Question

我正在制作一个简单的YouTube播放应用程序，似乎我被自定义列表视图适配器困住了。当我运行应用程序时，它会抛出有关java.lang.NullPointerException的错误。我似乎无法弄清楚问题。

这是主要的活动

public class MainActivity extends AppCompatActivity {
    private EditText searchInput;
    private ListView videosFound;
    private List<VideoItem> searchResults;
    private Handler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        searchInput = (EditText) findViewById(R.id.search_input);
        videosFound = (ListView) findViewById(R.id.videos_found);

        handler = new Handler();

        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 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);
            }

        });
    }

    private void searchOnYoutube(final String keywords) {
        new Thread() {
            public void run() {
                YoutubeConnector yc = new YoutubeConnector(MainActivity.this);
                searchResults = yc.search(keywords);
                handler.post(new Runnable() {
                    public void run() {
                        updateVideosFound();
                    }
                });
            }
        }.start();
    }

    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);
                }

                VideoItem searchResult = searchResults.get(position);

                ImageView thumbnail = (ImageView) convertView.findViewById(R.id.vid_thumbnail);
                TextView title = (TextView) convertView.findViewById(R.id.vid_title);
                TextView description = (TextView) convertView.findViewById(R.id.vid_desc);

                Picasso.with(getApplicationContext()).load(searchResult.getThumbnailURL()).into(thumbnail);
                title.setText(searchResult.getTitle());
                description.setText(searchResult.getDescription());
                return convertView;
            }
        };
        videosFound.setAdapter(adapter);
    }
}

这是LogCat

10-12 17:49:44.624 16028-16028/com.example.fadil.youtubeplayer W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x41678d58)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime: FATAL EXCEPTION: main
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime: Process: com.example.fadil.youtubeplayer, PID: 16028
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime: java.lang.NullPointerException
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.widget.ListView.setAdapter(ListView.java:480)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at com.example.fadil.youtubeplayer.MainActivity.updateVideosFound(MainActivity.java:104)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at com.example.fadil.youtubeplayer.MainActivity.access$200(MainActivity.java:25)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at com.example.fadil.youtubeplayer.MainActivity$3$1.run(MainActivity.java:75)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:733)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:95)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:136)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5113)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:515)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
10-12 17:49:44.634 16028-16028/com.example.fadil.youtubeplayer E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
10-12 17:49:48.184 16028-16028/com.example.fadil.youtubeplayer I/Process: Sending signal. PID: 16028 SIG: 9

请看看并帮助我。：）

Answer 1

我的猜测是你没有为searchResults分配任何值。您对searchResults = yc.search(keywords);的呼叫是异步呼叫吗？如果是，则提前致电updateVideosFound();。您应该等待响应，然后调用此方法。

Android编程java.lang.NullPointerException自定义适配器

1 个答案: