Android 后摄相机退出速度慢问题分析及优化

一、问题：

在MMITest中后主摄拍照完成点击通过或者失败，比前摄退出慢1s左右

二、问题分析

1、分析log如下：

前相机测试：S0020D3 01-02 01:13:38.000 789 5591 I ActivityTaskManager: START u0 {cmp=com.sprd.validationtools/.itemstest.camera.FrontCameraTestActivity (has extras)} with LAUNCH_MULTIPLE from uid 1000 pid 3884 (BAL_ALLOW_ALLOWLISTED_UID) result code=START_SUCCESS //点击进入前相机测试
M002276 01-02 01:13:38.357 3884 8970 I FrontCameraTestActivity: start preview //进入测试项开始预览
M002428 01-02 01:13:38.897 409 9003 I Cam3OEMIf: 4900, receivePreviewFrame: Launch Camera Time:687(ms).//打开预览耗时
M0027A9 01-02 01:13:42.718 3884 3884 D onclick : pass..com.sprd.validationtools.itemstest.camera.FrontCameraTestActivity@7e51409 //点击通过按钮
M0027AA 01-02 01:13:42.719 3884 3884 D BaseActivity: storeResult classname:com.sprd.validationtools.itemstest.camera.FrontCameraTestActivity //保存测试结果
S00298D 01-02 01:13:43.010 789 1147 I WindowManager: Input focus has changed to Window{50e05e4 u0 com.sprd.validationtools/com.sprd.validationtools.itemstest.ListItemTestActivity}, [type=1]-[Surface(name=*Title#590)/@0x7de640, shown=false, alpha=0.0, windowType=1] from c49cb57 com.sprd.validationtools/com.sprd.validationtools.itemstest.camera.FrontCameraTestActivity mDisplayId 0 updateInputWindows true//返回到测试列表界面
后相机测试：
S002AE1 01-02 01:13:44.510 789 3333 I ActivityTaskManager: START u0 {cmp=com.sprd.validationtools/.itemstest.camera.CameraTestActivity (has extras)} with LAUNCH_MULTIPLE from uid 1000 pid 3884 (BAL_ALLOW_ALLOWLISTED_UID) result code=START_SUCCESS //点击进入前相机测试
M002CC4 01-02 01:13:44.906 3884 3884 E CameraTestActivity: start preview //进入测试项开始预览
M002EA3 01-02 01:13:45.607 409 9080 I Cam3OEMIf: 4900, receivePreviewFrame: Launch Camera Time:933(ms).//打开预览耗时 测试10次，平均700ms
M003550 01-02 01:13:54.163 3884 3884 D onclick : pass..com.sprd.validationtools.itemstest.camera.CameraTestActivity@7076185 //点击通过按钮
M003551 01-02 01:13:54.163 3884 3884 D BaseActivity: storeResult classname:com.sprd.validationtools.itemstest.camera.CameraTestActivity//保存测试结果
S003652 01-02 01:13:54.712 789 813 W ActivityTaskManager: Activity pause timeout for ActivityRecord{1b0e20f u0 com.sprd.validationtools/.itemstest.camera.CameraTestActivity t12 d0 f}}
S003811 01-02 01:13:55.531 789 803 I WindowManager: Input focus has changed to Window{50e05e4 u0 com.sprd.validationtools/com.sprd.validationtools.itemstest.ListItemTestActivity}, [type=1]-[Surface(name=*Title#620)/@0x7fb3194, shown=false, alpha=0.0, windowType=1] from 63b0934 com.sprd.validationtools/com.sprd.validationtools.itemstest.camera.CameraTestActivity mDisplayId 0 updateInputWindows true//返回到测试列表界面

2、在log中发现异常：Activity pause timeout for ActivityRecord{1b0e20f u0 com.sprd.validationtools/.itemstest.camera.CameraTestActivity t12 d0 f}}，protected void onPause()后退出速度在300ms左右

3、问题定位：

@Override

protected void onPause() { ... ...}此方法执行出现问题

4、查看代码中的protected void onPause()方法，在 onPause()中有执行相机闪光灯模式关闭的操作。涉及到Camera对象的参数设置，可能需要一定的处理时间，尤其是在某些设备上可能较慢，如果放在onPause()里，这时候Activity可能还在进行其他暂停相关的操作，如果Camera操作耗时，会导致主线程被阻塞，从而延迟onPause()的完成，进而影响Activity切换的流畅度。onPause()是在Activity失去焦点但仍部分可见的时候调用，比如另一个Activity以对话框形式出现，所以，onPause()执行的时间点比较早，可能在界面还在部分显示的时候，这时候如果进行一些资源释放的操作，可能会阻塞主线程，导致界面卡顿，用户觉得退出慢

...
@Override
protectedvoid onStop() {
 super.onStop();
 if (mCamera != null) {
 Camera.Parameters parameters = mCamera.getParameters();
 parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
 mCamera.setParameters(parameters); }
}