Add delayed view size calculation

Author: solkin

imageloader/src/main/java/com/tomclaw/imageloader/core/ImageLoader.kt

@@ -31,7 +31,7 @@ class ImageLoaderImpl(
         uriString: String,
         handlers: Handlers<T>
     ) {
-        val size = view.getSize()
+        val size = view.optSize() ?: run { waitSizeAsync(view, uriString, handlers); return }
         val key = generateKey(uriString, size.width, size.height)
         val prevTag = view.tag
         view.tag = key
@@ -55,6 +55,19 @@ class ImageLoaderImpl(
             ?: loadAsync(view, size, uriString, key, handlers)
     }
 
+    private fun <T> waitSizeAsync(
+        view: ViewHolder<T>,
+        uriString: String,
+        handlers: Handlers<T>
+    ) {
+        backgroundExecutor.submit {
+            view.getSize()
+            mainExecutor.execute {
+                load(view, uriString, handlers)
+            }
+        }
+    }
+
     private fun <T> loadAsync(
         view: ViewHolder<T>,
         size: ViewSize,

imageloader/src/main/java/com/tomclaw/imageloader/core/ViewHolder.kt

@@ -2,6 +2,8 @@ package com.tomclaw.imageloader.core
 
 interface ViewHolder<T> {
 
+    fun optSize(): ViewSize?
+
     fun getSize(): ViewSize
 
     var tag: Any?

imageloader/src/main/java/com/tomclaw/imageloader/util/ImageViewHolder.kt

@@ -1,17 +1,61 @@
 package com.tomclaw.imageloader.util
 
+import android.view.ViewGroup.LayoutParams.MATCH_PARENT
+import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
+import android.view.ViewTreeObserver
 import android.widget.ImageView
 import com.tomclaw.imageloader.core.ViewHolder
 import com.tomclaw.imageloader.core.ViewSize
+import java.util.concurrent.CountDownLatch
 
 class ImageViewHolder(private val imageView: ImageView) : ViewHolder<ImageView> {
 
     override fun getSize(): ViewSize {
-        val w = imageView.measuredWidth.takeIf { it > 0 }
-            ?: imageView.resources.displayMetrics.widthPixels
-        val h = imageView.measuredHeight.takeIf { it > 0 }
-            ?: imageView.resources.displayMetrics.heightPixels
-        return ViewSize(w, h)
+        optSize()?.let { return it }
+
+        var viewSize = ViewSize(0, 0)
+        val latch = CountDownLatch(1)
+
+        val viewTreeObserver = imageView.viewTreeObserver
+        val preDrawListener = object : ViewTreeObserver.OnPreDrawListener {
+            private var isResumed = false
+
+            override fun onPreDraw(): Boolean {
+                val size = optSize()
+                if (size != null) {
+                    viewSize = size
+                    viewTreeObserver.removeOnPreDrawListener(this)
+
+                    if (!isResumed) {
+                        isResumed = true
+                        latch.countDown()
+                    }
+                }
+                return true
+            }
+        }
+        viewTreeObserver.addOnPreDrawListener(preDrawListener)
+
+        latch.await()
+        return viewSize
+    }
+
+    override fun optSize(): ViewSize? {
+        val width = (
+                imageView.layoutParams?.width?.takeIf { it > 0 }
+                    ?: imageView.width.takeIf { it > 0 }
+                    ?: MATCH_PARENT
+                )
+            .takeIf { it != WRAP_CONTENT }
+            ?: imageView.context.resources.displayMetrics.widthPixels
+        val height = (
+                imageView.layoutParams?.height?.takeIf { it > 0 }
+                    ?: imageView.height.takeIf { it > 0 }
+                    ?: MATCH_PARENT
+                )
+            .takeIf { it != WRAP_CONTENT }
+            ?: imageView.context.resources.displayMetrics.heightPixels
+        return ViewSize(width, height).takeIf { width > 0 && height > 0 }
     }
 
     override var tag: Any?