Android: How to switch to an existed activity?

Question

I'm writting a text editor, and I use

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

    <intent-filter>
        <action android:name="android.intent.action.VIEW"/>
        <category android:name="android.intent.category.DEFAULT"/>
        <category android:name="android.intent.category.BROWSABLE"/>
        <data android:scheme="file"/>
        <data android:scheme="content"/>
        <data android:scheme="http"/>
        <data android:scheme="https"/>
        <data android:mimeType="*/*"/>
    </intent-filter>
</activity>

in AndroidManifest.xml to let my editor can open file from other applications(for example, the default file broswer). But each time I open a file from other applications, my editor will create a new Editor activity, which causes that my editor will have many views and I need to quit many times.

So I'm thinking that when creating a new Editor activity before setContentView, to check whether there exists another Editor activity. If exists, switch to another Editor activity and destroy the current activity:

public class Editor extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if () {// TODO if exists another Editor
            ;// TODO destroy current Editor
            ;// TODO switch to another Editor
        } else {
            setContentView(...);
            ...
        }
    }
}

If it is feasible, how to accomplish the method?

(Because I'm not familiar with java/xml, I don't know whether this problem can be solved by just editting the code of AndroidManifest.xml.)

Answer 1

Add android:launchMode="singleTask" into your Activity as below. This line makes sure that your activity has only one instance (the one created the latest). Once added this code, you can delete if/else check in your Activity.

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

    <intent-filter>
        <action android:name="android.intent.action.VIEW"/>
        <category android:name="android.intent.category.DEFAULT"/>
        <category android:name="android.intent.category.BROWSABLE"/>
        <data android:scheme="file"/>
        <data android:scheme="content"/>
        <data android:scheme="http"/>
        <data android:scheme="https"/>
        <data android:mimeType="*/*"/>
    </intent-filter>
</activity>