我的做法可能不算优雅,但是我想要实现的是:连接到一个 Web 服务,获取 JSON 数据,将其解析,创建一个对象,并将该对象添加到 ArrayList 中,然后使用该 ArrayList 来填充我的 ListView。
我尝试使用 AsyncTask 来完成所有这些操作。
总结:doInBackground 接收一个 URL 字符串,用它来连接到 Web 服务。我将得到的 JSON 数据作为字符串进行解析,构造一个新的对象并将其添加到 ArrayList 中。在 onPostExecute
中,我尝试使用一个利用我的 ArrayList 的 ArrayAdapter
设置列表适配器。
下面是我的代码:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import org.json.JSONArray;
import org.json.JSONObject;
import oauth.signpost.OAuthConsumer;
import oauth.signpost.basic.DefaultOAuthConsumer;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ArrayAdapter;
public class AllOffersListActivity extends ListActivity {
private static final String CONSUMER_KEY = "bla";
private static final String CONSUMER_SECRET = "bla";
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new CreateArrayListTask().execute("http://example.com/sample.json");
}
private class CreateArrayListTask extends AsyncTask<String, Void, ArrayList<Offer>> {
private final ProgressDialog dialog = new ProgressDialog(AllOffersListActivity.this);
@Override
protected void onPreExecute() {
this.dialog.setMessage("Fetching offers...");
this.dialog.show();
}
@Override
protected ArrayList<Offer> doInBackGround(String...urls) {
ArrayList<Offer> offerList = new ArrayList<Offer>();
for(String url: urls) {
OAuthConsumer consumer = new DefaultOAuthConsumer(CONSUMER_KEY, CONSUMER_SECRET);
consumer.setTokenWithSecret("", "");
try {
URL url1 = new URL(url);
HttpURLConnection request = (HttpURLConnection) url1.openConnection();
// sign the request
consumer.sign(request);
// send the request
request.connect();
String JSONString = convertStreamToString(request.getInputStream());
JSONObject jObject = new JSONObject(JSONString);
JSONObject offerObject = jObject.getJSONObject("offer");
String titleValue = offerObject.getString("title");
//System.out.println(titleValue);
String descriptionValue = offerObject.getString("description");
//System.out.println(attributeValue);
JSONObject businessObject = offerObject.getJSONObject("business");
String nameValue = businessObject.getString("name");
Offer myOffer = new Offer(titleValue, descriptionValue, nameValue);
offerList.add(myOffer);
} catch (Exception e) {
e.printStackTrace();
}
}
return offerList;
}
@Override
protected void onPostExecute(ArrayList<Offer> offerList) {
if(this.dialog.isShowing())
this.dialog.dismiss();
setListAdapter(new ArrayAdapter<Offer>(AllOffersListActivity.this, android.R.layout.simple_list_item_1, offerList));
}
}
private String convertStreamToString(InputStream inputStream) throws IOException {
if(inputStream != null) {
Writer writer = new StringWriter();
char[] buffer = new char[1024];
try {
Reader reader = new BufferedReader( new InputStreamReader(inputStream, "UTF-8"));
int n;
while((n = reader.read(buffer)) != -1) {
writer.write(buffer, 0, n);
}
} finally {
inputStream.close();
}
return writer.toString();
} else {
return "";
}
}
}
我看到两个错误,一个是在我的私有异步类上:"The type AllOffersListActivity.CreateArrayListTask must implement the inherited abstract method AsyncTask<String,Void,ArrayList<Offer>>.doInBackground(String...)"
其次,在我的doInBackGround
覆盖方法中,我收到了以下错误信息:The method doInBackGround(String...) of type AllOffersListActivity.CreateArrayListTask must override or implement a supertype method
我错过了什么?
String before = writer.toString(); String after = before.substring(1, before.length()-2); return after;
返回after。 - LuxuryMode