Java Android试图调用虚拟方法JSON字符串
我正在尝试从数据库(phpmyadmin)获取数据,到目前为止,我使用了以下代码: 主要活动:Java Android试图调用虚拟方法JSON字符串,java,php,android,json,nullreferenceexception,Java,Php,Android,Json,Nullreferenceexception,我正在尝试从数据库(phpmyadmin)获取数据,到目前为止,我使用了以下代码: 主要活动: public class AllProductsActivity extends ListActivity { // Progress Dialog private ProgressDialog pDialog; // Creating JSON Parser object JSONParser jParser = new JSONParser(); Ar
public class AllProductsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://192.168.155.27:8000/gIndex";
// JSON Node names
private static final String TAG_SUCCESS = "id";
private static final String TAG_PRODUCTS = "name";
private static final String TAG_PID = "description";
private static final String TAG_NAME = "video_url";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),
EditProductActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, pid);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
}
});
}
// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
// adding HashList to ArrayList
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
NewProductActivity.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} 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 products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AllProductsActivity.this, productsList,
R.layout.list_item, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
公共类AllProductsActivity扩展了ListActivity{
//进度对话框
私人对话;
//创建JSON解析器对象
JSONParser jParser=新的JSONParser();
ArrayList productsList;
//获取所有产品列表的url
私有静态字符串url\u所有产品=”http://192.168.155.27:8000/gIndex";
//JSON节点名称
私有静态最终字符串标记\u SUCCESS=“id”;
私有静态最终字符串TAG_PRODUCTS=“name”;
私有静态最终字符串标记_PID=“description”;
私有静态最终字符串标记\u NAME=“video\u url”;
//产品JSONArray
JSONArray产品=null;
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.all_产品);
//ListView的Hashmap
productsList=新的ArrayList();
//在后台线程中加载产品
新建LoadAllProducts().execute();
//获取列表视图
ListView lv=getListView();
//论单产品的选择
//启动编辑产品屏幕
lv.setOnItemClickListener(新的OnItemClickListener(){
@凌驾
public void onItemClick(AdapterView父级、视图、,
内部位置,长id){
//从选定的ListItem获取值
字符串pid=((TextView)view.findViewById(R.id.pid)).getText()
.toString();
//开始新的意图
Intent in=新的Intent(getApplicationContext(),
EditProductActivity.class);
//将pid发送到下一个活动
in.putExtra(标签号PID,PID);
//开始新的活动并期望得到一些响应
startActivityForResult(in,100);
}
});
}
//编辑产品活动的响应
@凌驾
受保护的void onActivityResult(int请求代码、int结果代码、意图数据){
super.onActivityResult(请求代码、结果代码、数据);
//如果结果代码为100
如果(结果代码==100){
//如果收到结果代码100
//指用户编辑/删除的产品
//重新加载此屏幕
Intent=getIntent();
完成();
星触觉(意向);
}
}
/**
*通过发出HTTP请求加载所有产品的后台异步任务
* */
类LoadAllProducts扩展了AsyncTask{
/**
*在启动后台线程显示进度对话框之前
* */
@凌驾
受保护的void onPreExecute(){
super.onPreExecute();
pDialog=newprogressdialog(AllProductsActivity.this);
pDialog.setMessage(“正在加载产品。请稍候…”);
pDialog.setUndeterminate(假);
pDialog.setCancelable(假);
pDialog.show();
}
/**
*从url获取所有产品
* */
受保护的字符串doInBackground(字符串…args){
//建筑参数
List params=new ArrayList();
//从URL获取JSON字符串
JSONObject json=jParser.makeHttpRequest(url_all_products,“GET”,params);
//检查日志cat中的JSON响应
Log.d(“所有产品:,json.toString());
试一试{
//检查成功标签
int success=json.getInt(TAG_success);
如果(成功==1){
//发现的产品
//获取一系列产品
products=json.getJSONArray(TAG_products);
//在所有产品中循环
对于(int i=0;ivalue
地图放置(标签PID,id);
地图放置(标签名称、名称);
//将哈希列表添加到ArrayList
productsList.add(地图);
}
}否则{
//没有发现任何产品
//启动添加新产品活动
意图i=新意图(getApplicationContext(),
NewProductActivity.class);
//关闭以前的所有活动
i、 添加标志(意图、标志、活动、清除、顶部);
星触觉(i);
}
}捕获(JSONException e){
e、 printStackTrace();
}
返回null;
}
/**
*完成后台任务后,关闭“进度”对话框
* **/
受保护的void onPostExecute(字符串文件\u url){
//获取所有产品后关闭对话框
pDialog.disclose();
//从后台线程更新UI
runOnUiThread(新的Runnable(){
公开募捐{
/**
*将解析的JSON数据更新到ListView中
* */
ListAdapter=新的SimpleAdapter(
AllProductsActivity.this,productsList,
R.layout.list_项,新字符串[]{TAG_PID,
TAG_NAME},
新的int[]{R.id.pid,R.id.name});