我创建了一个自定义列表视图，可以保持关闭状态，但我无法弄清楚原因。我想我可能没有正确地命名其中一个视图，因为我正在将该视图建模为另一个视图。但是我找不到我的错误。
这是我的强制关闭错误：
08-30 22:04:44.073 4011-4011/com.beerportfolio.beerportfoliopro E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.beerportfoliopro.BreweryLocationInfoAdapter.getView(BreweryLocationInfoAdapter.java:50)
at android.widget.AbsListView.obtainView(AbsListView.java:2410)
at android.widget.ListView.makeAndAddView(ListView.java:1963)
at android.widget.ListView.fillDown(ListView.java:815)
at android.widget.ListView.fillFromTop(ListView.java:876)
at android.widget.ListView.layoutChildren(ListView.java:1813)
at android.widget.AbsListView.onLayout(AbsListView.java:2238)
at android.view.View.layout(View.java:13900)
at android.view.ViewGroup.layout(ViewGroup.java:4391)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
at android.view.View.layout(View.java:13900)
at android.view.ViewGroup.layout(ViewGroup.java:4391)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:13900)
at android.view.ViewGroup.layout(ViewGroup.java:4391)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
at android.view.View.layout(View.java:13900)
at android.view.ViewGroup.layout(ViewGroup.java:4391)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:13900)
at android.view.ViewGroup.layout(ViewGroup.java:4391)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2183)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1984)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1221)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4710)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:746)
at android.view.Choreographer.doCallbacks(Choreographer.java:572)
at android.view.Choreographer.doFrame(Choreographer.java:538)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:731)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:155)
at android.app.ActivityThread.main(ActivityThread.java:5536)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1074)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:841)
at dalvik.system.NativeStart.main(Native Method)
我的BreweryLocationInfoAdapter代码：
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.ArrayAdapter;
import android.widget.RatingBar;
import android.widget.TextView;
import com.beerportfolio.beerportfoliopro.R;
public class BreweryLocationInfoAdapter extends ArrayAdapter<BreweryLocationData>{
Context context;
int layoutResourceId;
List<BreweryLocationData> data = null;
public BreweryLocationInfoAdapter(Context context, int layoutResourceId, List<BreweryLocationData> data) {
super(context, layoutResourceId, data);
this.layoutResourceId = layoutResourceId;
this.context = context;
this.data = data;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
breweryHolder holder = null;
if(row == null)
{
LayoutInflater inflater = ((Activity)context).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent, false);
holder = new breweryHolder();
holder.txtBrewery = (TextView)row.findViewById(R.id.beerNameList);
holder.txtDistance = (TextView)row.findViewById(R.id.beerBreweryNameList);
row.setTag(holder);
}
else
{
holder = (breweryHolder)row.getTag();
}
BreweryLocationData beer = data.get(position);
holder.txtBrewery.setText(beer.brewery);
holder.txtBrewery.setText(beer.distance);
return row;
}
static class breweryHolder
{
TextView txtBrewery;
TextView txtDistance;
}
}
GetNearbyBreweries代码：
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
import com.beerportfolio.beerportfoliopro.R;
public class GetNearbyBreweries extends AsyncTask
<String, Void, String> {
Context c;
private ProgressDialog Dialog;
public GetNearbyBreweries (Context context)
{
c = context;
Dialog = new ProgressDialog(c);
}
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
return readJSONFeed(arg0[0]);
}
protected void onPreExecute() {
Dialog.setMessage("Locating Breweries");
Dialog.setTitle("Loading");
Dialog.setCancelable(false);
Dialog.show();
}
protected void onPostExecute(String result){
//decode json here
try{
JSONObject json = new JSONObject(result);
//acces listview
ListView lv = (ListView) ((Activity) c).findViewById(R.id.topTasteBeers);
//make array list for beer
final List<BreweryLocationData> tasteList = new ArrayList<BreweryLocationData>();
for(int i = 0; i < json.getJSONArray("data").length(); i++) {
String brewery = json.getJSONArray("data").getJSONObject(i).getJSONObject("brewery").getString("name");
String id = json.getJSONArray("data").getJSONObject(i).getJSONObject("brewery").getString("id");
String latitude = json.getJSONArray("data").getJSONObject(i).getString("latitude");
String longitude = json.getJSONArray("data").getJSONObject(i).getString("longitude");
String distance = json.getJSONArray("data").getJSONObject(i).getString("distance");
Toast.makeText(c, "Brewery: " + brewery, Toast.LENGTH_SHORT).show();
int count = i + 1;
//create object
BreweryLocationData tempLocation = new BreweryLocationData(brewery, id, longitude , latitude,distance);
//add to arraylist
tasteList.add(tempLocation);
//add items to listview
BreweryLocationInfoAdapter adapter1 = new BreweryLocationInfoAdapter(c ,R.layout.toptaste_layout, tasteList);
lv.setAdapter(adapter1);
//set up clicks
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
ShortBeerInfo o=(ShortBeerInfo)arg0.getItemAtPosition(arg2);
String tempID = o.id;
String tempBrewID = o.brewery;
Toast toast = Toast.makeText(c, tempID, Toast.LENGTH_SHORT);
toast.show();
//get beer details from id
Intent myIntent = new Intent(c, BeerPage2.class);
myIntent.putExtra("id", tempID);
myIntent.putExtra("breweryID", tempBrewID);
c.startActivity(myIntent);
}
});
}
}
catch(Exception e){
}
Dialog.dismiss();
}
public String readJSONFeed(String URL) {
StringBuilder stringBuilder = new StringBuilder();
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(URL);
try {
HttpResponse response = httpClient.execute(httpGet);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream inputStream = entity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
stringBuilder.append(line);
}
inputStream.close();
} else {
Log.d("JSON", "Failed to download file");
}
} catch (Exception e) {
Log.d("readJSONFeed", e.getLocalizedMessage());
}
return stringBuilder.toString();
}
}
答案 0 :(得分：1)
我认为由于某种原因，行没有被创建。
你可以通过调试那行来仔细检查！=到达set row.setTag（holder）时的null。
我只能猜测1.也许您用来获取inflater的上下文不正确，无论哪种方式我更喜欢使用以下方法
LayoutInflater.from(context).inflate(R.layout.cell, viewGroup, false);
或者，您的resourceID不对..
答案 1 :(得分：1)
您还没有在自定义适配器中编写getCount方法：
public int getCount() {
return //Something here
}
答案 2 :(得分：0)
第50行似乎是
holder.txtBrewery.setText(beer.brewery);
因此，应该具有标识R.id.beerNameList的TextView具有另一个标识或beer.brewery为空。
如果使用调试器，则可以快速解决这些类型的问题。只需在违规行放置断点，运行调试器，它将在给定行暂停。然后，您可以确切地查看哪个对象是null，从而可以立即解决问题。
答案 3 :(得分：0)
不要将数据保存在自定义适配器中。始终使用
BreweryLocationData beer = getItem（position）;
获取应该由适配器表示的对象。这样，您可以避免在适配器外部修改数据的问题。