我的应用程序总是强制关闭android上面的姜饼，大多数答案说我需要将我的代码转换为asynctask。我试过了，但总是失败了。有人可以帮帮我吗？下面是我的JSONParser类
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject getJSONListfromURL(String url,List<NameValuePair> params){
//initialize
InputStream is = null;
String result = "";
JSONObject jArray = null;
//http post
try{
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
httppost.setEntity(new UrlEncodedFormEntity(params));
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());
}
//try parse the string to a JSON object
try{
jArray = new JSONObject(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {
// Making HTTP request
try {
// 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();
} 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();
Log.e("JSON", json);
} 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 void SendJSONToURL(String url,List<NameValuePair> params){
//http post
try{
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
httppost.setEntity(new UrlEncodedFormEntity(params));
httpclient.execute(httppost);
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
}
}
以下是我的活动类，用于从服务器获取数据，然后将其放入listview
public class TransaksiList extends Activity {
EditText filter;
Button tambah;
ListView list;
/** Called when the activity is first created. */
List<String> items, items2,items3,items4,items5;
private JSONParser jsonParser;
String ServerURL = "http://10.0.2.2/fmapp/"; // alamat lokasi file untuk
// menangkap/mengirim JSON
String list_tag = "getDataTransaksi",pesan_tag="deleteTransaksi";
List<String> data=new ArrayList<String>();
ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.transaksi_list);
tambah = (Button) findViewById(R.id.btnTambah);
filter = (EditText) findViewById(R.id.filter);
list=(ListView) findViewById(R.id.listTransaksi);
registerForContextMenu(list);
tambah.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intentTransaksi = new Intent(TransaksiList.this,
TransaksiTambah.class);
startActivity(intentTransaksi);
}// onClick
});
filter.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// TODO Auto-generated method stub
TransaksiList.this.adapter.getFilter().filter(s);
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable s) {
// TODO Auto-generated method stub
}
});
}
@Override
protected void onStart() {
items = new ArrayList<String>();
items2 = new ArrayList<String>();
items3 = new ArrayList<String>();
items4 = new ArrayList<String>();
items5 = new ArrayList<String>();
items.clear();
items2.clear();
items3.clear();
items4.clear();
items5.clear();
this.data.clear();
// Memanggil class JSONParser
jsonParser = new JSONParser();
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", list_tag));
// Mengirim parameter yang akan di tangkap server
JSONObject json = jsonParser.getJSONFromUrl(ServerURL, params);
try {
JSONArray data = json.getJSONArray("transaksi"); // key ini didapat
// dari nama
// array yang
// kita buat di
// dalam JSON
for (int i = 0; i < data.length(); i++) {
JSONObject e = data.getJSONObject(i);
items.add(e.getString("id_transaksi"));
items2.add(e.getString("pancing"));
items3.add(e.getString("umpan"));
items4.add(e.getString("bakar"));
items5.add(e.getString("harga_total"));
this.data.add("id: "+items.get(i)+" "+"total: "+items5.get(i));
}
} catch (JSONException e) {
e.printStackTrace();
}
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, this.data);
list.setAdapter(adapter);
super.onStart();
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Take appropriate action for each action item click
switch (item.getItemId()) {
case R.id.transaksi_ikan:
// search action
Intent intentTransaksi = new Intent(TransaksiList.this,TransaksiIkan.class);
startActivity(intentTransaksi);
return true;
case R.id.ikan:
// search action
Intent intentIkan = new Intent(TransaksiList.this,IkanList.class);
startActivity(intentIkan);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
@Override
public boolean onContextItemSelected(MenuItem item) {
// Take appropriate action for each action item click
AdapterContextMenuInfo menuInfo=(AdapterContextMenuInfo) item.getMenuInfo();
String id=items.get((menuInfo.position));
switch (item.getItemId()) {
case R.id.edit:
Intent intentEdit = new Intent(TransaksiList.this,TransaksiEdit.class);
intentEdit.putExtra("id", id);
intentEdit.putExtra("pancing", items2.get((menuInfo.position)));
intentEdit.putExtra("umpan", items3.get((menuInfo.position)));
intentEdit.putExtra("bakar", items4.get((menuInfo.position)));
intentEdit.putExtra("harga", items5.get((menuInfo.position)));
startActivity(intentEdit);
return true;
case R.id.delete:
jsonParser = new JSONParser();
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", pesan_tag));
params.add(new BasicNameValuePair("id", id));
//Mengirim parameter yang akan di tangkap server
try{
jsonParser.SendJSONToURL(ServerURL, params);
Toast.makeText(getApplicationContext(), "Berhasil menghapus transaksi", Toast.LENGTH_LONG).show();
onStart();
}
catch(Exception e){
Toast.makeText(getApplicationContext(), "Gagal menghapus transaksi", Toast.LENGTH_LONG).show();
}
return true;
default:
return super.onContextItemSelected(item);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_transaksi, menu);
return true;
}
@Override
public void onCreateContextMenu (ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo){
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_dml, menu);
}
}
感谢您的帮助
答案 0 :(得分：1)
AsyncTasks非常易于使用。您必须找出使用它们的正确方法，并记住AsyncTask必须使用子类。子类将覆盖至少一个方法doInBackground（Params ...），并且通常会覆盖第二个方法。您可以右键单击并添加未实现方法以查看所有内容。这是docs的 并且不要忘记你必须在asynctask中调用你的web请求。
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
// Escape early if cancel() is called
if (isCancelled()) break;
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
}