我是 Android 开发的新手,我的应用程序开发遇到了停顿。我希望有人可以在这里帮助我。
我有一个名为 JSONActivity 的活动,在 JSONActivity 内部,我从 Web url 中提取 JSON 数据,并将其存储到 3 个 HashMap 中,具体取决于数据类型。
我想将 HashMap 传递给 3 个不同的片段。我将从只为一个片段开始,但是,我似乎无法传递数据。
有人可以指出我做错了什么,我能做些什么来解决它?
我可以保证 json 提取工作正常,因为可以使用Toast
JSONActivity.java
package com.example.json;
import android.os.Bundle;
import java.io.BufferedReader;
import java.io.IOException;
import android.app.Activity;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONObject;
import android.util.Log;
import android.os.AsyncTask;
public class JSONActivity extends Activity {
HashMap<Integer,String> imageList = new HashMap<Integer,String>();
HashMap<Integer,String> textList = new HashMap<Integer,String>();
HashMap<Integer,String> otherList = new HashMap<Integer,String>();
private static final String ID = "id";
private static final String TYPE = "type";
private static final String DATA = "data";
public String readJSONFeed(String URL) {
StringBuilder stringBuilder = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(URL);
try {
HttpResponse response = client.execute(httpGet);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
stringBuilder.append(line);
}
} else {
Log.e("JSON", "Failed to download file");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return stringBuilder.toString();
}
private class ReadJSONFeedTask extends AsyncTask<String, Void, String> {
protected String doInBackground(String... urls) {
return readJSONFeed(urls[0]);
}
protected void onPostExecute(String result) {
try {
JSONArray jsonArray = new JSONArray(result);
Log.i("JSON", "Number of json items: " +
jsonArray.length());
//---print out the content of the json feed---
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
int id = jsonObject.getInt(ID);
String type = jsonObject.getString(TYPE);
String data = jsonObject.getString(DATA);
if(type.equals("text"))
textList.put(id,data);
else if(type.equals("other"))
otherList.put(id,data);
else if(type.equals("image"))
imageList.put(id,data);
// Toast.makeText(getBaseContext(), jsonObject.getString("type") +
// " - " + jsonObject.getString("data"), Toast.LENGTH_SHORT).show();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new ReadJSONFeedTask().execute(
"sample url (not shown in this post)");
}
}
片段1.java:
package com.example.json;
import java.util.HashMap;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class fragment1 extends ListFragment {
@SuppressWarnings("unchecked")
public HashMap<Integer,String> textList =
(HashMap<Integer, String>) getArguments().getSerializable("textList");
public String[] vals = new String[textList.size()];
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
for(int i = 0; i < textList.size(); i++)
vals[i] = (String)textList.values().toArray()[i];
return inflater.inflate(R.layout.fragment1, container, false);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setListAdapter(new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, vals));
}
public void onListItemClick(ListView parent, View v, int position, long id)
{
Toast.makeText(getActivity(),
"You have selected " + vals[position], Toast.LENGTH_SHORT).show();
}
}
片段1.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="fill_parent"
android:orientation="vertical" >
<ListView
android:id="@id/android:list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:drawSelectorOnTop="false" />
</LinearLayout>
主.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="fill_parent"
android:orientation="horizontal" >
<fragment
android:id="@+id/fragment1"
android:name="com.example.json.Fragment1"
android:layout_width="0dp"
android:layout_height="200dp"
android:layout_weight="0.5" />
<fragment
android:id="@+id/fragment2"
android:name="com.example.json.Fragment1"
android:layout_width="0dp"
android:layout_height="300dp"
android:layout_weight="0.5" />
</LinearLayout>