我现在正在尝试理解JSON的工作原理,所以我想做一个小的JSON阅读项目来更好地学习。我希望用户可以使用EditText和搜索按钮,并查找用户输入的网站是否有任何JSON数据,然后在文本框中显示它。目前,我正在测试网站:itunes.apple.com/search?term=
正如您在我的代码中所看到的,我只是设置了那些变量,没有使用EditText和Search按钮,直到我把这个东西搞定。我得到了以下错误:
我相信这是由于以下这行代码引起的:HttpResponse r = client.execute(get);,但我不知道应该如何修复主机为空的错误。我觉得这可能与问号或其他某些东西有关。或者可能我是以错误的方式来解决这个问题。请考虑到这是我第一次使用JSON进行项目开发。也许我需要一个更简单的关于如何使用JSON的教程,以便我能够彻底理解它。谢谢!
11-03 20:30:58.545: E/AndroidRuntime(8608): FATAL EXCEPTION: AsyncTask #1
11-03 20:30:58.545: E/AndroidRuntime(8608): java.lang.RuntimeException: An error occured while executing doInBackground()
11-03 20:30:58.545: E/AndroidRuntime(8608): at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-03 20:30:58.545: E/AndroidRuntime(8608): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-03 20:30:58.545: E/AndroidRuntime(8608): at java.lang.Thread.run(Thread.java:856)
11-03 20:30:58.545: E/AndroidRuntime(8608): Caused by: java.lang.IllegalStateException:
Target host must not be null, or set in parameters. scheme=null, host=null, path=itunes.apple.com/search
我相信这是由于以下这行代码引起的:HttpResponse r = client.execute(get);,但我不知道应该如何修复主机为空的错误。我觉得这可能与问号或其他某些东西有关。或者可能我是以错误的方式来解决这个问题。请考虑到这是我第一次使用JSON进行项目开发。也许我需要一个更简单的关于如何使用JSON的教程,以便我能够彻底理解它。谢谢!
public class MainActivity extends Activity implements OnClickListener {
TextView fetchText;
EditText httpEntryBox,jsonEntryBox;
Button search_button_http, search_button_json;
HTTP_Fetcher http_fetch;
HttpClient client;
final static String URL = "itunes.apple.com/search?term=";
JSONObject json;
InputMethodManager imm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fetchText = (TextView) findViewById(R.id.fetchText);
client = new DefaultHttpClient();
new Read().execute("artistName");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public JSONObject search( String searchItem ) throws ClientProtocolException, IOException, JSONException, URISyntaxException{
StringBuilder url = new StringBuilder(URL);
url.append(searchItem);
String finished_url = url.toString();
HttpGet get = new HttpGet(finished_url);
HttpResponse r = client.execute(get);
int status = r.getStatusLine().getStatusCode();
if (status == 200){
HttpEntity e = r.getEntity();
String data = EntityUtils.toString(e);
JSONArray array = new JSONArray(data);
return array.getJSONObject(0);
}else{
Log.e("Search","fetch error");
return null;
}
}
public class Read extends AsyncTask<String, Integer, String>{
@Override
protected String doInBackground(String... params) {
try {
json = search("lilwayne");
return json.getString(params[0]);
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} catch (URISyntaxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
fetchText.setText(result);
}
}
}