您好我有一个应用程序，下载JSON Feed并开始变得长腿我知道我需要使用AsyncTask但是我不知道如何将其集成到我的代码中有没有人知道什么是最好的整合它的方式。
到目前为止我的原始代码
public class HomeActivity extends ListActivity {
private MergeAdapter adapter=null;
private ArrayAdapter<String> arrayAdapter=null;
private ArrayAdapter<String> arrayAdapter2=null;
private LazyAdapter arrayAdapter3=null;
private static final String apiKey = "7668hhf74hhd3dhhs";
private static final String apiUser = "androiduser";
private static String ChosenLeagueID = null;
private static String ChosenMethod = null;
private static String ChosenTeamId = null;
public String fulldata = null;
public String newsFeedRequest = null;
public String newsFeedURL = null;
public String resultsFeedURL = null;
public String lastMonth = null;
public String HomeTeam = null;
public String AwayTeam = null;
public String HomeScore = null;
public String AwayScore = null;
public String Attendance = null;
public String Division = null;
public String HomeScorers = null;
public String AwayScorers = null;
public String resultsFeedRequest = null;
public String chosenLeagueId = "40";
public List<String> newsList = null;
public List<String> newsList2 = null;
public List<String> newsList3 = null;
public List<String> imageList = null;
public JSONObject resultsDict = null;
public View resultsView = null;
public int newsAmount = 0;
long unixTimeStamp = System.currentTimeMillis() / 1000L;
//add Time Stamp to URL
//public String chosenMethod;
public class PostTask extends AsyncTask<Void, String, Boolean> {
@Override
protected Boolean doInBackground(Void... params) {
boolean result = false;
checkPreferences();
publishProgress("progress");
return result;
}
protected void onProgressUpdate(String... progress) {
StringBuilder str = new StringBuilder();
for (int i = 1; i < progress.length; i++) {
str.append(progress[i] + " ");
}
}
}
static String buildHmacSignature(String pKey, String pStringToSign)
{
String lSignature = "None";
try
{
Mac lMac = Mac.getInstance("HmacSHA256");
SecretKeySpec lSecret = new SecretKeySpec(pKey.getBytes(), "HmacSHA256");
lMac.init(lSecret);
byte[] lDigest = lMac.doFinal(pStringToSign.getBytes());
BigInteger lHash = new BigInteger(1, lDigest);
lSignature = lHash.toString(16);
if ((lSignature.length() % 2) != 0) {
lSignature = "0" + lSignature;
}
}
catch (NoSuchAlgorithmException lEx)
{
throw new RuntimeException("Problems calculating HMAC", lEx);
}
catch (InvalidKeyException lEx)
{
throw new RuntimeException("Problems calculating HMAC", lEx);
}
return lSignature;
}
public void checkPreferences(){
SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
ChosenMethod = preferences.getString("ChosenMethod", ChosenMethod);
ChosenLeagueID = preferences.getString("ChosenLeagueId", ChosenLeagueID);
ChosenTeamId = preferences.getString("ChosenTeamId", ChosenTeamId);
Log.v("lc", "newsurl" + newsFeedURL);
Log.v("myapp", "ChosenMethod Home = " + ChosenMethod);
Log.v("myapp", "ChosenLeagueID Home = " + ChosenLeagueID);
Log.v("myapp", "ChosenTeamID Home = " + ChosenTeamId);
if (ChosenMethod.equals("Team")) {
setContentView(R.layout.homeactteam2);
newsAmount = 5;
loadData();
} else {
setContentView(R.layout.homeact);
newsAmount = 10;
loadDataLeague();
}
}
public void loadresults(){
resultsFeedRequest = "1.0/league-website/" + chosenLeagueId + "/results?&team_id=" + ChosenTeamId + "&limit=31×tamp=" + unixTimeStamp;
resultsFeedURL = "https://www.website.com/_services/api/" + resultsFeedRequest;
String myhash = buildHmacSignature(apiKey, resultsFeedURL);
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(resultsFeedURL);
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
pairs.add(new BasicNameValuePair("requestToken", myhash));
pairs.add(new BasicNameValuePair("apiUser", apiUser));
try {
post.setEntity (new UrlEncodedFormEntity(pairs));
HttpResponse response = client.execute(post);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
fulldata = String.valueOf(json);
Log.v("myApp","resultsdata" + fulldata);
newsList = new ArrayList<String>();
newsList2 = new ArrayList<String>();
newsList3 = new ArrayList<String>();
imageList = new ArrayList<String>();
JSONObject obj = new JSONObject(json);
JSONObject objData = obj.getJSONObject("data");
JSONArray jArray = objData.getJSONArray("results");
if(jArray.length() < 1){
loadLastResults();
}else{
Log.v("lc", "this month has results");
}
//
// for(int t = 0; t < newsAmount; t++){
// JSONObject newsTitleDict = jArray.getJSONObject(t);
// imageList.add(newsTitleDict.getString("image_small"));
// newsList3.add(newsTitleDict.getString("title"));
//
// }
//
// for(int t = 0; t < 1; t++){
// JSONObject newsTitleDict = jArray.getJSONObject(t);
//
// newsList.add(newsTitleDict.getString("title"));
// newsList2.add(newsTitleDict.getString("title"));
//
// }
//
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void loadLastResults(){
resultsFeedRequest = "1.0/league-website/" + chosenLeagueId + "/results?month=04&team_id=" + ChosenTeamId + "&limit=31×tamp=" + unixTimeStamp;
resultsFeedURL = "https://www.website.com/_services/api/" + resultsFeedRequest;
String myhash = buildHmacSignature(apiKey, resultsFeedURL);
Date anotherCurDate = new Date();
SimpleDateFormat formatter = new SimpleDateFormat("MM");
String CurMonth = formatter.format(anotherCurDate);
int Int = Integer.parseInt(CurMonth);
int MonthInt = Int -1;
CurMonth = (String) (String.valueOf(MonthInt));
if (CurMonth.equals("1")){
lastMonth = "12";
}
else {
if(CurMonth.length() < 2){
lastMonth = "0" + CurMonth;
} else {
lastMonth = CurMonth;
}
}
Log.v("lc","month= " + CurMonth);
Log.v("lc","LastMonth= " + lastMonth);
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(resultsFeedURL);
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
pairs.add(new BasicNameValuePair("requestToken", myhash));
pairs.add(new BasicNameValuePair("apiUser", apiUser));
try {
post.setEntity (new UrlEncodedFormEntity(pairs));
HttpResponse response = client.execute(post);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
fulldata = String.valueOf(json);
Log.v("myApp","resultsdata" + fulldata);
newsList = new ArrayList<String>();
newsList2 = new ArrayList<String>();
newsList3 = new ArrayList<String>();
imageList = new ArrayList<String>();
JSONObject obj = new JSONObject(json);
JSONObject objData = obj.getJSONObject("data");
JSONArray jArray = objData.getJSONArray("results");
for(int t = 0; t < 1; t++){
resultsDict = jArray.getJSONObject(t);
HomeTeam = resultsDict.getString("hometeam");
AwayTeam = resultsDict.getString("awayteam");
HomeScore = resultsDict.getString("homescore");
AwayScore = resultsDict.getString("awayscore");
Attendance = resultsDict.getString("attendance");
Division = resultsDict.getString("division");
Log.v("lc","hometeam" + HomeTeam);
Log.v("lc","awayteam" + AwayTeam);
}
resultsView = LayoutInflater.from(getBaseContext()).inflate(R.layout.resultscell,
null);
TextView homeTeam = (TextView) resultsView.findViewById(R.id.HomeTeam);
homeTeam.setText(HomeTeam);
TextView awayTeam = (TextView) resultsView.findViewById(R.id.AwayTeam);
awayTeam.setText(AwayTeam);
TextView homeScore = (TextView) resultsView.findViewById(R.id.HomeScore);
homeScore.setText(HomeScore);
TextView awayScore = (TextView) resultsView.findViewById(R.id.AwayScore);
awayScore.setText(AwayScore);
TextView attendance = (TextView) resultsView.findViewById(R.id.Attendence);
attendance.setText("Att:" + Attendance);
TextView division = (TextView) resultsView.findViewById(R.id.Division);
division.setText(Division);
Log.v("lc", "resultsDict" + resultsDict);
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void loadnews(){
newsFeedRequest = "1.0/league-website/" + chosenLeagueId + "/news?timestamp=" + unixTimeStamp;
newsFeedURL = "https://www.website.com/_services/api/" + newsFeedRequest;
String myhash = buildHmacSignature(apiKey, newsFeedURL);
Log.v("lc" , "resultsurl=" + resultsFeedURL);
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(newsFeedURL);
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
pairs.add(new BasicNameValuePair("requestToken", myhash));
pairs.add(new BasicNameValuePair("apiUser", apiUser));
try {
post.setEntity (new UrlEncodedFormEntity(pairs));
HttpResponse response = client.execute(post);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
fulldata = String.valueOf(json);
Log.v("myApp","newsdata" + fulldata);
newsList = new ArrayList<String>();
newsList2 = new ArrayList<String>();
newsList3 = new ArrayList<String>();
imageList = new ArrayList<String>();
JSONObject obj = new JSONObject(json);
JSONObject objData = obj.getJSONObject("data");
JSONArray jArray = objData.getJSONArray("news");
Log.v("lc","newsAmount= " + newsAmount);
for(int t = 0; t < newsAmount; t++){
JSONObject newsTitleDict = jArray.getJSONObject(t);
imageList.add(newsTitleDict.getString("image_small"));
newsList3.add(newsTitleDict.getString("title"));
}
for(int t = 0; t < 1; t++){
JSONObject newsTitleDict = jArray.getJSONObject(t);
newsList.add(newsTitleDict.getString("title"));
// newsList2.add(newsTitleDict.getString("title"));
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void mergeAdapterSetup(){
arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);
arrayAdapter2 = new ArrayAdapter<String>(this, R.layout.resultscell, newsList2);
//arrayAdapter3 = new ArrayAdapter(this, R.layout.complex_item, newsList3);
String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);
arrayAdapter3 = new LazyAdapter(this, mStrings, news);
ListView list = getListView();
list.setTextFilterEnabled(true);
LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
View header = inflater.inflate( R.layout.homeheader, list, false);
View header2 = inflater.inflate( R.layout.homeheader2, list, false);
View header3 = inflater.inflate( R.layout.homeheader3, list, false);
//setListAdapter (arrayAdapter);
adapter = new MergeAdapter();
adapter.addView(header);
adapter.addAdapter(arrayAdapter);
adapter.addView(header2);
adapter.addView(resultsView);
adapter.addView(header3);
adapter.addAdapter(arrayAdapter3);
setListAdapter(adapter);
}
public void loadDataLeague(){
String myhash = buildHmacSignature(apiKey, newsFeedURL);
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(newsFeedURL);
List<NameValuePair> pairs = new ArrayList<NameValuePair>();
pairs.add(new BasicNameValuePair("requestToken", myhash));
pairs.add(new BasicNameValuePair("apiUser", apiUser));
try {
post.setEntity (new UrlEncodedFormEntity(pairs));
HttpResponse response = client.execute(post);
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
fulldata = String.valueOf(json);
Log.v("myApp","newsdata" + fulldata);
newsList = new ArrayList<String>();
newsList2 = new ArrayList<String>();
newsList3 = new ArrayList<String>();
imageList = new ArrayList<String>();
JSONObject obj = new JSONObject(json);
JSONObject objData = obj.getJSONObject("data");
JSONArray jArray = objData.getJSONArray("news");
Log.v("lc","newsAmount= " + newsAmount);
for(int t = 0; t < newsAmount; t++){
JSONObject newsTitleDict = jArray.getJSONObject(t);
imageList.add(newsTitleDict.getString("image_small"));
newsList3.add(newsTitleDict.getString("title"));
}
for(int t = 0; t < 1; t++){
JSONObject newsTitleDict = jArray.getJSONObject(t);
newsList.add(newsTitleDict.getString("title"));
newsList2.add(newsTitleDict.getString("title"));
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
arrayAdapter = new ArrayAdapter<String>(this, R.layout.single_item, newsList);
arrayAdapter2 = new ArrayAdapter<String>(this, R.layout.single_item, newsList2);
//arrayAdapter3 = new ArrayAdapter(this, R.layout.complex_item, newsList3);
String[] mStrings = (String[]) imageList.toArray(new String[imageList.size()]);
String[] news = (String[]) newsList3.toArray(new String[newsList3.size()]);
arrayAdapter3 = new LazyAdapter(this, mStrings, news);
ListView list = getListView();
list.setTextFilterEnabled(true);
LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE );
View header3 = inflater.inflate( R.layout.homeheader3, list, false);
//setListAdapter (arrayAdapter);
adapter = new MergeAdapter();
adapter.addView(header3);
adapter.addAdapter(arrayAdapter3);
setListAdapter(adapter);
}
public void loadData(){
loadresults();
loadnews();
mergeAdapterSetup();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
PostTask jsontask;
jsontask = new PostTask();
jsontask.execute();
Button backbtn = (Button) findViewById(R.id.backbtn);
//Listening to button event
backbtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
//Starting a new Intent
Intent previousScreen = new Intent(getApplicationContext(), ChooseTeamActivity.class);
ChosenMethod = "null";
SharedPreferences preferences = getSharedPreferences("prefs", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("ChosenMethod", ChosenMethod);
editor.commit();
previousScreen.putExtra("FullData", fulldata);
startActivity(previousScreen);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == R.id.home) {
startActivity(new Intent(HomeActivity.this, HomeActivity.class));
return(true);
}
if (item.getItemId() == R.id.match) {
startActivity(new Intent(HomeActivity.this, MatchActivity.class));
return(true);
}
if (item.getItemId() == R.id.teams) {
startActivity(new Intent(HomeActivity.this, TeamsActivity.class));
return(true);
}
if (item.getItemId() == R.id.twitter) {
startActivity(new Intent(HomeActivity.this, TwitterActivity.class));
return(true);
}
if (item.getItemId() == R.id.info) {
startActivity(new Intent(HomeActivity.this, InfoActivity.class));
return(true);
}
return(super.onOptionsItemSelected(item));
}
}
错误
java.lang.NullPointerException
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1821)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1842)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread.access$1500(ActivityThread.java:132)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1038)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.os.Handler.dispatchMessage(Handler.java:99)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.os.Looper.loop(Looper.java:143)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread.main(ActivityThread.java:4263)
06-07 12:56:34.338: E/AndroidRuntime(2688): at java.lang.reflect.Method.invokeNative(Native Method)
06-07 12:56:34.338: E/AndroidRuntime(2688): at java.lang.reflect.Method.invoke(Method.java:507)
06-07 12:56:34.338: E/AndroidRuntime(2688): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-07 12:56:34.338: E/AndroidRuntime(2688): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-07 12:56:34.338: E/AndroidRuntime(2688): at dalvik.system.NativeStart.main(Native Method)
06-07 12:56:34.338: E/AndroidRuntime(2688): Caused by: java.lang.NullPointerException
06-07 12:56:34.338: E/AndroidRuntime(2688): at HomeActivity.onCreate(HomeActivity.java:637)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
06-07 12:56:34.338: E/AndroidRuntime(2688): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1785)
答案 0 :(得分：1)
她是Async任务的一个例子，你应该把它放在异步任务中，因为在android 3.0＆gt;中关于它的一些规则不是......
你需要将它放在异步任务中，它不会在3.0＆gt;中的主线程中运行;
使用它：
public class JsonTask extends AsyncTask<Void, String, Boolean> {
@Override
protected Boolean doInBackground(Void... params) {
boolean result = false;
//All your code goes in here
//If you want to do something on the UI use progress update
publishProgress("progress");
return result;
}
protected void onProgressUpdate(String... progress) {
StringBuilder str = new StringBuilder();
for (int i = 1; i < progress.length; i++) {
str.append(progress[i] + " ");
}
}
}
您需要在异步任务之外引用它
JsonTask jsontask;
然后你需要启动它
jsontask = new JsonTask();
jsontask.execute();
前一段时间我遇到了完全相同的问题，goodluck