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Anroid startActivity not working after class switch

I want to start an activity and give out a Toast message after I parsed a JSON response.

public class Sign_Up extends AppCompatActivity {

....

register();


public void register()
{
final String url = "someURL";

new Json().checkJsonFile(url,getApplicationContext());
}

//Now in an non-activity

public class Json {

public void checkJsonFile(final String url, final Context context) {

new Thread(new Runnable() {
public void run() {
String result;
String line;

try {

URL obj = new URL(url);
HttpURLConnection conn = (HttpURLConnection) obj.openConnection();
conn.setReadTimeout(5000);
conn.addRequestProperty("Accept-Language", "en-US,en;q=0.8");
conn.addRequestProperty("User-Agent", "Mozilla");
conn.addRequestProperty("Referer", "google.com");


boolean redirect = false;

// normally, 3xx is redirect
int status = conn.getResponseCode();
if (status != HttpURLConnection.HTTP_OK) {
if (status == HttpURLConnection.HTTP_MOVED_TEMP
|| status == HttpURLConnection.HTTP_MOVED_PERM
|| status == HttpURLConnection.HTTP_SEE_OTHER)
redirect = true;
}

if (redirect) {

// get redirect url from "location" header field
String newUrl = conn.getHeaderField("Location");

// get the cookie if need, for login
String cookies = conn.getHeaderField("Set-Cookie");

// open the new connnection again
conn = (HttpURLConnection) new URL(newUrl).openConnection();
conn.setRequestProperty("Cookie", cookies);
conn.addRequestProperty("Accept-Language", "en-US,en;q=0.8");
conn.addRequestProperty("User-Agent", "Mozilla");
conn.addRequestProperty("Referer", "google.com");


}

BufferedReader in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));

StringBuilder sb = new StringBuilder();

while ((line = in.readLine()) != null) {
sb.append(line);

}
in.close();

result = sb.toString();

new Sign_Up().parseJSON(result);

} catch (Exception e) {
e.printStackTrace();
}
}
}).start();
}
}


//Back in Sign_Up class

public void parseJSON(String JSON){
int error = -1;
try {
JSONObject jsonObject = new JSONObject(JSON);

error = Integer.parseInt(jsonObject.getString("error_code"));

} catch (JSONException e) {
//Retry
register();

e.printStackTrace();
}

progressDialog.dismiss();

switch (error) {
case 0: //Successful
finish();
startActivity(new Intent(Sign_Up.this, Loading.class));
break;
case 1:
Toast.makeText(getApplicationContext(), "blabla", Toast.LENGTH_SHORT).show();
break;
case 2:
Toast.makeText(getApplicationContext(), "other blabla", Toast.LENGTH_SHORT).show();
break;
default:
register();
break;
}
}

However, when I put the Json stuff inside the Sign_Up class at least the startActivity works, but the Toast doesn't. As well, I would like to have the Json stuff in an seperate class.

Thank you very much in advance!

1 Answer
1

You cannot create an Activity by calling

new MyActivity()


and expect anything to work. The line

new Sign_Up().parseJSON(result);


is creating a new instance of the Sign_Up activity improperly, so it is not bound to a context and none of its lifecycle calls will be executed. You can't show a Toast in that state.

Sign_Up

A better solution would be to pass an interface from Sign_Up into the Json class to let it call back to the original Sign_Up instance rather than trying to make a new instance. For example:

Sign_Up

Json

Sign_Up

class Json {
public interface Callback {
public void run(String result);
}

private Callback callback

Json(Callback c) {
callback = c;
}

// later, replace new Sign_Up().parseJSON(result) with callback.run(result)
}


and to create it replace

new Json().checkJsonFile(url,getApplicationContext());


with

new Json(new Json.Callback() {
@Override
public void run(String result) {
parseJSON(result);
}
}).checkJsonFile(url,getApplicationContext());


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