我正在尝试从mysql数据库中检索一些数据，以便用该数据填充微调器。我设法将数据插入spinner到mysql数据库但是当我尝试检索它时，它在Logcat中显示spinner为null！ 我在网上搜索但我无法找到解决问题的方法。
这是从mysql数据库中检索数据的java代码：
private static final String TAG_FACULTY_NAME = "faculty_name";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.editactivity); //Connected to XML file for the interface
// save button
btnSave = (Button) findViewById(R.id.lecturerSave);
//Sharedpreference to get lecturer details
SharedPreferences sp = getSharedPreferences("logindetails", 0);
uid = sp.getString("uid", "-1");
// Getting complete lecturer details in background thread
new GetLecturerDetails().execute();
// save button click event
btnSave.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// starting background task to update lecturer account
new SaveLecturerDetails().execute();
}
});
}
/**
* Background Async Task to Get complete lecturer account details
* */
class GetLecturerDetails extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(EditActivity.this);
pDialog.setMessage("Loading. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* Getting lecturer account details in background thread
* */
protected String doInBackground(String... params) {
//updating UI from Background Thread
// runOnUiThread(new Runnable() {
// public void run() {
// Check for success tag
int success;
try {
// Building Parameters
List<NameValuePair> params1 = new ArrayList<NameValuePair>();
params1.add(new BasicNameValuePair("uid", uid));
// getting lecturer account details by making HTTP request
// Note that lecturer account details url will use GET request
JSONObject json = jsonParser.makeHttpRequest(
url_lecturer_details, "GET", params1);
// check your log for json response
Log.d("Single Product Details", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// successfully received lecturer account details
JSONArray productObj = json
.getJSONArray(TAG_PRODUCT); // JSON Array
// get first lecturer account object from JSON Array
final JSONObject product = productObj.getJSONObject(0);
// lecturer account with this uid found
// Edit Text
runOnUiThread(new Runnable() {
public void run() {
txtdrop_down = (Spinner) findViewById(R.id.spinner_faculty);
// display lecturer data in EditText
try
{
txtdrop_down.setTag(product.getString(TAG_FACULTY_NAME));
}catch (JSONException e)
{
e.printStackTrace();
}
}
});
} else{
// lecturer account with uid not found
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once got all details
pDialog.dismiss();
}
}
这是我从Logcat获得的错误：
11-23 12:25:02.543: E/AndroidRuntime(2499): FATAL EXCEPTION: main
11-23 12:25:02.543: E/AndroidRuntime(2499): java.lang.NullPointerException
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.widget.Spinner$DialogPopup.show(Spinner.java:935)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.widget.Spinner.performClick(Spinner.java:614)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.view.View$PerformClick.run(View.java:17721)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.os.Handler.handleCallback(Handler.java:730)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.os.Handler.dispatchMessage(Handler.java:92)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.os.Looper.loop(Looper.java:137)
11-23 12:25:02.543: E/AndroidRuntime(2499): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-23 12:25:02.543: E/AndroidRuntime(2499): at java.lang.reflect.Method.invokeNative(Native Method)
11-23 12:25:02.543: E/AndroidRuntime(2499): at java.lang.reflect.Method.invoke(Method.java:525)
11-23 12:25:02.543: E/AndroidRuntime(2499): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-23 12:25:02.543: E/AndroidRuntime(2499): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-23 12:25:02.543: E/AndroidRuntime(2499): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
上面的链接有一个示例，它在运行时从用户获取值并存储在DB中，然后显示在Spinner中。它将向您展示如何从DB中获取值并在Spinner中显示它
答案 1 :(得分：0)
class ItemUpdater extends AsyncTask<String, String, String>{
private ProgressDialog Dialog = new ProgressDialog(MobileQDC_Booking_Screen.this);
protected void onPreExecute() {
Dialog.setMessage("Please wait...");
Dialog.show();
Dialog.setCancelable(false);
}
@Override
protected String doInBackground(String... params) {
try {
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet("your web service url");
HttpResponse response = httpclient.execute(httpget);
BufferedReader in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String line = "";
String NL = System.getProperty("line.separator");
while ((line = in.readLine()) != null) {
sb.append(line + NL);
}
in.close();
String result = sb.toString();
Log.v("My Response :: ", result);
JSONObject jsonObject = new JSONObject(result);
JSONArray resultArray = jsonObject.getJSONArray("Customer");
for (int i = 0; i < resultArray.length(); i++) {
JSONObject c = resultArray.getJSONObject(i);
String sbs = c.getString("ItemName");
ItemsList.add(sbs);
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
SelectCloth.setAdapter(new ArrayAdapter<String>(MobileQDC_Booking_Screen.this, android.R.layout.simple_dropdown_item_1line, ItemsList));
new ProcessUpdater().execute();
Dialog.dismiss();
}
}