUnitTypesUsingOther(Quantity.Unit.pound);
} else if(currentUnit.equals("milliliter")){
updateUnitTypesUsingOther(Quantity.Unit.ml);
} else if(currentUnit.equals("liter")){
updateUnitTypesUsingOther(Quantity.Unit.liter);
} else if(currentUnit.equals("milligram")){
updateUnitTypesUsingOther(Quantity.Unit.mg);
} else {
updateUnitTypesUsingOther(Quantity.Unit.kg);
}
}
}
public void updateUnitTypesUsingTsp(Quantity.Unit currentUnit){
// Convert the value in the EditText box to a double
double doubleToConvert = Double.parseDouble(amountTextView.getText().toString());
// Combine value to unit
String teaspoonValueAndUnit = doubleToConvert + " tsp";
// Change the value for the teaspoon TextView
teaspoonTextView.setText(teaspoonValueAndUnit);
// Update all the Unit Text Fields
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.tbs, tablespoonTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.cup, cupTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.oz, ounceTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.pint, pintTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.quart, quartTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.gallon, gallonTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.pound, poundTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.ml, milliliterTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.liter, literTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.mg, milligramTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, Quantity.Unit.kg, kilogramTextView);
}
public void updateUnitTextFieldUsingTsp(double doubleToConvert, Quantity.Unit unitConvertingTo,
TextView theTextView){
Quantity unitQuantity = new Quantity(doubleToConvert, Quantity.Unit.tsp);
String tempUnit = unitQuantity.to(unitConvertingTo).toString();
theTextView.setText(tempUnit);
}
public void updateUnitTypesUsingOther(Quantity.Unit currentUnit){
// Convert the value in the EditText box to a double
double doubleToConvert = Double.parseDouble(amountTextView.getText().toString());
// Create a Quantity using the teaspoon unit
Quantity currentQuantitySelected = new Quantity(doubleToConvert, currentUnit);
// Create the String for the teaspoon TextView
String valueInTeaspoons = currentQuantitySelected.to(Quantity.Unit.tsp).toString();
// Set the text for the teaspoon TextView
teaspoonTextView.setText(valueInTeaspoons);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.tbs, tablespoonTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.cup, cupTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.oz, ounceTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.pint, pintTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.quart, quartTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.gallon, gallonTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.pound, poundTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.ml, milliliterTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.liter, literTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.mg, milligramTextView);
updateUnitTextFieldUsingTsp(doubleToConvert, currentUnit,
Quantity.Unit.kg, kilogramTextView);
// Set the currently selected unit to the number in the EditText
if(currentUnit.name().equals(currentQuantitySelected.unit.name())){
// Create the TextView text by taking the value in EditText and adding
// on the currently selected unit in the spinner
String currentUnitTextViewText = doubleToConvert + " " +
currentQuantitySelected.unit.name();
// Create the TextView name to change by getting the currently
// selected quantities unit name and tacking on _text_view
String currentTextViewName = currentQuantitySelected.unit.name() +
"_text_view";
// Get the resource id needed for the textView to use in findViewById
int currentId = getResources().getIdentifier(currentTextViewName, "id",
MainActivity.this.getPackageName());
// Create an instance of the TextView we want to change
TextView currentTextView = (TextView) findViewById(currentId);
// Put the right data in the TextView
currentTextView.setText(currentUnitTextViewText);
}
}
public void updateUnitTextFieldUsingTsp(double doubleToConvert, Quantity.Unit currentUnit,
Quantity.Unit preferredUnit, TextView targetTextView){
Quantity currentQuantitySelected = new Quantity(doubleToConvert, currentUnit);
// Algorithm used quantityInTbs.to(Unit.tsp).to(Unit.ounce)
String tempTextViewText = currentQuantitySelected.to(Quantity.Unit.tsp).
to(preferredUnit).toString();
targetTextView.setText(tempTextViewText);
}
}
Android Manifest.xml
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.newthinktank.derekbanas.conversion" > <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/Theme.AppCompat" > <activity android:name=".MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>