我正在尝试使用Bundle将Query类中的数据（我在Query类中设置参数“）传递给Fragment类之一（我需要在此片段类中使用”getArguments（）“ ），但是我已经使用日志进行了一些基本调试，并且已经看到在实现Query类之前创建了片段。因此，当我从片段类中获取“getArguments”时，它为NULL，因为尚未在Query类中设置参数。
我想在片段类中使用Query类中的数据。任何人都可以告诉我该做什么？ 你可能会说我对Android比较新，也不太了解片段。
上下文：我正在开发一个Weather应用程序。我今天有三个片段，明天和七天预测（灵感来自标签布局Google Now的天气卡）。我还有一个Query类，用于查询JSON数据的在线API以及主要的活动类。
MainActivity类：
package com.example.desno.testnavtablayout;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.ActivityCompat;
import android.util.Log;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.TextView;
import org.json.JSONObject;
import java.util.concurrent.ExecutionException;
import tabFragments.SevenDayFragment;
import tabFragments.TodayFragment;
import tabFragments.TomorrowFragment;
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
public Double latitude;
public Double longitude;
private static final String API_KEY = "&APPID="; // Placeholder for the openweathermaps API key
private static final String QUERY_URL = "http://api.openweathermap.org/data/2.5/weather?q="; // Placeholder for the openweathermaps URL
private static final String UNITS = "&mode=json&units=metric&cnt=7"; // Placeholder specifying the data type and unit type of this data being retrieved
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
// Initialise the Android location manager to get the users current location automatically:
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
String provider = locationManager.getBestProvider(new Criteria(), false);
// Handle what happens if the user doesn't grant permission for location (this has been generated automatically):
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
{
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
Location location = locationManager.getLastKnownLocation(provider); // Get last known location of the user
latitude = location.getLatitude(); // Storage variable for the users latitude
longitude = location.getLongitude(); // Storage variable for the users logitude
Query query = new Query(); // Create a new instance of the Query class, pass it the URL with the values of the users GPS coordinates embedded and execute it
query.execute("http://api.openweathermap.org/data/2.5/weather?lat=" + String.valueOf(latitude) + "&lon=" + String.valueOf(longitude) + UNITS + API_KEY);
}
// Receives the value of searchLocationQuery and manipulates it
private JSONObject queryForRequestedLocation(String location)
{
String parsedData = ""; // Placeholder for URL with embedded search value
try
{
parsedData = new Query().execute(QUERY_URL + location + UNITS + API_KEY).get(); // Pass the URL with embedded search, units and API key to the Query class for parsing
}
catch (InterruptedException e)
{
e.printStackTrace();
}
catch (ExecutionException e)
{
e.printStackTrace();
}
return null;
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@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;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
/*public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.content_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
switch(position){
case 0 : return TodayFragment.newInstance();
case 1 : return TomorrowFragment.newInstance();
case 2 : return SevenDayFragment.newInstance();
// default: return MyFragment.newInstance();
/* It is better to use default so that it always returns a fragment and no problems would ever occur */
}
return null; //if you use default, you would not need to return null
/*// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);*/
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "SECTION 1";
case 1:
return "SECTION 2";
case 2:
return "SECTION 3";
}
return null;
}
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
查询类：
package com.example.desno.testnavtablayout;
/**
* Created by desno on 30/05/2016.
*/
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import org.json.JSONObject;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import tabFragments.TodayFragment;
public class Query extends AsyncTask<String, Void, String>
{
private static String locationName;
// Query for the data
@Override
protected String doInBackground(String... urls)
{
String queryResult = ""; // Storage variable for the json data
URL url; // URL is used as address to the data needed
HttpURLConnection urlConnection = null; // Make a remote request using the HttpURLConnection class
// Surround with try/catch so the application doesn't crash in the case of an exception such as no internet connection
try
{
url = new URL(urls[0]); // Create a new URL from what is supplied
urlConnection = (HttpURLConnection) url.openConnection(); // Establish a URL connection and pass it to a HttpURLConnection
InputStream inputStream = urlConnection.getInputStream(); // Get an InputStream from the HttpURLConnection
InputStreamReader inputStreamReader = new InputStreamReader(inputStream); // Create an InputStreamReader to read the InputStream
int inputStreamData = inputStreamReader.read(); // Store the data from the InputStreamReader
// Need a while loop because when InputStreamReader is finished the result is equal to -1
while (inputStreamData != -1)
{
char current = (char) inputStreamData;
queryResult += current;
inputStreamData = inputStreamReader.read();
}
return queryResult;
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
// Parse the json data
@Override
protected void onPostExecute(String queryResult)
{
super.onPostExecute(queryResult);
try
{
JSONObject jsonObject = new JSONObject(queryResult); // Create a new json object and pass it the data from the queryResult string
JSONObject weatherData = new JSONObject(jsonObject.getString("main")); // Create another json object to contain more specific weather data such as all the data within the "main" braces
Double temperature = Double.parseDouble(weatherData.getString("temp")); // Grab the temperature value, which is currently stored as a string within the weatherData object, and store it as a double labeled "temperature"
locationName = jsonObject.getString("name"); // Create storage variable for the location name
Bundle args = new Bundle();
args.putString("LocationName", locationName);
TodayFragment todayFragment = new TodayFragment();
todayFragment.setArguments(args);
Log.i("Loc working in query=", args.toString());
// MainActivity.temperatureTextView.setText(temperature.toString()+ " °C"); // Set the value of the temperature TextView equal to the value of the temperature variable and add a degrees celsius symbol
// MainActivity.locationTextView.setText(locationName); // Set the value of the location TextView equal to the value of the locationName variable
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
TodayFragment类：
package tabFragments;
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 com.example.desno.testnavtablayout.Query;
import com.example.desno.testnavtablayout.R;
import java.security.PublicKey;
/**
* Created by desno on 09/09/2016.
*/
public class TodayFragment extends Fragment
{
Button ClickMe;
TextView tv;
public String loc;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle bundle = this.getArguments();
if (bundle == null)
{
//loc = bundle.getString("LocationName");
Log.i("Bundle is STILL null", "TodayFrag OnCreate()");
}
}
public TodayFragment()
{
}
public static TodayFragment newInstance()
{
TodayFragment fragment = new TodayFragment();
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View rootView = inflater.inflate(R.layout.fragment_today, container, false);
ClickMe = (Button) rootView.findViewById(R.id.button);
tv = (TextView) rootView.findViewById(R.id.textView2);
ClickMe.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
if(tv.getText().toString().contains("Hello"))
{
tv.setText("Hi");
}
else tv.setText("Hello");
}
});
/*String strtext = getArguments().getString("LocationName");
if (strtext != null)
{
Log.i("Location=", strtext.toString());
}*/
Bundle bundle = this.getArguments();
if (bundle == null)
{
//loc = bundle.getString("LocationName");
Log.i("Bundle is null", "TodayFrag OnCreateView()");
}
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Bundle bundle = this.getArguments();
if (bundle == null) {
//String i = bundle.getString("LocationName");
Log.i("Bundle is null", "in TodayFrag onActivityCreated()");
}
}
@Override
public void onViewStateRestored(Bundle savedInstanceState) {
super.onViewStateRestored(savedInstanceState);
Bundle bundle = this.getArguments();
if (bundle == null)
{
//loc = bundle.getString("LocationName");
Log.i("Bundle is STILL null", "TodayFrag OnViewStateRestored()");
}
}
}
答案 0 :(得分：0)
在您知道已创建片段后尝试运行Query。这是两个想法......
一种可能性是将查询参数传递给TodayFragment / TomorrowFragment / SevenDayFragment并让他们调用自己的查询。像这样的东西：
public class TodayFragment extends Fragment {
private static final String BUNDLE_KEY_SOME_PARAM = "BUNDLE_KEY_SOME_PARAM";
public static TodayFragment newInstance(String someParam) {
final Bundle creationArgs = new Bundle();
creationArgs.putString(BUNDLE_KEY_SOME_PARAM, someParam);
final TodayFragment instance = new TodayFragment();
instance.setArguments(creationArgs);
return instance;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// run the Query locally
final String someParam = getArguments().getString(BUNDLE_KEY_SOME_PARAM);
new Query().execute(someParam);
}
}
如果您不喜欢将这种类型的逻辑放在您的片段中，您可以让他们回调MainActivity以根据需要运行查询。也许是这样的：
interface QueryExecutor {
void query(String someParam);
}
interface QueryResultListener {
void results(String someResult);
}
public class TodayFragment extends Fragment implements QueryResultListener {
private static final String BUNDLE_KEY_SOME_PARAM = "BUNDLE_KEY_SOME_PARAM";
public static TodayFragment newInstance(String someParam) {
final Bundle creationArgs = new Bundle();
creationArgs.putString(BUNDLE_KEY_SOME_PARAM, someParam);
final TodayFragment instance = new TodayFragment();
instance.setArguments(creationArgs);
return instance;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
final QueryExecutor queryExecutor = (QueryExecutor)getActivity();
final String someParam = getArguments().getString(BUNDLE_KEY_SOME_PARAM);
queryExecutor.query(someParam);
}
@Override
public void results(String someResult) {
// handle the query results...
}
…
}
我希望有所帮助。
答案 1 :(得分：0)
为什么不简单地从Fragment中进行查询？我想这将是最简单的解决方案。