android– 如何从EditText处理华氏温度并打印其相应的摄氏温度？

概述我对在Android中创建监听器的概念感到困惑.我的程序的目的很简单：在单位之间进行转换(如华氏温度到摄氏温度,摄氏温度到华氏温度等).如何获取EditText对象中的文本,然后如何将其打印出来？我每次运行时都会收到错误(不幸的是,Converter.exe已停止.)这是我的代码到目前为止.请指教.im

我对在Android中创建监听器的概念感到困惑.我的程序的目的很简单：在单位之间进行转换(如华氏温度到摄氏温度,摄氏温度到华氏温度等).如何获取EditText对象中的文本,然后如何将其打印出来？我每次运行时都会收到错误(不幸的是,Converter.exe已停止.)这是我的代码到目前为止.请指教.

import androID.app.Activity;import androID.os.Bundle;import androID.vIEw.VIEw;import androID.Widget.button;import androID.Widget.EditText;import androID.Widget.TextVIEw;public class Converteractivity extends Activity{/** Called when the activity is first created. */@OverrIDepublic voID onCreate(Bundle savedInstanceState){    super.onCreate(savedInstanceState);    setContentVIEw(R.layout.main);    button button = (button) findVIEwByID(R.ID.temp_button);    button.setonClickListener(new VIEw.OnClickListener()     {        public voID onClick(VIEw v)        {            setContentVIEw(R.layout.body);        }    });      button ok = (button) findVIEwByID(R.ID.OK_button);    ok.setonClickListener(new VIEw.OnClickListener()     {        public voID onClick(VIEw v)        {            EditText et = (EditText) getText(0);            final int num = Integer.parseInt(et.toString());            double answer = (num - 32) * 5/9;            TextVIEw tv = (TextVIEw) findVIEwByID(R.ID.editText);            tv.setText(Double.toString(answer));        }    });}}

我也有两个布局(.xml)文件(我不确定这是否是正确的编程风格).

main只显示可以单击的按钮.然后,我点击按钮后出现第二个.xml文件.

main.xml中

<?xml version="1.0" enCoding="utf-8"?> <linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="fill_parent"androID:layout_height="fill_parent"androID:orIEntation="vertical" ><button    androID:ID="@+ID/temp_button"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="@string/F" /> <button    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="@string/C" /><button    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="@string/I" /><button    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="@string/Cm" /> </linearLayout>

body.xml(第二个) –

<?xml version="1.0" enCoding="utf-8"?><linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="fill_parent"androID:layout_height="wrap_content"androID:orIEntation="vertical" ><TextVIEw    androID:layout_wIDth="fill_parent"    androID:layout_height="wrap_content"    androID:layout_alignParentleft="true"    androID:text="Enter temperature:" /><EditText    androID:ID="@+ID/editText"    androID:layout_wIDth="fill_parent"    androID:layout_height="wrap_content"    androID:layout_alignParentleft="true"    androID:background="@androID:drawable/editBox_background"    androID:digits="1, 2, 3, 4, 5, 6, 7, 8, 9" /><button    androID:ID="@+ID/cancel_button"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="Cancel" /><button    androID:ID="@+ID/OK_button"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:text="OK" /> </linearLayout>

重申一下,我的问题出现在这段代码中：

 button ok = (button) findVIEwByID(R.ID.OK_button);   ok.setonClickListener(new VIEw.OnClickListener()    {       public voID onClick(VIEw v)        {            EditText et = (EditText) getText(0);            final int num = Integer.parseInt(et.toString());            double answer = (num - 32) * 5/9;           TextVIEw tv = (TextVIEw) findVIEwByID(R.ID.editText);           tv.setText(Double.toString(answer));        }   });

目的是从EditText对象中获取用户输入的数字,转换它并将其打印出来,但我不确定我是否正确,或者这是否在正确的位置.

**更新：这是日志.

02-06 19:53:36.148: D/AndroIDRuntime(529): Shutting down VM02-06 19:53:36.158: W/dalvikvm(529): threadID=1: thread exiting with uncaught exception (group=0x409c01f8)02-06 19:53:36.168: E/AndroIDRuntime(529): FATAL EXCEPTION: main02-06 19:53:36.168: E/AndroIDRuntime(529): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sapra.converter/com.sapra.converter.Converteractivity}: java.lang.NullPointerException02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:1956)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread.access0(ActivityThread.java:123)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.os.Handler.dispatchMessage(Handler.java:99)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.os.Looper.loop(Looper.java:137)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread.main(ActivityThread.java:4424)02-06 19:53:36.168: E/AndroIDRuntime(529):  at java.lang.reflect.Method.invokeNative(Native Method)02-06 19:53:36.168: E/AndroIDRuntime(529):  at java.lang.reflect.Method.invoke(Method.java:511)02-06 19:53:36.168: E/AndroIDRuntime(529):  at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)02-06 19:53:36.168: E/AndroIDRuntime(529):  at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:551)02-06 19:53:36.168: E/AndroIDRuntime(529):  at dalvik.system.NativeStart.main(Native Method)02-06 19:53:36.168: E/AndroIDRuntime(529): Caused by: java.lang.NullPointerException02-06 19:53:36.168: E/AndroIDRuntime(529):  at com.sapra.converter.Converteractivity.onCreate(Converteractivity.java:29)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.Activity.performCreate(Activity.java:4465)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)02-06 19:53:36.168: E/AndroIDRuntime(529):  at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:1920)02-06 19:53:36.168: E/AndroIDRuntime(529):  ... 11 more

解决方法:

这很简单,我想你可以从这里弄明白.

// This is the TextVIEw you set in your layout. It will display the temperature.    final TextVIEw tv = (TextVIEw) findVIEwByID(R.ID.tv);    // This sets up the EditText so you can capture the input and return the temperature.    final EditText edittext = (EditText) findVIEwByID(R.ID.et);    edittext.setonKeyListener(new OnKeyListener() {        public boolean onKey(VIEw v, int keyCode, KeyEvent event) {            // If the event is a key-down event on the "enter" button            if ((event.getAction() == KeyEvent.ACTION_DOWN)                    && (keyCode == KeyEvent.KEYCODE_ENTER)) {                // Perform action on key press                float f = float.parsefloat(edittext.getText().toString());                tv.setText(String.valueOf(convertCelciusToFahrenheit(f)));                return true;            }            return false;        }    });}// Converts to celciusprivate float convertFahrenheitToCelcius(float fahrenheit) {    return ((fahrenheit - 32) * 5 / 9);}// Converts to fahrenheitprivate float convertCelciusToFahrenheit(float celsius) {    return ((celsius * 9) / 5) + 32;}

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