我使用 AsyncTask 将数据从服务器加载到列表中，现在我想将此列表发送到主 Activity 。帮我怎么做
这是主要 Activity
@Override
protected void onCreate(Bundle savedInstanceState) {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads().detectDiskWrites().detectNetwork() // StrictMode is most commonly used to catch accidental disk or network access on the application's main thread
.penaltyLog().build());
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tx=(TextView)findViewById(R.id.textView);
ls=(ListView)findViewById(R.id.listView);
bn=(Button)findViewById(R.id.button);
new Dataload().execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
这是异步任务
class Dataload extends AsyncTask<String,Void,ArrayAdapter> {
String returnString, s = "";
String name;
int quantity,price;
ArrayList<String> list = new ArrayList<String>();
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(ArrayAdapter adapter) {
ls.setAdapter(adapter);
}
@Override
protected ArrayAdapter doInBackground(String... params) {
ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
// define the parameter
postParameters.add(new BasicNameValuePair("h", s));
String response = null;
// call executeHttpPost method passing necessary parameters
try {
response = CustomHttpClient.executeHttpPost(
"http://grclive.16mb.com/select_rum.php",
postParameters);
String result = response.toString();
try {
returnString = "";
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
name = json_data.getString("r_name");
quantity=json_data.getInt("r_quantity");
price=json_data.getInt("r_price");
list1.add(name + " " + quantity + " L" + " " + price + " ₹");
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
} catch (Exception e) {
Log.e("log_tag", "Error in http connection!!" + e.toString());
}
ArrayAdapter<String> adapter =
new ArrayAdapter<String>(getApplicationContext(),R.layout.textfield, list1);
return adapter;
}
}
我试了很多次请给个解决办法
最佳答案
您可以在 MainActivity 中实现 onPostExecute 或在 MainActivity 中创建 AsyncTask 类作为实习生类，如果您不想这样做，则可以创建一个监听器来获取此列表。例如创建一个接口(interface) OnDataloadListListener:
public interface OnDataloadListListener{
void onDataloadListReady(List<String> list);
}
然后在您的 Dataload 类中使用它。在 Dataload 构造函数中传递一个 OnDataloadListListener 实例。在 onPostExecute 中创建适配器，而不是在 doInBackground 中创建适配器:
class Dataload extends AsyncTask<String,Void,List<String>> {
public Dataload(OnDataloadListListener onDataloadListListener){
this.onDataloadListListener = onDataloadListListener;
}
String returnString, s = "";
String name;
int quantity,price;
ArrayList<String> list = new ArrayList<String>();
OnDataloadListListener onDataloadListListener;
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(List<String> list) {
if(onDataloadListListener != null){
onDataloadListListener.onDataloadListReady(list);
}
ArrayAdapter<String> adapter =
new ArrayAdapter<String>(getApplicationContext(),R.layout.textfield, list);
ls.setAdapter(adapter);
}
@Override
protected List<String> doInBackground(String... params) {
ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
// define the parameter
postParameters.add(new BasicNameValuePair("h", s));
String response = null;
// call executeHttpPost method passing necessary parameters
try {
response = CustomHttpClient.executeHttpPost(
"http://grclive.16mb.com/select_rum.php",
postParameters);
String result = response.toString();
try {
returnString = "";
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
name = json_data.getString("r_name");
quantity=json_data.getInt("r_quantity");
price=json_data.getInt("r_price");
list1.add(name + " " + quantity + " L" + " " + price + " ₹");
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
} catch (Exception e) {
Log.e("log_tag", "Error in http connection!!" + e.toString());
}
return list1;
}
}
并通过以下方式使用它:
@Override
protected void onCreate(Bundle savedInstanceState) {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads().detectDiskWrites().detectNetwork() // StrictMode is most commonly used to catch accidental disk or network access on the application's main thread
.penaltyLog().build());
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tx=(TextView)findViewById(R.id.textView);
ls=(ListView)findViewById(R.id.listView);
bn=(Button)findViewById(R.id.button);
new Dataload(
new OnDataloadListListener(){
onDataloadListReady(List<String> list){
//You have your list here
}
}
).execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
更新:我给你一个关于如何在不审查或测试代码的情况下做到这一点的想法。
关于android - 如何从 AsyncTask 获取列表项到主要 Activity ？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36389375/