如何解析Sub JSONArray并显示图像？
邓丰
问题内容：
问题答案：
我是一名PHP程序员，正在尝试学习JAVA。我在尝试解析json文件时遇到问题。已经三天了..对此感到头疼。我正在创建一个Android应用程序（使用JAVA）来解析json文件。这是示例json数据（http://metalgearrisingguide.com/samplejson.json）以及如何显示图像？
当我尝试时，我的logcat出现以下错误，模拟器上没有任何显示
Error parsing data org.json.JSONException: Value {"product":[{"summary":"Speak a word and the knob will turn by itself","state":"good","image":"http:\/\/upload.wikimedia.org\/wikipedia\/commons\/e\/e9\/Door_Knob_with_Lock_USA.jpg","title":"Special Door knob requires no holding just music","address":[{"address":"Merchant address 1"},{"address":"merchant address 2"}],"url":"http:\/\/merchantwebsite.com"},{"summary":"This door bell will detect faces of known people and change music if unknown","state":"good","image":"http:\/\/www.thedoorbell.net\/images\/DoorbellHeader.jpg","title":"Special Door Bell that uses face recognition technology","address":[{"address":"Merchant address 1"},{"address":"merchant address 2"}],"url":"http:\/\/merchantwebsite2.com"},{"summary":"Can't wake up in the morning?\r\nWill you be awake for party? Listen to your favourite song that will awake you!","state":"refurnished","image":"http:\/\/jgrundig.wpengine.netdna-cdn.com\/wp-content\/uploads\/2011\/08\/RCA-Alarm-Clock-with-Charging-Cord-RC107.jpg","title":"The only alarm clock that plays your favourite song from your smartphone","address":[{"address":"Merchant address 1"},{"address":"merchant address 2"}],"url":"http:\/\/merchantwebsite3.com"}],"site":{"sitename":"Simple Product Find","imgprefix":"http:\/\/mydomain.com\/","urlprefix":"http:\/\/mydomain.com\/"}} at data of type org.json.JSONObject cannot be converted to JSONArray
这是我的JSONfunctions类：
public class JSONfunctions {
public static JSONObject getJSONfromURL(String url){
InputStream is = null;
String result = "";
JSONObject jArray = null;
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
try{
jArray = new JSONObject(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
//return result;
}
}
这是我的代码：
public class Main extends ListActivity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listplaceholder);
ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
JSONObject json = JSONfunctions.getJSONfromURL("http://metalgearrisingguide.com/samplejson.json");
try{
JSONArray data = json.getJSONArray("data");
JSONArray products = data.getJSONArray(1);
for(int i=0;i<products.length();i++){
HashMap<String, String> map = new HashMap<String, String>();
JSONObject e = products.getJSONObject(i);
map.put("id", String.valueOf(i));
map.put("title", "Product name:" + e.getString("title"));
map.put("state", "Condition:" + e.getString("state"));
map.put("summary", "Description: " + e.getString("summary"));
mylist.add(map);
Set set = map.entrySet();
// Get an iterator
Iterator o = set.iterator();
// Display elements
while(o.hasNext()) {
Map.Entry me = (Map.Entry)o.next();
System.out.print(me.getKey() + ": ");
System.out.println(me.getValue());
}
System.out.println();
}
}catch(JSONException e) {
Log.e("log_tag", "Error parsing data "+e.toString());
}
ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main,
new String[] { "state", "summary" },
new int[] { R.id.item_title, R.id.item_subtitle });
setListAdapter(adapter);
final ListView lv = getListView();
lv.setTextFilterEnabled(true);
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
@SuppressWarnings("unchecked")
HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);
Toast.makeText(Main.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show();
}
});
}
}
问题答案：
您有两个问题，第一个是如何解析sub json；第二个是如何解析sub
json。第二，如何从网上显示图像；我通过您的示例json网址成功进行了演示，如下所示：
首先，定义一个数据类：Data.java
package com.example.jsonparser;
import java.util.ArrayList;
public class Data {
private String mState;
private String mImageUrl;
private String mTitle;
private String mSummary;
private ArrayList<String> mAddList;
private String mUrl;
public Data(String mState, String mImageUrl, String mTitle,
String mSummary, ArrayList<String> addList, String mUrl) {
super();
this.mState = mState;
this.mImageUrl = mImageUrl;
this.mTitle = mTitle;
this.mSummary = mSummary;
this.mAddList = addList;
this.mUrl = mUrl;
}
public String getmState() {
return mState;
}
public void setmState(String mState) {
this.mState = mState;
}
public String getmImageUrl() {
return mImageUrl;
}
public void setmImageUrl(String mImageUrl) {
this.mImageUrl = mImageUrl;
}
public String getmTitle() {
return mTitle;
}
public void setmTitle(String mTitle) {
this.mTitle = mTitle;
}
public String getmSummary() {
return mSummary;
}
public void setmSummary(String mSummary) {
this.mSummary = mSummary;
}
public ArrayList<String> getmAddress1() {
return mAddList;
}
public void setmAddress1(ArrayList<String> mAddress1) {
this.mAddList = mAddress1;
}
public String getmUrl() {
return mUrl;
}
public void setmUrl(String mUrl) {
this.mUrl = mUrl;
}
}
其次，定义用于解析json字符串的解析器类：Parser.java
package com.example.jsonparser;
import java.util.ArrayList;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.util.Log;
public class Parser {
private ArrayList<Data> mDataSource = new ArrayList<Data>();
public Parser(String json) {
jsonParser(json);
}
private void jsonParser(String json) {
try {
JSONObject obj = new JSONObject(json);
JSONObject var = obj.getJSONObject("data");
JSONArray list = var.getJSONArray("product");
int len = list.length();
for (int i = 0; i < len; i++) {
try {
JSONObject data = list.getJSONObject(i);
String state = data.getString("state");
String image = data.getString("image");
String title = data.getString("title");
String summary = data.getString("summary");
String url = data.getString("url");
ArrayList<String> addList = new ArrayList<String>();
JSONArray addArray = data.getJSONArray("address");
int size = addArray.length();
/**
* parser sub json
*/
for(int j = 0; j < size; j++) {
addList.add(addArray.getJSONObject(j).getString("address"));
}
mDataSource.add(new Data(state, image, title, summary, addList, url));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public ArrayList<Data> getSource() {
return mDataSource;
}
}
第三，通过URL定义任务下载图像：DownloadImageTask.java
package com.example.jsonparser;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;
public class DownloadImageTask extends AsyncTask<Void, Void, Bitmap> {
private String mUrl;
private ImageView mImageView = null;
public DownloadImageTask(String Url, ImageView imageView) {
mUrl = Url;
this.mImageView = imageView;
}
protected void onPostExecute(Bitmap result) {
super.onPostExecute(result);
if (result != null) {
mImageView.setImageBitmap(result);
}
}
protected Bitmap doInBackground(Void... params) {
Bitmap bitmap = getBitmap(mUrl);
return bitmap;
}
public Bitmap getBitmap(String imageUrl) {
Bitmap mBitmap = null;
try {
URL url = new URL(imageUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
InputStream is = conn.getInputStream();
mBitmap = BitmapFactory.decodeStream(is);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return mBitmap;
}
}
第四，定义一个适配器扩展BaseAdapter来显示数据和图像：Adapter.java
package com.example.jsonparser;
import java.util.ArrayList;
import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.RecyclerListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class Adapter extends BaseAdapter {
private static final String TAG = "Adapter";
private Activity mActivity;
public ArrayList<Data> mObjects;
static class ViewHolder {
ImageView icon;
TextView title;
DownloadImageTask mTask;
}
public Adapter(Activity activity, ArrayList<Data> mObjects) {
this.mActivity = (Activity) activity;
this.mObjects = mObjects;
}
public void setObjects(ArrayList<Data> mObjects) {
this.mObjects = mObjects;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Data item = mObjects.get(position);
View rowView = convertView;
if (rowView == null) {
LayoutInflater inflater = mActivity.getLayoutInflater();
rowView = inflater.inflate(R.layout.item, parent, false);
ViewHolder viewHolder = new ViewHolder();
viewHolder.icon = (ImageView) rowView.findViewById(R.id.image);
viewHolder.title = (TextView) rowView.findViewById(R.id.title);
rowView.setTag(viewHolder);
}
ViewHolder holder = (ViewHolder) rowView.getTag();
holder.title.setText(item.getmTitle());
holder.icon.setBackgroundResource(R.drawable.ic_launcher);
holder.mTask = new DownloadImageTask(item.getmImageUrl(), holder.icon);
if (!holder.mTask.isCancelled()) {
holder.mTask.execute();
}
return rowView;
}
@Override
public int getCount() {
return (this.mObjects.size());
}
@Override
public Object getItem(int position) {
return (this.mObjects.get(position));
}
@Override
public long getItemId(int position) {
return (position);
}
public AbsListView.RecyclerListener mRecyclerListener = new RecyclerListener( ){
public void onMovedToScrapHeap(View view) {
ViewHolder viewHolder = (ViewHolder) view.getTag();
DownloadImageTask imagetask = viewHolder.mTask;
if (imagetask != null) {
imagetask.cancel(true);
}
}
};
}
最后，在活动中使用以下类：MainActivity.java
package com.example.jsonparser;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.ListView;
public class MainActivity extends Activity {
private ListView mListView;
private Adapter mAdapter;
private ArrayList<Data> mSource = new ArrayList<Data>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mListView = (ListView) findViewById(android.R.id.list);
mAdapter = new Adapter(this, mSource);
mListView.setAdapter(mAdapter);
mListView.setRecyclerListener(mAdapter.mRecyclerListener);
final String url = "http://metalgearrisingguide.com/samplejson.json";
new Thread(new Runnable() {
@Override
public void run() {
Parser parser = new Parser(getJSONfromURL(url));
mSource = parser.getSource();
Message msg = mHandler.obtainMessage();
mHandler.sendMessage(msg);
}
}).start();
}
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
mAdapter.setObjects(mSource);
mAdapter.notifyDataSetChanged();
}
};
public String getJSONfromURL(String url) {
InputStream is = null;
String result = "";
// http post
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
// convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
return result;
}
}
activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:cacheColorHint="@android:color/transparent" />
</LinearLayout>
item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageView
android:id="@+id/image"
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_gravity="left|top"
android:layout_marginBottom="10dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp" />
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:gravity="left|top"
android:lineSpacingExtra="3.0dp"
android:textColor="#ffffff"
android:textSize="15sp" />
</LinearLayout>
就这样。
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