如何创建类似WhatsApp和Massanger的来电活动

Question

即使应用程序不是在后台运行，我也希望启动诸如whatsapp和facebook messenger之类的来电活动。

此刻，只有在应用程序在后台运行时，呼叫活动才会启动。

public class callActivity extends AppCompatActivity {

    Button acceptCall;
    Button delinceCall;

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

        Window window = getWindow();
        window.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        acceptCall = findViewById(R.id.answer_call_btn);
        delinceCall = findViewById(R.id.reject_call_btn);
        try {
            Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_RINGTONE);
            Ringtone r = RingtoneManager.getRingtone(getApplicationContext(), notification);
            r.play();
        } catch (Exception e) {
            e.printStackTrace();
        }
        acceptCall.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sendToVideoCall();
            }
        });
    }

    private void sendToVideoCall() {
            Intent mainIntent = new Intent(callActivity.this, videoCallActivity.class);
            startActivity(mainIntent);
            finish();
    }


}