launch the app on Hardware camera button click

app/src/main/AndroidManifest.xml

@@ -46,5 +46,15 @@
             android:name=".AboutActivity"
             android:label="@string/about"
             android:screenOrientation="portrait"/>
+
+        <receiver
+            android:name=".HardwareShutterReceiver"
+            android:enabled="true"
+            android:exported="true">
+            <intent-filter android:priority="999">
+                <action android:name="android.intent.action.CAMERA_BUTTON"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+            </intent-filter>
+        </receiver>
     </application>
 </manifest>

app/src/main/java/com/simplemobiletools/camera/HardwareShutterReceiver.java

@@ -0,0 +1,15 @@
+package com.simplemobiletools.camera;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+public class HardwareShutterReceiver extends BroadcastReceiver {
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        Intent mainIntent = new Intent(context.getApplicationContext(), MainActivity.class);
+        mainIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
+        context.startActivity(mainIntent);
+    }
+}

app/src/main/java/com/simplemobiletools/camera/MainActivity.java

@@ -112,7 +112,7 @@ public class MainActivity extends AppCompatActivity implements SensorEventListen
 
     private void handleIntent() {
         final Intent intent = getIntent();
-        if (intent != null) {
+        if (intent != null && intent.getAction() != null) {
             if (intent.getExtras() != null && intent.getAction().equals(MediaStore.ACTION_IMAGE_CAPTURE)) {
                 isImageCaptureIntent = true;
                 hideToggleModeAbout();