基本上我有单一活动，在通过URL获取JSON数据后显示有关单个项目的信息。当我尝试nullpointerexception setVisibility.GONE内的单选按钮时，我得到onPostExecute（请查看logcat输出）。
添加if else语句以检查产品属于哪个类别。例如，Pizza可以有多种尺寸，因此我显示4种价格，而尺寸不适用于边线，因此只显示一个价格。所以为了实现这个功能，如果产品类别是“副业”，我试图隐藏其他3个radiobuttons。我希望你明白。
@Override
protected void onPostExecute(String file_url) {
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
@Override
public void run() {
/**
* Updating parsed JSON data into ListView
* */
if(check<=2)
{
Log.i("Check Value","The check value is" + check);
Log.i("Adapter:"," Category Value is less than 2");
ListAdapter adapter = new SimpleAdapter(
SingleItemActivity.this, selquesList,
R.layout.single_item_layout, new String[] { TAG_newPID,
TAG_NAME, TAG_INFO,TAG_SMALLPRICE,TAG_MEDIUMPRICE,TAG_LARGE,TAG_xLARGE },
new int[] { R.id.itemid, R.id.itemname, R.id.iteminfo,R.id.smallprice, R.id.mediumprice, R.id.largeprice,R.id.xlargeprice});
// updating listview
setListAdapter(adapter);
}
else
{
ListAdapter adapter2 = new SimpleAdapter(
SingleItemActivity.this, selquesList,
R.layout.single_item_layout, new String[] { TAG_newPID,
TAG_NAME, TAG_INFO, TAG_PRICE },
new int[] { R.id.itemid, R.id.itemname, R.id.iteminfo, R.id.price});
RadioButton mediumRadioButton = (RadioButton) findViewById(R.id.medium);
RadioButton largeRadioButton = (RadioButton) findViewById(R.id.large);
RadioButton xlargeRadioButton = (RadioButton) findViewById(R.id.xlarge);
Intent intentradiocheck = getIntent();
int radioavailcheck = intentradiocheck.getIntExtra("int_value", 0);
Log.i("SingleItemActivity","Value of radioavailcheck: "+radioavailcheck);
if(radioavailcheck > 2)
{
Log.i("SingleItemActivity","Inside the if loop because radioavailcheck>2");
mediumRadioButton.setVisibility(View.GONE);
largeRadioButton.setVisibility(View.GONE);
xlargeRadioButton.setVisibility(View.GONE);
}
setListAdapter(adapter2);
}
}
});
}
LogCat输出：
06-10 18:32:23.885: I/SingleItemActivity(306): Inside oncreate
06-10 18:32:24.704: D/dalvikvm(306): GC_FOR_MALLOC freed 3410 objects / 387688 bytes in 341ms
06-10 18:32:25.624: D/All Items:(306): {"success":1,"menu":[{"price":"3.95","itemID":"8","categoryID":"3","itemname":"Beer Nastro","iteminfo":"Beer","small":"0","large":"0","medium":"0","xlarge":"0","discount":"0"}]}
06-10 18:32:25.634: I/SingleItemActivity(306): Value of radioavailcheck: 3
06-10 18:32:25.634: I/SingleItemActivity(306): Inside the if loop because radioavailcheck>2
06-10 18:32:25.634: D/AndroidRuntime(306): Shutting down VM
06-10 18:32:25.634: W/dalvikvm(306): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
06-10 18:32:25.644: E/AndroidRuntime(306): FATAL EXCEPTION: main
06-10 18:32:25.644: E/AndroidRuntime(306): java.lang.NullPointerException
06-10 18:32:25.644: E/AndroidRuntime(306): at com.wbs.ginos.SingleItemActivity$LoadAllSelques$1.run(SingleItemActivity.java:243)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.app.Activity.runOnUiThread(Activity.java:3707)
06-10 18:32:25.644: E/AndroidRuntime(306): at com.wbs.ginos.SingleItemActivity$LoadAllSelques.onPostExecute(SingleItemActivity.java:207)
06-10 18:32:25.644: E/AndroidRuntime(306): at com.wbs.ginos.SingleItemActivity$LoadAllSelques.onPostExecute(SingleItemActivity.java:1)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.os.AsyncTask.finish(AsyncTask.java:417)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.os.AsyncTask.access$300(AsyncTask.java:127)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.os.Handler.dispatchMessage(Handler.java:99)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.os.Looper.loop(Looper.java:123)
06-10 18:32:25.644: E/AndroidRuntime(306): at android.app.ActivityThread.main(ActivityThread.java:4627)
06-10 18:32:25.644: E/AndroidRuntime(306): at java.lang.reflect.Method.invokeNative(Native Method)
06-10 18:32:25.644: E/AndroidRuntime(306): at java.lang.reflect.Method.invoke(Method.java:521)
06-10 18:32:25.644: E/AndroidRuntime(306): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-10 18:32:25.644: E/AndroidRuntime(306): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-10 18:32:25.644: E/AndroidRuntime(306): at dalvik.system.NativeStart.main(Native Method)
`
single_item_layout.xml中的Radiogroup代码
<RadioGroup
android:id="@+id/group1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="90"
android:orientation="vertical" >
<RadioButton
android:id="@+id/small"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true" />
<RadioButton
android:id="@+id/medium"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RadioButton
android:id="@+id/large"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RadioButton
android:id="@+id/xlarge"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RadioGroup>
答案 0 :(得分：0)
我的猜测是onPostExecute（）在调用setContentView（）之前完成。既然您似乎在onCreate中启动了AsyncTask，我建议您延迟到调用setContentView（）之后吗？ 如果这不是原因，那么单选按钮的ID是错误的。
在旁注中，您不需要添加对runOnUiThread()的调用，onPostExecute（）将始终在UI线程上运行，如下所述：http://android-developers.blogspot.ca/2009/05/painless-threading.html
答案 1 :(得分：0)
findViewById()将无法在ListView项目中找到单选按钮。这就是getView()的用途。
答案 2 :(得分：0)
您需要更改getView()或ViewBinder内的可见性。基本上，以下调用将返回null：
RadioButton mediumRadioButton = (RadioButton) findViewById(R.id.medium);
RadioButton largeRadioButton = (RadioButton) findViewById(R.id.large);
RadioButton xlargeRadioButton = (RadioButton) findViewById(R.id.xlarge);
因为您正在主布局中的ListView内搜索对象（ListView之外）