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How can I pass parameters between two Activity but one must only support the first one

I have an activity that very quickly has to process data and then return to the previous activity, I give an example: I have a MainActivity class that passes information through Intent to another Loader class, this processes the data and sends it back to the MainActivity. I don't know how to put this procedure into practice...

From your MainActivity call the TargetActivity using startActivityForResult()-
For example:
Intent intent = new Intent(this, TargetActivity.class);
intent.putExtra(); // sent your putExtra data here to pass through intent
startActivityForResult(intent, 1000);
In your intent set the data which you want to return back to MainActivity. If you don't want to return back any data then you don't need to set any data.
For example:
In TargetActivity if you want to send back data:
Intent returnIntent = new Intent();
returnIntent.putExtra("result", result);
setResult(Activity.RESULT_OK, returnIntent);
finish();
If you don't want to return data:
Intent returnIntent = new Intent();
setResult(Activity.RESULT_CANCELED, returnIntent);
finish();
Now in your MainActivity class write following code for the onActivityResult() method.
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1000) {
if(resultCode == Activity.RESULT_OK){
String result=data.getStringExtra("result");
}
if (resultCode == Activity.RESULT_CANCELED) {
// Do your task here.
}
}
}

//do Some work
Intent i = new Intent(this,MainActivity2..class);
startActivityForResult(i,12);
}
In MainActivity2.class
// after your work complete
Intent i =new Intent();
i.putExtra("result",true);// any data you want to pass
setResult(RESULT_OK,i);
After this we handle result
protected void onActivityResult(int requestCode, int resultCode, #Nullable Intent data) {
switch(requestCode){
case 12:
if(resultCode == Activity.RESULT_OK){// onsuccess do something
boolean isSucces = data.getBooleanExtra("result",false);
if(isSuccess)// perform action
{// show toast}
}
}
}

I find the best to use callbacks.
in Loader:
Create inner class
MyCallback callback;
viod setCallback(MyCallback callback){
this.callback = callback;
}
viod onStop(){
callback = null;
}
interface MyCallback{
void doSomething(Params params);
}
in MainActivity:
implement MyCallback
set reference in onCreate
Loader loader = new Loader();
loader.setCallback(this);
override method doSomething()
#override
void doSomething(Params params){
//do your thing with the params…
}
when the job is done inside Loader call MainActivity:
callback.doSomething(params);
destroy reference inside MainActivity in onStop()
loader.onStop();

By the help of android startActivityForResult() method, you can get result from another activity.
By the help of android startActivityForResult() method, you can send information from one activity to another and vice-versa. The android startActivityForResult method, requires a result from the second activity (activity to be invoked).
In such case, we need to override the onActivityResult method that is invoked automatically when second activity returns result.
MainActivity.java
public class MainActivity extends Activity {
TextView textView1;
Button button1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView1=(TextView)findViewById(R.id.textView1);
button1=(Button)findViewById(R.id.button1);
button1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent=new Intent(MainActivity.this,SecondActivity.class);
startActivityForResult(intent, 2);// Activity is started with
requestCode 2
}
});
}
// Call Back method to get the Message form other Activity
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
// check if the request code is same as what is passed here it is 2
if(requestCode==2)
{
String message=data.getStringExtra("MESSAGE");
textView1.setText(message);
}
}
SecondActivity.java
public class SecondActivity extends Activity {
EditText editText1;
Button button1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
editText1=(EditText)findViewById(R.id.editText1);
button1=(Button)findViewById(R.id.button1);
button1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
String message=editText1.getText().toString();
Intent intent=new Intent();
intent.putExtra("MESSAGE",message);
setResult(Activity.RESULT_OK,intent);
finish();//finishing activity
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.second, menu);
return true;
}
}

How to pass the image from Activity B to previous Activity A on Back pressed by shared preference android

I want to change the image of previous activity if I changed the image of second activity and when I return back to previous activity the image should be changed.
https://i.stack.imgur.com/7bTnj.png

Try to customize following code within your code. And it will work.
Here is the first activity where you want to track if the image is changed and want to load changed image.
public class A extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_a);
//YOUR OTHER CODE HERE..
startActivityForResult(new Intent(A.this, B.class), 111);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 111 && resultCode == RESULT_OK) {
if (data.getExtras() != null) {
//set your image path which has been returned by previous activity to your imageview here
//data.getExtras().getString("image_path")
}
}
super.onActivityResult(requestCode, resultCode, data);
}
}
Here is your next activity where you are changing image
public class B extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_b);
//YOUR OTHER CODE HERE..
}
#Override
public void onBackPressed() {
Intent intent = new Intent();
intent.putExtra("image_path", "CHANGED_IMAGE_PATH");
setResult(RESULT_OK, intent);
super.onBackPressed();
}
}

onActivityResult doesn't get called by finish() when the parent activity is passed as parameter to an intent in a non-activity class

I've got a class which handles a question sequence. It doesn't extend Activity. In the class there is the method:
public class QuizMaster {
public void startQuiz(Activity activity, Model model) {
//switch - case statement using model
Intent intent = new Intent(activity, QuestionTextActivity.class)
activity.startActivityForResult(intent, requestCode);
//other case statements with other intents
}
}
When I call this method from a working activity with
mQuizMaster.startQuiz(this, mModel);
And I finish() the child activity:
Intent returnIntent = new Intent();
returnIntent.putExtra(ARG_SELECTED_CHECKBOX, checkedBox);
setResult(RESULT_CODE, returnIntent);
finish();
it doesn't execute the parent activity's
#Override
protected void onActivityResult(final int requestCode, final int resultCode, final Intent data) {
Log.d(LOG_TAG, "OnActivityResult called in SignDetailsActivity. Resultcode is: ");
}
But when I execute the
Intent intent = new Intent(activity, QuestionTextActivity.class)
activity.startActivityForResult(intent, requestCode);
in the actual parent activity file, it does execute the onActivityResult method.
Why doesn't the child activity run the onActivityResult in the parent activity if sent with a non-activity class? How do i fix this?
I haven't found anyone with the same problem with executing new Intent() in a non-activity class like this. If there is someone, i didn't use the right search keywords and some others might type in the same as I did and come on this page.

You need to call setResult(int) before call finish(). This is from Activity documentation:
When an activity exits, it can call setResult(int) to return data back
to its parent. It must always supply a result code, which can be the
standard results RESULT_CANCELED, RESULT_OK, or any custom values
starting at RESULT_FIRST_USER. In addition, it can optionally return
back an Intent containing any additional data it wants. All of this
information appears back on the parent's Activity.onActivityResult(),
along with the integer identifier it originally supplied.
Here is my implementation, which worked:
MainActivity.java (parent activity)
public class MainActivity extends AppCompatActivity {
private Sample sample;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btn = (Button) findViewById(R.id.button);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
sample = new Sample();
sample.startActivity(MainActivity.this);
}
});
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Log.d("TEST", "DONE");
}
}
LaunchActivity.java (child activity)
public class LaunchActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launch);
Button btn = (Button) findViewById(R.id.button2);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
setIntent(new Intent());
finish();
}
});
}
}
Sample.java (class start activity)
public class Sample {
public Sample () {}
public void startActivity (Activity a) {
Intent it = new Intent(a, LaunchActivity.class);
a.startActivityForResult(it, 0);
}
}

Why onStop() is called after onCreate() when starting an Activity within onActivityResult()

I have the following workflow:
startActivityForResult(Activity1)
finish() called on Activity1 (when pushing a button)
onActivityResult() ==> startActivityForResult(Activity2)
===> Activity2.onCreate() is called before Activity1.onStop()
Why I have that?
Edited:
Here is the code:
1- MainActivity.java
// On click on a button
public void start(View view) {
Intent activityIntent = new Intent(this, Activity2.class);
startActivityForResult(activityIntent, 0);
}
protected void onActivityResult(int requestCode,
int resultCode,
Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Intent activityIntent = new Intent(this, Activity3.class);
startActivityForResult(activityIntent, 0);
}
2- Activity2.java
// A button to finish the activity
public void stop(View view) {
finish();
}
#Override
protected void onStop() {
super.onStop();
}
3- Activity3.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_activity3);
}

Because of the lifecycle. onStop isn't called until after an Activity is removed from view. So onStop won't be called until something else is blocking it from the user- activity2 in this case. That means Activity2 will already have to have been created, because you can't block another activity if you don't exist.

Show a button on a previous activity when going back from current activity

I want to visible a edit button on my previous activity by going back using back button. But when I am using
#Override
public void onClick(View arg0) {
// finish the current activity
finish();
}
on my current activity, it is going back to previous activity, but edit button doesn't become visible.
If I am using onResume on previous activity
#Override
protected void onResume() {
super.onResume();
btnEdit.setVisibility(View.VISIBLE);
}
then it's always visible, no matter if the activity is resuming or created for the first time.
I am new in Android development, please help me to solve this problem.

Ok,
When you start the Activity, instead of startActivity(intent) use startActivityForResult(intent, 1989) (The 1989 can be whatever int you want).
When you return from the new Activity, before calling finish() do the following:
Intent returnIntent = new Intent();
returnIntent.putExtra("resultBool", true);
//Null checks, not strictly neccescary
if (getParent() == null)
{
setResult(Activity.RESULT_OK, returnIntent);
}
else
{
getParent().setResult(Activity.RESULT_OK, returnIntent);
}
finish();
Then in your first Activity override onActivityResult() like so:
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
// The int you initially used
if (requestCode == 1989)
{
if (resultCode == RESULT_OK)
{
boolean result = data.getBooleanExtra("resultBool", false)
if (result)
//Show the button now
}
}
}

You can make a boolean variable which can be set to true when you finish and make a check with this boolean in your onResume method

Override onRestart() method
#Override
protected void onRestart () {
super.onResume();
btnEdit.setVisibility(View.VISIBLE);
}
Or start Activity with
startActivityForResult (Intent intent, int requestCode)
method and override
#Override
protected void onActivityResult (int requestCode, int resultCode, Intent data){
super.onActivityResult (requestCode,resultCode,data);
btnEdit.setVisibility(View.VISIBLE);
}