下面是我的listview适配器，当我点击一个项目跳转到下一个活动并返回之后，它不会显示这些项目。数据从数据库接收。
public class CropSelectionActivity extends Activity implements
android.widget.AdapterView.OnItemClickListener {
private static final String TAG = CropSelectionActivity.class.getName();
private static CropsAdapter listAdapter;
private static ListView listView;
public static String selectedCrop = null;
private static PendingIntent pendingIntent;
private static AlarmManager alarmManager;
private static PendingIntent pendingIntent1;
private static AlarmManager alarmManager1;
private static final long SYNCALARAMINTERVEL = 15 * 60 * 1000;
private static final long DELETIONINTERVEL = 15 * 60 * 1000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.displaypoints);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
Log.i(TAG, "----onCreate()-----");
fireAlarm();
final String details[] = DALAccessLayer.getUserMailAndId(CropSelectionActivity.this);
ActionBar actionbar = getActionBar();
actionbar.setTitle("Esap Expert"+"("+details[1]+")");
actionbar.setHomeButtonEnabled(true);
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork() // or .detectAll() for all detectable problems
.penaltyLog()
.build());
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
.penaltyLog()
.penaltyDeath()
.build());
listView = (ListView) findViewById(R.id.list);
listView.setOnItemClickListener(this);
listAdapter = new CropsAdapter(this,R.layout.listview);
}
@Override
protected void onPostResume() {
super.onPostResume();
Map<String, Integer> list = DALAccessLayer.getCrops(getApplicationContext(), DatabaseConstantsString.status_unresolve.getValue(), "0");
int pointsCount = 0;
for (String key : list.keySet()) {
CropPojo cp = new CropPojo();
cp.setCropName(key);
pointsCount = pointsCount+list.get(key);
Log.i(TAG, "pointsCount ="+pointsCount);
cp.setCount(list.get(key));
listAdapter.add(cp);
}
listView.setAdapter(listAdapter);
Log.i(TAG, "number of existing points ="+pointsCount);
}
@Override
protected void onDestroy() {
super.onDestroy();
listAdapter.clear();
listView.setAdapter(listAdapter);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
CropPojo cp = (CropPojo) listView.getItemAtPosition(position);
selectedCrop = cp.getCropName();
Intent intent = new Intent(this, DisplayPoints.class);
startActivity(intent);
}
@Override
public void onBackPressed() {
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.mainmenu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
switch (item.getItemId()){
case R.id.logout:
Intent i = new Intent(getApplicationContext(),MainActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(i);
return true;
case R.id.refresh:
startService(new Intent(getApplicationContext(), MyService.class));
return true;
case R.id.getexpertporfile:
CommunicationHandler.getExpertProfile(getApplicationContext());
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public class CropsAdapter extends ArrayAdapter<CropPojo>{
private int textViewResourceId;
public CropsAdapter(Context context, int textViewResourceId) {
super(context, textViewResourceId);
this.textViewResourceId = textViewResourceId;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final View view = getWorkingView(convertView);
final ViewHolder viewHolder = getViewHolder(view);
final CropPojo cropPojo = getItem(position);
viewHolder.titleView.setText(cropPojo.getCropName());
viewHolder.locationView.setText(String.valueOf(cropPojo.getCount()));
return view;
}
private View getWorkingView(final View convertView) {
// The workingView is basically just the convertView re-used if possible
// or inflated new if not possible
View workingView = null;
if(null == convertView) {
final Context context = getContext();
final LayoutInflater inflater = (LayoutInflater)context.getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
workingView = inflater.inflate(textViewResourceId, null);
} else {
workingView = convertView;
}
return workingView;
}
private ViewHolder getViewHolder(final View workingView) {
// The viewHolder allows us to avoid re-looking up view references
// Since views are recycled, these references will never change
final Object tag = workingView.getTag();
ViewHolder viewHolder = null;
if(null == tag || !(tag instanceof ViewHolder)) {
viewHolder = new ViewHolder();
viewHolder.titleView = (TextView) workingView.findViewById(R.id.firstLine);
viewHolder.locationView = (TextView) workingView.findViewById(R.id.location);
workingView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) tag;
}
return viewHolder;
}
/**
* ViewHolder allows us to avoid re-looking up view references
* Since views are recycled, these references will never change
*/
private static class ViewHolder {
public TextView titleView;
public TextView locationView;
}
}