我正在创建一个应用程序，它从我的网站获取json并将json解析为android上的listview。
我使用http请求获取json然后使2个数组网站保存所有网站名称和链接以保存链接。我希望listview显示网站名称，然后单击然后在浏览器中打开网站。
任何人都可以帮助我。尽我所能。帮我解决问题或告诉我另一种方法来做这件事。
尝试获取json并将其解析为listView以下是我的代码：
public class GetWebsiteList extends AsyncTask<String, String, String> {
// Creating JSON Parser object
ArrayList<HashMap<String, String>> productsList;
String websites[]=new String[10];
String links[]=new String[10];
// url to get all products list
private String url_all_products = "http://androidtest.cu.cc/getwebsites.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_WEBSITES = "websites";
private static final String TAG_SNO = "sno";
private static final String TAG_NAME = "name";
private static final String TAG_LINK = "link";
// products JSONArray
JSONArray products = null;
// Progress Dialog
private ProgressDialog pDialog;
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(mainpage.this);
pDialog.setMessage("Loading Website List.Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... arg0) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
//ArrayAdapter adapter = ArrayAdapter.
// Check your log cat for JSON reponse
Log.d("nitrek All Products: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
String suc;
switch(success)
{
case 1:
suc="True";
break;
case 0:
suc="False";
break;
default:
suc="unkonwn";
break;
}
if (success == 1) {
// products found
// Getting Array of Products
Log.d(" nitrek success",suc);
products = json.getJSONArray(TAG_WEBSITES);
// looping through All Products
Log.d(" nitrek websites", products.toString());
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_SNO);
String name = c.getString(TAG_NAME);
String link= c.getString(TAG_LINK);
Log.d("nitrek website",id+name+link);
// websites[i]=new String();
websites[i]=name;
links[i]=link;
Log.d("nitrek web",websites[i]+links[i]);
/* creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
try {
map.put(TAG_SNO, id);
map.put(TAG_NAME, name);
productsList.add(map);
}
catch (Exception e)
{
e.printStackTrace();
}
// adding HashList to ArrayList
*/
}
} else {
// no products found
// Launch Add New product Activity
Toast.makeText(mainpage.this,"no website found", Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(final String result) {
pDialog.dismiss();
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
*/
//ListAdapter adapter = new SimpleAdapter(mainpage.this, productsList, R.layout.listitem, new String[]{TAG_SNO, TAG_NAME},new int[]{R.id.sno, R.id.name});
// updating listview
try {
//ArrayAdapter<String> adapter = new ArrayAdapter<String>(mainpage.this, R.layout.listitem, R.id.name, websites);
final ArrayList<String> list = new ArrayList<String>();
for (int i = 0; i < websites.length; ++i) {
list.add(websites[i]);
}
final StableArrayAdapter adapter = new StableArrayAdapter(mainpage.this, R.layout.listitem, list);
//ArrayAdapter<String> ad = new ArrayAdapter<String>(mainpage.this, R.layout.listitem, websites);
ListView lv = (ListView) findViewById(R.id.list);
lv.setAdapter(adapter);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//Intent intent = new Intent(this, homepage.class);
count = 0;
String url = links[position];
Toast.makeText(mainpage.this, "Opening: " + url, Toast.LENGTH_SHORT).show();
Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
//notify_test(url);
startActivity(i);
}
});
} catch (Exception e) {
Log.d("error list nitrekerror", "below");
e.printStackTrace();
}
Toast.makeText(mainpage.this, result, Toast.LENGTH_LONG).show();
int i = 0;
while (i < websites.length && i < 3) {
Toast.makeText(mainpage.this, websites[i] + " " + links[i], Toast.LENGTH_LONG).show();
i++;
}
}
});
}
}
private class StableArrayAdapter extends ArrayAdapter<String> {
HashMap<String, Integer> mIdMap = new HashMap<String, Integer>();
public StableArrayAdapter(Context context, int textViewResourceId,
List<String> objects) {
super(context, textViewResourceId, objects);
for (int i = 0; i < objects.size(); ++i) {
mIdMap.put(objects.get(i), i);
}
}
@Override
public long getItemId(int position) {
String item = getItem(position);
return mIdMap.get(item);
}
@Override
public boolean hasStableIds() {
return true;
}
}
但我收到此错误并且无法弄清楚原因？ 下面是logcat：
07-08 00:58:34.245 27826-27826/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: nitz.nitrek.myrtoguide, PID: 27826
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java)
at android.widget.AbsListView.obtainView(AbsListView.java)
at android.widget.ListView.measureHeightOfChildren(ListView.java)
at android.widget.ListView.onMeasure(ListView.java)
at android.view.View.measure(View.java)
at android.widget.RelativeLayout.measureChild(RelativeLayout.java)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.FrameLayout.onMeasure(FrameLayout.java)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java)
at android.widget.LinearLayout.measureVertical(LinearLayout.java)
at android.widget.LinearLayout.onMeasure(LinearLayout.java)
at android.view.View.measure(View.java)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.FrameLayout.onMeasure(FrameLayout.java)
at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java)
at android.widget.LinearLayout.measureVertical(LinearLayout.java)
at android.widget.LinearLayout.onMeasure(LinearLayout.java)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.FrameLayout.onMeasure(FrameLayout.java)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java)
at android.widget.LinearLayout.measureVertical(LinearLayout.java)
at android.widget.LinearLayout.onMeasure(LinearLayout.java)
at android.view.View.measure(View.java)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java)
at android.widget.FrameLayout.onMeasure(FrameLayout.java)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java)
at android.view.View.measure(View.java)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java)
at android.view.Choreographer.doCallbacks(Choreographer.java)
at android.view.Choreographer.doFrame(Choreographer.java)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java)
at android.os.Handler.handleCallback(Handler.java)
at android.os.Handler.dispatchMessage(Handler.java)
at android.os.Looper.loop(Looper.java)
at android.app.ActivityThread.main(ActivityThread.java)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
07-08 00:58:34.245 780-3917/? E/ActivityManager﹕ App crashed! Process: nitz.nitrek.myrtoguide
答案 0 :(得分：1)
你已经声明了大小为10的网站数组，但是你只用2-3个条目来填充它，这取决于你作为响应获得的网站数量，所以将整个数组传递给arrayadapter你得到一个空指针异常。所以你获得了响应中收到的网站数量，并动态声明了该大小的数组。
答案 1 :(得分：0)
您忘记覆盖关闭ArrayAdapter的getView。并同步viewHolder以获得更高的性能。您可以阅读此https://github.com/codepath/android_guides/wiki/Using-an-ArrayAdapter-with-ListView
您需要覆盖此方法以使视图膨胀，否则任何视图都是由您的适配器创建并抛出null异常。
覆盖示例：
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// Get the data item for this position
Object data = yourTabObj[position]
// Check if an existing view is being reused, otherwise inflate the view
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_listView, parent, false);
}
// Lookup view for data population
TextView title = (TextView) convertView.findViewById(R.id.title);
title.setText(data.name);
// Return the completed view to render on screen
return convertView;
}
在您了解到想到viewHolder以提高性能之后。