Android相机实时自动对焦的完美实现

想写这篇文章很久了，去年十月份接触了相机这一块的知识，由于android碎片化严重，而且各大厂商极有可能去修改相关API的实现，其中遇到了不少坑，包括实时相机高斯模糊，自动对焦的兼容问题，以及一系列性能问题。换过很多搜索引擎，访问过很多网站，访问过很多网站，拜读过很多代码，没有发现对于相机实时自动对焦特别完美的实现方式。现对相机的自动对焦问题单独做一个记录，算是对这部分的一个总结。也希望后人在这部分能够快速地解决问题，不必浪费过多的时间。测试手机包括：MX4 pro，小米4，华为荣耀3C等等。

参考过@yanzi1225627 大神的一些做法，测试结果不是特别满意。

一，一些对焦方案的尝试

1，autoFocus()的尝试:

private Camera.AutoFocusCallback mAutoFocusCallback;mAutoFocusCallback = new Camera.AutoFocusCallback() {public void onAutoFocus(boolean success, Camera camera) {// TODO Auto-generated method stubif(success){myCamera.setOneShotPreviewCallback(null);Toast.makeText(TestPhotoActivity.this,"自动聚焦成功" , Toast.LENGTH_SHORT).show();}}}; myCamera.autoFocus(mAutoFocusCallback);

在一部分手机上，始终只对焦一次，也就是说根本不能实现。即使是在按下拍照的时候去调用一次对焦，等对焦成功后再进行拍照，实现的效果也不是很完美。

还见部分博客把autoFocus()方法放在Camera预览SurfaceView的surfaceChanged()中的一些实现，发现也只对焦了一次。

2，设置对焦模式FOCUS_MODE_CONTINUOUS_PICTURE

/*** 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";

setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

在大部分手机上实现了自动对焦，而且效果还不错，而且不需要去额外调用方法。但是测试后发现小米4机型不会自动对焦。

3，设置对焦模式为FOCUS_MODE_CONTINUOUS_VIDEO

/*** 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";

setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);

经过测试，发现大部分手机可以连续对焦，但是在对焦过程中屏幕会连续闪烁，而且体验极其不好。魅族MX4不支持此种方式的对焦。也就是说第二，第三种方案都要放弃。

4，触摸对焦

本来在一番焦头烂额后准备妥协，先把触摸对焦实现吧。基本思路是支持定点对焦，就调用定点对焦，否则调用autoFocus()。

/*** 手动聚焦** @param point 触屏坐标*/protected boolean onFocus(Point point, Camera.AutoFocusCallback callback) {if (mCamera == null) {return false;}Camera.Parameters parameters = null;try {parameters = mCamera.getParameters();} catch (Exception e) {e.printStackTrace();return false;}//不支持设置自定义聚焦，则使用自动聚焦，返回if(Build.VERSION.SDK_INT >= 14) {if (parameters.getMaxNumFocusAreas() <= 0) {return focus(callback);}Log.i(TAG, "onCameraFocus:" + point.x + "," + point.y);//定点对焦List<Camera.Area> areas = new ArrayList<Camera.Area>();int left = point.x - 300;int top = point.y - 300;int right = point.x + 300;int bottom = point.y + 300;left = left < -1000 ? -1000 : left;top = top < -1000 ? -1000 : top;right = right > 1000 ? 1000 : right;bottom = bottom > 1000 ? 1000 : bottom;areas.add(new Camera.Area(new Rect(left, top, right, bottom), 100));parameters.setFocusAreas(areas);try {//本人使用的小米手机在设置聚焦区域的时候经常会出异常，看日志发现是框架层的字符串转int的时候出错了，//目测是小米修改了框架层代码导致，在此try掉，对实际聚焦效果没影响mCamera.setParameters(parameters);} catch (Exception e) {// TODO: handle exceptione.printStackTrace();return false;}}return focus(callback);}private boolean focus(Camera.AutoFocusCallback callback) {try {mCamera.autoFocus(callback);} catch (Exception e) {e.printStackTrace();return false;}return true;}

二，自动对焦方案

在实现无力的情况下，打开了其他已经实现自定义相机而且能够完美对焦的app，一番操作后，发现很多app都是在我移动手机或者有轻微晃动才进行了第二次对焦，等等，这不就是基于传感器实现的吗？

我们完全可以判断手机的运动状态啊，比如静止和移动。在移动一定时间后去对焦。

核心代码：

package com.jerry.sweetcamera;import android.app.Activity;import android.hardware.Sensor;import android.hardware.SensorEvent;import android.hardware.SensorEventListener;import android.hardware.SensorManager;import android.util.Log;import java.util.Calendar;/*** 加速度控制器 用来控制对焦** @author jerry* @date -09-25*/public class SensorControler implements IActivityLifiCycle, SensorEventListener {public static final String TAG = "SensorControler";private SensorManager mSensorManager;private Sensor mSensor;private int mX, mY, mZ;private long lastStaticStamp = 0;Calendar mCalendar;boolean isFocusing = false;boolean canFocusIn = false; //内部是否能够对焦控制机制boolean canFocus = false;public static final int DELEY_DURATION = 500;public static final int STATUS_NONE = 0;public static final int STATUS_STATIC = 1;public static final int STATUS_MOVE = 2;private int STATUE = STATUS_NONE;private CameraFocusListener mCameraFocusListener;private static SensorControler mInstance;private int foucsing = 1; //1 表示没有被锁定 0表示被锁定private SensorControler() {mSensorManager = (SensorManager) SweetApplication.CONTEXT.getSystemService(Activity.SENSOR_SERVICE);mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);// TYPE_GRAVITY}public static SensorControler getInstance() {if (mInstance == null) {mInstance = new SensorControler();}return mInstance;}public void setCameraFocusListener(CameraFocusListener mCameraFocusListener) {this.mCameraFocusListener = mCameraFocusListener;}@Overridepublic void onStart() {restParams();canFocus = true;mSensorManager.registerListener(this, mSensor,SensorManager.SENSOR_DELAY_NORMAL);}@Overridepublic void onStop() {mSensorManager.unregisterListener(this, mSensor);canFocus = false;}@Overridepublic void onAccuracyChanged(Sensor sensor, int accuracy) {}@Overridepublic void onSensorChanged(SensorEvent event) {if (event.sensor == null) {return;}if (isFocusing) {restParams();return;}if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {int x = (int) event.values[0];int y = (int) event.values[1];int z = (int) event.values[2];mCalendar = Calendar.getInstance();long stamp = mCalendar.getTimeInMillis();// 1393844912int second = mCalendar.get(Calendar.SECOND);// 53if (STATUE != STATUS_NONE) {int px = Math.abs(mX - x);int py = Math.abs(mY - y);int pz = Math.abs(mZ - z);//Log.d(TAG, "pX:" + px + " pY:" + py + " pZ:" + pz + " stamp:"// + stamp + " second:" + second);double value = Math.sqrt(px * px + py * py + pz * pz);if (value > 1.4) {//textviewF.setText("检测手机在移动..");//Log.i(TAG,"mobile moving");STATUE = STATUS_MOVE;} else {//textviewF.setText("检测手机静止..");//Log.i(TAG,"mobile static");//上一次状态是move，记录静态时间点if (STATUE == STATUS_MOVE) {lastStaticStamp = stamp;canFocusIn = true;}if (canFocusIn) {if (stamp - lastStaticStamp > DELEY_DURATION) {//移动后静止一段时间，可以发生对焦行为if (!isFocusing) {canFocusIn = false;// onCameraFocus();if (mCameraFocusListener != null) {mCameraFocusListener.onFocus();}// Log.i(TAG,"mobile focusing");}}}STATUE = STATUS_STATIC;}} else {lastStaticStamp = stamp;STATUE = STATUS_STATIC;}mX = x;mY = y;mZ = z;}}private void restParams() {STATUE = STATUS_NONE;canFocusIn = false;mX = 0;mY = 0;mZ = 0;}/*** 对焦是否被锁定** @return*/public boolean isFocusLocked() {if(canFocus) {return foucsing <= 0;}return false;}/*** 锁定对焦*/public void lockFocus() {isFocusing = true;foucsing--;Log.i(TAG, "lockFocus");}/*** 解锁对焦*/public void unlockFocus() {isFocusing = false;foucsing++;Log.i(TAG, "unlockFocus");}public void restFoucs() {foucsing = 1;}public interface CameraFocusListener {void onFocus();}}

onSensorChanged（）来判断手机的运动状态，自动去调用mCameraFocusListener.onFocus();

在mCameraFocusListener中可以调用触摸对焦的方法，这样基本上可以兼容大部分手机的自动对焦功能，而且可以比较好的控制对焦的显示以及对焦区域。foucsing用于对焦的计数，用来锁定对焦。

具体实现可以参考：

/huweigoodboy/SweetCamera