#104 - Add support for redrawing plots inside recyclerview + example (#113)

Author: halfhp

androidplot-core/src/main/java/com/androidplot/Plot.java

@@ -212,6 +212,8 @@ public enum RenderMode {
      *  that is being used.
      */
     private static class BufferedCanvas {
+        private int lastHeight = 0;
+        private int lastWidth = 0;
         private volatile Bitmap bgBuffer;  // all drawing is done on this buffer.
         private volatile Bitmap fgBuffer;
         private Canvas canvas = new Canvas();
@@ -226,11 +228,21 @@ public synchronized void swap() {
             fgBuffer = tmp;
         }
 
+        /**
+         * Used when rendering in background mode and a view is attached
+         * but not resized, so that rendering buffers will be reinitialized.
+         */
+        public void resizeToLast() {
+            resize(lastHeight, lastWidth);
+        }
+
         public synchronized void resize(int h, int w) {
             if (w <= 0 || h <= 0) {
                 bgBuffer = null;
                 fgBuffer = null;
             } else {
+                lastHeight = h;
+                lastWidth = w;
                 try {
                     bgBuffer = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
                     fgBuffer = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
@@ -408,35 +420,43 @@ protected final void init(Context context, AttributeSet attrs, int defStyle) {
 
         layoutManager.onPostInit();
         if (renderMode == RenderMode.USE_BACKGROUND_THREAD) {
-            renderThread = new Thread(new Runnable() {
-                @Override
-                public void run() {
-
-                    keepRunning = true;
-                    while (keepRunning) {
-                        isIdle = false;
-                        synchronized (pingPong) {
-                            Canvas c = pingPong.getCanvas();
-                            renderOnCanvas(c);
-                            pingPong.swap();
-                        }
-                        synchronized (renderSync) {
-                            postInvalidate();
-                            // prevent this thread from becoming an orphan
-                            // after the view is destroyed
-                            if (keepRunning) {
-                                try {
-                                    renderSync.wait();
-                                } catch (InterruptedException e) {
-                                    keepRunning = false;
-                                }
-                            }
+            startBackgroundRendering();
+        }
+    }
+
+    protected void startBackgroundRendering() {
+        if(renderThread != null) {
+            return;
+        }
+
+        renderThread = new Thread(() -> {
+            System.out.println("Thread started with id " + this.hashCode());
+
+            keepRunning = true;
+            while (keepRunning) {
+                isIdle = false;
+                synchronized (pingPong) {
+                    Canvas c = pingPong.getCanvas();
+                    renderOnCanvas(c);
+                    pingPong.swap();
+                }
+                synchronized (renderSync) {
+                    postInvalidate();
+                    // prevent this thread from becoming an orphan
+                    // after the view is destroyed
+                    if (keepRunning) {
+                        try {
+                            renderSync.wait();
+                        } catch (InterruptedException e) {
+                            keepRunning = false;
                         }
                     }
-                    pingPong.recycle();
                 }
-            }, "Androidplot renderThread");
-        }
+            }
+            System.out.println("Thread exited with id " + this.hashCode());
+            renderThread = null;
+            pingPong.recycle();
+        }, "Androidplot renderThread");
     }
 
     /**
@@ -745,11 +765,12 @@ public void redraw() {
             // only enter synchronized block if the call is expected to block OR
             // if the render thread is idle, so we know that we won't have to wait to
             // obtain a lock.
-            if (isIdle) {
+            if (renderThread != null && isIdle) {
                 synchronized (renderSync) {
                     renderSync.notify();
                 }
             }
+
         } else if(renderMode == RenderMode.USE_MAIN_THREAD) {
 
             // are we on the UI thread?
@@ -778,6 +799,17 @@ protected void onDetachedFromWindow() {
         }
     }
 
+    @Override
+    protected void onAttachedToWindow() {
+        super.onAttachedToWindow();
+
+        // necessary to support rendering in recyclerview etc.
+        if(renderMode == RenderMode.USE_BACKGROUND_THREAD && renderThread == null) {
+            pingPong.resizeToLast();
+            startBackgroundRendering();
+            renderThread.start();
+        }
+    }
 
     @Override
     protected synchronized void onSizeChanged (int w, int h, int oldw, int oldh) {

demoapp/build.gradle

@@ -15,12 +15,13 @@
  */
 
 buildscript {
-
+    ext.kotlin_version = '1.5.31'
     repositories {
         mavenCentral()
     }
     dependencies {
         classpath 'com.github.triplet.gradle:play-publisher:3.6.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
 
@@ -29,9 +30,14 @@ plugins {
     id 'com.github.triplet.play' version '3.6.0'
 }
 
+apply plugin: 'kotlin-android'
+
 dependencies {
+    implementation "androidx.core:core-ktx:1.6.0"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 	implementation project(':androidplot-core')
     implementation 'com.crittercism:crittercism-android-agent:5.4.0'
+    implementation 'androidx.recyclerview:recyclerview:1.2.1'
 
     debugImplementation 'com.squareup.leakcanary:leakcanary-android:1.6.3'
 
@@ -43,6 +49,10 @@ dependencies {
 android {
     compileSdkVersion theCompileSdkVersion
 
+    buildFeatures {
+        viewBinding true
+    }
+
     defaultConfig {
         versionCode theVersionCode
         versionName theVersionName
@@ -82,3 +92,6 @@ play {
     serviceAccountCredentials.set(file(System.getenv("PUBLISHER_ACCT_JSON_FILE") ?: "publisher.json"))
     track = 'beta'
 }
+repositories {
+    mavenCentral()
+}

demoapp/src/main/AndroidManifest.xml

@@ -95,6 +95,7 @@
             </intent-filter>
         </activity>
         <activity android:name=".ListViewActivity" android:label="ListView Example"/>
+        <activity android:name=".RecyclerViewActivity" android:label="RecyclerView Example"/>
         <activity android:name=".XYRegionExampleActivity" android:label="XYRegion Example">
             <intent-filter>
                 <category android:name="android.intent.category.LAUNCHER" />