在ArrayList中遇到了NullPointerException
。我使用下面的代码记录ArrayList的大小,但我总是得到NPE。
可能的原因是什么?
Log.d("catArrayList:Size:New", ""+categoryArrayList.size());
这里有更多的代码:
protected void onPostExecute(Boolean result) {
dialog.cancel();
Log.d("catArrayList:Size", ""+categoryArrayList.size());
Log.d("typArrayList:Size", ""+typeArrayList.size());
Log.d("serArrayList:Size", ""+serviceArrayList.size());
Log.d("cArrayList:Size", ""+cArrayList.size());
Log.d("tArrayList:Size", ""+tArrayList.size());
Log.d("sArrayList:Size", ""+sArrayList.size());
Category c = categoryArrayList.get(0);
typeArrayList = c.getTypeArrayList();
Log.d("catArrayList:Size:New", ""+categoryArrayList.size());
for(int i=0;i<typeArrayList.size();i++) {
tArrayList.add(typeArrayList.get(i).getName());
}
spinner1.setAdapter(new ArrayAdapter<String>(CategoryActivity.this,
android.R.layout.simple_spinner_dropdown_item,
cArrayList));
spinner2.setAdapter(new ArrayAdapter<String>(CategoryActivity.this,
android.R.layout.simple_spinner_dropdown_item,
tArrayList));
spinner3.setAdapter(new ArrayAdapter<String>(CategoryActivity.this,
android.R.layout.simple_spinner_dropdown_item,
sArrayList));
}
日志显示:
09-12 11:05:54.585: D/catArrayList:Size(30919): 2
09-12 11:05:54.585: D/typArrayList:Size(30919): 2
09-12 11:05:54.585: D/serArrayList:Size(30919): 2
09-12 11:05:54.585: D/cArrayList:Size(30919): 2
09-12 11:05:54.590: D/tArrayList:Size(30919): 2
09-12 11:05:54.590: D/sArrayList:Size(30919): 2
09-12 11:05:54.590: D/AndroidRuntime(30919): Shutting down VM
09-12 11:05:54.590: W/dalvikvm(30919): threadid=1: thread exiting with uncaught exception (group=0x40f9f2a0)
09-12 11:05:54.590: E/AndroidRuntime(30919): FATAL EXCEPTION: main
09-12 11:05:54.590: E/AndroidRuntime(30919): java.lang.NullPointerException
09-12 11:05:54.590: E/AndroidRuntime(30919): at com.example.modulewise.CategoryActivity$JSONAsyncTask.onPostExecute(CategoryActivity.java:178)
09-12 11:05:54.590: E/AndroidRuntime(30919): at com.example.modulewise.CategoryActivity$JSONAsyncTask.onPostExecute(CategoryActivity.java:1)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.os.AsyncTask.finish(AsyncTask.java:631)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.os.AsyncTask.access$600(AsyncTask.java:177)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.os.Handler.dispatchMessage(Handler.java:99)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.os.Looper.loop(Looper.java:137)
09-12 11:05:54.590: E/AndroidRuntime(30919): at android.app.ActivityThread.main(ActivityThread.java:4921)
09-12 11:05:54.590: E/AndroidRuntime(30919): at java.lang.reflect.Method.invokeNative(Native Method)
09-12 11:05:54.590: E/AndroidRuntime(30919): at java.lang.reflect.Method.invoke(Method.java:511)
09-12 11:05:54.590: E/AndroidRuntime(30919): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1036)
09-12 11:05:54.590: E/AndroidRuntime(30919): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:803)
09-12 11:05:54.590: E/AndroidRuntime(30919): at dalvik.system.NativeStart.main(Native Method)
178
行吗? - ρяσѕρєя KcategoryArrayList
是空的。我们无法确定它的来源,所以也不知道原因。 - JB Nizet