I wonder if there is a way to get the context of current running activity on android. For example, I have an Activity Class and it is running. What I want is to call another Simple Class to run some functions which called from Activity Class. By doing this, I need to set up a context of Activity Class on Simple Class; On the other way, I need to have the context of Current Running Activity, so that my Simple Class can actually run the functions called from Current Running Activity.
Below is the soft code from my project.
public class Main1 extends Activity {
private static GetAPNsInfo getAPNsInfo = new GetAPNsInfo();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
getAPNsInfo.doSomething();
}
}
public class GetAPNsInfo {
public void doSomething() {
Button button = currentRunningActivityContext.findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
}
});
}
}
Finally, my purpose of this thread is that I need a good way to get the current running activity info.
This is a solution that I found my self. But it doesn't totally solve this case. We can add a receiver in Manifest.xml. This will run a background application.
<receiver android:name=".RunningActivityCapture">
<intent-filter android:priority="-1">
<action android:name="android.intent.action.NEW_OUTGOING_CALL"></action>
</intent-filter>
</receiver>
The background application interface look like this:
public class RunningActivityCapture extends BroadcastReceiver {
#Override
public void onReceive(Context aContext, Intent intent) {
String action = intent.getAction();
if (action.equals(Intent.ACTION_ALL_APPS)) {
Activity activty = intent.getCurrentActivity();
Session session = new Session();
session.setRunningActivity(activty);
}
return;
}
}
I only get the activity from session class which setting from my background application. This is my first idea to solve this problem. But the code is not correct. So I need your help.
If you are asking how to use this MainActivity in your helper class, you can pass the Activity itself into your class, as an activity is a Context. So your constructor will be:
public GetAPNsInfo(Context context) {
...
}
where you store the context in a field and use it later. You will initialize with
private static GetAPNsInfo getAPNsInfo = new GetAPNsInfo(this);
if you are asking how to get the context for ANY activity in your application, I don't think that is recommended.
Related
I am trying to define global objects using the application class.
I therefore define the following class.
public class MyApplication extends Application {
private MyObject myObject=new MyObject();
public MyObject getMyObject(){
return this.myObject;
}
}
Then, I use it in an activity, but I get an error (Cannot resolve method getApplication()):
public class AnActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mood);
Button buttonMusic=(Button) findViewById(R.id.button5);
buttonMusic.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
MyApplication myApplication = ((MyApplication)this.getApplication());
Toast.makeText(MoodActivity.this, "playing music", Toast.LENGTH_SHORT).show();
}
});
}
}
I have no clue why I get this error, as it for example works when calling the getApplication() in another activity.
I'm pretty new to Android and Java, so please excuse the ingenuity of the question.
UPDATE
Then I do MyObject myObject=myApplication.getMyObject(); and I don't get any compilation issue but the app dies as soon as I get in that activity.
As I understand it is not advised to use the Application class for such use, what would be a good alternative?
You're getting this error because you call this.getApplication() inside the View.OnClickListener. Because of this, this now references the listener and not the activity.
To do what you need, just create a Context object outside of the listener in your activity's onCreate method and assign this to it. And, inside the listener, use context instead of this. Something like this :-
public class AnActivity extends Activity {
Context context;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mood);
context = this;
Button buttonMusic=(Button) findViewById(R.id.button5);
buttonMusic.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
MyApplication myApplication = ((MyApplication)context.getApplication());//Changed "the" to "context"
Toast.makeText(MoodActivity.this, "playing music", Toast.LENGTH_SHORT).show();
}
});
}
}
Edit after question update :-
Instead of using the application class, use static objects to achieve global variables. static objects are independent of objects and can be referenced using the class that they belong to. For example, if you define a static variable in your MainActivity.class and name it testObject, then it can be accessed using the following code regardless of your current activity :-
YourObject object = MainActivity.testObject;
Unless you have a specific reason for extending the Application class in Android you probably shouldn't. For reference, look at the note in the documentation for this: https://developer.android.com/reference/android/app/Application.html .
If you are trying to create an object that you can use in your Android app, simply do that as you would in Java:
public class MyObject {
//Your stuff here
}
If there is a reason that you're specifically wanting to extend the Application class then perhaps there's more that people can do to help you if you explain what you're trying to do. I just don't necessarily see a need to go through all that complexity based on your example :)
Change this to AnActivity.this.
Inside the code below the meaning of this changes from AnActivity to View.onClickListener as it is another object and inside those braces you are in the scope of the click listener class
new View.OnClickListener() {
public void onClick(View v) {
MyApplication myApplication = ((MyApplication)this.getApplication());
Toast.makeText(MoodActivity.this, "playing music", Toast.LENGTH_SHORT).show();
}
}
So the code above should become
new View.OnClickListener() {
public void onClick(View v) {
MyApplication myApplication = ((MyApplication)AnActivity.this.getApplication());
Toast.makeText(MoodActivity.this, "playing music", Toast.LENGTH_SHORT).show();
}
}
You can read a bit more about it here
I'd like to implement an update checker in an application, and I obviously only need this to show up once when you start the application. If I do the call in the onCreate() or onStart() method, it'll be shown every time the activity is created and this is not a viable solution.
So my question is: Is there a way to do something, like check for updates, just once per application start / launch?
I'm sorry if it's a bit hard to understand, I'm having difficulties explaning myself on this one.
SharedPreferences seems like ugly solution to me. It's much more neat when you use application constructor for such purposes.
All you need is to use your own Application class, not default one.
public class MyApp extends Application {
public MyApp() {
// this method fires only once per application start.
// getApplicationContext returns null here
Log.i("main", "Constructor fired");
}
#Override
public void onCreate() {
super.onCreate();
// this method fires once as well as constructor
// but also application has context here
Log.i("main", "onCreate fired");
}
}
Then you should register this class as your application class inside AndroidManifest.xml
<application android:label="#string/app_name" android:name=".MyApp"> <------- here
<activity android:name="MyActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
You even can press Back button, so application go to background, and will not waste your processor resources, only memory resource, and then you can launch it again and constructor still not fire since application was not finished yet.
You can clear memory in Task Manager, so all applications will be closed and then relaunch your application to make sure that your initialization code fire again.
looks like you might have to do something like this
PackageInfo info = getPackageManager().getPackageInfo(PACKAGE_NAME, 0);
int currentVersion = info.versionCode;
this.versionName = info.versionName;
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
int lastVersion = prefs.getInt("version_code", 0);
if (currentVersion > lastVersion) {
prefs.edit().putInt("version_code", currentVersion).commit();
// do the activity that u would like to do once here.
}
You can do this every time, to check if the app has been upgraded, so it runs only once for app upgrade
The shared preferences approach is messy, and the application class has no access to an activity.
Another alternative I've used is to have a retained fragment instance, and within that instance, a lot more stuff can be done especially if you need access to the main activity UI.
For this example, I've used asynctask within the retained fragment. My AsyncTask has callbacks to the parent activity. It is guaranteed to run only once per application because the fragment is never destroyed-recreated when the same activity is destroyed-recreated. It is a retained fragment.
public class StartupTaskFragment extends Fragment {
public interface Callbacks {
void onPreExecute();
void onProgressUpdate(int percent);
void onCancelled();
void onPostExecute();
}
public static final String TAG = "startup_task_fragment";
private Callbacks mCallbacks;
private StartupTask mTask;
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
mCallbacks = (Callbacks) activity;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true); // this keeps fragment in memory even if parent activity is destroyed
mTask = new StartupTask();
mTask.execute();
}
#Override
public void onDetach() {
super.onDetach();
mCallbacks = null;
}
private class StartupTask extends AsyncTask<Void, Integer, Void> {
#Override
protected void onPreExecute() {
if (mCallbacks != null) {
mCallbacks.onPreExecute();
}
}
#Override
protected Void doInBackground(Void... ignore) {
// do stuff here
return null;
}
#Override
protected void onProgressUpdate(Integer... percent) {
if (mCallbacks != null) {
mCallbacks.onProgressUpdate(percent[0]);
}
}
#Override
protected void onCancelled() {
if (mCallbacks != null) {
mCallbacks.onCancelled();
}
}
#Override
protected void onPostExecute(Void ignore) {
if (mCallbacks != null) {
mCallbacks.onPostExecute();
}
}
}
}
Then, in main (or parent) activity where you want this startup task fragment to run once.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentManager fm = getFragmentManager();
StartupTaskFragment st = (StartupTaskFragment) fm.findFragmentByTag(StartupTaskFragment.TAG);
if(st == null) {
fm.beginTransaction().add(mStartupTaskFragment = new StartupTaskFragment(), StartupTaskFragment.TAG).commit();
}
...
}
Ideas for retained fragment came from here: http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html. I just figured out its other uses aside from config changes.
Yes you can do it Using SharedPrefernce concept of android. Just create a boolean flag and save it in SharedPrefernce and check its value in your onCreate() method .
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
if (!prefs.getBoolean("onlyonce", false)) {
// <---- run your one time code here
// mark once runned.
SharedPreferences.Editor editor = prefs.edit();
editor.putBoolean("onlyonce", true);
editor.commit();
}
}
This continues on #Vitalii's answer.
After having setup the Application class, if access to the Activity is required, we can use the aptly named android library "Once" https://github.com/jonfinerty/Once.
In the Application class's onCreate method
Once.initialise(this)
In the Activity / Fragment class's onCreate / onViewCreated method.
val helloTag = "hello"
if (!Once.beenDone(Once.THIS_APP_SESSION, helloTag)) {
//Do something that needs to be done only once
Once.markDone(helloTag) //Mark it done
}
I do this the same way as described in the other answer. I just have a global variable in the first activity which matches the release number from the manifest. I increment it for every upgrade and when the check sees a higher number, it executes the one-time code.
If successful, it writes the new number to shared preferences so it wont do it again until the next upgrade.
Make sure you assign the default to -1 when you retrieve the version from shared preferences so that you error on the side of running the code again as opposed to not running it and not having your app update correctly.
Use SharedPreference for this-
If you are not restarting your launcher activity again once your app is active then in that case you case use it.
Use this in a Splash screen if you are implementing it in the app.
If you are not using any splash screen then you need to create a activity with no view set and on it's oncreate call you can do start updation and start your main activity.
you can use counter value or boolean for this.
Here is SharedPreference doc:
http://developer.android.com/reference/android/content/SharedPreferences.html
try {
boolean firstboot = getSharedPreferences("BOOT_PREF",MODE_PRIVATE)
.getBoolean("firstboot", true);
if(firstboot){
//place your code that will run single time
getSharedPreferences("BOOT_PREF",MODE_PRIVATE).edit().
putBoolean("firstboot", false)
.commit();
}
I just solved doing this myself, I reopen my main activity multiple times throughout the application's execution. While the constructor is a valid approach for some things it doesn't let you access the current Application context to write toasts among other things.
My solution was to create a simple 'firstRun' boolean set to true in the class of my MainActivity, from there I run the contents of the if statement then set it to true. Example:
public class MainActivity extends AppCompatActivity
{
private static boolean firstRun = true;
#Override
protected void onCreate(Bundle savedInstanceState)
{
if(firstRun)
{
Toast.makeText(getApplicationContext(), "FIRST RUN", Toast.LENGTH_SHORT).show();
//YOUR FIRST RUN CODE HERE
}
firstRun = false;
super.onCreate(savedInstanceState);
//THE REST OF YOUR CODE
}
I am working on an SMS application and I have a method in my MainActivity to perform a button click:
public void updateMessage() {
ViewMessages.performClick();
}
This method works fine and performs the button click when I call this method from inside the MainActivity class.
But, when I call this method from any other class as shown below, where I call the Main Activity's updateMessage method from the IntentServiceHandler class, I am getting a NullPointerException:
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.widget.Button.performClick()' on a null object reference
public class IntentServiceHandler extends IntentService {
public IntentServiceHandler() {
super("IntentServiceHandler");
}
#Override
protected void onHandleIntent(Intent intent) {
String message = intent.getStringExtra("message");
TransactionDataBase transactionDB = new TransactionDataBase(this, 1);
transactionDB.addMessage(message);
MainActivity mainActivity = new MainActivity();
mainActivity.updateMessage();
}
}
How can I handle this?
Edit: I even tried to make the updateMessage method static, and now i get the following exception
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
Don't call the method of Activity in an IntentService, try to use Intent to communicate between Activity and IntentService.
Replace the last two statements onHandleIntent() with
Intent intent = new Intent();
broadcastIntent.setAction(MainActivity.UPDATE_MESSAGE);
broadcastIntent.addCategory(Intent.CATEGORY_DEFAULT);
sendBroadcast(intent);
And you should register a BroadcastReceiver in onCreate() of MainAcitivty like
private BroadcastReceiver receiver;
#Override
public void onCreate(Bundle savedInstanceState){
// ....
IntentFilter filter = new IntentFilter();
filter.addAction(UPDATE_MESSAGE);
receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
// do something based on the intent's action
// for example, call updateMessage()
}
};
registerReceiver(receiver, filter);
}
onHandleIntent of IntentService run in another thread (instead of main thread / ui thread), so Updating UI components in onHandleIntent isn't permitted.
I have a service that is, among other things, downloading images from internet. When this is done I want to show this image in a custom Activity that has a dialog theme. But I only want to use this pop up if the app is running, otherwise I just want to create a notification.
But I get an exception when I try to start an activity from my service and i feel that maybe this isn't the right way to do it?
It says:
android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?
So my question is if this is the right way to do this by setting that flag or how should I get my downloaded image from my service to an activity. Can I in some way tell an activity to start a new activity from my service class?
I think using Broadcast Receiver is better option for you.
Add Below Method in Service and call this method when image Download Complete.
private void updateMyActivity(Context context) {
if(MainActivity.activityStatusFlag){
//update the activity if activityStatusFlag=true;
Intent intent = new Intent("mUpdateActivity");
context.sendBroadcast(intent);
}else{
//display notification if activityStatusFlag=false;
}
}
In Activity Add Following Code.
public class MainActivity extends Activity{
public static boolean activityStatusFlag= false;
//define this variable to check if activity is running or not.
#Override
protected void onResume() {
super.onResume();
activityStatusFlag = true;
this.getApplicationContext().
registerReceiver(mMessageReceiver,new IntentFilter("mUpdateActivity"));
}
#Override
protected void onPause() {
super.onPause();
activityStatusFlag = false;
this.getApplicationContext().unregisterReceiver(mMessageReceiver);
}
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
//Display Popup or update Activity
}
};
}
I have a rather commonly occurring situation in Android, which has to do with the previous asynctask updating the activity, whilst the activity has been lost because of a change in orientation.
I have an activity, Activity A.
Activity A implements OnDownloadCompleteListener {
public void sync()
{
new SyncAttestationInfoTask(this).execute();
}
#Override
public void onComplete()
{
loadAttestationInfo();
}
}
Here is my asynctask shortened:
package com.evento.mofa.backgroundtasks;
import java.util.ArrayList;
import java.util.List;
/**
* #author Ahmed
*
*/
public class SyncAttestationInfoTask extends AsyncTask<Void, Void,Void> {
/*TIP*/
//TO SPEED UP THIS OPERATION WE CAN USE THE EXECUTEONEXECUTOR .
private ProgressDialog pd;
private OnDownloadComplete parentActivityContext;
EntityConvert convert = new EntityConvert();
private AttestationDao aDao = new AttestationDao();
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
if (Locale.getDefault().getLanguage().equals("ar"))
{
/*EMPTY ALL THE TABLES THEN START PROCESSING*/
aDao.flushTables(Locale.getDefault().getLanguage());
syncAttestLocations(Webservices.ATTEST_LOCATION_AR,1);
syncDocumentTypes(Webservices.DOCUMENT_TYPES_AR,1);
syncAttestationInfo(Webservices.ATTESTATION_INFO_AR,1);
} else {
/*EMPTY ALL THE TABLES THEN START PROCESSING*/
aDao.flushTables(Locale.getDefault().getLanguage());
syncAttestLocations(Webservices.ATTEST_LOCATION,0);
syncDocumentTypes(Webservices.DOCUMENT_TYPES,0);
syncAttestationInfo(Webservices.ATTESTATION_INFO,0);
}
return null;
}
public SyncAttestationInfoTask(OnDownloadComplete context) {
parentActivityContext = context;
}
#Override
protected void onPreExecute() {
pd = new ProgressDialog((Context)parentActivityContext);
pd.setTitle("Loading...");
pd.setMessage("Updating Data.");
pd.setCancelable(false);
pd.setIndeterminate(true);
pd.show();
}
#Override
protected void onPostExecute(Void result) {
pd.dismiss();
parentActivityContext.onComplete();
// findViewById(R.id.the_button).setEnabled(true);
}
}
There is something strange with my Activity.
I put a breakpoint on the onComplete callback inside my activity
I start a progress dialog inside the sync async task.
As soon as the progress dialog displays on the screen I landscape my device.
The dialog box vanishes, and pd.dismiss() raises a "View not attached" error (I understand that the activity that it was attached to no longer exists).
The above means that parentActivityContext().oncomplete should also throw the same error, however it does not.
I commented the pd.Dismiss(), and found out that the breakpoint on onComplete() is invoked? Isn't this strange given the fact that the reference to the activity has been lost at this point?
Please give me insight into this.
I would do this
Add this line to your Manifest.xml file, this will prevent of calling onCreate() when screen rotates.
<activity android:name=".yourActivity" android:configChanges="keyboardHidden|orientation">
Version above Android 3.2, you also need to add "screenSize":
<activity android:name=".yourActivity" android:configChanges="keyboardHidden|orientation|screenSize">
This will prevent activity from restarting on orientation change, and you should not have any problems (except maybe some layout fixes)
The previous Activty is being referenced by the AsyncTask via a strong reference.
AsyncTask constructed with Activity 1 (parentActivityContex =
Activity 1)
Activity 1 "destroyed" and Activity 2 comes into foreground
AsyncTask completes, calls parentActivityContext (Activity 1) onComplete
Activity 2 just sits there doing nothing
Activity 1 no longer has active references pointing to it, is collected
You could try doing your task in a Service and having whatever Activity is in the foreground receive a broadcast, or you could try having your AsyncTask reference a Fragment with setRetainInstance(true). Below is an example of the second case. Note that you might want to handle the case where the AsyncTask completes while the Fragment is detached from one Activity and not yet attached to the next Activity
public class ExampleDownloadFragment extends Fragment {
#Override
public void onCreate(final Bundle savedInstanceState) {
setRetainInstance(true);
new SyncAttestationInfoTask(this).execute();
}
public void onComplete() {
final Activity activity = getActivity();
if (activity != null && activity instanceof A) {
((A) activity).onComplete();
}
}
}