這陣子公司安排進行8.0的適配，就對比著代碼進行差異化分析，發現InCallUi的變化很大，整體架構變了，變的更加清晰。界面變的更加漂亮了，跟之前的版本相比，可以說的上是天壤之別啊。InCallUi8.0也增加了一些比較實用的功能，比如說是來電防誤觸。我們把手機放在口袋，這時候來電，可能就會出現誤觸，將電話掛斷或者接聽，而我們可能并不知道，這明顯很不好。仔細的看了一下8.0防誤觸功能的實現，做一下筆記。

在AnswerScreenPresenter中的onCreate方法中，根據條件判斷決定是否將距離傳感器初始化好，AnswerScreenPresenter就相當于之前版本的AnswerPresenter。

    PseudoScreenState pseudoScreenState = InCallPresenter.getInstance().getPseudoScreenState();
    if (AnswerProximitySensor.shouldUse(context, call)) {
      new AnswerProximitySensor(context, call, pseudoScreenState);
    } else {
      pseudoScreenState.setOn(true);
    }

我們現在來看看詳細的判斷：
1.不是來電狀態
2.不允許使用來電傳感器
3.不支持距離傳感器
4.當前狀態時亮屏

public static boolean shouldUse(Context context, DialerCall call) {
    // Don't use the AnswerProximitySensor for call waiting and other states. Those states are
    // handled by the general ProximitySensor code.
    if (call.getState() != State.INCOMING) {               
      LogUtil.i("AnswerProximitySensor.shouldUse", "call state is not incoming");
      return false;
    }

    if (!ConfigProviderBindings.get(context)
        .getBoolean(CONFIG_ANSWER_PROXIMITY_SENSOR_ENABLED, true)) {
      LogUtil.i("AnswerProximitySensor.shouldUse", "disabled by config");
      return false;
    }

    if (!context
        .getSystemService(PowerManager.class)
        .isWakeLockLevelSupported(PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK)) {
      LogUtil.i("AnswerProximitySensor.shouldUse", "wake lock level not supported");
      return false;
    }

    if (isDefaultDisplayOn(context)) {
      LogUtil.i("AnswerProximitySensor.shouldUse", "display is already on");
      return false;
    }

    return true;
  }

PseudoScreenState類的代碼如下：

 public class PseudoScreenState {

  /** Notifies when the on state has changed. */
  public interface StateChangedListener {
    void onPseudoScreenStateChanged(boolean isOn);
  }

  private final Set<StateChangedListener> listeners = new ArraySet<>();

  private boolean on = true;

  public boolean isOn() {
    return on;
  }

  public void setOn(boolean value) {
    if (on != value) {
      on = value;
      for (StateChangedListener listener : listeners) {
        listener.onPseudoScreenStateChanged(on);
      }
    }
  }

  public void addListener(StateChangedListener listener) {
    listeners.add(listener);
  }

  public void removeListener(StateChangedListener listener) {
    listeners.remove(listener);
  }
}

AnswerProximitySensor的構造函數如下：

public AnswerProximitySensor(
      Context context, Call call, PseudoScreenState pseudoScreenState) {
    this.call = call;
    Log.d("AnswerProximitySensor.constructor", "acquiring lock");
    if (ConfigProviderBindings.get(context).getBoolean(CONFIG_ANSWER_PSEUDO_PROXIMITY_WAKE_LOCK_ENABLED, true)) {
      answerProximityWakeLock = new PseudoProximityWakeLock(context, pseudoScreenState);
    } else {
      // TODO: choose a wake lock implementation base on framework/device.
      // These bugs requires the PseudoProximityWakeLock workaround:
      // b/30439151 Proximity sensor not working on M
      // b/31499931 fautly touch input when screen is off on marlin/sailfish
      answerProximityWakeLock = new SystemProximityWakeLock(context);
    }
    answerProximityWakeLock.setScreenOnListener(this);
    answerProximityWakeLock.acquire();

    CallList.getInstance().addListener(this);
  }

在電話狀態發生改變和遠離距離傳感器的情況下，將
在InCallActiivityde onResume方法中進行了調用：

PseudoScreenState pseudoScreenState = InCallPresenter.getInstance().getPseudoScreenState();
pseudoScreenState.addListener(this);
onPseudoScreenStateChanged(pseudoScreenState.isOn());

在onPause方法中將監聽移除：

InCallPresenter.getInstance().getPseudoScreenState().removeListener(this);

在InCallActivity中，pseudoBlackScreenOverlay是一個黑色的浮層，當滿足來電防誤觸的情況下時，將浮層設置為VISIBLE，使得觸摸事件不響應，同時在dispatchTouchEvent方法中，直接返回true，不繼續分發觸摸事件

    private View pseudoBlackScreenOverlay;
    private boolean touchDownWhenPseudoScreenOff;

    @Override
    public void onPseudoScreenStateChanged(boolean isOn) {
        Log.d("InCallActivity.onPseudoScreenStateChanged", "isOn: " + isOn);
        pseudoBlackScreenOverlay.setVisibility(isOn ? View.GONE : View.VISIBLE);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        // Reject any gesture that started when the screen is in the fake off state.
        if (touchDownWhenPseudoScreenOff) {
            if (event.getAction() == MotionEvent.ACTION_UP) {
                touchDownWhenPseudoScreenOff = false;
            }
            return true;
        }
        // Reject all touch event when the screen is in the fake off state.
        if (!InCallPresenter.getInstance().getPseudoScreenState().isOn()) {
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                touchDownWhenPseudoScreenOff = true;
                Log.d("InCallActivity.dispatchTouchEvent", "touchDownWhenPseudoScreenOff");
            }
            return true;
        }
        return super.dispatchTouchEvent(event);
    }