Android Camera开发系列：设置对焦模式模式
你对android camera的对焦模式熟悉吗？ 知道什么场景下该设置哪种对焦模式吗？
本文针对下面2点展开介绍，和大家一起学习~
一、有哪几种对焦模式？
二、如何使用各种对焦模式？
一、有哪几种对焦模式？
1）获取设备支持的对焦模式
Google为我们提供了查询当前设备支持的对焦模式的接口~
Camera1获取对焦模式接口：
----- Camera.java
public String getFocusMode() {
return get(KEY_FOCUS_MODE);
}
Camera2获取对焦模式接口：
----- CameraCharacteristics.java
@PublicKey
public static final Key<int[]> CONTROL_AF_AVAILABLE_MODES =
new Key<int[]>("android.control.afAvailableModes", int[].class);
2）各种对焦模式的介绍
这里只介绍常用的几种对焦模式，详解的介绍，可以查看文末附的源码内容。
我们常用的也就下面4种对焦模式。
public static final String FOCUS_MODE_AUTO = "auto";
public static final String FOCUS_MODE_FIXED = "fixed";
public static final String FOCUS_MODE_CONTINUOUS_VIDEO = "continuous-video";
public static final String FOCUS_MODE_CONTINUOUS_PICTURE = "continuous-picture";
FOCUS_MODE_AUTO：自动对焦，这个只会触发一次对焦，并且是需要在预览开启后，调用autoFocus接口后才会触发，
像触点对焦、和拍照对焦都可以用到该模式；
FOCUS_MODE_FIXED：定焦，有些摄像头本身不支持对焦；
FOCUS_MODE_CONTINUOUS_VIDEO：录像的时候，可以采用该模式，会持续对焦，设置parameter参数后就会生效；
FOCUS_MODE_CONTINUOUS_PICTURE ：拍照的时候，可以采用该模式，会持续对焦，设置parameter参数后就会生效，对焦速度相对
FOCUS_MODE_CONTINUOUS_VIDEO 会快点；
三、如何使用各种对焦模式？
上面第二点针对4种常见的对焦模式，做了简单的介绍，我们也知道，除了auto模式，像 FOCUS_MODE_CONTINUOUS_VIDEO、FOCUS_MODE_CONTINUOUS_PICTURE 模式，是在设置camera parameter参数后就生效。
下面来看下google给我们提供了哪些调用接口：
1）Camera1
public final void autoFocus(AutoFocusCallback cb)
{
...
}
public void setFocusMode(String value) {
...
}
public void setParameters(Parameters params) {
...
}
public final void cancelAutoFocus()
{
...
}
2）Camera2
request.set(CaptureRequest.CONTROL_AF_MODE, int focusMode);
附：
各种对焦模式的介绍？（贴的Android源码里面的介绍，写的够详细）
/**
* Auto-focus mode. Applications should call {@link
* #autoFocus(AutoFocusCallback)} to start the focus in this mode.
*/
public static final String FOCUS_MODE_AUTO = "auto";
/**
* Focus is set at infinity. Applications should not call
* {@link #autoFocus(AutoFocusCallback)} in this mode.
*/
public static final String FOCUS_MODE_INFINITY = "infinity";
/**
* Macro (close-up) focus mode. Applications should call
* {@link #autoFocus(AutoFocusCallback)} to start the focus in this
* mode.
*/
public static final String FOCUS_MODE_MACRO = "macro";
/**
* Focus is fixed. The camera is always in this mode if the focus is not
* adjustable. If the camera has auto-focus, this mode can fix the
* focus, which is usually at hyperfocal distance. Applications should
* not call {@link #autoFocus(AutoFocusCallback)} in this mode.
*/
public static final String FOCUS_MODE_FIXED = "fixed";
/** @hide
* Normal focus mode. Applications should call
* {@link #autoFocus(AutoFocusCallback)} to start the focus in this
* mode.
*/
public static final String FOCUS_MODE_NORMAL = "normal";
/**
* Extended depth of field (EDOF). Focusing is done digitally and
* continuously. Applications should not call {@link
* #autoFocus(AutoFocusCallback)} in this mode.
*/
public static final String FOCUS_MODE_EDOF = "edof";
/**
* Continuous auto focus mode intended for video recording. The camera
* continuously tries to focus. This is the best choice for video
* recording because the focus changes smoothly . Applications still can
* call {@link #takePicture(Camera.ShutterCallback,
* Camera.PictureCallback, Camera.PictureCallback)} in this mode but the
* subject may not be in focus. Auto focus starts when the parameter is
* set.
*
* <p>Since API level 14, applications can call {@link
* #autoFocus(AutoFocusCallback)} in this mode. The focus callback will
* immediately return with a boolean that indicates whether the focus is
* sharp or not. The focus position is locked after autoFocus call. If
* applications want to resume the continuous focus, cancelAutoFocus
* must be called. Restarting the preview will not resume the continuous
* autofocus. To stop continuous focus, applications should change the
* focus mode to other modes.
*
* @see #FOCUS_MODE_CONTINUOUS_PICTURE
*/
public static final String FOCUS_MODE_CONTINUOUS_VIDEO = "continuous-video";
/**
* Continuous auto focus mode intended for taking pictures. The camera
* continuously tries to focus. The speed of focus change is more
* aggressive than {@link #FOCUS_MODE_CONTINUOUS_VIDEO}. Auto focus
* starts when the parameter is set.
*
* <p>Applications can call {@link #autoFocus(AutoFocusCallback)} in
* this mode. If the autofocus is in the middle of scanning, the focus
* callback will return when it completes. If the autofocus is not
* scanning, the focus callback will immediately return with a boolean
* that indicates whether the focus is sharp or not. The apps can then
* decide if they want to take a picture immediately or to change the
* focus mode to auto, and run a full autofocus cycle. The focus
* position is locked after autoFocus call. If applications want to
* resume the continuous focus, cancelAutoFocus must be called.
* Restarting the preview will not resume the continuous autofocus. To
* stop continuous focus, applications should change the focus mode to
* other modes.
*
* @see #FOCUS_MODE_CONTINUOUS_VIDEO
*/
public static final String FOCUS_MODE_CONTINUOUS_PICTURE = "continuous-picture";
=======================================================================
*本人从事Android Camera相关开发已有5年，
*目前在深圳上班，
*小伙伴记得点我头像关注，也可以关注我的微信公众号【小驰笔记】，希望和更多的小伙伴一起交流 ~
---- 2020.01.04 深圳
