我对android很新。在这个程序中，我试图让它成为当在编辑文本中键入名字时，它将显示我已经在现有MySQL数据库中的人的信息。你能告诉我如何改进这一点吗？我也无法弄清楚如何摆脱红色突出显示（错误“'是'无法解决”）在线上的“是”
更新*这是我的代码的样子。 “无法解决”问题消失了。
public class PS extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final EditText et_Text = (EditText) findViewById(R.id.et_Text);
//add new KeyListener Callback (to record key input)
et_Text.setOnKeyListener(new OnKeyListener() {
//function to invoke when a key is pressed
public boolean onKey(View v, int keyCode, KeyEvent event) {
//check if there is
if (event.getAction() == KeyEvent.ACTION_DOWN) {
//check if the right key was pressed
if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
InputStream is = null;
String result = "";
//the name data to send
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("name", et_Text.getText().toString()));
//http post
if (is != null) {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://******/sampleDB/testSend.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
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());
}
//parse json data
try {
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
Log.i("log_tag", "PersonID: " + json_data.getInt("PersonID")
+ ", FirstName: " + json_data.getString("FirstName")
+ ", LastName: " + json_data.getString("LastName")
+ ", Age: " + json_data.getInt("Age"));
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
;
}
et_Text.setText("");
//and clear the EditText control
}
return true;
}
return false;
}
});
}
}
我还没有else语句，但是“if”下的代码被认为是死代码...我应该在try语句中使用if语句吗？ / p>
答案 0 :(得分：0)
问题是在第一个try块中声明了is，这限制了它对该块的可见性。试试这个
// move is declaration before the try-catch
InputStream is = null;
try{
....
// just use it here
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
// it will still be available here.
这将起作用，因为它将在try-except块之外声明。不要忘记添加一些错误检查，至少if (is != null)周围使用is
编辑 - 错误检查，我的意思是：避免错误导致用户未处理，不整洁，令人困惑，最重要的是他们会购买你的竞争对手。如果出现问题，你应该采取措施保护用户，比如
if (is != null) {
// wrapped in if because this code assumes is exists
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();
} else {
// do whatever you have to do to signal to the user that something went wrong.
}
EDIT2：你的（是！= null）检查是在一个非常奇怪的地方。将它移到一个更好的位置，在我原来的答案中提出，见下文。
最后一个建议：不知道你使用的编辑器，但缩进是一个可怕的混乱，如果没有合理的缩进，代码很难阅读。
public class PS extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final EditText et_Text = (EditText) findViewById(R.id.et_Text);
//add new KeyListener Callback (to record key input)
et_Text.setOnKeyListener(new OnKeyListener() {
//function to invoke when a key is pressed
public boolean onKey(View v, int keyCode, KeyEvent event) {
//check if there is
if (event.getAction() == KeyEvent.ACTION_DOWN) {
//check if the right key was pressed
if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
InputStream is = null;
String result = "";
//the name data to send
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("name", et_Text.getText().toString()));
//http post
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://******/sampleDB/testSend.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
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());
}
// At this point is should be set, if it isn't, tell user what went wrong
if (is != null) {
//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());
}
//parse json data
try {
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
Log.i("log_tag", "PersonID: " + json_data.getInt("PersonID")
+ ", FirstName: " + json_data.getString("FirstName")
+ ", LastName: " + json_data.getString("LastName")
+ ", Age: " + json_data.getInt("Age"));
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
et_Text.setText("");
//and clear the EditText control
} else {
// Hey user, this went horribly wrong
}
}
return true;
}
return false;
}
});
}
}