All about Intents in Android

!!intents.md

Intents

Explicit v.s. Implicit

A quick demo of implicit and explicit intents.

Requesting data from another activity

1. Use startActivityForResult() to start the second Activity
2. To return data from the second Activity:
   • Create a new Intent
   • Put the response data in the Intent using putExtra()
   • Set the result to Activity.RESULT_OK or RESULT_CANCELED, if the user cancelled out
   • Set result can has a version without an intent, just a code: setResult(RESULT_COLOR_RED);
   • call finish() to close the Activity
3. Implement onActivityResult() in first Activity

Delegating onActivityResult() to an Adapter/ViewModel etc.

Delegation to adaptor + preserving the position

• https://stackoverflow.com/questions/20015950/can-we-call-startactivityforresult-from-adapterhow-to-get-the-response
• https://stackoverflow.com/questions/50700309/how-to-assign-onactivityresult-values-to-the-listview

From a Service

• https://stackoverflow.com/questions/3248132/analog-of-startactivityforresult-for-service

From a ViewModel

• https://stackoverflow.com/questions/49814894/mvvm-startactivityforresult

Allowing other apps to start your activity

Implement an Intetent filter

01_implicit.java

//Implicit
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, textMessage);
sendIntent.setType("text/plain")
startactivity(sendIntent);

02_explicit.java

//Explicit: Explicit intent when you call you're on application activity from one activity to another
// e.g. first activity to second activity:
Intent intent = new Intent(first.this, second.class);
startactivity(intent);

03_start.java

Intent intent = new Intent(first.this, second.class);

//just navigate
startActivity(intent);
//to start activity and get response back
startActivityForResult(intent,code);
//start a service
startService(intent);
//start service in background  
startForeGroundService(intent);

04_pass_uri.java

intent.setData(Uri.parse(""http://www.google.com"")); 
intent.setData(Uri.fromFile(new File(""/sdcard/sample.jpg"")));

05_pass_a_bundle.java

Bundle extras = new Bundle();
extras.putString(EXTRA_MESSAGE, ""this is my message"");
extras.putInt(EXTRA_POSITION_X, 100);
extras.putInt(EXTRA_POSITION_Y, 500);
putExtras(bundle);

06_retreive_Intent_and_data.java

Intent intent = getIntent();
intent.getData();
int res = intent.getIntExtra (String name, int defaultValue)
Bundle bundle = intent.getExtras(); 

07_returning_result.java

//Started by using startActivityForResult(messageIntent, TEXT_REQUEST);

//get the TEXT_REQUEST code, to return it so that the requesting activity will know what to expect.
int positionX = intent.getIntExtra(MainActivity.EXTRA_POSITION_X);

//avoid confusing sent and returned data, by using a new Intent.
Intent replyIntent = new Intent();
//used an established this is some shared key
public final static String EXTRA_RETURN_MESSAGE = "com.example.mysampleapp.RETURN_MESSAGE";
//the reutrned data
returnIntent.putExtra(EXTRA_RETURN_MESSAGE, mMessage);
//set the response 
setResult(RESULT_OK,replyIntent);
//close the activity
finish();

08_returning_not_returning_result.java

//Started by using startActivityForResult(messageIntent, TEXT_REQUEST);

//avoid confusing sent and returned data, by using a new Intent.
Intent replyIntent = new Intent();
//user canceled
setResult(RESULT_CANCELED,replyIntent);
//close the activity
finish();

09_processing_result.java

"public void onActivityResult(int requestCode, int resultCode,  Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == TEXT_REQUEST) {
        if (resultCode == RESULT_OK) {
            String reply = 
               data.getStringExtra(SecondActivity.EXTRA_RETURN_MESSAGE);
               // process data
        }
    }
}"

10_delegation_to_adapter.java

//in the activity/fragment 

//here we override
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    mAdapter.onActivityResult(requestCode, resultCode, data);  //delegate handling to madapter
}


//////////////////////////////////////////////////////////////////////////////////////////////////////

//in the Adapter (note: this is not an overide!)
public  void onActivityResult(int requestCode, int resultCode, Intent data) {
    Log.d("MyAdapter", "onActivityResult");
}

//p.s. this means we are handling a response for a list/recycler item event (click/swipe)
  
  holder.EditRemnant1.Click += delegate (object sender, System.EventArgs args)
    {
        if (remnantModel != null)
        {
            Intent intent = new Intent(context, typeof(EditRemnant));
            intent.PutExtra("OpenPopType", 2);
            intent.PutExtra("Position", position );  //well need this to be passed from incoming to result intent in the invoked activity
            context.StartActivityForResult(intent, 1);
        }
    };

11_onServiceForResult.java

public class SomeService extends Service {

    /**
     * Code for a successful result, mirrors {@link Activity.RESULT_OK}.
     */
    public static final int RESULT_OK = -1;

    /**
     * Key used in the intent extras for the result receiver.
     */
    public static final String KEY_RECEIVER = "KEY_RECEIVER";

    /**
     * Key used in the result bundle for the message.
     */
    public static final String KEY_MESSAGE = "KEY_MESSAGE";

    // ...

    /**
     * Used by an activity to send a result back to our service.
     */
    class MessageReceiver extends ResultReceiver {

        public MessageReceiver() {
            // Pass in a handler or null if you don't care about the thread
            // on which your code is executed.
            super(null);
        }

        /**
         * Called when there's a result available.
         */
        @Override
        protected void onReceiveResult(int resultCode, Bundle resultData) {
            // Define and handle your own result codes
            if (resultCode != RESULT_OK) {
                return;
            }

            // Let's assume that a successful result includes a message.
            String message = resultData.getString(KEY_MESSAGE);

            // Now you can do something with it.
        }

    }

}

/**
 * Starts an activity for retrieving a message.
 */
private void startMessageActivity() {
    Intent intent = new Intent(this, MessageActivity.class);

    // Pack the parcelable receiver into the intent extras so the
    // activity can access it.
    intent.putExtra(KEY_RECEIVER, new MessageReceiver());

    startActivity(intent);
}


public class MessageActivity extends Activity {

    // ...

    @Override
    public void finish() {
        // Unpack the receiver.
        ResultReceiver receiver =
                getIntent().getParcelableExtra(SomeService.KEY_RECEIVER);

        Bundle resultData = new Bundle();

        resultData.putString(SomeService.KEY_MESSAGE, "Hello world!");

        receiver.send(SomeService.RESULT_OK, resultData);

        super.finish();
    }

}

12_intent_filter.xml

<activity android:name="ShareActivity">
    <intent-filter>
        <action android:name="android.intent.action.SEND"/>
        <category android:name="android.intent.category.DEFAULT"/>
        <data android:mimeType="text/plain"/>
        <data android:mimeType="image/*"/>
    </intent-filter>
</activity>

13_share_action.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/menu_item_share"
        android:showAsAction="ifRoom"
        android:title="Share"
        android:actionProviderClass="android.widget.ShareActionProvider" />
    ...
</menu>

14_share_intent.java

private ShareActionProvider mShareActionProvider;
...

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate menu resource file.
    getMenuInflater().inflate(R.menu.share_menu, menu);

    // Locate MenuItem with ShareActionProvider
    MenuItem item = menu.findItem(R.id.menu_item_share);

    // Fetch and store ShareActionProvider
    mShareActionProvider = (ShareActionProvider) item.getActionProvider();

    // Return true to display menu
    return true;
}

// Call to update the share intent
private void setShareIntent(Intent shareIntent) {
    if (mShareActionProvider != null) {
        mShareActionProvider.setShareIntent(shareIntent);
    }
}