udacityAS学习笔记.1.2-1.3

此部分笔记的主要内容是优达学城网上课程的简单交互与面向对象编程。然后在此的基础之上完成一个coffee购买的app。相对而言是简单易懂的，详情可以参阅我的github：WilliamYi96。

以下是xml源码：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_main"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.example.dell1.justjava.MainActivity">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="quantity"        android:textAllCaps="true"        android:paddingBottom="16dp"        android:textSize="16sp"/>    <LinearLayout        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:paddingBottom="16dp">        <Button            android:layout_width="48dp"            android:layout_height="48dp"            android:text="+"            android:onClick="increment"/>        <TextView            android:id="@+id/quantity_text_view"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:paddingLeft="8dp"            android:paddingBottom="16dp"            android:paddingRight="8dp"            android:text="2"            android:textSize="16sp"            android:textColor="#000"/>        <Button            android:layout_width="48dp"            android:layout_height="48dp"            android:text="-"            android:onClick="decrement"/>    </LinearLayout>    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="price(￥5 each)"        android:textAllCaps="true"        android:textSize="16sp"        android:paddingBottom="16dp"/>    <TextView        android:id="@+id/price_text_view"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="￥10"        android:textColor="#000"        android:textSize="16sp"        android:paddingBottom="16dp"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="ORDER"        android:onClick="submitOrder"/></LinearLayout>

以下是MainActivity.java文件：

package com.example.dell1.justjava;import android.icu.text.NumberFormat;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.TextView;public class MainActivity extends AppCompatActivity {    int quantity = 2;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    public void increment(View view) {        quantity++;        display(quantity);    }    public void decrement(View view) {        quantity--;        display(quantity);    }    public void submitOrder(View view) {        int price = quantity * 5;        String priceMessage = "Total: ￥" + price;        priceMessage = priceMessage + "\nThank you!";        display(quantity);        //displayPrice(price);        displayMessage(priceMessage);    }    private void display(int number) {        TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);        quantityTextView.setText("" + number);    }    private void displayPrice(int number) {        TextView priceTextView = (TextView) findViewById(R.id.price_text_view);        priceTextView.setText("￥" + number + ".00");    }    private void displayMessage(String message) {        TextView priceTextView = (TextView) findViewById(R.id.price_text_view);        priceTextView.setText(message);    }}

以下是项目展示图：