{ Android Studio } Explicit Intent & Implicit Intent View binding (2)

Explicit Intent & Implicit Intent View binding

What is intent?

Intent allows us transfer data from sender activity to receiver activity
It is used to run an activity in another activity
After creating an Intent, we store data which we wish to send into the Intent
So, It is possible to execute the desired components in the activity; there are two methods

Explicit Intent ←→ Implicit Intent

Explicit Intent

실행하고자 하는 컴포넌트가 ‘명확’ 할 때 사용
e.g. The operation intention itself are
1. Sending a ’ Input value ‘ from MainActivity to SecondActivity.
2. Returning a ’ Input value ‘ form SecondActivity to MainAcitivy.

Source Code

// In MainActivity.java
    public void sendText(View view) {

        Intent i = new Intent(this, SecondActivity.class);
        // Want to send this specific string to SecondActivity
        String myString = binding.editText1.getText().toString();
        // Add the string to the intent
        i.putExtra("qString", myString);
        // Launch SecondActivity
        startForResult.launch(i);
    }

// In SecondActivity.java
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    ...
        // Return the activity started this activity.
        // Get data from the intent
        Bundle extra = getIntent().getExtras();
        // If there is no data from the intent, escape onCreate
        if(extra == null) {
            return;
        }

        // Retrieve extended string related with the key "qString"
        String qString = extra.getString("qString");
        binding.textView2.setText(qString);
    }

    ...
    // Return a String
    public void returnText(View view) {
        finish();
    }

    @Override
    public void finish() {

        Intent data = new Intent();
        String returnString = binding.editText2.getText().toString();
        data.putExtra("returnData", returnString);
        // Set the result that this activity will return to its caller.
        setResult(RESULT_OK, data);
        super.finish();
    }

    // In MainActivity.java

    // ActivityResultLauncher: a launcher for a previously-prepared call to
    // start the process of executing an ActivityResultContracts & ActivityResultCallback
    ActivityResultLauncher<Intent> startForResult = registerForActivityResult(
            new ActivityResultContracts.StartActivityForResult(),
            new ActivityResultCallback<ActivityResult>() {
                @Override
                public void onActivityResult(ActivityResult result) {
                    if(result.getResultCode() == Activity.RESULT_OK) {
                        // Get a returned string
                        Intent data = result.getData();
                        String returnString = data.getExtras().getString("returnData");
                        binding.textView1.setText(returnString);
                    }
                }
            });

Implicit Intent

You can execute the desired component with any intention.
Intents that do not specify the name of the component, but only contains a list of the features of the component to be called
Android system retrieves intent filters to be matched with the feature
e.g. If you want to display a location on a map, you can ask another app with that feature.

Example app

Source Code

    public void showWebPage(View view) {

        Intent intent = new Intent(Intent.ACTION_VIEW,
                Uri.parse("http://www.msn.com"));

        startActivity(intent);
    }

Intent solution process finds two activities matched with implicit intent using the intent filter

// Another web view app
    private void handleIntent() {
        // Return the intent that started this activity
        Intent intent = getIntent();
        // Retrieve data this intent is operating on.
        Uri data = intent.getData();
        URL url = null;

        try {
            // Get scheme, host, and decoded-path
            // In Manifest file, <data android:scheme="https" android:host="www.msn.com" />
            url = new URL(data.getScheme(), data.getHost(), data.getPath());
        } catch (Exception e) {
            e.printStackTrace();
        }
        // Load url
        binding.webView1.loadUrl(url.toString());
    }


    // In Manifest file
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
            // Set actions
            <action android:name="android.intent.action.VIEW" />
                <category android:name="android.intent.category.BROWSABLE" />
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:scheme="https" android:host="www.msn.com" />
            </intent-filter>
        </activity>