我来自php背景，我正在尝试学习android。我在一个示例代码中看到了这个，我正在查看类中的类定义。这怎么样？有人可以向我解释一下吗？您可以看到LongOperation类是在RestfulServices类中定义的。
public class RestFulWebservice extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.rest_ful_webservice);
final Button GetServerData = (Button) findViewById(R.id.GetServerData);
GetServerData.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// WebServer Request URL
String serverURL = "http://androidexample.com/media/webservice/JsonReturn.php";
// Use AsyncTask execute Method To Prevent ANR Problem
new LongOperation().execute(serverURL);
}
});
}
// Class with extends AsyncTask class
private class LongOperation extends AsyncTask<String, Void, Void> {
// Required initialization
private final HttpClient Client = new DefaultHttpClient();
private String Content;
private String Error = null;
private ProgressDialog Dialog = new ProgressDialog(RestFulWebservice.this);
String data ="";
TextView uiUpdate = (TextView) findViewById(R.id.output);
TextView jsonParsed = (TextView) findViewById(R.id.jsonParsed);
int sizeData = 0;
EditText serverText = (EditText) findViewById(R.id.serverText);
protected void onPreExecute() {
// NOTE: You can call UI Element here.
//Start Progress Dialog (Message)
Dialog.setMessage("Please wait..");
Dialog.show();
try{
// Set Request parameter
data +="&" + URLEncoder.encode("data", "UTF-8") + "="+serverText.getText();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// Call after onPreExecute method
protected Void doInBackground(String... urls) {
/************ Make Post Call To Web Server ***********/
BufferedReader reader=null;
// Send data
try
{
// Defined URL where to send data
URL url = new URL(urls[0]);
// Send POST data request
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.write( data );
wr.flush();
// Get the server response
reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
// Read Server Response
while((line = reader.readLine()) != null)
{
// Append server response in string
sb.append(line + "\n");
}
// Append Server Response To Content String
Content = sb.toString();
}
catch(Exception ex)
{
Error = ex.getMessage();
}
finally
{
try
{
reader.close();
}
catch(Exception ex) {}
}
/*****************************************************/
return null;
}
protected void onPostExecute(Void unused) {
// NOTE: You can call UI Element here.
// Close progress dialog
Dialog.dismiss();
if (Error != null) {
uiUpdate.setText("Output : "+Error);
} else {
// Show Response Json On Screen (activity)
uiUpdate.setText( Content );
/****************** Start Parse Response JSON Data *************/
String OutputData = "";
JSONObject jsonResponse;
try {
/****** Creates a new JSONObject with name/value mappings from the JSON string. ********/
jsonResponse = new JSONObject(Content);
/***** Returns the value mapped by name if it exists and is a JSONArray. ***/
/******* Returns null otherwise. *******/
JSONArray jsonMainNode = jsonResponse.optJSONArray("Android");
/*********** Process each JSON Node ************/
int lengthJsonArr = jsonMainNode.length();
for(int i=0; i < lengthJsonArr; i++)
{
/****** Get Object for each JSON node.***********/
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
/******* Fetch node values **********/
String name = jsonChildNode.optString("name").toString();
String number = jsonChildNode.optString("number").toString();
String date_added = jsonChildNode.optString("date_added").toString();
OutputData += " Name : "+ name +" \n "
+ "Number : "+ number +" \n "
+ "Time : "+ date_added +" \n "
+"--------------------------------------------------\n";
//Log.i("JSON parse", song_name);
}
/****************** End Parse Response JSON Data *************/
//Show Parsed Output on screen (activity)
jsonParsed.setText( OutputData );
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
}
答案 0 :(得分：1)
Java语法允许此构造。它被称为内部阶级。 http://docs.oracle.com/javase/tutorial/java/javaOO/innerclasses.html
内部类是一种特殊的嵌套类。 http://docs.oracle.com/javase/tutorial/java/javaOO/nested.html
答案 1 :(得分：1)
Java中允许这样做。 LongOperation范围之外的RestfulServices很可能不需要LongOperation。因此，开发人员可能会选择在RestfulServices内嵌套{{1}}。