Android JNI tutorial code

Android/AndroidJNIBasics/.gitignore

@@ -0,0 +1,13 @@
+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild

Android/AndroidJNIBasics/app/.gitignore

@@ -0,0 +1 @@
+/build

Android/AndroidJNIBasics/app/build.gradle

@@ -0,0 +1,39 @@
+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 28
+    defaultConfig {
+        applicationId "com.journaldev.androidjnibasics"
+        minSdkVersion 25
+        targetSdkVersion 28
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        externalNativeBuild {
+            cmake {
+                cppFlags ""
+            }
+        }
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    externalNativeBuild {
+        cmake {
+            path "src/main/cpp/CMakeLists.txt"
+            version "3.10.2"
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
+    testImplementation 'junit:junit:4.12'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+}

Android/AndroidJNIBasics/app/proguard-rules.pro

@@ -0,0 +1,21 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

Android/AndroidJNIBasics/app/src/androidTest/java/com/journaldev/androidjnibasics/ExampleInstrumentedTest.java

@@ -0,0 +1,26 @@
+package com.journaldev.androidjnibasics;
+
+import android.content.Context;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static org.junit.Assert.*;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+    @Test
+    public void useAppContext() {
+        // Context of the app under test.
+        Context appContext = InstrumentationRegistry.getTargetContext();
+
+        assertEquals("com.journaldev.androidjnibasics", appContext.getPackageName());
+    }
+}

Android/AndroidJNIBasics/app/src/main/AndroidManifest.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.journaldev.androidjnibasics">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

Android/AndroidJNIBasics/app/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,44 @@
+# For more information about using CMake with Android Studio, read the
+# documentation: https://d.android.com/studio/projects/add-native-code.html
+
+# Sets the minimum version of CMake required to build the native library.
+
+cmake_minimum_required(VERSION 3.4.1)
+
+# Creates and names a library, sets it as either STATIC
+# or SHARED, and provides the relative paths to its source code.
+# You can define multiple libraries, and CMake builds them for you.
+# Gradle automatically packages shared libraries with your APK.
+
+add_library( # Sets the name of the library.
+             native-lib
+
+             # Sets the library as a shared library.
+             SHARED
+
+             # Provides a relative path to your source file(s).
+             native-lib.cpp )
+
+# Searches for a specified prebuilt library and stores the path as a
+# variable. Because CMake includes system libraries in the search path by
+# default, you only need to specify the name of the public NDK library
+# you want to add. CMake verifies that the library exists before
+# completing its build.
+
+find_library( # Sets the name of the path variable.
+              log-lib
+
+              # Specifies the name of the NDK library that
+              # you want CMake to locate.
+              log )
+
+# Specifies libraries CMake should link to your target library. You
+# can link multiple libraries, such as libraries you define in this
+# build script, prebuilt third-party libraries, or system libraries.
+
+target_link_libraries( # Specifies the target library.
+                       native-lib
+
+                       # Links the target library to the log library
+                       # included in the NDK.
+                       ${log-lib} )

Android/AndroidJNIBasics/app/src/main/cpp/native-lib.cpp

@@ -0,0 +1,68 @@
+#include <jni.h>
+#include <string>
+#include <android/log.h>
+#include <string.h>
+
+extern "C" JNIEXPORT jstring JNICALL
+Java_com_journaldev_androidjnibasics_MainActivity_stringFromJNI(
+        JNIEnv* env,
+        jobject /* this */) {
+    std::string hello = "Hello from C++";
+
+    __android_log_write(ANDROID_LOG_DEBUG, "API123", "Debug Log");
+
+    return env->NewStringUTF(hello.c_str());
+}
+
+
+extern "C" JNIEXPORT jstring JNICALL
+Java_com_journaldev_androidjnibasics_MainActivity_sendYourName(
+        JNIEnv* env,
+        jobject, jstring firstName, jstring lastName) {
+    char returnString[20];
+    const char *fN = env->GetStringUTFChars(firstName, NULL);
+    const char *lN = env->GetStringUTFChars(lastName, NULL);
+
+
+
+
+
+    strcpy(returnString,fN); // copy string one into the result.
+    strcat(returnString,lN); // append string two to the result.
+
+    env->ReleaseStringUTFChars(firstName, fN);
+    env->ReleaseStringUTFChars(lastName, lN);
+
+    __android_log_write(ANDROID_LOG_DEBUG, "API123", returnString);
+
+    return env->NewStringUTF(returnString);
+}
+
+extern "C"
+JNIEXPORT jobjectArray JNICALL Java_com_journaldev_androidjnibasics_MainActivity_stringArrayFromJNI(JNIEnv *env, jobject jobj)
+{
+
+    char *days[]={"Java",
+                  "Android",
+                  "Django",
+                  "SQL",
+                  "Swift",
+                  "Kotlin",
+                  "Springs"};
+
+    jstring str;
+    jobjectArray day = 0;
+    jsize len = 7;
+    int i;
+
+    day = env->NewObjectArray(len,env->FindClass("java/lang/String"),0);
+
+    for(i=0;i<7;i++)
+    {
+        str = env->NewStringUTF(days[i]);
+        env->SetObjectArrayElement(day,i,str);
+    }
+
+    return day;
+}
+

Android/AndroidJNIBasics/app/src/main/java/com/journaldev/androidjnibasics/MainActivity.java

@@ -0,0 +1,59 @@
+package com.journaldev.androidjnibasics;
+
+import android.support.v7.app.AppCompatActivity;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.TextView;
+import android.widget.Toast;
+
+public class MainActivity extends AppCompatActivity {
+
+    // Used to load the 'native-lib' library on application startup.
+    static {
+        System.loadLibrary("native-lib");
+    }
+
+    Button btnJNI, btnJNIStringArray;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        // Example of a call to a native method
+        TextView tv = findViewById(R.id.sample_text);
+        tv.setText(stringFromJNI());
+
+        btnJNI = findViewById(R.id.btnJni);
+        btnJNIStringArray = findViewById(R.id.btnJniStringArray);
+        btnJNI.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String result = sendYourName("Anupam", "Chugh");
+                Toast.makeText(getApplicationContext(), "Result from JNI is " + result, Toast.LENGTH_LONG).show();
+            }
+        });
+
+        btnJNIStringArray.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String[] strings = stringArrayFromJNI();
+
+                Toast.makeText(getApplicationContext(), "First element is "+strings[0], Toast.LENGTH_LONG).show();
+
+            }
+        });
+
+    }
+
+    /**
+     * A native method that is implemented by the 'native-lib' native library,
+     * which is packaged with this application.
+     */
+    public native String stringFromJNI();
+    public native String sendYourName(String firstName, String lastName);
+    public native String[] stringArrayFromJNI();
+
+
+}

Android/AndroidJNIBasics/app/src/main/res/drawable-v24/ic_launcher_foreground.xml

@@ -0,0 +1,34 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillType="evenOdd"
+        android:pathData="M32,64C32,64 38.39,52.99 44.13,50.95C51.37,48.37 70.14,49.57 70.14,49.57L108.26,87.69L108,109.01L75.97,107.97L32,64Z"
+        android:strokeWidth="1"
+        android:strokeColor="#00000000">
+        <aapt:attr name="android:fillColor">
+            <gradient
+                android:endX="78.5885"
+                android:endY="90.9159"
+                android:startX="48.7653"
+                android:startY="61.0927"
+                android:type="linear">
+                <item
+                    android:color="#44000000"
+                    android:offset="0.0" />
+                <item
+                    android:color="#00000000"
+                    android:offset="1.0" />
+            </gradient>
+        </aapt:attr>
+    </path>
+    <path
+        android:fillColor="#FFFFFF"
+        android:fillType="nonZero"
+        android:pathData="M66.94,46.02L66.94,46.02C72.44,50.07 76,56.61 76,64L32,64C32,56.61 35.56,50.11 40.98,46.06L36.18,41.19C35.45,40.45 35.45,39.3 36.18,38.56C36.91,37.81 38.05,37.81 38.78,38.56L44.25,44.05C47.18,42.57 50.48,41.71 54,41.71C57.48,41.71 60.78,42.57 63.68,44.05L69.11,38.56C69.84,37.81 70.98,37.81 71.71,38.56C72.44,39.3 72.44,40.45 71.71,41.19L66.94,46.02ZM62.94,56.92C64.08,56.92 65,56.01 65,54.88C65,53.76 64.08,52.85 62.94,52.85C61.8,52.85 60.88,53.76 60.88,54.88C60.88,56.01 61.8,56.92 62.94,56.92ZM45.06,56.92C46.2,56.92 47.13,56.01 47.13,54.88C47.13,53.76 46.2,52.85 45.06,52.85C43.92,52.85 43,53.76 43,54.88C43,56.01 43.92,56.92 45.06,56.92Z"
+        android:strokeWidth="1"
+        android:strokeColor="#00000000" />
+</vector>