我的活动正在崩溃 - 我想这可能是因为我的适配器无法找到活动。我希望在活动中看到我的ListView，但我看不到它。
这是我的HacibabaActivity.java：
package arslan.aybars.menudroid.hacibaba;
import java.util.ArrayList;
import java.util.List;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.ListView;
import android.widget.Toast;
import arslan.aybars.menudroid.MainActivity;
import arslan.aybars.menudroid.R;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
public class HacibabaActivity extends Activity {
// Log tag
private static final String TAG = HacibabaActivity.class.getSimpleName();
// Movies json url
private static final String url = "http://api.androidhive.info/json/movies.json";
private ProgressDialog pDialog;
private List<Movie> movieList = new ArrayList<Movie>();
private ListView listView;
private CustomListAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_hacibaba);
listView = (ListView) findViewById(R.id.list);
adapter = new CustomListAdapter(this, movieList);
listView.setAdapter(adapter);
pDialog = new ProgressDialog(this);
// Showing progress dialog before making http request
pDialog.setMessage("Loading...");
pDialog.show();
// changing action bar color
getActionBar().setBackgroundDrawable(
new ColorDrawable(Color.parseColor("#D1D1D4")));
// Creating volley request obj
JsonArrayRequest movieReq = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
hidePDialog();
// Parsing json
for (int i = 0; i < response.length(); i++) {
try {
JSONObject obj = response.getJSONObject(i);
Movie movie = new Movie();
movie.setTitle(obj.getString("title"));
movie.setThumbnailUrl(obj.getString("image"));
// adding movie to movies array
movieList.add(movie);
} catch (JSONException e) {
e.printStackTrace();
}
}
// notifying list adapter about data changes
// so that it renders the list view with updated data
adapter.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
hidePDialog();
}
});
// Adding request to request queue
AppController.getInstance().addToRequestQueue(movieReq);
}
@Override
public void onDestroy() {
super.onDestroy();
hidePDialog();
}
private void hidePDialog() {
if (pDialog != null) {
pDialog.dismiss();
pDialog = null;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
这是我的适配器：
package arslan.aybars.menudroid.hacibaba;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import arslan.aybars.menudroid.R;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.NetworkImageView;
public class CustomListAdapter extends BaseAdapter {
private Activity activity;
private LayoutInflater inflater;
private List<Movie> movieItems;
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
public CustomListAdapter(Activity activity, List<Movie> movieItems) {
this.activity = activity;
this.movieItems = movieItems;
}
@Override
public int getCount() {
return movieItems.size();
}
@Override
public Object getItem(int location) {
return movieItems.get(location);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (inflater == null)
inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (convertView == null)
convertView = inflater.inflate(R.layout.list_row, null);
if (imageLoader == null)
imageLoader = AppController.getInstance().getImageLoader();
NetworkImageView thumbNail = (NetworkImageView) convertView
.findViewById(R.id.thumbnail);
TextView title = (TextView) convertView.findViewById(R.id.title);
// getting movie data for the row
Movie m = movieItems.get(position);
// thumbnail image
thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader);
// title
title.setText(m.getTitle());
return convertView;
}
}
以下是LogCat给我的错误：
01-13 03:18:56.470: D/AndroidRuntime(4970): Shutting down VM
01-13 03:18:56.470: W/dalvikvm(4970): threadid=1: thread exiting with uncaught exception (group=0xa4b62648)
01-13 03:18:56.474: E/AndroidRuntime(4970): FATAL EXCEPTION: main
01-13 03:18:56.474: E/AndroidRuntime(4970): java.lang.RuntimeException: Unable to start activity ComponentInfo{arslan.aybars.menudroid/arslan.aybars.menudroid.hacibaba.HacibabaActivity}: java.lang.NullPointerException
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.os.Handler.dispatchMessage(Handler.java:99)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.os.Looper.loop(Looper.java:137)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread.main(ActivityThread.java:5103)
01-13 03:18:56.474: E/AndroidRuntime(4970): at java.lang.reflect.Method.invokeNative(Native Method)
01-13 03:18:56.474: E/AndroidRuntime(4970): at java.lang.reflect.Method.invoke(Method.java:525)
01-13 03:18:56.474: E/AndroidRuntime(4970): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
01-13 03:18:56.474: E/AndroidRuntime(4970): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-13 03:18:56.474: E/AndroidRuntime(4970): at dalvik.system.NativeStart.main(Native Method)
01-13 03:18:56.474: E/AndroidRuntime(4970): Caused by: java.lang.NullPointerException
01-13 03:18:56.474: E/AndroidRuntime(4970): at arslan.aybars.menudroid.hacibaba.CustomListAdapter.<init>(CustomListAdapter.java:21)
01-13 03:18:56.474: E/AndroidRuntime(4970): at arslan.aybars.menudroid.hacibaba.HacibabaActivity.onCreate(HacibabaActivity.java:45)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.Activity.performCreate(Activity.java:5133)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-13 03:18:56.474: E/AndroidRuntime(4970): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
01-13 03:18:56.474: E/AndroidRuntime(4970): ... 11 more
AppController.class
package arslan.aybars.menudroid.hacibaba;
import android.app.Application;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;
public class AppController extends Application {
public static final String TAG = AppController.class.getSimpleName();
private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;
private static AppController mInstance;
@Override
public void onCreate() {
super.onCreate();
mInstance = this;
}
public static synchronized AppController getInstance() {
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(getApplicationContext());
}
return mRequestQueue;
}
public ImageLoader getImageLoader() {
getRequestQueue();
if (mImageLoader == null) {
mImageLoader = new ImageLoader(this.mRequestQueue,
new LruBitmapCache());
}
return this.mImageLoader;
}
public <T> void addToRequestQueue(Request<T> req, String tag) {
// set the default tag if tag is empty
req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
getRequestQueue().add(req);
}
public <T> void addToRequestQueue(Request<T> req) {
req.setTag(TAG);
getRequestQueue().add(req);
}
public void cancelPendingRequests(Object tag) {
if (mRequestQueue != null) {
mRequestQueue.cancelAll(tag);
}
}
}
我运行app并在此处崩溃：adapter = new CustomListAdapter(this, movieList);
我不知道该怎么做。我需要使用asynTask吗？
答案 0 :(得分：2)
看起来你的适配器中存在问题：
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
getInstance（）返回null，看起来你的AppController中的mInstance还没有被初始化。
您是否在Manifest.xml文件中指定了自定义Application类的名称？
<application android:icon="@drawable/icon" android:label="@string/app_name"
android:name="arslan.aybars.menudroid.hacibaba.AppController">