Explicit and implicit form of the same intent

Question

How would the same custom intent look in forms of explicit and implicit one? By "custom" I mean it's not ACTION_VIEW or something like that. It is intent used to open one activity (for example called activB) from another (activA) in the same app and return some results (a couple of boolean vars) to the first activity (activA). How would one able to implement that?

Answer 1

Define an integer constant, for example:

private static final int REQUEST_CODE = 1;

Create a new Intent in your Activity class:

Intent intent = new Intent(this, DestinationActivity.class);
startActivityForResult(intent, REQUEST_CODE);

In this Activity class override following method:

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
        // do something
    }
}

In your destination Activity class, DestinationActivity, you have to create a new Intent to hold a data:

Intent data = new Intent();
data.putExtra("boolean1", true);
data.putExtra("boolean2", false);

To pass data back to the source Activity you have to call the following method:

setResult(REQUEST_CODE, data); // will call onActivityResult() method

For more info look here and there

If you would like to send a text through other app in your phone you can use an explicit intent or ShareCompat class (which is provided by v4 Support Library). Example with ShareCompat:

Intent shareIntent = ShareCompat.IntentBuilder.from(this)
                    .setType("text/plain")
                    .setSubject("ShareCompat")
                    .setText("I am using ShareCompat class")
                    .setChooserTitle("Sending Text")
                    .createChooserIntent();

if (shareIntent.resolveActivity(getPackageManager()) != null)
    startActivity(shareIntent);

Example of explicit and implicit intents:

1) manifest file:

<activity android:name=".MainActivity">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

<activity android:name=".SecondActivity">
    <intent-filter>
        <action android:name="tj.xona.customaction" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
</activity>

2) MainActivity class:

public class MainActivity extends AppCompatActivity {

    private TextView textView;
    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = (TextView) findViewById(R.id.outputText);
        button = (Button) findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //Intent intent = new Intent(MainActivity.this, SecondActivity.class); // Explicit intent
                Intent intent = new Intent(); // Implicit intent
                intent.setAction("tj.xona.customaction"); // custom action
                startActivityForResult(intent, SecondActivity.CUSTOM_INTENT);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == SecondActivity.CUSTOM_INTENT && resultCode == RESULT_OK) {
            String msg = data.getStringExtra(SecondActivity.MESSAGE_BACK);
            textView.setText(msg);
        }
    }
}

3) SecondActivity class:

public class SecondActivity extends AppCompatActivity {

    public static final int CUSTOM_INTENT = 1;
    public static final String MESSAGE_BACK = "message";

    private EditText edit;
    private Button send;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        edit = (EditText) findViewById(R.id.edit);
        send = (Button) findViewById(R.id.send);

        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String msg = edit.getText().toString();

                Intent intent = new Intent();
                intent.putExtra(MESSAGE_BACK, msg);

                setResult(RESULT_OK, intent);
                finish();
            }
        });
    }
}

Conclusion: You can use explicit and implicit intents for the Activity which is defined with intent-filter in your app. But if you want to use an activity from another app you must use implicit intent. Inside your app it's better to use explicit intent to start an activity. The idea of using implicit intent is reusing some activity from another apps in your phone. When you follow standard action names that will make easy to use some functionality and most interesting you can have multiple choices. By using custom action for your activity you restrict your app because nobody knows about this custom action, such as in this example: "tj.xona.customaction".