I would like to call a function from my main activity class after my preferences are updated, but I can't use onResume() because I have other classes that will trigger onResume (I believe).
Snippet from AndroidGPSTrackingActivity.java:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.settings:
startActivity(new Intent(this, SettingsActivity.class));
break;
}
return false;
}
SettingsActivity.java:
package com.example.gpstracking;
import android.os.Bundle;
import android.preference.PreferenceActivity;
public class SettingsActivity extends PreferenceActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
}
}
After my preferences close, I want to call a function from my Main Activity, however it MUST be from my main activity because I need to send a context from my Main Activity. I've tried so much and just can't seem to get it.
onResume() is triggered when the Activity comes to the foreground. You should never be "triggering" onResume() other than leaving/returning to the Activity (if you're ever directly calling onResume(), you're doing it wrong).
Assuming you're needing to check for the updated value when you return to your Activity, then yes, onResume() is where you should probably do that. If the user returns to MainActivity after viewing SettingsActivity, then onResume() will be called, and you can check the updated preference value there.
EDIT: So I think honestly you'd be better off checking the preference values in onResume(), and not caching them globally. They aren't expensive to look up. Also, for immediate notifications, you could register a listener for preference changes, like so:
public class MainActivity extends Activity
implements SharedPreferences.OnSharedPreferenceChangeListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
registerPreferenceListener();
}
#Override
protected void onDestroy() {
super.onDestroy();
unregisterPreferenceListener();
}
private void registerPreferenceListener() {
PreferenceManager.getDefaultSharedPreferences(this)
.registerOnSharedPreferenceChangeListener(this);
}
private void unregisterPreferenceListener() {
PreferenceManager.getDefaultSharedPreferences(this)
.unregisterOnSharedPreferenceChangeListener(this);
}
#Override
public void onSharedPreferenceChanged(
SharedPreferences sharedPreferences, String key) {
if ("the_key_i'm_interested_in".equals(key)) {
// Update stuff
}
}
}
Related
When I need a callback from Activity B back to Activity A I usually make the reference variable in Activity B 'static'. I realize that if the user rotates the device the Life Cycle methods will remove my reference.
Is this the only drawback and is there a better way to register without a static reference. Is it better to simply put all data in the Application class ? - Thank you.
public class MainActivity extends Activity implements InterfaceMainActivityTwo {
static Main2Activity main2Activity;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
main2Activity = new Main2Activity();
main2Activity.setDataListener(this);
}
#Override
public void getDataMainActivityTwo(String string) {
tvTextData.setText(string);
}
}
public class Main2Activity extends Activity {
static InterfaceMainActivityTwo mGetDataInterface;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
}
public void getDataSaveBtn(View v) {
if (mGetDataInterface != null)
mGetDataInterface.getDataMainActivityTwo(fullName);
else
Toast.makeText(this, "IS NULL.INTERFACE NOT INITIALIZED !!!!", Toast.LENGTH_SHORT).show();
}
/////////// interface setup
interface InterfaceMainActivityTwo {
void getDataMainActivityTwo(String string);
}
public void setDataListener(InterfaceMainActivityTwo listener) {
this.mGetDataInterface = listener;
}
}
You should never need a callback between two activities. You're doing something wrong if you do. If you need to pass data from A to B, pass it in the bundle. If you need to pass it back from B to A, use startActivityForResult and pass it in the result. If you need to share data between many activities, it should be held in some globally accessible data structure, either in memory or on disk.
Is there a way to make an alert only appear when the app is opened? I'm creating an alert in onStart() in my MainActivity and whenever I go back to that activity in the app, it shows the alert again which can be annoying to the user. Or is there a way to create a "got it" button and then turn off the alert? Here is my code:
protected void onStart() {
super.onStart();
new AlertDialog.Builder(this)
.setTitle("Instructions")
.setMessage("Hello! To begin, select a map from the list to train with. Make sure" +
" you are on the correct floor.")
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
})
.setIcon(R.drawable.ic_launcher)
.show();
}
This is because when another activity comes to foreground upon your MainActivity makes your activity goes to OnPause().
Then when you go back to your MainActivity. The system calls
onStart() again. See The activity life cycle
-First Solution
public class TestActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
showAlertDialog();
}
}
private void showAlertDialog() {
// code to show alert dialog.
}
}
-Second Solution
public class TestActivity extends ActionBarActivity {
private static boolean isAlertDialogShownBefore = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (!isAlertDialogShownBefore) {
showAlertDialog();
isAlertDialogShownBefore = true;
}
}
private void showAlertDialog() {
// code to show alert dialog.
}
#Override
public void onBackPressed() {
isAlertDialogShownBefore = false;
super.onBackPressed();
}
}
Put that code in onCreate method of your activity. Check for saveInstanceState for null, if it is then show your alertDialog
I have an activity with multiple AsyncTask's, but when i press back button, the Activity is reloaded and the AsyncTask's are executed again. what should i do to Back to the previous activity and not reload the activity and asynctask ? please help.
public class LugarActivity extends SherlockActivity {
CargarDatos cargarDatos;
CargarComentarios cargarComentarios;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_lugar);
cargarDatos = new CargarDatos();
cargarCometarios = new CargarComentarios();
loadData();
}
public void loadData(){
cargarDatos.execute();
}
public void loadOtherData(){
cargarComentarios.execute();
}
public class CargarDatos extends AsyncTask<Integer, Integer, String>{
#Override
protected String doInBackground(Integer... params) {
// here download data
}
#Override
protected void onPostExecute(String html) {
loadOtherData();
}
}
public class CargarComentarios extends AsyncTask<Integer, Integer, String>{
#Override
protected String doInBackground(Integer... params) {
// here download data
}
}
}
FIXED!
i fixed the problem with Singleton class:
public class DataManager {
private static DataManager instance = null;
protected static boolean isShowingTheView = false;
protected DataManager() { }
public static synchronized DataManager getInstance() {
if (instance == null) {
instance = new DataManager();
}
return instance;
}
}
in the activity i add this code:
DataManager dataManager = new DataManager();
if(!dataManager.isShowingTheView){
loadData();
dataManager.isShowingTheView = true;
}else{
finish();
}
and finally i override the onDestroy() method
#Override
public void onDestroy(){
dataManager.isShowingTheView = false;
super.onDestroy();
}
Remove loadData() from onCreate and call somewhere else.
Use Fragments
http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html
A fragment can stay in memory during a configuration change and therefore you can run your asynctask inside itself. You can then query the fragment for any state information you require from your tasks and update your Activity accordingly.
If your Activity is destroyed before the other activity starts, using the back button will call onCreate again, instead of onRestart or onResume.
See here for details.
As Kuffs already mentions, using Fragments is the way to go.
Uglier solution, you could also set a shared preference holding a boolean once your AsyncTask is launched (or on its onPostExecute) so that it won't launch again after checking for that preference on your Activity's onCreate.
I am trying to automatically capture and log Android lifecycle events using ActivityLifecycleCallbacks, however documentation on this matter is scarce, to say the least:
public void registerActivityLifecycleCallbacks (Application.ActivityLifecycleCallbacks callback)
I don't want to have to extend the Activity class or override the existing lifecycle methods (onCreate, onResume, etc...) I'm looking to have a separate class listening for these events and acting accordingly.
Does anyone have any experience in this, or have links to good solid documentation or tutorials on how this works? Specifically, how to register for ActivityLifecycleCallbacks, and how to handle them?
I don't have any firsthand experience but judging from the API you can just write your own class that implements the Application.ActivityLifecycleCallbacks interface and register that class on the provided Application class instance
getApplicaton().registerActivityLifecycleCallbacks(yourCustomClass);
This class will receive the same callbacks as your individual activities. Good luck.
PS. This is API level 14 btw, so it won't work on older phones.
I did my own implementation of Application.ActivityLifecycleCallbacks. I'm using SherlockActivity, but for normal Activity class might work.
First, I'm creating an interface that have all methods for track the activities lifecycle:
public interface ActivityLifecycleCallbacks{
public void onActivityStopped(Activity activity);
public void onActivityStarted(Activity activity);
public void onActivitySaveInstanceState(Activity activity, Bundle outState);
public void onActivityResumed(Activity activity);
public void onActivityPaused(Activity activity);
public void onActivityDestroyed(Activity activity);
public void onActivityCreated(Activity activity, Bundle savedInstanceState);
}
Second, I implemented this interface in my Application's class:
public class MyApplication extends Application implements my.package.ActivityLifecycleCallbacks{
#Override
public void onCreate() {
super.onCreate();
}
#Override
public void onActivityStopped(Activity activity) {
Log.i("Tracking Activity Stopped", activity.getLocalClassName());
}
#Override
public void onActivityStarted(Activity activity) {
Log.i("Tracking Activity Started", activity.getLocalClassName());
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
Log.i("Tracking Activity SaveInstanceState", activity.getLocalClassName());
}
#Override
public void onActivityResumed(Activity activity) {
Log.i("Tracking Activity Resumed", activity.getLocalClassName());
}
#Override
public void onActivityPaused(Activity activity) {
Log.i("Tracking Activity Paused", activity.getLocalClassName());
}
#Override
public void onActivityDestroyed(Activity activity) {
Log.i("Tracking Activity Destroyed", activity.getLocalClassName());
}
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
Log.i("Tracking Activity Created", activity.getLocalClassName());
}
}
Third, I'm creating a class that extends from SherlockActivity:
public class MySherlockActivity extends SherlockActivity {
protected MyApplication nMyApplication;
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
nMyApplication = (MyApplication) getApplication();
nMyApplication.onActivityCreated(this, savedInstanceState);
}
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
nMyApplication.onActivityResumed(this);
}
#Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
nMyApplication.onActivityPaused(this);
}
#Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
nMyApplication.onActivityDestroyed(this);
}
#Override
protected void onStart() {
super.onStart();
nMyApplication.onActivityStarted(this);
}
#Override
protected void onStop() {
super.onStop();
nMyApplication.onActivityStopped(this);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
nMyApplication.onActivitySaveInstanceState(this, outState);
}
}
Fourth, all class that extend from SherlockActivity, I replaced for MySherlockActivity:
public class MainActivity extends MySherlockActivity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
Now, in the logcat you will see the logs programmed in the Interface implementation made in MyApplication.
UPDATE
This implementation was tested from API Level 9 (Gingerbread), API Level 12 (Honeycomb) and API Level 17 (Jelly Bean) and works fine. Might works in Android's older versions.
Try this: http://engineering.meetme.com/2015/04/android-determine-when-app-is-opened-or-closed/#comment-202
It proposes an AppForegroundStateManager to which each activity reports through its onStop() and onStart() functions like this:
#Override
protected void onStart() {
super.onStart();
AppForegroundStateManager.getInstance().onActivityVisible(this);
}
#Override
protected void onStop() {
AppForegroundStateManager.getInstance().onActivityNotVisible(this);
super.onStop();
}
Your Application class implements a listener like this:
public class MyApplication extends Application {
#Override
public void onCreate() {
super.onCreate();
AppForegroundStateManager.getInstance().addListener(this);
}
#Override
public void onAppForegroundStateChange(AppForegroundStateManager.AppForegroundState newState) {
if (AppForegroundStateManager.AppForegroundState.IN_FOREGROUND.equals(newState)) {
// App just entered the foreground. Do something here!
Log.i(TAG, "App Just Entered the Foreground with launch mechanism of: " + mLaunchMechanism);
} else {
// App just entered the background. Set our launch mode back to the default of direct.
mLaunchMechanism = LaunchMechanism.DIRECT;
}
}
}
It also includes tips and tricks for determining how the app was opened - from a notification, a URL opening your app or directly from the Apps menu. This is done through an Enum in the Application class:
public enum LaunchMechanism {
DIRECT,
NOTIFICATION,
URL,
BACKGROUND
}
private LaunchMechanism mLaunchMechanism = LaunchMechanism.DIRECT;
public void setLaunchMechanism(LaunchMechanism launchMechanism) {
mLaunchMechanism = launchMechanism;
}
In our implementation of this, we have flags for when we start an activity that will launch a third-party activity, like if the user makes a phone call from our app or if a browser is launched. In the launching activity's onStop() we then do a check like this to only report the activity's not-visibility when those flags are false:
if(!flag_userLaunchedThirdPartyActivity){
AppForegroundStateManager.getInstance().onActivityNotVisible(this);
}
For checking whether or not the application goes into the background - for example when the device's screen goes dark or the user receives a phone call - it works like this:
public static boolean isApplicationGoingToBackground(final Context context) {
ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
List<RunningTaskInfo> tasks = am.getRunningTasks(1);
if (!tasks.isEmpty()) {
ComponentName topActivity = tasks.get(0).topActivity;
if (!topActivity.getPackageName().equals(context.getPackageName())) {
setLaunchMechanism(LaunchMechanism.BACKGROUND);
return true;
}
}
setLaunchMechanism(LaunchMechanism.DIRECT);
return false;
}
This solution is not dependent on an API level, so it should work all the way back to API level 1.
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(MyApplication.this/*(Your Application Name)*/);
}
Only add this line on Application class and all works well.
I have this preferences class (below) that saves two ListPreferences, but if the ListPreferences are changed and the back button is pressed, the changes don't take affect unless the application is restarted. Did I miss something? Have been looking everywhere, but just can't seem to find an answer the fits or works. Please help.
public class Preferences extends PreferenceActivity {
#Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
}
#Override
public void onPause() {
super.onPause();
}
#Override
public void onResume() {
super.onResume();
}
}
Application Code
public class Quotes extends Activity implements OnClickListener {
ProgressDialog dialog;
private WebView webview;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
String q = SP.getString("appViewType","http://www.google.com");
String c = SP.getString("appRefreshRate","20");
webview = (WebView) findViewById(R.id.scroll);
webview.getSettings().setJavaScriptEnabled(true);
webview.setWebViewClient(new QuotesWebView(this));
webview.loadUrl(q);
ScheduledExecutorService timer = Executors.newSingleThreadScheduledExecutor();
timer.scheduleAtFixedRate(new Runnable() {
#Override
public void run() {
webview.reload();
}
}, 10, Long.parseLong(c),TimeUnit.SECONDS);
findViewById(R.id.refresh).setOnClickListener(this);
}
#Override
public void onPause(){
super.onPause();
}
#Override
public void onResume(){
super.onResume();
}
public void onClick(View v){
switch(v.getId()){
case R.id.refresh:
webview.reload();
break;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
MenuItem about = menu.getItem(0);
about.setIntent(new Intent(this, About.class));
MenuItem preferences = menu.getItem(1);
preferences.setIntent(new Intent(this, Preferences.class));
return true;
}
}
You need to somehow reload your preferences when the preferences activity finishes. I thought Dirol's suggestion of loading them in onResume() instead of onCreate() was excellent; have you tried it? Or am I misunderstanding the problem as well.
In my own case, I launched the preferences activity with startActivityForResult() and then on the activity result callback, I reloaded the preferences.
Code snippets:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case MENU_PREFERENCES:
Intent intent = new Intent().setClass(this, CalcPreferences.class);
startActivityForResult(intent, MENU_PREFERENCES);
break;
default: return super.onOptionsItemSelected(item);
}
return true;
}
#Override
protected void onActivityResult(int req, int result, Intent data) {
switch( req ) {
case MENU_PREFERENCES:
SharedPreferences sp =
PreferenceManager.getDefaultSharedPreferences(this);
updatePreferences(sp);
break;
default:
super.onActivityResult(req, result, data);
break;
}
}
#Override
protected void updatePreferences(SharedPreferences sp) {
super.updatePreferences(sp);
keyclick = sp.getBoolean("keyclick", keyclick);
}
Anyway, this is what works for me. I may try moving my updatePreferences() call to onResume() myself to see if that works too.
Try overriding the onBackPressed() method.
If your "Up" button (top left <-) provides the correct result, then you can set the Back button to behave like the Up button.
#Override
public void onBackPressed() {
super.onBackPressed();
NavUtils.navigateUpFromSameTask(this);
}
You load preferences only on onCreate() method. That method called only when a fresh activity starts up. The addPreferencesFromResource inflates the xml file into the preferences, so you only get the info, which is already has been stored in the xml at the moment addPreferencesFromResource was called, not after.
Try to move that method to onResume. But watch for the memory leak. I don't know exactly what the addPreferencesFromResource do, but from the documentation - I would be very suspicious about that method activity.
I had the same problem and solved it as follows:
The main activity class implements OnSharedPreferenceChangeListener:
public class Activity_name extends Activity implements OnSharedPreferenceChangeListener {
...
}
Inside the main activity class the onSharedPreferenceChanged is run whenever a preference entry changes. I simply update all my variables from the preferences as i did in onCreate:
#Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
<read all preferences as you did in onCreate()>
}
This does the trick and I hope it saves you some time in searching for a solution.
I've had the same problem...
Try to create preference instance and load its data in every class and every activity where you need it.
It worked for me...Hope it helps.
You will need to reload your view or whatever object which uses those preferences, preferably when preference activity closes.
Preference activities do not change nothing but an internal file with your preferences(key=value list). When it is changed, preferenceActivity calls onPreferenceChaged() and nothing more. It doesn't refresh your stuff by itself. You need to reload prefs and to reuse them in onResume() method or equivalent.