Android如何快速闪烁led /手电筒

Question

我想用led /手电筒给一些效果。但它并不快速闪烁，即使我尝试了睡眠（2），但它需要时间眨眼。我想快点闪烁。

public void flash_effect() throws InterruptedException 
{ 
    cam = Camera.open();  
    final Parameters p = cam.getParameters(); 
    p.setFlashMode(Parameters.FLASH_MODE_TORCH); 


    Thread a = new Thread() 
    { 
     public void run() 
     { 
      for(int i =0; i < 10; i++) 
      { 
       cam.setParameters(p); 
       cam.startPreview(); 
       try { 
        Thread.sleep(50); 
       } catch (InterruptedException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
       cam.stopPreview(); 
       try { 
        Thread.sleep(50); 
       } catch (InterruptedException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 

      } 
     } 
    }; 
    a.start(); 
} 

Answer 1

你在哪里设置预览显示？

https://developer.android.com/reference/android/hardware/Camera.html

重要：传递一个完全初始化SurfaceHolder到 setPreviewDisplay（SurfaceHolder）。如果没有表面，相机将无法启动预览功能 。

cam.setPreviewDisplay(null); 

也许你应该试试这个：

Thread t = new Thread() { 
    public void run() { 
     try { 
      // Switch on the cam for app's life 
      if (mCamera == null) { 
       // Turn on Cam 
       mCamera = Camera.open(); 
       try { 
        mCamera.setPreviewDisplay(null); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
       mCamera.startPreview(); 
      } 

      for (int i=0; i < times*2; i++) { 
       toggleFlashLight(); 
       sleep(delay); 
      } 

      if (mCamera != null) { 
       mCamera.stopPreview(); 
       mCamera.release(); 
       mCamera = null; 
      } 
     } catch (Exception e){ 
      e.printStackTrace(); 
     } 
    } 
}; 

t.start(); 

需要的功能：

/** Turn the devices FlashLight on */ 
public void turnOn() { 
    if (mCamera != null) { 
    // Turn on LED 
    mParams = mCamera.getParameters(); 
    mParams.setFlashMode(Parameters.FLASH_MODE_TORCH); 
    mCamera.setParameters(mParams); 

    on = true; 
} 
} 

/** Turn the devices FlashLight off */ 
public void turnOff() { 
    // Turn off flashlight 
    if (mCamera != null) { 
     mParams = mCamera.getParameters(); 
     if (mParams.getFlashMode().equals(Parameters.FLASH_MODE_TORCH)) { 
      mParams.setFlashMode(Parameters.FLASH_MODE_OFF); 
      mCamera.setParameters(mParams); 
     } 
    } 
    on = false; 
} 

/** Toggle the flashlight on/off status */ 
public void toggleFlashLight() { 
    if (!on) { // Off, turn it on 
     turnOn(); 
    } else { // On, turn it off 
     turnOff(); 
    } 
} 

，需要实例瓦尔：

Camera mCamera; 
Camera.Parameters mParameters; 
int delay = 100; // in ms