如何在Android中检测呼叫状态

<uses-permission android:name="android.permission.READ_PHONE_STATE" />

TelephonyManager telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);

private class MyPhoneStateListener extends PhoneStateListener {
    @Override
    public void onCallStateChanged(int state, String incomingNumber) {
        switch (state) {
            case TelephonyManager.CALL_STATE_IDLE:
                // 电话空闲状态
                break;
            case TelephonyManager.CALL_STATE_RINGING:
                // 电话响铃状态
                break;
            case TelephonyManager.CALL_STATE_OFFHOOK:
                // 电话接通状态
                break;
        }
    }
}

MyPhoneStateListener phoneStateListener = new MyPhoneStateListener();
telephonyManager.listen(phoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);