android手机用闪光灯做成手电筒的应用非常多，可是有的不能用。

后来发现是除了把 camera device的 flashmode设置成torch外还要打开预览：

以下是代码：

MainActivity.java

package com.android.flashlight;

import android.app.Activity;

import android.os.Bundle;

import android.view.MotionEvent;

import android.widget.ImageView;

public class MainActivity extends Activity{

private FlashlightSurface mSurface;

private ImageView mImageView;

private boolean isFlashlightOn = false;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Contants.LogI("MainActivity: onCreate()");

mSurface = (FlashlightSurface) findViewById(R.id.surfaceview);

mImageView = (ImageView) findViewById(R.id.image);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

if(MotionEvent.ACTION_UP == event.getAction()){

Contants.LogI("MainActivity: onTouchEvent() : ACTION_UP");

if(isFlashlightOn){

mSurface.setFlashlightSwitch(false);

isFlashlightOn = false;

mImageView.setImageResource(R.drawable.flashlight_off);

}else{

mSurface.setFlashlightSwitch(true);

isFlashlightOn = true;

mImageView.setImageResource(R.drawable.flashlight_on);

}

}

return super.onTouchEvent(event);

}

}

FlashlightSurface.java

package com.android.flashlight;

import android.content.Context;

import android.graphics.PixelFormat;

import android.hardware.Camera;

import android.util.AttributeSet;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

public class FlashlightSurface extends SurfaceView implements SurfaceHolder.Callback{

private SurfaceHolder mHolder;

private Camera mCameraDevices;

private Camera.Parameters mParameters;

public FlashlightSurface(Context context, AttributeSet attrs) {

super(context, attrs);

Contants.LogI("FlashlightSurface");

mHolder = this.getHolder();

mHolder.addCallback(this);

mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

}

@Override

public void surfaceChanged(SurfaceHolder holder, int format, int width,

int height) {

Contants.LogI("surfaceChanged");

mParameters = mCameraDevices.getParameters();

if(mParameters != null)

mParameters.setPictureFormat(PixelFormat.JPEG);

mParameters.setPreviewSize(320, 480);

mParameters.setPictureSize(320, 480);

mCameraDevices.setParameters(mParameters);

mCameraDevices.startPreview();

}

@Override

public void surfaceCreated(SurfaceHolder holder) {

Contants.LogI("surfaceCreated");

try {

mCameraDevices = Camera.open();

mCameraDevices.setPreviewDisplay(mHolder);

} catch (Exception e) {

if(mCameraDevices != null)

mCameraDevices.release();

mCameraDevices = null;

}

}

@Override

public void surfaceDestroyed(SurfaceHolder holder) {

Contants.LogI("surfaceDestroyed");

if(mCameraDevices == null) return;

mCameraDevices.stopPreview();

mCameraDevices.release();

mCameraDevices = null;

}

/**

* 设置手电筒的开关状态

* @param on ： true则打开，false则关闭

*/

public void setFlashlightSwitch(boolean on){

if(mCameraDevices == null) return;

if(mParameters == null){

mParameters = mCameraDevices.getParameters();

}

if(on){

mParameters.setFlashMode(Contants.FLASH_MODE_TORCH);

}else{

mParameters.setFlashMode(Contants.FLASH_MODE_OFF);

}

Contants.LogI("setFlashlightSwitch-----------------" + on);

mCameraDevices.setParameters(mParameters);

}

}

布局文件main.xml

android:layout_width="fill_parent"

android:layout_height="fill_parent" >

android:id="@+id/surfaceview"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

>

android:id="@+id/image"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:src="@drawable/flashlight_off"

android:background="#FFFFFFFF"

/>

显然这里打开了一个预览，可是被图片盖上了，看不见而已。不然闪光灯不亮。

包含widget窗体小部件的使用方法和手电筒的功能实现，安装后，加入窗体小部件(手电筒)到桌面，然后点击小部件后，打开手电筒的界面

点击界面，实现 打开/关闭 手电筒。