线上bug修复之takePicture failed

友盟日志如下：

java.lang.RuntimeException: takePicture failed
    at android.hardware.Camera.native_takePicture(Native Method)
    at android.hardware.Camera.takePicture(Camera.java:1872)
    at android.hardware.Camera.takePicture(Camera.java:1817)
    at com.xxxx.xxxx.xxxx.CameraActivity.onClick(SourceFile:127)
    at android.view.View.performClick(View.java:4909)
    at android.view.View$PerformClick.run(View.java:20390)
    at android.os.Handler.handleCallback(Handler.java:815)
    at android.os.Handler.dispatchMessage(Handler.java:104)
    at android.os.Looper.loop(Looper.java:192)
    at android.app.ActivityThread.main(ActivityThread.java:5878)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1089)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:855)

复现原因：拍照按钮被重复点击时会出现这个bug。
修复：申明一个boolean变量

private boolean safeToTakePicture = false;

在startPreview之后safeToTakePicture = true;
在拍照点击事件中

if (safeToTakePicture) { 
  camera.takePicture(null, null, mPicture); 
  safeToTakePicture = false;
}

在PictureCallback回调方法中的，safeToTakePicture = true;