我试图从mysql数据库中显示项目的列表视图。我得到了正确的JSON响应，但我的listview没有显示任何内容。有什么问题？
这是要显示的内容的XML：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<!-- Product id (pid) - will be HIDDEN - used to pass to other activity -->
<TextView
android:id="@+id/pid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone" />
<!-- Name Label -->
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="6dip"
android:paddingLeft="6dip"
android:textSize="17sp"
android:textStyle="bold" />
<TextView
android:id="@+id/budget"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
列表活动的布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
这是它的代码：
public class DisplayReqItem 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://10.0.2.2:8000/project/display_req.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "product";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_BUDGET = "price";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_requested);
// 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(),
MainMenu.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(DisplayReqItem.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);
String budget = c.getString(TAG_BUDGET);
// 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);
map.put(TAG_BUDGET, budget);
// adding HashList to ArrayList
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
MainMenu.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(
DisplayReqItem.this, productsList,
R.layout.activity_display_requested, new String[] { TAG_PID,
TAG_NAME, TAG_BUDGET},
new int[] { R.id.pid, R.id.name, R.id.price });
// updating listview
setListAdapter(adapter);
}
});
}
}}`
答案 0 :(得分：0)
方法onPostExecute（）用于更新UI，因此无需运行后台线程来执行此操作。
更新 - 为您创建了一个自定义适配器，因此请尝试按如下所示更改onPostExecute（）并将此类ProductsAdapter添加到您的项目中
更新2 - ＆gt;＆gt;我的所有Code to Now都使用了Product Class而不是HashMap，我不认为你需要在这里使用HashMap所以试试这段代码吧。希望这就是你现在所需要的一切
如果所有Else失败，处理任何事情的最佳方法是构建自定义
onPostExecute（）方法：
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
if(productsList.size() > 0){
/**
* Updating parsed JSON data into ListView
* */
// Added a Custom Adapter instead of SimpleAdapter
ProductsAdapter adapter = new ProductsAdapter(getBaseContext(), productsList);
if(getListView() != null){
// updating listview
setListAdapter(adapter);
}else{
Log.d("ListView-Reference", "ListView is null");
}
}else{
Log.d("Product List", "Products list is empty");
}
}
自定义适配器类
public class ProductsAdapter extends BaseAdapter {
private Arraylist<Product> m_productsList = null;
private LayoutInflater mInflater = null;
private class Row{
TextView mTextViewPID;
TextView mTextViewName;
TextView mTextViewPrice;
}
public ProductsAdapter(Context context, Arraylist<Product> productsList){
this.mInflater = LayoutInflater.from(context);
this.m_productsList = productsList;
}
// --------------------------------------------------
// BaseAdapter Overrides
// --------------------------------------------------
@Override
public int getCount() {
int count = 0;
if((m_productsList !=null) && (m_productsList.size() >= 1)){
count = m_productsList.size();
}
return count;
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return m_productsList.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Row theRow;
// If ConvertVIew is null
if(convertView == null){
theRow = new Row();
convertView = mInflater.inflate(R.layout.activity_display_requested, null);
theRow.mTextViewPID = (TextView) convertView.findViewById(R.id.pid);
theRow.mTextViewName = (TextView) convertView.findViewById(R.id.name);
theRow.mTextViewPrice = (TextView) convertView.findViewById(R.id.budget);
convertView.setTag(theRow);
}else{
theRow = (Row) convertView.getTag();
}
theRow.mTextViewPID.setText(m_productsList.get(position).pid);
theRow.mTextViewName.setText(m_productsList.get(position).name);
theRow.mTextViewPrice.setText(m_productsList.get(position).budget);
return convertView;
}
添加产品类
public class Product{
// Simple Variables for this Item
public int pid = -1;
public String name = null;
public String budget = null;
}
我不确定为什么要为这些值而不是对象使用HashMap但这就是我要做的事情
然后使用ArrayList而不是使用HashMap，如下所示：
使用产品对象的ArrayList而不是Hashmap
ArrayList<Product> productsList = new ArrayList<Product>();
新的doInBackground（）方法
/**
* 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);
String budget = c.getString(TAG_BUDGET);
// Create a new Product Obect, set its Values
Product mProduct = new Product();
mProduct.pid = id;
mProduct.name = name;
mProduct.budget = budget;
// adding Product to ArrayList
productsList.add(mProduct);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
MainMenu.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
答案 1 :(得分：0)
在自定义适配器类“SimpleAdapter”中，您必须覆盖方法getCount()。
此方法返回要创建的列表视图行数，这是 productsList
的大小所以请在productsList.size()方法中返回getCount()。
@Override
public getCount(){
return productList.size();
}