我是Java / ADT的新手，我正试图从“活动A”到“活动B”获得一个数组。该应用程序从网页获取信息，然后将其保存在一对数组中并显示信息。我想点击“转到图表”按钮（调用viewallday（））重定向到活动B，活动B将显示包含所有这些信息的图形。
问题是它们是一个自刷新阵列（1秒刷新），并且当应用程序处于图形模式（活动B）时不想放弃此功能。关于如何做到这一点的任何想法？
提前感谢大家，我从这个网站上学到很多东西。
UPDATE ：我正在尝试使用Singleton模式。但LogCat说：
02-26 22：21：59.300：E / AndroidRuntime（2677）：致命异常：主要 02-26 22：21：59.300：E / AndroidRuntime（2677）：java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.Chispa / com.example.Chispa.Activity_allday}：android.os.NetworkOnMainThreadException 02-26 22：21：59.300：E / AndroidRuntime（2677）：引起：android.os.NetworkOnMainThreadException
更新2：终于搞定了!!这是我使用的代码：
以下是活动A的代码：
public class MainActivity extends Activity {
private TextView tvmax, tvmid, tvmin, tvactualval,tvvaloractual,tvdate;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvdate=(TextView)findViewById(R.id.tvdate);
tvvaloractual=(TextView)findViewById(R.id.tvvaloractual);
tvmax=(TextView)findViewById(R.id.tvmaximo);
tvmid=(TextView)findViewById(R.id.tvmedio);
tvmin=(TextView)findViewById(R.id.tvminimo);
new BackGroundTask().execute();
callAsynchronousTask();
}
public void callAsynchronousTask() {
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask doAsynchronousTask = new TimerTask() {
@Override
public void run() {
handler.post(new Runnable() {
public void run() {
try {
BackGroundTask performBackgroundTask = new BackGroundTask();
// PerformBackgroundTask this class is the class that extends AsynchTask
performBackgroundTask.execute();
} catch (Exception e) {
// TODO Auto-generated catch block
}
}
});
}
};
timer.schedule(doAsynchronousTask, 0, 1000); //execute in every 1000 ms
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public class Pair
{
public String[] bar;
public String[] values;
}
public void viewallday(View view) {
Intent intent = new Intent(MainActivity.this, Activity_allday.class);
startActivity(intent);
}
class BackGroundTask extends AsyncTask<Void, Void, Pair> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
public String[] getValuesGraph(Document doc) {
int cont=24,var=7;
String bar[] = new String[cont];
/*
* Getting elements from the graphic in an array from 0-23. 0 it's 1:00am, 23 it's 00:00am
*/
for (cont=0; cont < 24; cont++){
String onMouseOver = doc.select("a").get(var+cont).attr("onMouseOver");
bar[cont] = onMouseOver.split("'")[9];
}
return bar;
}
public String[] getValuesFooter(Document doc) {
String values[] = new String[7];
/*
* Getting elements from the graphic footer
*/
String delimiters= "[ /]+";
Elements elements = doc.select("td.cabeceraRutaTexto");
elements.size(); // 6
/* Getting text from table */
values[0] = elements.get(0).text(); // TITLE
values[1] = elements.get(1).text(); // TEXT MAX VALUE
values[2] = elements.get(2).text(); // TEXT MIDDLE VALUE
values[3] = elements.get(3).text(); // TEXTO MIN VALUE
/* Getting numbers from table */
values[4] = elements.get(4).text().split(delimiters)[0]; // NUMBER MAX VALUE
values[5] = elements.get(5).text().split(delimiters)[0]; // NUMBER MIDDLE VALUE
values[6] = elements.get(6).text().split(delimiters)[0]; // NUMBER MIN VALUE
return values;
}
public Document getUrl(){
try {
URL url= new URL("http://www.endesaonline.com/canal/precios/Canal_Preciosdelpool.asp?FECHA=20140226");
/*URL url= new URL("http://www.endesaonline.com/canal/precios/Canal_Preciosdelpool.asp?lang=es&frameId=4064&segmento=1&promocion=");*/
Document doc = Jsoup.connect(url.toString()).get();
return doc;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
public Pair doInBackground(Void... params) {
Pair p = new Pair();
GlobalVariables gs = (GlobalVariables) getApplication();
gs.setBar(getValuesGraph(getUrl()));
p.bar = getValuesGraph(getUrl());
p.values = getValuesFooter(getUrl());
return p;
}
public String ActualHourValue() {
Format formatter = new SimpleDateFormat("H");
String onlyhour = formatter.format(new Date());
return onlyhour;
}
public void ShowDateHour(){
Calendar c = Calendar.getInstance();
SimpleDateFormat df3 = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss a");
String formattedDate3 = df3.format(c.getTime());
tvdate.setText("Fecha y hora actuales : "+formattedDate3);
}
@Override
protected void onPostExecute(Pair p) {
int hour = Integer.parseInt(ActualHourValue());
tvvaloractual.setText(p.bar[hour]+" €/MWh");
tvmax.setText(p.values[4]+" €/MWh");
tvmid.setText(p.values[5]+" €/MWh");
tvmin.setText(p.values[6]+" €/MWh");
ShowDateHour();
/*super.onPostExecute(p.values);*/
}
}
}
以下是活动B的代码：
public class Activity_allday extends MainActivity {
private TextView tvall;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.all_day_price);
TextView tvall=(TextView)findViewById(R.id.tvall);
GlobalVariables gs = (GlobalVariables) getApplication();
String[] s = gs.getBar();
tvall.setText(s[0]);
}
}
这是一个GlobalVariable类，它捕获我想要发送给Activity B的数组：
public class Activity_allday extends MainActivity {
private TextView tvall;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.all_day_price);
TextView tvall=(TextView)findViewById(R.id.tvall);
GlobalVariables gs = (GlobalVariables) getApplication();
String[] s = gs.getBar();
tvall.setText(s[0]);
}
}
这就是全部！希望它对未来的用户有所帮助。
感谢大家的帮助。
答案 0 :(得分：0)
您可以尝试以下方法：
在AsyncTask中，定义一个接口及其中的方法，将数据传递回调用活动，并在该方法内部调用下一个活动并将数据设置为额外的。
这是最简单的方法。
在AsyncTask中，在onPostExecute（result）中，使用try块来调用属于上述接口的方法，该方法必须由调用活动实现。
<强> HomeActivity.java
/public class SampleActivity extends Activity implements SampleAsyncTask.OnUpdateListener{
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
executeAsync();
}
public void executeAsync(){
new SampleAsyncTask(this).execute("someFlagToCheck");
}
@Override
public void onDataProcessed(String result){
Intent intent = new Intent(this, SecondActivity.class);
intent.putExtra("data", result);
startActivity(intent);
}
}
<强> SampleAsyncTask.java
public class SampleAsyncTask extends AsyncTask<Void, Void, String>{
Context context;
//constructor
SampleAsyncTask(Context context){
this.context = context;
}
@Override
public void doInBackground(String... params){
//do something depending on the arguments in params
return "data";
}
@Override
public void onPostExecute(String result){
try{
((OnUpdateListener) context).onDataProcessed(result);
}catch(Exception e){
e.printStackTrace();
}
}
public interface OnUpdateListener{
public void onDataProcessed(String data);
}
}
请按照此示例操作。调用活动实现AsyncTask的接口并覆盖其方法，当异步任务完成结果时将调用该方法。
我希望这会有所帮助。
答案 1 :(得分：0)
解决方案：
以下是活动A的代码：
public class MainActivity extends Activity {
private TextView tvmax, tvmid, tvmin, tvactualval,tvvaloractual,tvdate;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvdate=(TextView)findViewById(R.id.tvdate);
tvvaloractual=(TextView)findViewById(R.id.tvvaloractual);
tvmax=(TextView)findViewById(R.id.tvmaximo);
tvmid=(TextView)findViewById(R.id.tvmedio);
tvmin=(TextView)findViewById(R.id.tvminimo);
new BackGroundTask().execute();
callAsynchronousTask();
}
public void callAsynchronousTask() {
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask doAsynchronousTask = new TimerTask() {
@Override
public void run() {
handler.post(new Runnable() {
public void run() {
try {
BackGroundTask performBackgroundTask = new BackGroundTask();
// PerformBackgroundTask this class is the class that extends AsynchTask
performBackgroundTask.execute();
} catch (Exception e) {
// TODO Auto-generated catch block
}
}
});
}
};
timer.schedule(doAsynchronousTask, 0, 1000); //execute in every 1000 ms
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public class Pair
{
public String[] bar;
public String[] values;
}
public void viewallday(View view) {
Intent intent = new Intent(MainActivity.this, Activity_allday.class);
startActivity(intent);
}
class BackGroundTask extends AsyncTask<Void, Void, Pair> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
public String[] getValuesGraph(Document doc) {
int cont=24,var=7;
String bar[] = new String[cont];
/*
* Getting elements from the graphic in an array from 0-23. 0 it's 1:00am, 23 it's 00:00am
*/
for (cont=0; cont < 24; cont++){
String onMouseOver = doc.select("a").get(var+cont).attr("onMouseOver");
bar[cont] = onMouseOver.split("'")[9];
}
return bar;
}
public String[] getValuesFooter(Document doc) {
String values[] = new String[7];
/*
* Getting elements from the graphic footer
*/
String delimiters= "[ /]+";
Elements elements = doc.select("td.cabeceraRutaTexto");
elements.size(); // 6
/* Getting text from table */
values[0] = elements.get(0).text(); // TITLE
values[1] = elements.get(1).text(); // TEXT MAX VALUE
values[2] = elements.get(2).text(); // TEXT MIDDLE VALUE
values[3] = elements.get(3).text(); // TEXTO MIN VALUE
/* Getting numbers from table */
values[4] = elements.get(4).text().split(delimiters)[0]; // NUMBER MAX VALUE
values[5] = elements.get(5).text().split(delimiters)[0]; // NUMBER MIDDLE VALUE
values[6] = elements.get(6).text().split(delimiters)[0]; // NUMBER MIN VALUE
return values;
}
public Document getUrl(){
try {
URL url= new URL("http://www.endesaonline.com/canal/precios/Canal_Preciosdelpool.asp?FECHA=20140226");
/*URL url= new URL("http://www.endesaonline.com/canal/precios/Canal_Preciosdelpool.asp?lang=es&frameId=4064&segmento=1&promocion=");*/
Document doc = Jsoup.connect(url.toString()).get();
return doc;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
public Pair doInBackground(Void... params) {
Pair p = new Pair();
GlobalVariables gs = (GlobalVariables) getApplication();
gs.setBar(getValuesGraph(getUrl()));
p.bar = getValuesGraph(getUrl());
p.values = getValuesFooter(getUrl());
return p;
}
public String ActualHourValue() {
Format formatter = new SimpleDateFormat("H");
String onlyhour = formatter.format(new Date());
return onlyhour;
}
public void ShowDateHour(){
Calendar c = Calendar.getInstance();
SimpleDateFormat df3 = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss a");
String formattedDate3 = df3.format(c.getTime());
tvdate.setText("Fecha y hora actuales : "+formattedDate3);
}
@Override
protected void onPostExecute(Pair p) {
int hour = Integer.parseInt(ActualHourValue());
tvvaloractual.setText(p.bar[hour]+" €/MWh");
tvmax.setText(p.values[4]+" €/MWh");
tvmid.setText(p.values[5]+" €/MWh");
tvmin.setText(p.values[6]+" €/MWh");
ShowDateHour();
/*super.onPostExecute(p.values);*/
}
}
}
活动B：
public class Activity_allday extends MainActivity {
private TextView tvall;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.all_day_price);
TextView tvall=(TextView)findViewById(R.id.tvall);
GlobalVariables gs = (GlobalVariables) getApplication();
String[] s = gs.getBar();
tvall.setText(s[0]);
}
}
全局变量类，它捕获我想要发送到活动B的数组：
public class Activity_allday extends MainActivity {
private TextView tvall;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.all_day_price);
TextView tvall=(TextView)findViewById(R.id.tvall);
GlobalVariables gs = (GlobalVariables) getApplication();
String[] s = gs.getBar();
tvall.setText(s[0]);
}
}
谢谢大家的帮助!!