我正在使用AsyncTask从数据库中插入，更新和删除数据。我使用此代码来插入，更新，删除，并且工作正常。但是，当我要使用select并在EditText中显示数据时，我无法从doInBackground()到onPostExecute()取值，它什么也没显示。
这是我的代码：
MenuUtama.java
public class MenuUtama extends Activity {
/** Called when the activity is first created. */
private TextView nama_user;
private String nm_user = "";
private EditText kode, nama, harga, deskripsi;
private Button insert, update, delete, cek;
private String kode1, nama1, harga1, deskripsi1;
JSONArray data = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
kode = (EditText) findViewById(R.id.editKode);
nama = (EditText) findViewById(R.id.editNama);
harga = (EditText) findViewById(R.id.editHarga);
deskripsi = (EditText) findViewById(R.id.editDes);
cek = (Button) findViewById(R.id.btnCek);
insert = (Button) findViewById(R.id.buttonInsert);
update = (Button) findViewById(R.id.buttonUpdate);
delete = (Button) findViewById(R.id.buttonDelete);
nama_user = (TextView) findViewById(R.id.textView3);
Intent i = getIntent();
nm_user = i.getStringExtra("nama_user");
nama_user.setText(nm_user);
insert.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String url = "";
url = "http://192.168.1.10/crudsederhana/aksi.php";
try {
String ko = URLEncoder.encode(kode.getText().toString(),"utf-8");
String n = URLEncoder.encode(nama.getText().toString(),"utf-8");
String hr = URLEncoder.encode(harga.getText().toString(),"utf-8");
String d = URLEncoder.encode(deskripsi.getText().toString(), "utf-8");
url += "?a=insert&kd=" + ko + "&nm=" + n + "&hrg=" + hr + "&deskripsi=" + d;
new CRUD().execute(url);
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
});
update.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
String url = "";
url = "http://192.168.1.10/crudsederhana/aksi.php";
try {
String ko = URLEncoder.encode(kode.getText().toString(),"utf-8");
String n = URLEncoder.encode(nama.getText().toString(),"utf-8");
String hr = URLEncoder.encode(harga.getText().toString(),"utf-8");
String d = URLEncoder.encode(deskripsi.getText().toString(), "utf-8");
url += "?a=update&kd=" + ko + "&nm=" + n + "&hrg=" +hr+ "&des=" + d;
new CRUD().execute(url);
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
});
delete.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String url = "";
kode1 = kode.getText().toString();
url = "http://192.168.1.10/crudsederhana/aksi.php?a=delete&kd=" + kode1;
new CRUD().execute(url);
}
});
cek.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String url = "";
kode1 = kode.getText().toString();
url = "http://192.168.1.10/crudsederhana/aksi.php?a=read&kd="+kode1;
new CRUD().execute(url);
}
});
}
public class CRUD extends AsyncTask<String, String, String> {
String success;
String kode_d, nama_d, harga_d, des_d;
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(String... params) {
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(params[0]);
try {
success = json.getString("success");
Log.e("error", "nilai sukses=" + success);
JSONArray hasil = json.getJSONArray("login");
if (success.equals("1")) {
for (int i = 0; i < hasil.length(); i++) {
JSONObject c = hasil.getJSONObject(i);
kode_d = c.getString("kd");
nama_d = c.getString("nm");
harga_d = c.getString("hrg");
des_d = c.getString("deskripsi");
}
}
else {
Log.e("erro", "tidak bisa ambil data 0");
}
}
catch (Exception e) {
// TODO: handle exception
Log.e("erro", "tidak bisa ambil data 1");
}
return kode_d;
}
protected void onPostExecute(String result) {
super.onPostExecute(result);
kode.setText(kode_d);
nama.setText(nama_d);
harga.setText(harga_d);
deskripsi.setText(des_d);
}
}
}
JSONParser.java
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject getJSONFromUrl(String url) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
catch (ClientProtocolException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
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();
json = sb.toString();
}
catch (Exception e) {
Log.e("Buffer Error", "Error converting result " +e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
}
catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " +e.toString());
}
// return JSON String
return jObj;
}
public JSONObject makeHttpRequest(String url, String method, List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
catch (ClientProtocolException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
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();
json = sb.toString();
}
catch (Exception e) {
Log.e("Buffer Error", "Error converting result " +e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
}
catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " +e.toString());
}
// return JSON String
return jObj;
}
}
答案 0 :(得分：0)
这是因为您没有从doInBackground()返回任何值（总是返回null），并且没有在onPostExecute(String result)形式参数中使用'string'。垃圾进垃圾出
答案 1 :(得分：0)
您的doInBackground()仅返回一个字符串return kode_d;，然后在您的onPostExecute(String result)（需要一个字符串）中，使用为空的kode_d。
如果您希望返回所有这些值，请创建一个ArrayList()，在doInBackground()末尾将其返回，并在onPostExecute(ArrayList result)中进行迭代，然后将其传递给文本视图。
甚至更好地创建一个对象并将值添加到每个字段中。您的字段是kode_d, nama_d, harga_d, des_d
这就是onPostExecute的作用
/**
* <p>Runs on the UI thread after {@link #doInBackground}. The
* specified result is the value returned by {@link #doInBackground}.
* To better support testing frameworks, it is recommended that this be
* written to tolerate direct execution as part of the execute() call.
* The default version does nothing.</p>
*
* <p>This method won't be invoked if the task was cancelled.</p>
*
* @param result The result of the operation computed by {@link #doInBackground}.
*
* @see #onPreExecute
* @see #doInBackground
* @see #onCancelled(Object)
*/