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小应用主要包含了四个功能:今日历史、新闻、手电筒和找手机;今日历史和新闻模块之前已经介绍过(参考:3.【小萌伴Android】新闻/H5游戏模块及广告过滤),本篇只介绍手电筒功能及其实现,后续再聊找手机功能。
原理
手电筒功能其实是利用手机照相机的闪光灯(LED发光二极管),这个组件最初是用于手机在黑暗环境下拍照使用的,后来利用它发光的特性,做了手机手电筒功能(这里提示,手电筒功能其实也是对闪关灯的一种损坏,虽然LED灯寿命比较长,但是长时间持续使用有损该元件,建议只在应急情况下使用,特别是在手机发热严重时请停止使用)。

实现
在支持闪光灯的手机中,我们可以利用Camera类检测并开启闪光灯:
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<span class="hljs-comment">/** * 是否支持手电筒功能 * <span class="hljs-doctag">@param</span> context * <span class="hljs-doctag">@return</span> */</span> <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">boolean</span> <span class="hljs-title">hasFlash</span><span class="hljs-params">(Context context)</span> </span>{ PackageManager pm = context.getPackageManager(); FeatureInfo[] featureInfos = pm.getSystemAvailableFeatures(); <span class="hljs-keyword">for</span> (FeatureInfo f : featureInfos) { <span class="hljs-keyword">if</span> (PackageManager.FEATURE_CAMERA_FLASH.equals(f.name)) { <span class="hljs-keyword">return</span> <span class="hljs-keyword">true</span>; } } <span class="hljs-keyword">return</span> <span class="hljs-keyword">false</span>; } |
获取Camera实体,这里先使用open类,有的手机需要指定cameraId:
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<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> Camera getCamera(Context context) { <span class="hljs-keyword">if</span> (!hasFlash(context)) <span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>; <span class="hljs-keyword">if</span> (sCamera == <span class="hljs-keyword">null</span>) { <span class="hljs-keyword">try</span> { sCamera = Camera.open(); } <span class="hljs-keyword">catch</span> (<span class="hljs-keyword">Exception</span> e) { <span class="hljs-keyword">try</span> { sCamera = Camera.open(Camera.getNumberOfCameras() - <span class="hljs-number">1</span>); } <span class="hljs-keyword">catch</span> (<span class="hljs-keyword">Exception</span> e1) { TastyToastUtil.toast(E7App.mApp, R.string.flashlight_open_error); } } } <span class="hljs-keyword">return</span> sCamera; } |
开启与关闭闪光灯
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<span class="hljs-function"><span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">ensureCamera</span><span class="hljs-params">(Context context)</span> </span>{ getCamera(context); } <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">openFlash</span><span class="hljs-params">(Context context)</span> </span>{ ensureCamera(context); <span class="hljs-keyword">if</span> (sCamera == <span class="hljs-keyword">null</span>) <span class="hljs-keyword">return</span>; <span class="hljs-keyword">try</span> { Camera.Parameters parameters = sCamera.getParameters(); parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH); sCamera.setParameters(parameters); sCamera.cancelAutoFocus(); sCamera.startPreview(); } <span class="hljs-keyword">catch</span> (Exception e) { } } <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">closeFlash</span><span class="hljs-params">()</span> </span>{ <span class="hljs-keyword">if</span> (sCamera == <span class="hljs-keyword">null</span>) <span class="hljs-keyword">return</span>; <span class="hljs-keyword">try</span> { Camera.Parameters parameters = sCamera.getParameters(); parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF); sCamera.setParameters(parameters); } <span class="hljs-keyword">catch</span> (Exception e) { } } |
通知及广播
在打开闪光灯后,可能我们退出了应用,这时候想要关闭闪光灯还得重新进入应用,比较麻烦,所以通过发送一个通知栏消息,点击通知即可关闭闪光灯:
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<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">NotificationControl</span> {</span> <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> final <span class="hljs-keyword">int</span> sNotificationId = <span class="hljs-number">318</span>; <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">showNotification</span><span class="hljs-params">(Context context)</span> </span>{ NotificationCompat.Builder builder = <span class="hljs-keyword">new</span> NotificationCompat.Builder(context) .setSmallIcon(R.drawable.ic_notify) .setContentTitle(context.getString(R.<span class="hljs-built_in">string</span>.app_name)) .setContentText(context.getString(R.<span class="hljs-built_in">string</span>.notification_text)); PendingIntent pendingIntent = PendingIntent.getBroadcast(context, <span class="hljs-number">0</span>, <span class="hljs-keyword">new</span> Intent(FlashLightWidget.ACTION_LED_OFF), <span class="hljs-number">0</span>); builder.setContentIntent(pendingIntent); NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE); manager.notify(sNotificationId, builder.build()); } <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">cancelNotification</span><span class="hljs-params">(Context context)</span> </span>{ NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE); manager.cancel(sNotificationId); } } |
这里还定义了一个广播接收:
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BroadcastReceiver mReceiver = <span class="hljs-keyword">new</span> BroadcastReceiver() { <span class="hljs-meta">@Override</span> <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onReceive</span><span class="hljs-params">(Context context, Intent intent)</span> </span>{ <span class="hljs-keyword">if</span> (FlashLightWidget.ACTION_LED_ON.equals(intent.getAction())) { flashOpend(); } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (FlashLightWidget.ACTION_LED_OFF.equals(intent.getAction())) { flashClosed(); } } }; |

小组件
为了方便使用,手电筒功能添加了桌面小组件FlashLightWidget,继承AppWidgetProvider,在onReceive中处理ACTION_LED_ON和ACTION_LED_OFF并且在onUpdate进行更新:(onReceive代码比较多就不放出来了)
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<span class="hljs-meta">@Override</span> <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onUpdate</span><span class="hljs-params">(Context context, AppWidgetManager appWidgetManager, <span class="hljs-keyword">int</span>[] appWidgetIds)</span> </span>{ <span class="hljs-comment">// There may be multiple widgets active, so update all of them</span> <span class="hljs-keyword">for</span> (<span class="hljs-keyword">int</span> widgetId : appWidgetIds) { updateAppWidget(context, appWidgetManager, widgetId); } } <span class="hljs-function"><span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">updateAppWidget</span><span class="hljs-params">(Context context, AppWidgetManager appWidgetManager, <span class="hljs-keyword">int</span> appWidgetId)</span> </span>{ RemoteViews views = <span class="hljs-keyword">new</span> RemoteViews(context.getPackageName(), R.layout.flash_light_widget); views.setImageViewResource(R.id.widget_led, R.drawable.widget_led); views.setInt(R.id.widget_led, <span class="hljs-string">"setBackgroundResource"</span>, R.drawable.widget_led_bg); views.setOnClickPendingIntent(R.id.widget_led, PendingIntent.getBroadcast(context, <span class="hljs-number">0</span>, <span class="hljs-keyword">new</span> Intent(ACTION_LED_ON), <span class="hljs-number">0</span>)); appWidgetManager.updateAppWidget(appWidgetId, views); } |
这样,就可以将小组件拖到桌面,点击桌面图标就可以控制手电筒的开关了。
简书:ThinkinLiu 博客: IT老五

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