MTK 平台自带的相机是没有触摸拍照功能的，要加这个功能得先跟大量代码，去看快门按钮是如何响应的，预览界面是如何响应触摸对焦的。过程太繁琐，这里就不介绍如何定位代码、跟代码了，下面直接上解决办法。

    1、在vendor/mediatek/proprietary/packages/apps/Camera/src/com/android/camera/bridge/CameraAppUiImpl.java 中添加快门按钮单击事件的包装方法：

    1. public class CameraAppUiImpl implements ICameraAppUi {
    2.     ......
    3.     @Override
    4.     public ImageView getPhotoShutter() {
    5.         return mShutterManager.getPhotoShutter();
    6.     }
    7.     /// START. Add "Touch to capture" feature. By ShawnXiaFei, 20170504.
    8.     public void performPhotoShutter(){
    9.         if(null == mShutterManager){
    10.             throw new IllegalStateException("mShutterManager is null.");
    11.         }
    12.         mShutterManager.performPhotoShutter();
    13.     }
    14.     /// END. Add "Touch to capture" feature. By ShawnXiaFei, 20170504.
    15.     ......
    16. }

    这里我加了个 null 判断，为 null 时直接抛异常，这样能方便定位问题。
    因为 ShutterManager 里面已经有了perform方法，所以我这里是直接调用了 ShutterManager.performPhotoShutter()，当然也可以通过 getPhotoShutter() 拿到快门按钮对象后，再设置相应逻辑。

    1. public class ShutterManager extends ViewManager {
    2.     ......
    3.     public ShutterButton getPhotoShutter() {
    4.         return mPhotoShutter;
    5.     }
    6.     ......
    7.     public boolean performPhotoShutter() {
    8.         boolean performed = false;
    9.         if (mPhotoShutter != null && mPhotoShutter.isEnabled()) {
    10.             mPhotoShutter.performClick();
    11.             performed = true;
    12.         }
    13.         Log.d(TAG, "performPhotoShutter() mPhotoShutter=" + mPhotoShutter + ", return "
    14.                 + mPhotoShutter);
    15.         return performed;
    16.     }
    17.     ......
    18. }

    2、在vendor/mediatek/proprietary/packages/apps/Camera/src/com/android/camera/CameraActivity.java 文件的 onSingleTapUp 方法中添加触摸判断逻辑：

    1. public class CameraActivity extends ActivityBase implements
    2.         PreviewFrameLayout.OnSizeChangedListener,
    3.         ActivityCompat.OnRequestPermissionsResultCallback {
    4.     ......
    5.     public void onSingleTapUp(View view, int x, int y) {
    6.         ......
    7.             if (isCancelSingleTapUp()) {
    8.                 Log.i(TAG, "will cancel this singleTapUp event");
    9.                 return;
    10.             }
    12.             if (!mCameraAppUi.collapseSetting(true)) {
    13.                 if (mCameraActor.getonSingleTapUpListener() != null) {
    14.                     mCameraActor.getonSingleTapUpListener().onSingleTapUp(view,
    15.                             x, y);
    16.                 }
    17.             }
    19.             /// START. Add "Touch to capture" feature. By XiaFei, 20170504.
    20.             if(getCameraId() == 1){
    21.                 mCameraAppUi.performPhotoShutter();
    22.                 return;
    23.             }
    24.             /// END. Add "Touch to capture" feature. By XiaFei, 20170504.
    25.         }
    26.     }
    27.     ......
    28. }

    到这触摸拍照功能就实现了，虽然分析的时候跟了很多代码，但最后解决方法很简单，满满的收获感。