[英]TextView not retaining the value I give it
In my app, I'm getting JSON data from a php script. 在我的应用程序中,我从php脚本获取JSON数据。 When I get the data, I have an
onClick()
method in my Fragment which changes a TextView
to the parsed JSON. 当我获取数据时,我在Fragment中有一个
onClick()
方法,该方法将TextView
更改为已解析的JSON。
However, when I swipe to a different fragment(it's a swipe/tabbed activity) my TextView
does not retain the value I gave it, it changes to the original value. 但是,当我滑动到另一个片段(这是滑动/标签式活动)时,我的
TextView
不会保留我给它的值,它会更改为原始值。
I want it to retain the value. 我希望它保留价值。
MainActivity.java (I don't think this is important) MainActivity.java(我认为这不重要)
package me.anshsehgal.lunchmenu;
import android.content.Intent;
import android.support.v4.app.Fragment;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.app.FragmentManager;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.RelativeLayout;
public class MainActivity extends AppCompatActivity {
String JSON_STRING;
Toolbar toolbar;
TabLayout tabLayout;
ViewPager viewPager;
ViewPagerAdapter viewPagerAdapter; //make all the variables
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar)findViewById(R.id.toolBar);
setSupportActionBar(toolbar);
tabLayout = (TabLayout)findViewById(R.id.tabLayout);
viewPager = (ViewPager)findViewById(R.id.viewPager); //reference them
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPagerAdapter.addFragments(new HomeFragment(),"Mon");
viewPagerAdapter.addFragments(new MondayFragment(),"Tue");
viewPagerAdapter.addFragments(new TuesdayFragment(),"Wed");
viewPagerAdapter.addFragments(new WednesdayFragment(), "Thu");
viewPagerAdapter.addFragments(new ThursdayFragment(), "Fri"); //adding fragments to view page adapter
viewPager.setAdapter(viewPagerAdapter);
tabLayout.setupWithViewPager(viewPager);
HomeFragment frag = (HomeFragment)getSupportFragmentManager().findFragmentById(R.id.homeFragment);
}
HomeFragment.java (this is where things going wrong) HomeFragment.java(这是出问题的地方)
package me.anshsehgal.lunchmenu;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.RelativeLayout;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.lang.Void;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
* A simple {@link Fragment} subclass.
*/
public class HomeFragment extends Fragment implements View.OnClickListener {
String JSON_STRING;
String jsonData;
TextView txt;
String day;
String soup;
String non_veg_main;
String non_veg_side;
String veg_main;
String veg_side;
String MondayMenu;
public HomeFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_home, container, false);
txt = (TextView) view.findViewById(R.id.textJSON);
Button btn = (Button) view.findViewById(R.id.buttonGetJSON);
btn.setOnClickListener(this);
new BackgroundTask().execute();
return view;
}
@Override
public void onClick(View v) {
MainActivity activity = (MainActivity) getActivity();
try{
//JSON parsing
JSONObject parentObject = new JSONObject(jsonData);
JSONArray parentArray = parentObject.getJSONArray("server_response");
JSONObject finalObject = parentArray.getJSONObject(0);
//JSON data assigning to variables
day = finalObject.getString("day");
soup = finalObject.getString("soup");
non_veg_main = finalObject.getString("non_veg_main");
non_veg_side = finalObject.getString("non_veg_side");
veg_main = finalObject.getString("veg_main");
veg_side = finalObject.getString("veg_side");
}catch (JSONException e){
e.printStackTrace();
}
MondayMenu = "Soup: "+soup+"\n"+"Non Veg Main: "+non_veg_main+"\n"+"Non Veg Side: "+non_veg_side+"\n"+"Veg Main: "+veg_main+"\n"+"Veg Side: "+veg_side;
txt.setText(MondayMenu);
}
class BackgroundTask extends AsyncTask<Void,Void,String>{
String json_url;
@Override
protected void onPreExecute() {
json_url="http://192.168.0.12/json_get_data.php";
}
@Override
protected String doInBackground(Void... params) {
try {
URL url = new URL(json_url);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder = new StringBuilder();
while ((JSON_STRING = bufferedReader.readLine()) != null) {
stringBuilder.append(JSON_STRING + "\n");
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
return stringBuilder.toString().trim();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
jsonData = result;
}
}
}
That's because getView is being called everytime you switch from a page to the other. 这是因为每次从页面切换到另一个页面时都会调用getView。 So the TextView is being re-created.
因此,正在重新创建TextView。 Create a ViewHolder with that text, set it on the creator of the ViewHolder class, so you won't lose the value when you re-draw the fragment.
用该文本创建一个ViewHolder,将其设置在ViewHolder类的创建者上,这样在您重新绘制片段时不会丢失该值。 Official viewHolder tutorial
官方视图持有人教程
Since you only want to keep the state of the fragment when you switching between different tabs, you can follow the implementation below: 由于只希望在不同的选项卡之间切换时保持片段的状态,因此可以按照以下实现:
TextView vstup;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.whatever);
vstup = (TextView)findViewById(R.id.whatever);
/* (...) */
}
@Override
public void onSaveInstanceState(Bundle state) {
super.onSaveInstanceState(state);
state.putCharSequence(App.VSTUP, vstup.getText());
}
@Override
public void onRestoreInstanceState(Bundle state) {
super.onRestoreInstanceState(state);
vstup.setText(state.getCharSequence(App.VSTUP));
}
Hope this solve your problem. 希望这能解决您的问题。
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