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Android如何集成一个AsyncTask

转载 作者:行者123 更新时间:2023-11-30 04:10:30 26 4
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您好,我有一个下载 JSON 提要的应用程序,它开始变长了,我知道我需要使用 AsyncTask,但我不确定如何将它集成到我的代码中,有人知道吗什么是整合它的最佳方式。

到目前为止,这是我的原始代码

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&timestamp=" + 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&timestamp=" + 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)

最佳答案

她是一个异步任务的例子,你真的应该把它放在一个异步任务中,因为在 android 3.0 中 > 有一些关于它的规则......

你需要把它放在一个Async任务中,它不会在3.0的主线程中运行>

使用这个:

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] + " ");
}

}
}

你需要在异步任务之外引用它

JsonTask jsontask;

那么你需要启动它

jsontask = new JsonTask();
jsontask.execute();

我刚才遇到了完全相同的问题,祝你好运

关于Android如何集成一个AsyncTask,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/10931543/

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