<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.flash" />

import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.AsyncTask;

/**
 *Caution: On some devices, this method may take a long time to complete. It is best 
 *to call this method from a worker thread (possibly using android.os.AsyncTask) to 
 *avoid blocking the main application UI thread.
 */

public class FlashlightUtil extends AsyncTask<String, String, String> {

 private Camera camera;
 private int cameraId = 0; // 此功能目前不實用，這里不做實現(xiàn) ， 但不能刪除
 private Parameters parameters;
 public boolean isTorch = false;
 private boolean canFinish = false;
 private static FlashlightUtil flashlightUtil;

 private FlashlightUtil() {

 }

 /**
  * 設置手電筒開關，打開或關閉手電筒，根據(jù)手電筒的狀態(tài)來設置相反的狀態(tài) void 2016年1月12日
  */
 public static void setSwitch() {
  if (null == flashlightUtil) {
   flashlightUtil = new FlashlightUtil();
   flashlightUtil.execute("");
  }
  flashlightUtil.setONOFF();
 }

 @Override
 protected String doInBackground(String... params) {
  // TODO Auto-generated method stub

  while (!canFinish) {
   if (null == camera) {
    camera = Camera.open(cameraId);
   }
   parameters = camera.getParameters();
   if (isTorch) {
    if (parameters.getFlashMode().equals(Parameters.FLASH_MODE_OFF)) {
     // 打開鎂光燈
     parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);
     camera.setParameters(parameters);
     camera.startPreview();
    }
   } else {
    if (parameters.getFlashMode().equals(
      Parameters.FLASH_MODE_TORCH)) {
     // 關閉鎂光燈
     camera.stopPreview(); // 關掉亮燈
     camera.release(); // 關掉照相機
     camera = null;
    }
   }
  }

  return null;
 }

 /**
  * 此功能暫時關閉
  * @hide
  */
 public FlashlightUtil setCameraId(int cameraId) {
  this.cameraId = cameraId;
  return flashlightUtil;
 }

 /**
  * 打開關閉手電筒，默認第一次為打開 2016年1月12日
  */
 private void setONOFF() {
  isTorch = !isTorch;
 }


}

/**
 * 打開手電筒
 */
public void openFlashlight(View view) {
 FlashlightUtil.setSwitch() ;
}