8.【小萌伴Android】手电筒功能及其实现

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前面三篇介绍了【小萌伴】百宝箱中的三款原生小游戏，这里说说百宝箱中另一功能模块--实用小应用...

【小萌伴】手电筒.gif

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）。

【小萌伴】手电筒.jpg

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：

    <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>;
    }

/**

* 是否支持手电筒功能

* @param context

* @return

*/

public static boolean hasFlash(Context context) {

PackageManager pm = context.getPackageManager();

FeatureInfo[] featureInfos = pm.getSystemAvailableFeatures();

for (FeatureInfo f : featureInfos) {

if (PackageManager.FEATURE_CAMERA_FLASH.equals(f.name)) {

return true;

}

return false;

}

获取Camera实体，这里先使用open类，有的手机需要指定cameraId：

    <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;
    }

public static Camera getCamera(Context context) {

if (!hasFlash(context)) return null;

if (sCamera == null) {

try {

sCamera = Camera.open();

} catch (Exception e) {

try {

sCamera = Camera.open(Camera.getNumberOfCameras() - 1);

} catch (Exception e1) {

TastyToastUtil.toast(E7App.mApp, R.string.flashlight_open_error);

}

return sCamera;

}

开启与关闭闪光灯

    <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) {
        }
    }

private static void ensureCamera(Context context) {

getCamera(context);

}

public static void openFlash(Context context) {

ensureCamera(context);

if (sCamera == null) return;

try {

Camera.Parameters parameters = sCamera.getParameters();

parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);

sCamera.setParameters(parameters);

sCamera.cancelAutoFocus();

sCamera.startPreview();

} catch (Exception e) {

}

public static void closeFlash() {

if (sCamera == null) return;

try {

Camera.Parameters parameters = sCamera.getParameters();

parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);

sCamera.setParameters(parameters);

} catch (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：

<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);
    }
}

public class NotificationControl {

public static final int sNotificationId = 318;

public static void showNotification(Context context) {

NotificationCompat.Builder builder = new NotificationCompat.Builder(context)

.setSmallIcon(R.drawable.ic_notify)

.setContentTitle(context.getString(R.string.app_name))

.setContentText(context.getString(R.string.notification_text));

PendingIntent pendingIntent =

PendingIntent.getBroadcast(context, 0, new Intent(FlashLightWidget.ACTION_LED_OFF), 0);

builder.setContentIntent(pendingIntent);

NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

manager.notify(sNotificationId, builder.build());

}

public static void cancelNotification(Context context) {

NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

manager.cancel(sNotificationId);

}

这里还定义了一个广播接收：

    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();
            }
        }
    };

BroadcastReceiver mReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

if (FlashLightWidget.ACTION_LED_ON.equals(intent.getAction())) {

flashOpend();

} else if (FlashLightWidget.ACTION_LED_OFF.equals(intent.getAction())) {

flashClosed();

}

};

【小萌伴】手电筒2.jpg

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）

    <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);
    }

@Override

public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {

// There may be multiple widgets active, so update all of them

for (int widgetId : appWidgetIds) {

updateAppWidget(context, appWidgetManager, widgetId);

}

static void updateAppWidget(Context context, AppWidgetManager appWidgetManager,

int appWidgetId) {

RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.flash_light_widget);

views.setImageViewResource(R.id.widget_led, R.drawable.widget_led);

views.setInt(R.id.widget_led, "setBackgroundResource", R.drawable.widget_led_bg);

views.setOnClickPendingIntent(R.id.widget_led, PendingIntent.getBroadcast(context, 0, new Intent(ACTION_LED_ON), 0));

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。

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8.【小萌伴Android】手电筒功能及其实现

原理

实现

通知及广播

小组件

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原理

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通知及广播

小组件

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