安卓:JSON来的ListView [英] Android: JSON to ListView
问题描述
我想从我的PHP一个JSON传递给我的Android应用程序。那么Android将填充JSON成的ListView
。该JSON已成功传递给我的Android应用程序。但问题是,它一直就扔 NullPointerException异常
给我。 IM都强调了,因为我已经花了很多次找我已经做了错误。下面是codeS:
进口的java.util.ArrayList;
进口的java.util.List;进口org.apache.http.NameValuePair;
进口org.apache.http.message.BasicNameValuePair;
进口org.json.JSONArray;
进口org.json.JSONException;
进口org.json.JSONObject;进口android.app.Activity;
进口android.os.Bundle;
进口android.view.LayoutInflater;
进口android.view.View;
进口android.view.ViewGroup;
进口android.widget.ArrayAdapter;
进口android.widget.ImageView;
进口android.widget.ListView;
进口android.widget.TextView;
进口android.widget.Toast;公共类PlacesActivity延伸活动{清单<&地方GT;模型=新的ArrayList<&地方GT;();
PlacesAdapter适配器=新PlacesAdapter();
@燮pressWarnings(静态访问)
@覆盖
公共无效的onCreate(捆绑savedInstanceState){
LV的ListView =(ListView控件)findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
的setContentView(R.layout.places); ArrayList的<&的NameValuePair GT; postParameters =新的ArrayList<&的NameValuePair GT;();
postParameters.add(新BasicNameValuePair(请求,request_for_places)); 串响应=无效; 尝试{
响应= CustomHttpClient.executeHttpPost(http://www.test.com/requestPlaces.php,postParameters);
字符串资源=响应; 尝试{
JSONArray ARR =新JSONArray(RES);
的for(int i = 0; I< arr.length();我++)
{
JSONObject的jsonObj = arr.getJSONObject(I)
地方newPlace =新的地方();
newPlace.setPlace(jsonObj.optString(\"placeID\"),jsonObj.optString(\"placeName\"),jsonObj.optString(\"placeType\"),jsonObj.optString(\"placeLat\"),jsonObj.optString(\"placeLng\"),jsonObj.optString(\"placePict\"));
model.add(newPlace);
} }赶上(JSONException E){
Toast.makeText(getApplicationContext(),:,Toast.LENGTH_LONG错误JSONException!).show();
} lv.setAdapter(适配器);
}赶上(例外五){
Toast.makeText(getApplicationContext(),E +,Toast.LENGTH_LONG).show();
}
}类PlacesAdapter扩展ArrayAdapter<&地方GT;
{
PlacesAdapter()
{
超(PlacesActivity.this,android.R.layout.simple_list_item_1,模型);
} 公共查看getView(INT位置,查看convertView,父母的ViewGroup)
{
查看排= convertView;
占位符持有人= NULL; 如果(行== NULL)
{
LayoutInflater吹气= getLayoutInflater();
行= inflater.inflate(R.layout.row,父母,假);
持有人=新的占位符(行);
}
其他
{
支架=(预留)row.getTag();
} holder.populateFrom(model.get(位置)); 返回行;
}
}静态类的占位符{ 私人TextView的地名= NULL;
私人TextView的placeType = NULL;
私人ImageView的图标= NULL; 占位符(查看行){
地名=(TextView中)row.findViewById(R.id.placeName);
placeType =(TextView中)row.findViewById(R.id.placeType);
图标=(ImageView的)row.findViewById(R.id.icon);
} 无效populateFrom(宿P){
placeName.setText(p.getPlaceName());
placeType.setText(p.getType()); 如果(p.getType()。等于(教育)){
icon.setImageResource(R.drawable.ball_red);
}
否则,如果(p.getType()。等于(闲)){
icon.setImageResource(R.drawable.ball_yellow);
}
其他{
icon.setImageResource(R.drawable.ball_green);
} }
}
}
这是JSON从PHP返回
[{placeID:P0001,地名:英迪国际University\",\"placeType\":\"Education\",\"placeLat\":\"2.813997\",\"placeLng\":\"101.758229\",\"placePict\":\"http:\\/\\/test.com\\/placesImage\\/inti_iu.JPG\"},
{placeID:P0002,地名:汝来国际College\",\"placeType\":\"Education\",\"placeLat\":\"2.814179\",\"placeLng\":\"101.7700107\",\"placePict\":\"http:\\/\\/test.com\\/placesImage\\/nilai_uc.jpg\"}]
这是我的 Places.java
公共类的地方{私人静态字符串地名;
私人静态字符串placeImg;
私人静态字符串placeLat;
私人静态字符串placeLng;
私人静态字符串placeType;
私人静态字符串placeID;公共场所()
{
placeID =;
}
//设置方法
公共静态无效setPlace(字符串place_id,PLACE_NAME字符串,字符串place_type,字符串place_lat,字符串place_lng,字符串place_img){
Places.placeName = PLACE_NAME;
Places.placeID = place_id;
Places.placeImg = place_img;
Places.placeLat = place_lat;
Places.placeLng = place_lng;
Places.placeType = place_type;
}//获取方法
公共静态字符串getPlaceName(){
返回地名;
}公共静态字符串getPlaceID(){
返回placeID;
}公共静态字符串GETIMG(){
返回placeImg;
}公共静态字符串getLat(){
返回placeLat;
}公共静态字符串getLng(){
返回placeLng;
}公共静态字符串的getType(){
返回placeType;
}}
编辑:下面的logcat
02-17 17:10:03.595:W / System.err的(1994年):显示java.lang.NullPointerException
02-17 17:10:03.615:W / System.err的(1994):在com.application.fyp.PlacesActivity.onCreate(PlacesActivity.java:50)
02-17 17:10:03.615:W / System.err的(1994):在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
02-17 17:10:03.615:W / System.err的(1994):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
02-17 17:10:03.615:W / System.err的(1994):在android.app.ActivityThread.startActivityNow(ActivityThread.java:1692)
02-17 17:10:03.625:W / System.err的(1994):在android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
02-17 17:10:03.625:W / System.err的(1994):在android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
02-17 17:10:03.625:W / System.err的(1994):在android.widget.TabHost $ IntentContentStrategy.getContentView(TabHost.java:656)
02-17 17:10:03.625:W / System.err的(1994):在android.widget.TabHost.setCurrentTab(TabHost.java:326)
02-17 17:10:03.625:W / System.err的(1994):在android.widget.TabHost $ 2.onTabSelectionChanged(TabHost.java:132)
02-17 17:10:03.625:W / System.err的(1994):在android.widget.TabWidget $ TabClickListener.onClick(TabWidget.java:458)
02-17 17:10:03.625:W / System.err的(1994):在android.view.View.performClick(View.java:2533)
02-17 17:10:03.625:W / System.err的(1994):在android.view.View $ PerformClick.run(View.java:9320)
02-17 17:10:03.635:W / System.err的(1994):在android.os.Handler.handleCallback(Handler.java:587)
02-17 17:10:03.635:W / System.err的(1994):在android.os.Handler.dispatchMessage(Handler.java:92)
02-17 17:10:03.635:W / System.err的(1994):在android.os.Looper.loop(Looper.java:150)
02-17 17:10:03.635:W / System.err的(1994):在android.app.ActivityThread.main(ActivityThread.java:4385)
02-17 17:10:03.635:W / System.err的(1994):在java.lang.reflect.Method.invokeNative(本机方法)
02-17 17:10:03.635:W / System.err的(1994):在java.lang.reflect.Method.invoke(Method.java:507)
02-17 17:10:03.635:W / System.err的(1994):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:849)
02-17 17:10:03.635:W / System.err的(1994):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
02-17 17:10:03.645:W / System.err的(1994):在dalvik.system.NativeStart.main(本机方法)
我觉得这行的原因NPE。
adapter.add(newPlace);
您错过了初始化的 PlacesAdapter适配器;
适配器=新PlacesAdapter();
更新:
这么多错误,
第一:我上面提到的,
二:
列表<&地方GT;模型=新的ArrayList<&地方GT;();
因此, adapter.add(newPlace);
此行应该是 model.add(newPlace);
第三:
有什么用适配器?意味着你在哪里设置适配器?任何的ListView GridView的还是?
问题看上去基本,你要看一看有关列表显示JSON数据..
的一些基本教程编辑:
1
列表<&地方GT;模型=新的ArrayList<&地方GT;();
PlacesAdapter适配器=新PlacesAdapter();
应该是
列表<&地方GT;模型=新的ArrayList<&地方GT;();
PlacesAdapter适配器;
2
的ListView LV =(ListView控件)findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
的setContentView(R.layout.places);
应该是
super.onCreate(savedInstanceState);
的setContentView(R.layout.places);
LV的ListView =(ListView控件)findViewById(R.id.placesListView);
3。
lv.setAdapter(适配器);
应该是,
适配器=新PlacesAdapter();
lv.setAdapter(适配器);
谢谢..
I am trying to pass a JSON from my PHP to my Android app. Then the Android will populate the JSON into a ListView
. The JSON has successfully been passed to my Android app. But the problem is, it keeps on throwing NullPointerException
to me. Im all stressed out as I've been spending a lot of times looking for the error I've done. Below are the codes:
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class PlacesActivity extends Activity {
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter = new PlacesAdapter();
@SuppressWarnings("static-access")
@Override
public void onCreate(Bundle savedInstanceState) {
ListView lv = (ListView) findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("request","request_for_places"));
String response = null;
try{
response = CustomHttpClient.executeHttpPost("http://www.test.com/requestPlaces.php", postParameters);
String res = response;
try{
JSONArray arr = new JSONArray(res);
for(int i = 0; i < arr.length(); i++)
{
JSONObject jsonObj = arr.getJSONObject(i);
Places newPlace = new Places();
newPlace.setPlace(jsonObj.optString("placeID"),jsonObj.optString("placeName"),jsonObj.optString("placeType"),jsonObj.optString("placeLat"),jsonObj.optString("placeLng"),jsonObj.optString("placePict"));
model.add(newPlace);
}
}catch(JSONException e){
Toast.makeText(getApplicationContext(), "Error : JSONException!", Toast.LENGTH_LONG).show();
}
lv.setAdapter(adapter);
}catch(Exception e){
Toast.makeText(getApplicationContext(), e+"", Toast.LENGTH_LONG).show();
}
}
class PlacesAdapter extends ArrayAdapter<Places>
{
PlacesAdapter()
{
super(PlacesActivity.this,android.R.layout.simple_list_item_1,model);
}
public View getView(int position, View convertView, ViewGroup parent)
{
View row = convertView;
PlaceHolder holder = null;
if(row == null)
{
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.row, parent,false);
holder = new PlaceHolder(row);
}
else
{
holder = (PlaceHolder)row.getTag();
}
holder.populateFrom(model.get(position));
return row;
}
}
static class PlaceHolder{
private TextView placeName = null;
private TextView placeType = null;
private ImageView icon = null;
PlaceHolder(View row){
placeName = (TextView)row.findViewById(R.id.placeName);
placeType = (TextView)row.findViewById(R.id.placeType);
icon = (ImageView)row.findViewById(R.id.icon);
}
void populateFrom(Places p){
placeName.setText(p.getPlaceName());
placeType.setText(p.getType());
if(p.getType().equals("Education")){
icon.setImageResource(R.drawable.ball_red);
}
else if (p.getType().equals("Leisure")){
icon.setImageResource(R.drawable.ball_yellow);
}
else{
icon.setImageResource(R.drawable.ball_green);
}
}
}
}
This is the JSON returned from PHP:
[{"placeID":"p0001","placeName":"INTI International University","placeType":"Education","placeLat":"2.813997","placeLng":"101.758229","placePict":"http:\/\/test.com\/placesImage\/inti_iu.JPG"},
{"placeID":"p0002","placeName":"Nilai International College","placeType":"Education","placeLat":"2.814179","placeLng":"101.7700107","placePict":"http:\/\/test.com\/placesImage\/nilai_uc.jpg"}]
This is my Places.java
public class Places{
private static String placeName;
private static String placeImg;
private static String placeLat;
private static String placeLng;
private static String placeType;
private static String placeID;
public Places()
{
placeID = "";
}
//set method
public static void setPlace(String place_id, String place_name, String place_type, String place_lat, String place_lng, String place_img) {
Places.placeName = place_name;
Places.placeID = place_id;
Places.placeImg = place_img;
Places.placeLat = place_lat;
Places.placeLng = place_lng;
Places.placeType = place_type;
}
//get methods
public static String getPlaceName(){
return placeName;
}
public static String getPlaceID(){
return placeID;
}
public static String getImg(){
return placeImg;
}
public static String getLat(){
return placeLat;
}
public static String getLng(){
return placeLng;
}
public static String getType(){
return placeType;
}
}
edit:logcat below
02-17 17:10:03.595: W/System.err(1994): java.lang.NullPointerException
02-17 17:10:03.615: W/System.err(1994): at com.application.fyp.PlacesActivity.onCreate(PlacesActivity.java:50)
02-17 17:10:03.615: W/System.err(1994): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
02-17 17:10:03.615: W/System.err(1994): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1836)
02-17 17:10:03.615: W/System.err(1994): at android.app.ActivityThread.startActivityNow(ActivityThread.java:1692)
02-17 17:10:03.625: W/System.err(1994): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
02-17 17:10:03.625: W/System.err(1994): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:656)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost.setCurrentTab(TabHost.java:326)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:132)
02-17 17:10:03.625: W/System.err(1994): at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:458)
02-17 17:10:03.625: W/System.err(1994): at android.view.View.performClick(View.java:2533)
02-17 17:10:03.625: W/System.err(1994): at android.view.View$PerformClick.run(View.java:9320)
02-17 17:10:03.635: W/System.err(1994): at android.os.Handler.handleCallback(Handler.java:587)
02-17 17:10:03.635: W/System.err(1994): at android.os.Handler.dispatchMessage(Handler.java:92)
02-17 17:10:03.635: W/System.err(1994): at android.os.Looper.loop(Looper.java:150)
02-17 17:10:03.635: W/System.err(1994): at android.app.ActivityThread.main(ActivityThread.java:4385)
02-17 17:10:03.635: W/System.err(1994): at java.lang.reflect.Method.invokeNative(Native Method)
02-17 17:10:03.635: W/System.err(1994): at java.lang.reflect.Method.invoke(Method.java:507)
02-17 17:10:03.635: W/System.err(1994): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
02-17 17:10:03.635: W/System.err(1994): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
02-17 17:10:03.645: W/System.err(1994): at dalvik.system.NativeStart.main(Native Method)
I think this line cause NPE..
adapter.add(newPlace);
You missed to initialize PlacesAdapter adapter;
adapter = new PlacesAdapter();
Updated:
So many mistakes,
First: I mentioned above,
Second:
List<Places> model = new ArrayList<Places>();
So, adapter.add(newPlace);
this line should be, model.add(newPlace);
Third:
Whats the use of Adapter? means where you set adapter? Any ListView or GridView?
Question looks basic, you have to take a look at some basic tutorial about display json data on list..
EDIT:
1.
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter = new PlacesAdapter();
it should be
List<Places> model = new ArrayList<Places>();
PlacesAdapter adapter;
2.
ListView lv = (ListView) findViewById(R.id.placesListView);
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
it should be
super.onCreate(savedInstanceState);
setContentView(R.layout.places);
ListView lv = (ListView) findViewById(R.id.placesListView);
3.
lv.setAdapter(adapter);
it should be,
adapter = new PlacesAdapter();
lv.setAdapter(adapter);
Thanks..
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