Convert Java files to Kotlin (#328)

* Convert Java files to Kotlin

* Update following @thagikura's comments

build.gradle

@@ -17,6 +17,21 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
+    ext {
+        minSdkVersion = 9
+        targetSdkVersion = 25
+        compileSdkVersion = 25
+        buildToolsVersion = "25.0.3"
+        androidGradlePluginVersion = "2.3.3"
+        androidMavenGradlePluginVersion = "1.5"
+        gradleBintrayPluginVersion = "1.6"
+        kotlinVersion = "1.1.3"
+        supportLibVersion = "25.3.1"
+        espressoVersion = "2.2.2"
+        testRunnerVersion = "0.5"
+        junitVersion = "4.12"
+    }
+
     repositories {
         jcenter()
         maven {
@@ -24,25 +39,15 @@ buildscript {
         }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.3'
-        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.5'
-        classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.6'
+        classpath "com.android.tools.build:gradle:$androidGradlePluginVersion"
+        classpath "com.github.dcendents:android-maven-gradle-plugin:$androidMavenGradlePluginVersion"
+        classpath "com.jfrog.bintray.gradle:gradle-bintray-plugin:$gradleBintrayPluginVersion"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
     }
 }
 
-ext {
-    minSdkVersion = 9
-    targetSdkVersion = 25
-    compileSdkVersion = 25
-    buildToolsVersion = "25.0.3"
-    supportLibVersion = "25.3.1"
-    espressoVersion = "2.2.2"
-    testRunnerVersion = "0.5"
-    junitVersion = "4.12"
-}
-
 allprojects {
     repositories {
         jcenter()
@@ -63,9 +68,9 @@ project.ext.preDexLibs = !project.hasProperty('disablePreDex')
 
 subprojects {
     project.plugins.whenPluginAdded { plugin ->
-        if ("com.android.build.gradle.AppPlugin".equals(plugin.class.name)) {
+        if ("com.android.build.gradle.AppPlugin" == plugin.class.name) {
             project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
-        } else if ("com.android.build.gradle.LibraryPlugin".equals(plugin.class.name)) {
+        } else if ("com.android.build.gradle.LibraryPlugin" == plugin.class.name) {
             project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
         }
     }

demo-cat-gallery/build.gradle

@@ -15,6 +15,7 @@
  */
 
 apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion rootProject.ext.compileSdkVersion
@@ -39,8 +40,9 @@ android {
 }
 
 dependencies {
+    compile project(path: ":flexbox")
     compile "com.android.support:appcompat-v7:${rootProject.ext.supportLibVersion}"
     compile "com.android.support:design:${rootProject.ext.supportLibVersion}"
     compile "com.android.support:recyclerview-v7:${rootProject.ext.supportLibVersion}"
-    compile project(path: ":flexbox")
+    compile "org.jetbrains.kotlin:kotlin-stdlib:${rootProject.ext.kotlinVersion}"
 }

demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatAdapter.java → demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatAdapter.kt

@@ -14,66 +14,51 @@
  * limitations under the License.
  */
 
-package com.google.android.flexbox.apps.catgallery;
+package com.google.android.flexbox.apps.catgallery
 
-import android.content.Context;
-import android.graphics.drawable.Drawable;
-import android.support.v4.content.res.ResourcesCompat;
-import android.support.v7.widget.RecyclerView;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
+import android.support.v7.widget.RecyclerView
+import android.view.LayoutInflater
+import android.view.ViewGroup
 
 /**
  * Adapter class that handles the data set with the {@link RecyclerView.LayoutManager}
  */
-class CatAdapter extends RecyclerView.Adapter<CatViewHolder> {
+internal class CatAdapter : RecyclerView.Adapter<CatViewHolder>() {
 
-    private static final int[] CAT_IMAGE_IDS = new int[]{
-            R.drawable.cat_1,
-            R.drawable.cat_2,
-            R.drawable.cat_3,
-            R.drawable.cat_4,
-            R.drawable.cat_5,
-            R.drawable.cat_6,
-            R.drawable.cat_7,
-            R.drawable.cat_8,
-            R.drawable.cat_9,
-            R.drawable.cat_10,
-            R.drawable.cat_11,
-            R.drawable.cat_12,
-            R.drawable.cat_13,
-            R.drawable.cat_14,
-            R.drawable.cat_15,
-            R.drawable.cat_16,
-            R.drawable.cat_17,
-            R.drawable.cat_18,
-            R.drawable.cat_19,
-    };
-
-    private Context mContext;
-
-    CatAdapter(Context context) {
-        mContext = context;
+    companion object {
+        private val CAT_IMAGE_IDS = intArrayOf(
+                R.drawable.cat_1,
+                R.drawable.cat_2,
+                R.drawable.cat_3,
+                R.drawable.cat_4,
+                R.drawable.cat_5,
+                R.drawable.cat_6,
+                R.drawable.cat_7,
+                R.drawable.cat_8,
+                R.drawable.cat_9,
+                R.drawable.cat_10,
+                R.drawable.cat_11,
+                R.drawable.cat_12,
+                R.drawable.cat_13,
+                R.drawable.cat_14,
+                R.drawable.cat_15,
+                R.drawable.cat_16,
+                R.drawable.cat_17,
+                R.drawable.cat_18,
+                R.drawable.cat_19
+        )
     }
 
-    @Override
-    public CatViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-        View view = LayoutInflater.from(parent.getContext())
-                .inflate(R.layout.viewholder_cat, parent, false);
-        return new CatViewHolder(view);
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CatViewHolder {
+        val view = LayoutInflater.from(parent.context)
+                .inflate(R.layout.viewholder_cat, parent, false)
+        return CatViewHolder(view)
     }
 
-    @Override
-    public void onBindViewHolder(CatViewHolder holder, int position) {
-        int pos = position % CAT_IMAGE_IDS.length;
-        Drawable drawable = ResourcesCompat.getDrawable(mContext.getResources(),
-                CAT_IMAGE_IDS[pos], null);
-        holder.bindTo(drawable);
+    override fun onBindViewHolder(holder: CatViewHolder, position: Int) {
+        val pos = position % CAT_IMAGE_IDS.size
+        holder.bindTo(CAT_IMAGE_IDS[pos])
     }
 
-    @Override
-    public int getItemCount() {
-        return CAT_IMAGE_IDS.length * 4;
-    }
+    override fun getItemCount() = CAT_IMAGE_IDS.size * 4
 }

demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.java → demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.kt

@@ -14,34 +14,26 @@
  * limitations under the License.
  */
 
-package com.google.android.flexbox.apps.catgallery;
+package com.google.android.flexbox.apps.catgallery
 
-import android.graphics.drawable.Drawable;
-import android.support.v7.widget.RecyclerView;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ImageView;
-
-import com.google.android.flexbox.FlexboxLayoutManager;
+import android.support.annotation.DrawableRes
+import android.support.v7.widget.RecyclerView
+import android.view.View
+import android.widget.ImageView
+import com.google.android.flexbox.FlexboxLayoutManager
 
 /**
  * ViewHolder that represents a cat image.
  */
-class CatViewHolder extends RecyclerView.ViewHolder {
-
-    private ImageView mImageView;
+internal class CatViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
 
-    CatViewHolder(View itemView) {
-        super(itemView);
-        mImageView = (ImageView) itemView.findViewById(R.id.imageview);
-    }
+    private val imageView = itemView.findViewById(R.id.imageview) as ImageView
 
-    void bindTo(Drawable drawable) {
-        mImageView.setImageDrawable(drawable);
-        ViewGroup.LayoutParams lp = mImageView.getLayoutParams();
-        if (lp instanceof FlexboxLayoutManager.LayoutParams) {
-            FlexboxLayoutManager.LayoutParams flexboxLp = (FlexboxLayoutManager.LayoutParams) lp;
-            flexboxLp.setFlexGrow(1.0f);
+    internal fun bindTo(@DrawableRes drawableRes: Int) {
+        imageView.setImageResource(drawableRes)
+        val lp = imageView.layoutParams
+        if (lp is FlexboxLayoutManager.LayoutParams) {
+            lp.flexGrow = 1f
         }
     }
 }

demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.java → demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.kt

@@ -14,18 +14,16 @@
  * limitations under the License.
  */
 
-package com.google.android.flexbox.apps.catgallery;
+package com.google.android.flexbox.apps.catgallery
 
-import android.os.Bundle;
-import android.support.v7.app.AppCompatActivity;
-import android.support.v7.widget.RecyclerView;
-import android.support.v7.widget.Toolbar;
-
-import com.google.android.flexbox.AlignItems;
-import com.google.android.flexbox.FlexDirection;
-import com.google.android.flexbox.FlexWrap;
-import com.google.android.flexbox.FlexboxLayout;
-import com.google.android.flexbox.FlexboxLayoutManager;
+import android.os.Bundle
+import android.support.v7.app.AppCompatActivity
+import android.support.v7.widget.RecyclerView
+import android.support.v7.widget.Toolbar
+import com.google.android.flexbox.AlignItems
+import com.google.android.flexbox.FlexDirection
+import com.google.android.flexbox.FlexWrap
+import com.google.android.flexbox.FlexboxLayoutManager
 
 /**
  * Launcher Activity for the cat gallery demo app that demonstrates the usage of the
@@ -34,22 +32,25 @@ import com.google.android.flexbox.FlexboxLayoutManager;
  * Thus compared to using the {@link FlexboxLayout}, it's much less likely to abuse the memory,
  * which some times leads to the OutOfMemoryError.
  */
-public class MainActivity extends AppCompatActivity {
+class MainActivity : AppCompatActivity() {
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+
+        val toolbar = findViewById(R.id.toolbar) as Toolbar
+        setSupportActionBar(toolbar)
 
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setContentView(R.layout.activity_main);
-        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
-        setSupportActionBar(toolbar);
+        val flexboxLayoutManager = FlexboxLayoutManager(this).apply {
+            flexWrap = FlexWrap.WRAP
+            flexDirection = FlexDirection.ROW
+            alignItems = AlignItems.STRETCH
+        }
 
-        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
-        FlexboxLayoutManager layoutManager = new FlexboxLayoutManager(this);
-        layoutManager.setFlexWrap(FlexWrap.WRAP);
-        layoutManager.setFlexDirection(FlexDirection.ROW);
-        layoutManager.setAlignItems(AlignItems.STRETCH);
-        recyclerView.setLayoutManager(layoutManager);
-        RecyclerView.Adapter adapter = new CatAdapter(this);
-        recyclerView.setAdapter(adapter);
+        val recyclerView = findViewById(R.id.recyclerview) as RecyclerView
+        recyclerView.apply {
+            layoutManager = flexboxLayoutManager
+            adapter = CatAdapter()
+        }
     }
 }