好的，所以我实现了一个可搜索的列表视图。它还可以，但我希望listview项目有popupmenu。所以我试着在listview上设置一些代码来实现这个popupmenu，并显示另一个活动的完整项目细节。但是我得到了一个运行时异常，我不知道该怎么做。它说“无法在albusmActivity java.lang.NullPointerException上启动componentInfo”。任何帮助都会很棒。感谢。
@SuppressLint("NewApi")
public class AlbumsActivity extends ListActivity {ConnectionDetector cd;
AlertDialogManager alert = new AlertDialogManager();
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
ArrayList<HashMap<String, String>> albumsList;
// albums JSONArray
JSONArray albums = null;
EditText inputSearch;
ImageView imgClick;
SimpleAdapter adapter = null;
// albums JSON url
private static final String URL_ALBUMS = "http://api.androidhive.info/songs/album.php";
// ALL JSON node names
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_SONGS_COUNT = "songs_count";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_albums);
getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#3b5998")));
getActionBar().setIcon(new ColorDrawable(getResources().getColor(android.R.color.transparent)));
cd = new ConnectionDetector(getApplicationContext());
// Check for internet connection
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(AlbumsActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Hashmap for ListView
albumsList = new ArrayList<HashMap<String, String>>();
inputSearch = (EditText) findViewById(R.id.inputSearch);
inputSearch.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
// When user changed the Text
AlbumsActivity.this.adapter.getFilter().filter(cs.toString());
}
@Override
public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
}
});
// Loading Albums JSON in Background Thread
new LoadAlbums().execute();
// get listview
ListView lv = getListView();
/**
* Listview item click listener
* TrackListActivity will be lauched by passing album id
* */
lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// on selecting a single album
// TrackListActivity will be launched to show tracks inside the album
Intent i = new Intent(getApplicationContext(), TrackListActivity.class);
// send album id to tracklist activity to get list of songs under that album
String album_id = ((TextView) view.findViewById(R.id.album_id)).getText().toString();
i.putExtra("album_id", album_id);
startActivity(i);
}
});
imgClick = (ImageView) findViewById(R.id.row_click_imageView1);
imgClick.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v){
PopupMenu pop = new PopupMenu(AlbumsActivity.this,imgClick);
pop.getMenuInflater().inflate(R.menu.menu,pop.getMenu());
pop.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener(){
@Override
public boolean onMenuItemClick(MenuItem item){
Toast.makeText(AlbumsActivity.this,"text"+item.getTitle(),Toast.LENGTH_SHORT).show();
Intent intent = new Intent(AlbumsActivity.this,NexActivity.class);
startActivityForResult(intent, 2);
return true;
}
});
pop.show();
}
});
}
protected void onActivityResult(int requestCode, int resultCode, Intent data){
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == 2){
String message = data.getStringExtra("Message");
TextView text = (TextView) findViewById(R.layout.activity_main);
text.setText(message);
}
}
/**
* Background Async Task to Load all Albums by making http request
* */
class LoadAlbums extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AlbumsActivity.this);
pDialog.setMessage("Listing Albums ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting Albums JSON
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_ALBUMS, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Albums JSON: ", "> " + json);
try {
albums = new JSONArray(json);
if (albums != null) {
// looping through All albums
for (int i = 0; i < albums.length(); i++) {
JSONObject c = albums.getJSONObject(i);
// Storing each json item values in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String songs_count = c.getString(TAG_SONGS_COUNT);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_SONGS_COUNT, songs_count);
// adding HashList to ArrayList
albumsList.add(map);
}
}else{
Log.d("Albums: ", "null");
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all albums
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
/* ListAdapter adapter = new SimpleAdapter(
AlbumsActivity.this, albumsList,
R.layout.list_item_albums, new String[] { TAG_ID,
TAG_NAME, TAG_SONGS_COUNT }, new int[] {
R.id.album_id, R.id.album_name, R.id.songs_count });
// updating listview
setListAdapter(adapter);*/
AlbumsActivity.this.adapter = new SimpleAdapter(AlbumsActivity.this, albumsList, R.layout.list_item_albums, new String[] { TAG_ID, TAG_NAME, TAG_SONGS_COUNT }, new int[] {R.id.album_id, R.id.album_name, R.id.songs_count });
// updating listview
setListAdapter(AlbumsActivity.this.adapter);
}
});
}
}
}
this is the line from 138-144
@Override
public boolean onMenuItemClick(MenuItem item){
Toast.makeText(AlbumsActivity.this,"text"+item.getTitle(),Toast.LENGTH_SHORT).show();
Intent intent = new Intent(AlbumsActivity.this,NexActivity.class);
startActivityForResult(intent, 2);
return true;
}
这是我的日志详细信息
09-23 21:29:54.161: D/dalvikvm(867): Not late-enabling CheckJNI (already on)
09-23 21:29:55.721: E/Trace(867): error opening trace file: No such file or directory (2)
09-23 21:29:57.711: D/dalvikvm(867): GC_CONCURRENT freed 146K, 10% free 2626K/2912K, paused 10ms+16ms, total 138ms
09-23 21:29:57.882: D/AndroidRuntime(867): Shutting down VM
09-23 21:29:57.892: W/dalvikvm(867): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
09-23 21:29:57.992: E/AndroidRuntime(867): FATAL EXCEPTION: main
09-23 21:29:57.992: E/AndroidRuntime(867): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.projectsoftware/com.projectsoftware.AlbumsActivity}: java.lang.NullPointerException
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread.access$600(ActivityThread.java:141)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.os.Handler.dispatchMessage(Handler.java:99)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.os.Looper.loop(Looper.java:137)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread.main(ActivityThread.java:5041)
09-23 21:29:57.992: E/AndroidRuntime(867): at java.lang.reflect.Method.invokeNative(Native Method)
09-23 21:29:57.992: E/AndroidRuntime(867): at java.lang.reflect.Method.invoke(Method.java:511)
09-23 21:29:57.992: E/AndroidRuntime(867): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
09-23 21:29:57.992: E/AndroidRuntime(867): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
09-23 21:29:57.992: E/AndroidRuntime(867): at dalvik.system.NativeStart.main(Native Method)
09-23 21:29:57.992: E/AndroidRuntime(867): Caused by: java.lang.NullPointerException
09-23 21:29:57.992: E/AndroidRuntime(867): at com.projectsoftware.AlbumsActivity.onCreate(AlbumsActivity.java:138)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.Activity.performCreate(Activity.java:5104)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
09-23 21:29:57.992: E/AndroidRuntime(867): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
09-23 21:29:57.992: E/AndroidRuntime(867): ... 11 more
09-23 21:30:06.961: I/Process(867): Sending signal. PID: 867 SIG: 9
答案 0 :(得分：0)
当onPostExecute你已经在Ui Thread上运行了。
protected void onPostExecute(String file_url) {
pDialog.dismiss();
AlbumsActivity.this.adapter = new SimpleAdapter(AlbumsActivity.this, albumsList, R.layout.list_item_albums, new String[] { TAG_ID, TAG_NAME, TAG_SONGS_COUNT }, new int[] {R.id.album_id, R.id.album_name, R.id.songs_count });
setListAdapter(AlbumsActivity.this.adapter);
}
你的textview定义是错误的使用
TextView text = (TextView) findViewById(R.id.textView1);
而不是
TextView text = (TextView) findViewById(R.layout.activity_main);
答案 1 :(得分：0)
@santalu - 这是138-144的行
@Override
public boolean onMenuItemClick(MenuItem item){
Toast.makeText(AlbumsActivity.this,"text"+item.getTitle(),Toast.LENGTH_SHORT).show();
Intent intent = new Intent(AlbumsActivity.this,NexActivity.class);
startActivityForResult(intent, 2);
return true;
}