Android相机实时自动对焦的完美实现

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 stub
if(success){
myCamera.setOneShotPreviewCallback(null);
Toast.makeText(TestPhotoActivity.this,
"自动聚焦成功" , Toast.LENGTH_SHORT).show();
}
}
};
myCamera.autoFocus(mAutoFocusCallback);

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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";

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setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

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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";

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setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);

1

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 exception
e.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;
}

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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 2015-09-25
*/
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;
}

@Override
public void onStart() {
restParams();
canFocus = true;
mSensorManager.registerListener(this, mSensor,
SensorManager.SENSOR_DELAY_NORMAL);
}

@Override
public void onStop() {
mSensorManager.unregisterListener(this, mSensor);
canFocus = false;
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

@Override
public 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();// 1393844912

int second = mCalendar.get(Calendar.SECOND);// 53

if (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();
}
}

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Start检测手机是否移动对焦几秒后yes

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： 
https://github.com/huweigoodboy/SweetCamera