Android的RESTful客户端 [英] Android RESTful client
问题描述
我有一个RESTful Web服务,我想从Android的访问。
I have a RESTful web service and I want to access it from Android.
public class AndroidClientActivity extends Activity {
private EditText text;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
text = (EditText) findViewById(R.id.editText1);
}
public void myClickHandler(View view){
switch (view.getId()) {
case R.id.button1:
MyClient c = new MyClient();
c.execute(text);
break;
}
}
}
public class MyClient extends AsyncTask<EditText, Integer, String> {
protected String doInBackground(EditText... strings) {
WebResource wbr;
Client client = Client.create();
wbr = client.resource("http://my.ip.address:8080/MazeService/rest/service/hello");
String result = wbr.queryParam("number", "10").accept(MediaType.APPLICATION_JSON).get(String.class);
strings[0].setText(result);
return result;
}
protected void onProgressUpdate(Integer... progress) {
}
protected void onPostExecute(Long result) {
}
}
我得到这个堆栈跟踪在LogCat中:
I get this stacktrace in LogCat:
02-09 00:06:38.593: E/AndroidRuntime(795): Caused by: java.lang.NullPointerException
02-09 00:06:38.593: E/AndroidRuntime(795): at javax.ws.rs.core.MediaType.valueOf(MediaType.java:119)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.ClientResponse.getType(ClientResponse.java:615)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:532)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:506)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.WebResource.handle(WebResource.java:674)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:503)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.maze.client.MyClient.doInBackground(MyClient.java:19)
02-09 00:06:38.593: E/AndroidRuntime(795): at com.maze.client.MyClient.doInBackground(MyClient.java:1)
02-09 00:06:38.593: E/AndroidRuntime(795): at android.os.AsyncTask$2.call(AsyncTask.java:264)
02-09 00:06:38.593: E/AndroidRuntime(795): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
02-09 00:06:38.593: E/AndroidRuntime(795): ... 5 more
问题出在哪里?
Where is the problem?
推荐答案
我觉得你试图访问从doInBackground方法UI线程,这不是一个好地方,要做到这一点,而不是改变文本 onPostExecute
这样的方法,你可以安全地访问UI线程像这样
I think you are trying to access the UI thread from the doInBackground method and it's not a good place to do that instead change the text in onPostExecute
method like this you can access the ui thread safely like this
先定义你的AsyncTask类的私有类在你的Activity类
first define you AsyncTask class as a private class in your Activity class
private class MyClient extends AsyncTask<EditText, Void, String> {
protected String doInBackground(EditText... strings) {
WebResource wbr;
Client client = Client.create();
wbr = client.resource("http://my.ip.address:8080/MazeService/rest/service/hello");
String result = wbr.queryParam("number", "10").accept(MediaType.APPLICATION_JSON).get(String.class);
return result;
}
protected void onPostExecute(String result) {
if(result != null)
text.setText(result);
}
}
然后访问UI线程的 onPostExecute
注意,你要定义一个龙
参数为 onPostExecute
和多数民众错误的,因为你把它定义采取字符串
类在你的AsyncTask定义
note that you are defining a Long
parameter for the onPostExecute
and thats wrong since you define it to take a String
class in your AsyncTask definition
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