android 手电筒的实现

android手机用闪光灯做成手电筒的应用很多，但是有的不能用。

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

下面是代码：

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

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

<com.android.flashlight.FlashlightSurface
android:id="@+id/surfaceview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
></com.android.flashlight.FlashlightSurface>
<ImageView
android:id="@+id/image"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:src="@drawable/flashlight_off"
android:background="#FFFFFFFF"
/>

</RelativeLayout>

显然这里打开了一个预览，但是被图片盖上了，看不见而已。不然闪光灯不亮。

这里有个Demo：http://download.csdn.net/detail/liu_zhen_wei/4801779

包括widget窗口小部件的用法和手电筒的功能实现，安装后，添加窗口小部件（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。