【发布时间】：2016-03-25 00:53:25
【问题描述】：
由于某种原因，当它确实不为空时，我得到一个指向 videosFound 的空指针异常。甚至传入的参数 adapter 也不为空。我只需打印出它是否为空（它们都不是空的）来检查和验证这一点。那么有人可以告诉我我是如何得到这个错误的吗？
private ListView videosFound;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
searchInput = (EditText)findViewById(R.id.search_input);
videosFound = (ListView)findViewById(R.id.videos_found);
handler = new Handler();
addClickListener();
searchInput.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_DONE) {
searchOnYoutube(v.getText().toString());
return false;
}
return true;
}
});
}
private void updateVideosFound(){
ArrayAdapter<VideoItem> adapter = new ArrayAdapter<VideoItem>(getApplicationContext(), R.layout.video_item, searchResults){
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
convertView = getLayoutInflater().inflate(R.layout.video_item, parent, false);
}
ImageView thumbnail = (ImageView)convertView.findViewById(R.id.video_thumbnail);
TextView title = (TextView)convertView.findViewById(R.id.video_title);
TextView description = (TextView)convertView.findViewById(R.id.video_description);
VideoItem searchResult = searchResults.get(position);
Picasso.with(getApplicationContext()).load(searchResult.getThumbnailURL()).into(thumbnail);
title.setText(searchResult.getTitle());
description.setText(searchResult.getDescription());
return convertView;
}
};
if(videosFound == null){
System.out.println("videoFound is null***********");
}else{
System.out.println("videoFound is NOT null***********");
}
if(adapter == null){
System.out.println("adapter is null***********");
}else{
System.out.println("adapter is NOT null***********");
}
videosFound.setAdapter(adapter);//ERROR HERE. neither videosFound no adapter are null
}
private void addClickListener(){
videosFound.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> av, View v, int pos,
long id) {
Intent intent = new Intent(getApplicationContext(), PlayerActivity.class);
intent.putExtra("VIDEO_ID", searchResults.get(pos).getId());
startActivity(intent);
}
});
}
XML
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/search"
android:id="@+id/search_input"
android:singleLine="true" />
<ListView
android:id="@+id/videos_found"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:dividerHeight="5dp" />
</LinearLayout>
控制台：
03-24 18:04:31.833 17014-17440/com.example.shawn.myyoutube D/YC: Could not search: com.google.api.client.googleapis.json.GoogleJsonResponseException: 403 Forbidden
{
"code" : 403,
"errors" : [ {
"domain" : "usageLimits",
"message" : "There is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your API key configuration if request from this IP or referer should be allowed.",
"reason" : "ipRefererBlocked",
"extendedHelp" : "https://console.developers.google.com"
} ],
"message" : "There is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your API key configuration if request from this IP or referer should be allowed."
}
03-24 18:04:31.833 17014-17014/com.example.shawn.myyoutube I/System.out: videoFound is NOT null***********
03-24 18:04:31.833 17014-17014/com.example.shawn.myyoutube I/System.out: adapter is NOT null***********
03-24 18:04:31.843 17014-17014/com.example.shawn.myyoutube D/AndroidRuntime: Shutting down VM
03-24 18:04:31.843 17014-17014/com.example.shawn.myyoutube E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.shawn.myyoutube, PID: 17014
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
at android.widget.ListView.setAdapter(ListView.java:502)
at com.example.shawn.myyoutube.SearchActivity.updateVideosFound(SearchActivity.java:98)
at com.example.shawn.myyoutube.SearchActivity.access$200(SearchActivity.java:23)
at com.example.shawn.myyoutube.SearchActivity$2$1.run(SearchActivity.java:61)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
【问题讨论】：
-
你能发布堆栈跟踪吗？
-
我认为是
searchResults，即null。 -
当您设置适配器时，该调用的一部分会获取计数，这是发生 NPE 的位置，但这不在您的代码中，因此该行是唯一可以将错误显示为的人类可读行其余的在 Android 代码中。
-
@bobdylan 我必须承认，我有点惊讶你在
ArrayAdapter构造函数中没有得到NullPointerException- 但这是android，所以希望它有点废话。您可以从堆栈跟踪中看到它不能是videosFound，即null- 如果是，那么方法setAdapter将不会被执行。始终查看最顶部 - 在这种情况下，在接受的答案中突出显示的行。
标签： java android nullpointerexception android-adapter