preload images

contributes to #94
niccokunzmann · Mar 12, 2020 · 013cfef · 013cfef
1 parent 2298ead
commit 013cfef
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Showing 4 changed files with 53 additions and 3 deletions.
diff --git a/build.gradle b/build.gradle
@@ -24,7 +24,7 @@ dependencies {
     implementation 'commons-io:commons-io:2.4'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
     implementation 'androidx.recyclerview:recyclerview:1.1.0'
-    implementation 'androidx.appcompat:appcompat:1.0.2'
+    implementation 'androidx.appcompat:appcompat:1.1.0'
     testImplementation 'junit:junit:4.12'
 }
 

diff --git a/src/main/java/org/androidsoft/coloring/ui/activity/ChoosePictureActivity.java b/src/main/java/org/androidsoft/coloring/ui/activity/ChoosePictureActivity.java
@@ -15,12 +15,17 @@
  */
 package org.androidsoft.coloring.ui.activity;
 
+import android.app.Activity;
+import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
+
+import android.util.DisplayMetrics;
 import android.view.WindowManager;
 
+import org.androidsoft.coloring.ui.widget.PreCachingLayoutManager;
 import org.androidsoft.coloring.util.ScreenUtils;
 import org.androidsoft.coloring.util.Settings;
 import org.androidsoft.coloring.util.images.ImageDB;
@@ -50,6 +55,10 @@ public void onCreate(Bundle savedInstanceState)
 
         setContentView(R.layout.choose_picture);
         RecyclerView imagesView = findViewById(R.id.images);
+        // load images ahead
+        int space = getScreenHeight() / 2;
+        LinearLayoutManager manager = new PreCachingLayoutManager(this, space);
+        imagesView.setLayoutManager(manager);
 
         // use this setting to improve performance if you know that changes
         // in content do not change the layout size of the RecyclerView
@@ -99,4 +108,11 @@ public void onWindowFocusChanged(boolean hasFocus)
             ScreenUtils.setFullscreen(this);
         }
     }
+
+    private int getScreenHeight() {
+        // from https://stackoverflow.com/a/4744499
+        DisplayMetrics displayMetrics = new DisplayMetrics();
+        this.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
+        return displayMetrics.heightPixels;
+    }
 }
diff --git a/src/main/java/org/androidsoft/coloring/ui/widget/PreCachingLayoutManager.java b/src/main/java/org/androidsoft/coloring/ui/widget/PreCachingLayoutManager.java
@@ -0,0 +1,33 @@
+package org.androidsoft.coloring.ui.widget;
+
+import android.content.Context;
+import android.util.AttributeSet;
+
+import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+/* This layout manager loads images ahead.
+ * see https://developer.android.com/reference/android/support/v7/widget/LinearLayoutManager#setsmoothscrollbarenabled
+ * thanks to https://developer.android.com/reference/android/support/v7/widget/LinearLayoutManager#getextralayoutspace
+ * thanks to https://github.com/ovy9086/recyclerview-playground/blob/master/app/src/main/java/com/olu/recyclerview/widget/PreCachingLayoutManager.java
+ * thanks to https://androiddevx.wordpress.com/2014/12/05/recycler-view-pre-cache-views/
+ * thanks to https://github.com/facebook/fresco/issues/335#issuecomment-110280822
+ * also https://github.com/ovy9086/recyclerview-playground/blob/master/app/src/main/java/com/olu/recyclerview/fragments/CatsListFragment.java#L45
+ * deprecated, see https://developer.android.com/reference/androidx/recyclerview/widget/LinearLayoutManager?hl=en#getExtraLayoutSpace(androidx.recyclerview.widget.RecyclerView.State)
+ * see https://developer.android.com/reference/androidx/recyclerview/widget/LinearLayoutManager?hl=en#calculateExtraLayoutSpace(androidx.recyclerview.widget.RecyclerView.State,%20int%5B%5D)
+ */
+public class PreCachingLayoutManager extends LinearLayoutManager {
+    private final int extraLayoutSpace;
+
+    public PreCachingLayoutManager(Context context, int extraLayoutSpace) {
+        super(context);
+        this.extraLayoutSpace = extraLayoutSpace;
+    }
+
+    @Override
+    protected void calculateExtraLayoutSpace(@NonNull RecyclerView.State state, @NonNull int[] extraLayoutSpace) {
+        extraLayoutSpace[0] = this.extraLayoutSpace;
+        extraLayoutSpace[1] = this.extraLayoutSpace;
+    }
+}
diff --git a/src/main/res/layout/choose_picture_line.xml b/src/main/res/layout/choose_picture_line.xml
@@ -17,7 +17,7 @@
         android:adjustViewBounds="true"
         android:background="#FFFFFF"
         android:scaleType="fitXY"
-        android:src="@drawable/ic_logo"
+        android:src="@drawable/download"
         tools:ignore="ContentDescription" />
 
     <ImageView
@@ -28,7 +28,8 @@
         android:layout_weight="1"
         android:adjustViewBounds="true"
         android:background="#FFFFFF"
+        android:overScrollMode="never"
         android:scaleType="fitXY"
-        android:src="@drawable/ic_logo"
+        android:src="@drawable/download"
         tools:ignore="ContentDescription" />
 </LinearLayout>