Android攻略--单位转化器UC--Units Converter(学习笔记)

1创建工程

注意这个名称的命名：

3. UC结构及相关代码

UC.java 用于执行单位换算的Activity

// UC.java

package com.apress.uc;

import android.app.Activity;

import android.os.Bundle;

import android.text.Editable;
import android.text.TextWatcher;

import android.view.View;

import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;

public class UC extends Activity
{
   private int position = 0;

   private double[] multipliers =
   {
      0.0015625,         // Acres to square miles
      101325.0,          // Atmospheres to Pascals
      100000.0,          // Bars to Pascals
      0,                 // Degrees Celsius to Degrees Fahrenheit (placeholder)
      0,                 // Degrees Fahrenheit to Degrees Celsius (placeholder)
      0.00001,           // Dynes to Newtons
      0.3048,            // Feet/Second to Metres/Second
      0.0284130625,      // Fluid Ounces (UK) to Litres
      0.0295735295625,   // Fluid Ounces (US) to Litres
      746.0,             // Horsepower (electric) to Watts
      735.499,           // Horsepower (metric) to Watts
      1/1016.0469088,    // Kilograms to Tons (UK or long)
      1/907.18474,       // Kilograms to Tons (US or short)
      1/0.0284130625,    // Litres to Fluid Ounces (UK)
      1/0.0295735295625, // Litres to Fluid Ounces (US)
      331.5,             // Mach Number to Metres/Second
      1/0.3048,          // Metres/Second to Feet/Second
      1/331.5,           // Metres/Second to Mach Number
      0.833,             // Miles/Gallon (UK) to Miles/Gallon (US)
      1/0.833,           // Miles/Gallon (US) to Miles/Gallon (UK)
      100000.0,          // Newtons to Dynes
      1/101325.0,        // Pascals to Atmospheres
      0.00001,           // Pascals to Bars
      640.0,             // Square Miles to Acres
      1016.0469088,      // Tons (UK or long) to Kilograms
      907.18474,         // Tons (US or short) to Kilograms
      1/746.0,           // Watts to Horsepower (electic)
      1/735.499          // Watts to Horsepower (metric)
   };

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);

      final EditText etUnits = (EditText) findViewById(R.id.units);

      final Spinner spnConversions = (Spinner) findViewById(R.id.conversions);
      ArrayAdapter<CharSequence> aa;
      aa = ArrayAdapter.
             createFromResource(this, R.array.conversions,
                                android.R.layout.simple_spinner_item);
      aa.setDropDownViewResource(android.R.layout.simple_spinner_item);
      spnConversions.setAdapter(aa);

      AdapterView.OnItemSelectedListener oisl;
      oisl = new AdapterView.OnItemSelectedListener()
      {
         @Override
         public void onItemSelected(AdapterView<?> parent, View view,
                                    int position, long id)
         {
            UC.this.position = position;
         }

         @Override
         public void onNothingSelected(AdapterView<?> parent)
         {
            System.out.println("nothing");
         }
      };
      spnConversions.setOnItemSelectedListener(oisl);

      final Button btnClear = (Button) findViewById(R.id.clear);
      AdapterView.OnClickListener ocl;
      ocl = new AdapterView.OnClickListener()
      {
         @Override
         public void onClick(View v)
         {
            etUnits.setText("");
         }
      };
      btnClear.setOnClickListener(ocl);
      btnClear.setEnabled(false);

      final Button btnConvert = (Button) findViewById(R.id.convert);
      ocl = new AdapterView.OnClickListener()
      {
         @Override
         public void onClick(View v)
         {
            String text = etUnits.getText().toString();
            double input = Double.parseDouble(text);
            double result = 0;
            if (position == 3)
               result = input*9.0/5.0+32; // Celsius to Fahrenheit
            else
            if (position == 4)
               result = (input-32)*5.0/9.0; // Fahrenheit to Celsius
            else
               result = input*multipliers[position];
            etUnits.setText(""+result);
         }
      };
      btnConvert.setOnClickListener(ocl);
      btnConvert.setEnabled(false);

      Button btnClose = (Button) findViewById(R.id.close);
      ocl = new AdapterView.OnClickListener()
      {
         @Override
         public void onClick(View v)
         {
            finish();
         }
      };
      btnClose.setOnClickListener(ocl);

      TextWatcher tw;
      tw = new TextWatcher()
      {
         @Override
         public void afterTextChanged(Editable s)
         {
         }

         @Override
         public void beforeTextChanged(CharSequence s, int start, int count,
                                       int after)
         {
         }

         @Override
         public void onTextChanged(CharSequence s, int start, int before,
                                   int count)
         {
            if (etUnits.getText().length() == 0)
            {
               btnClear.setEnabled(false);
               btnConvert.setEnabled(false);
            }
            else
            {
               btnClear.setEnabled(true);
               btnConvert.setEnabled(true);
            }
         }
      };
      etUnits.addTextChangedListener(tw);
   }
}

main.xml  用于保存小部件和布局信息的main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:gravity="center_vertical"
   android:background="@drawable/gradientbg"
   android:padding="5dip">
   <LinearLayout android:layout_width="fill_parent"
      android:layout_height="wrap_content">
      <TextView android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginRight="10dip"
         android:text="@string/units"
         android:textColor="#000000"
         android:textSize="15sp"
         android:textStyle="bold"/>
      <EditText android:id="@+id/units"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:hint="type a number"
         android:inputType="numberDecimal|numberSigned"
         android:maxLines="1"/>
   </LinearLayout>
   <Spinner android:id="@+id/conversions"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:prompt="@string/prompt"/>
   <LinearLayout android:layout_width="fill_parent"
      android:layout_height="wrap_content">
      <Button android:id="@+id/clear"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:text="@string/clear"/>
      <Button android:id="@+id/convert"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:text="@string/convert"/>
      <Button android:id="@+id/close"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:text="@string/close"/>
   </LinearLayout>
</LinearLayout>

strings.xml 保存了应用中的字符串

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <string name="app_name">Units Converter</string>
   <string name="clear">Clear</string>
   <string name="close">Close</string>
   <string name="convert">Convert</string>
   <string name="prompt">Select a conversion</string>
   <string name="units">Units</string>
</resources>

arrays.xml 文件中保存了换算类型的字符串数组

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <string-array name="conversions">
      <item>Acres to Square Miles</item>
      <item>Atmospheres to Pascals</item>
      <item>Bars to Pascals</item>
      <item>Degrees Celsius to Degrees Fahrenheit</item>
      <item>Degrees Fahrenheit to Degrees Celsius</item>
      <item>Dynes to Newtons</item>
      <item>Feet/Second to Metres/Second</item>
      <item>Fluid Ounces (UK) to Litres</item>
      <item>Fluid Ounces (US) to Litres</item>
      <item>Horsepower (electric) to Watts</item>
      <item>Horsepower (metric) to Watts</item>
      <item>Kilograms to Tons (UK or long)</item>
      <item>Kilograms to Tons (US or short)</item>
      <item>Litres to Fluid ounces (UK)</item>
      <item>Litres to Fluid ounces (US)</item>
      <item>Mach Number to Metres/Second</item>
      <item>Metres/Second to Feet/Second</item>
      <item>Metres/Second to Mach Number</item>
      <item>Miles/Gallon (UK) to Miles/Gallon (US)</item>
      <item>Miles/Gallon (US) to Miles/Gallon (UK)</item>
      <item>Newtons to Dynes</item>
      <item>Pascals to Atmospheres</item>
      <item>Pascals to Bars</item>
      <item>Square Miles to Acres</item>
      <item>Tons (UK or long) to Kilograms</item>
      <item>Tons (US or short) to Kilograms</item>
      <item>Watts to Horsepower (electric)</item>
      <item>Watts to Horsepower (metric)</item>
   </string-array>
</resources>

gradientbg.xml 文件保存了用于Activity背景色的渐变形状

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
   <gradient android:startColor="#fccb06" 
      android:endColor="#fd6006"
      android:angle="270"/>
   <corners android:radius="10dp"/>
</shape>

4 虚拟机运行结果

注意：

其中的uc.xml 换成以下代码可以运行

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.apress.uc.UC" >
</menu>