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Updating list in one class after action in another

I have a problem where by I have two activities, activity 1 and activity 2. Activity 1 contains a listview of contents in my SQLite database, activity 2 contains a button that when pressed preforms a query on the database. This query when run will alter the information in activity 1's list.
When I press the button the query works fine but the listview in activity 1 does not get updated. I know I have to use notifyDataSetChanged on the listview in order to have the list information updated.
My problem is how do I call this method on the list in activity 1 from the button listener in activity 2?
Listview and adapter in activity 1
String[] columns = new String[] {adapter.KEY_CONTENTS_NAME, adapter.KEY_CONTENTS_MEASUREMENT, adapter.KEY_CONTENTS_UNIT};
int[] to = new int[] {R.id.ingredientName, R.id.ingredientMeasurement, R.id.ingredientUnit};
SimpleCursorAdapter myCursorAdapter = new SimpleCursorAdapter(this,R.layout.row2, cursor, columns, to, 0);
ListView ingredientList = (ListView) findViewById(R.id.ingredientList);
ingredientList.setAdapter(myCursorAdapter);
Button in activity 2
Button cookButton = (Button) findViewById(R.id.cookButton);
cookButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//simple SQL query
//call to activity 2 to update the list
}
});

You can use startActivityForResult to achieve this.
In your first activity when you want to start the second activity like this using startActivityForResult.
Intent myIntent = new Intent(FirstActivity.this, SecondActivity.class);
int FIRST_ACTIVITY_CODE = 100
startActivityForResult(intent, FIRST_ACTIVITY_CODE);
In your second activity when doing the click you want to setResult okay and then quit the activity to return to the first activity.
Button cookButton = (Button) findViewById(R.id.cookButton);
cookButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//simple SQL query
setResult(RESULT_OK);
finish();
}
});
In your first activity you have to override onActivityResult and then update your list.
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == FIRST_ACTIVITY_CODE) {
myCursorAdapter.notifyDataSetChanged();
}
}
So you can communicate with activities by using onActivityResult. If you want to pass the data you got back from your SQL query in the second activity to your first activity you can use setResult(int resultCode, Intent data)

Then write this function in your list activity:
#onResume
public void onResume(){
super.onResume();
myCursorAdapter.notifyDataSetChanged();
}
As you go back to that activity, this function will be called and you can notify about the changes here by calling notifyDataSetChanged.

You could start activity using startActivityForResult. Here is the documentation and an example: http://developer.android.com/training/basics/intents/result.html
On the first activity you should have something like this:
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == SECOND_ACTIVITY_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// load data from db
// add data to the list view (create a new adapter or clear the items from the old one and add the new items)
// notifyDataSetChanged on adapter
}
}
}
Before calling notifyDataSetChanged. Load again info from db (and check if it was updated) and add it to the list view. Then call notifyDataSetChanged

Android: How to know when an activity finish?

I have a main activity A -> call activity B -> call activity C -> call activity D.
Activity is called by startActivity(intent).
Activity D have a "Close" button.
How to I notify to Activity A when hit "close" button on Activity D?
Any help is appreciated.

Try this:
Use SharedPreference to store the status of button in Activity D.
In activity A under onResume() get the status of button from the SharedPreference.

//* start the activity with enum defined int activity D to identify your activity
startActivityForResult(intent, DActivity.D_REQUEST_CODE);
//in your D activity define this
private static final int D_REQUEST_CODE = 1;
//* when the button is clicked to close in your D activity, call this in the button event listner
setResult(Activity.RESULT_OK, intent);
//* implement this in your A activity
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
if(data==null)return;
if (requestCode == DActivity.D_REQUEST_CODE)
{
switch (resultCode)
{
case Activity.RESULT_OK:
//* do something
break;
default:
break;
}
}

findViewById(R.id.button_close).setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view) {
startActivity(new Intent(this, Activity_A.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK));
}
});
This will work if you are looking to simply show Activity A while clearing the activity stack. If you just want to know when you return to Activity A, you can save status in SharedPrefs as answered above.

Coming back from intent, do something

I have an android application which is using listView. After clicking on any item on the list it shows you AlertDialog where you can chose either edit or delete. After clicking edit it starts a new intent sending some extra strings to fill up the form for editing. I would like to refresh the list after I click on button save in that EditActivity.
I have read about notifyDataSetChanged() and I think it could work I just would like to know if there is any method which is in MainClass (listView class) and it is executed right after I came back from intent, right after clicking save button in EditActivity.
Or may I just add notifyDataSetChanged() method after I start an activity in the MainActivity?

public class yourClass extends ListActivity {
//define a class variable here.
private ArrayAdapter<Friend> adapter;
#Override
public void onCreate(Bundle savedInstanceState){
//Change this line setListAdapter(new ArrayAdapter<Friend>(this, android.R.layout.simple_list_item_1, db.getAllFriends()));
to
adapter = new ArrayAdapter<Friend>(this, android.R.layout.simple_list_item_1, db.getAllFriends());
setListAdapter(adapter);
}
#Override
public void onResume(){
super.onResume();
adapter.notifyDataSetChanged();
}
}

You can add listView.notifyDataSetChanged() in your activity onResume() function.
#Override
public void onResume(){
super.onResume();
yourListView.notifyDataSetChanged();
}

Use the method startActivityForResult() when opening your EditActivity then implement onActivityResult method in your main class. There you will be able to use notifyDataSetChanged
Read this from the doc

use startActivityForResult to call your EditActivity (this isn't simplest way to do what you want but is good way to do), by using this you can find out what is the result of your edit
Intent i = new Intent(this, EditActivity.class);
startActivityForResult(i, 1);
In your EActivity set the data which you want to return back to MainActivity
Intent returnIntent = new Intent();
returnIntent.putExtra("result",YOUR_RESULT); // skip if you do not want to return special result
setResult(RESULT_OK,returnIntent);
finish();
if you want to send cancel action (in your case fail edit) use this
Intent returnIntent = new Intent();
setResult(RESULT_CANCELED, returnIntent);
finish();
Now in your MainActivity class write following code for onActivityResult() method
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1) {
if(resultCode == RESULT_OK){
String result=data.getStringExtra("result"); // result sent from EditActivity
listViewAdapter. notifyDataSetChanged();
}
if (resultCode == RESULT_CANCELED) {
//Write your code if there's no result
}
}
}//onActivityResult

restart activity in android

I have one activity A, that has one button and one list view which shows names of books . on click of the button, activity B starts, there user fill the book form and save it . when he press back button , user comes to activity A. Here the book name should be updated in listview. I think I have to write some code in onResume() . Can u please tell me what to write. I am using customised list view.

Start activity B with startActivityForResult() and use method onActivityResult() to restart or process the new data
For example, to start Activity B:
String callingActivity = context.getLocalClassName();
Intent newActivity = new Intent(getApplicationContext(),ActivityB.class);
newActivity.setData(Uri.parse(callingActivity));
startActivityForResult(newActivity, 0);
Then somewhere in your Activity A class:
protected void onActivityResult(int requestCode, int resultCode, Intent data){
if(requestCode == 0){
// do processing here
}
}
The other answers should suffice, but onResume() can be called in cases where the activity is resumed by other means.
To simply restart Activity A when user presses back button from Activity B, then put the following inside the onActivityResult:
if(requestCode == 0){
finish();
startActivity(starterintent);
}
And in the onCreate of Activity A, add starterintent = getIntent();
Just remember to initiate the variable with Intent starterintent; somewhere before your onCreate is called.
e.g.
public class ActivityA extends ListActivity {
Intent starterintent;
public void onCreate(Bundle b){
starterintent = getIntent();
}
protected void onActivityResult(int requestCode, int resultCode, Intent data){
if(requestCode == 0){
finish();
startActivity(starterintent);
}
}
private void startActivityB(){
String callingActivity = context.getLocalClassName();
Intent newActivity = new Intent(getApplicationContext(),ActivityB.class);
newActivity.setData(Uri.parse(callingActivity));
startActivityForResult(newActivity, 0);
}
}
Then just call startActivityB() from a button click or whatever

YES you are right. Write code in onResume.
When you updated date just call notifyDataSetChanged(); for your ListView adapter
Hope, it help you!

You can either start the activity when user press on Save, and it will fix it for you.
Or if you want to press back:
#Override
public void onResume(){
super.onResume();
list.clear();
list.addAll(getBooks());
adapter.notifyDataSetChanged();
}

Switching between activity?

In an given Android activity, I would like to start a new activity for the user at some point. Once they leave the first activity and arrive at the second, the first activity is hidden..
Now my question is
I want to bring back the first activity (i dont want to create a new instance of the first activity but to bring back the already existing instance of the first activity) when a button is clicked in the second activity ...
thanks :)

so simple. integrate the below code in your second activity
Button b = (Button)findViewById(yourbuttonid here);
b.setOnClickListener(new View.onClickListener(){
public void onClick(View v){
finish();
}
});
This will work

You would define the first activity with launchMode="singleInstance", then you would start the activity as usual.

Depending on the usage of your second activity, you could also use startActivityForResult() when you start your second activity...

FirstActivity.java{
private static final int SECOND_ACTIVITY = 0;
openSecondActivity(){
Intent forChildIntent= new Intent( this ,FirstActivity. class );
//data for second activity
forChildIntent.putExtra("userName", getUsrName());
this.startActivityForResult(forChildIntent, SECOND_ACTIVITY);
}
protected void onActivityResult(int requestCode, int resultCode, Intent data){
switch (resultCode) {
case RESULT_OK: //do something
default:break;
}
}
SecondActivity.java{
goBackButtonClick(){
Intent retData=new Intent();
//set data to pass back ,if required
//retData.putExtra("userName", getUsrName());
setResult(RESULT_OK, retData);
finish();//will take you to the first activity
}
}