android: gradle-based package and samples

- drop hello-android sample

samples/android/face-detection/build.gradle.in

@@ -0,0 +1,43 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion @ANDROID_COMPILE_SDK_VERSION@
+    defaultConfig {
+        applicationId "org.opencv.samples.facedetect"
+        minSdkVersion @ANDROID_MIN_SDK_VERSION@
+        targetSdkVersion @ANDROID_TARGET_SDK_VERSION@
+        versionCode 301
+        versionName "3.01"
+
+        externalNativeBuild {
+            cmake {
+                arguments "-DOpenCV_DIR=" + project(':opencv').projectDir + "/@ANDROID_PROJECT_JNI_PATH@"@OPENCV_ANDROID_CMAKE_EXTRA_ARGS@
+                targets "detection_based_tracker"
+            }
+        }
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+    sourceSets {
+        main {
+            java.srcDirs = @ANDROID_SAMPLE_JAVA_PATH@
+            aidl.srcDirs = @ANDROID_SAMPLE_JAVA_PATH@
+            res.srcDirs = @ANDROID_SAMPLE_RES_PATH@
+            manifest.srcFile '@ANDROID_SAMPLE_MANIFEST_PATH@'
+        }
+    }
+    externalNativeBuild {
+        cmake {
+             path '@ANDROID_SAMPLE_JNI_PATH@/CMakeLists.txt'
+        }
+    }
+}
+
+dependencies {
+    //implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation project(':opencv')
+}

samples/android/face-detection/gradle/AndroidManifest.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="org.opencv.samples.facedetect"
+>
+
+    <application
+        android:label="@string/app_name"
+        android:icon="@drawable/icon"
+        android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
+
+        <activity android:name="FdActivity"
+                  android:label="@string/app_name"
+                  android:screenOrientation="landscape"
+                  android:configChanges="keyboardHidden|orientation">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+    <supports-screens android:resizeable="true"
+                      android:smallScreens="true"
+                      android:normalScreens="true"
+                      android:largeScreens="true"
+                      android:anyDensity="true" />
+
+    <uses-permission android:name="android.permission.CAMERA"/>
+
+    <uses-feature android:name="android.hardware.camera" android:required="false"/>
+    <uses-feature android:name="android.hardware.camera.autofocus" android:required="false"/>
+    <uses-feature android:name="android.hardware.camera.front" android:required="false"/>
+    <uses-feature android:name="android.hardware.camera.front.autofocus" android:required="false"/>
+
+</manifest>

samples/android/face-detection/jni/CMakeLists.txt

@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.6)
+
+# Enable C++11
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
+
+set(target detection_based_tracker)
+project(${target} CXX)
+
+set(ANDROID_OPENCV_COMPONENTS "opencv_java" CACHE STRING "")
+message(STATUS "ANDROID_ABI=${ANDROID_ABI}")
+find_package(OpenCV REQUIRED COMPONENTS ${ANDROID_OPENCV_COMPONENTS})
+
+file(GLOB srcs *.cpp *.c)
+file(GLOB hdrs *.hpp *.h)
+
+include_directories("${CMAKE_CURRENT_LIST_DIR}")
+add_library(${target} SHARED ${srcs} ${hdrs})
+target_link_libraries(${target} ${ANDROID_OPENCV_COMPONENTS})

samples/android/face-detection/jni/DetectionBasedTracker_jni.cpp

@@ -96,8 +96,8 @@ JNIEXPORT jlong JNICALL Java_org_opencv_samples_facedetect_DetectionBasedTracker
             je = jenv->FindClass("java/lang/Exception");
         jenv->ThrowNew(je, e.what());
     }
-        catch (...)
-        {
+    catch (...)
+    {
         LOGD("nativeCreateObject caught unknown exception");
         jclass je = jenv->FindClass("java/lang/Exception");
         jenv->ThrowNew(je, "Unknown exception in JNI code of DetectionBasedTracker.nativeCreateObject()");