我目前卡住了Logcat的以下错误.我已经查看了其他十多个与此问题类似的帖子,但找不到我的问题的解决方案.
03-22 17:55:58.777: E/Trace(1172): error opening trace file: No such file or directory (2)
03-22 17:55:58.947: E/AndroidRuntime(1172): FATAL EXCEPTION: main
03-22 17:55:58.947: E/AndroidRuntime(1172): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.schoolwork.capstoneproject/com.schoolwork.capstoneproject.StartingPoint}: java.lang.NullPointerException
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.os.Handler.dispatchMessage(Handler.java:99)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.os.Looper.loop(Looper.java:137)
03-22 17:55:58.947: E/AndroidRuntime(1172): at android.app.ActivityThread.main(ActivityThread.java:5039)
03-22 17:55:58.947: E/AndroidRuntime(1172): at java.lang.reflect.Method.invokeNative(Native Method)
03-22 17:55:58.947: E/AndroidRuntime(1172): at java.lang.reflect.Method.invoke(Method.java:511)
03-22 17:55:58.947: E/AndroidRuntime(1172): at …我正在尝试创建一个小HTML表单,我的用户需要从复选框和下拉列表中选择一些选项.预期结果是在用户更改其选择时动态生成的文本.这个想法确实有效,但我不断从下拉框中获取"[object HTMLSelectElement]"而不是所选选项的值.如果你们中的一位经验丰富的JavaScript程序员能给我你的意见我会非常感激!我花了很多时间仔细检查所有内容,我很确定我的代码在语法上是正确的,但是如果没有意识到,我可能完全错了.我是JavaScript的新手,所以我还处于学习阶段.
HTML代码:
<form name="input" action="" method="get">
<input type="checkbox" name="stCode" id="ai1" onChange="generateSTcode()">
Analog Input B1
<select name="sensorType" id="sensorType1" onChange="generateSTcode()">
<option value="2">0-1 Vdc</option>
<option value="3">0-10 Vdc</option>
<option value="4">4-20mA</option>
<option value="5">Off/On</option>
<option value="6">0-5 Vdc</option>
</select>
<select name="sensor" id="sensor1" onChange="generateSTcode()">
<option value="oatp_ai">Outside air temperature</option>
<option value="satp_ai">Supply air temperature</option>
<option value="ratp_ai">Return air temperature</option>
<option value="mxtp_ai">Mixed air temperature</option>
</select><br><br>
<input type="checkbox" name="stCode" id="ai2" onChange="generateSTcode()">
Analog Input B2
<select name="sensorType" id="sensorType2" onChange="generateSTcode()">
<option value="2">0-1 Vdc</option>
<option value="3">0-10 Vdc</option>
<option value="4">4-20mA</option>
<option value="5">Off/On</option>
<option value="6">0-5 Vdc</option>
</select> …