Targeting API 28. Added workaround for pruned canvas save(int) method. SRC: https://developer.android.com/sdk/api_diff/28/changes/android.graphics.Canvas

Author: alt236

library/build.gradle

@@ -11,7 +11,7 @@ dependencies {
 }
 
 android {
-    compileSdkVersion 26
+    compileSdkVersion 28
     buildToolsVersion "26.0.1"
     lintOptions {
         abortOnError false

library/src/main/java/com/sothree/slidinguppanel/SlidingUpPanelLayout.java

@@ -22,6 +22,8 @@
 import android.view.animation.AnimationUtils;
 import android.view.animation.Interpolator;
 
+import com.sothree.slidinguppanel.canvassaveproxy.CanvasSaveProxy;
+import com.sothree.slidinguppanel.canvassaveproxy.CanvasSaveProxyFactory;
 import com.sothree.slidinguppanel.library.R;
 
 import java.util.List;
@@ -218,6 +220,8 @@ public enum PanelState {
     private View.OnClickListener mFadeOnClickListener;
 
     private final ViewDragHelper mDragHelper;
+    private final CanvasSaveProxyFactory mCanvasSaveProxyFactory;
+    private CanvasSaveProxy mCanvasSaveProxy;
 
     /**
      * Stores whether or not the pane was expanded the last time it was slideable.
@@ -272,6 +276,7 @@ public SlidingUpPanelLayout(Context context, AttributeSet attrs) {
 
     public SlidingUpPanelLayout(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
+        mCanvasSaveProxyFactory = new CanvasSaveProxyFactory();
 
         if (isInEditMode()) {
             mShadowDrawable = null;
@@ -1186,7 +1191,12 @@ private void onPanelDragged(int newTop) {
     @Override
     protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
         boolean result;
-        final int save = canvas.save(Canvas.CLIP_SAVE_FLAG);
+
+        if(mCanvasSaveProxy == null ||!mCanvasSaveProxy.isFor(canvas)) {
+            mCanvasSaveProxy = mCanvasSaveProxyFactory.create(canvas);
+        }
+
+        final int save = mCanvasSaveProxy.save(); // canvas.save(Canvas.CLIP_SAVE_FLAG);
 
         if (mSlideableView != null && mSlideableView != child) { // if main view
             // Clip against the slider; no sense drawing what will immediately be covered,

library/src/main/java/com/sothree/slidinguppanel/canvassaveproxy/AndroidPCanvasSaveProxy.java

@@ -0,0 +1,28 @@
+package com.sothree.slidinguppanel.canvassaveproxy;
+
+import android.graphics.Canvas;
+import android.os.Build;
+import android.support.annotation.RequiresApi;
+import android.util.Log;
+
+@RequiresApi(api = Build.VERSION_CODES.P)
+class AndroidPCanvasSaveProxy implements CanvasSaveProxy {
+    private static final String TAG = CanvasSaveProxy.class.getSimpleName();
+    private final Canvas mCanvas;
+
+    AndroidPCanvasSaveProxy(final Canvas canvas) {
+        Log.d(TAG, "New AndroidPCanvasSaveProxy");
+
+        mCanvas = canvas;
+    }
+
+    @Override
+    public int save() {
+        return mCanvas.save();
+    }
+
+    @Override
+    public boolean isFor(final Canvas canvas) {
+        return canvas == mCanvas;
+    }
+}

library/src/main/java/com/sothree/slidinguppanel/canvassaveproxy/CanvasSaveProxy.java

@@ -0,0 +1,9 @@
+package com.sothree.slidinguppanel.canvassaveproxy;
+
+import android.graphics.Canvas;
+
+public interface CanvasSaveProxy {
+    int save();
+
+    boolean isFor(final Canvas canvas);
+}

library/src/main/java/com/sothree/slidinguppanel/canvassaveproxy/CanvasSaveProxyFactory.java

@@ -0,0 +1,16 @@
+package com.sothree.slidinguppanel.canvassaveproxy;
+
+import android.graphics.Canvas;
+import android.os.Build;
+
+public class CanvasSaveProxyFactory {
+
+    public CanvasSaveProxy create(final Canvas canvas) {
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            return new AndroidPCanvasSaveProxy(canvas);
+        } else {
+            return new LegacyCanvasSaveProxy(canvas);
+        }
+    }
+}

library/src/main/java/com/sothree/slidinguppanel/canvassaveproxy/LegacyCanvasSaveProxy.java

@@ -0,0 +1,67 @@
+package com.sothree.slidinguppanel.canvassaveproxy;
+
+import android.graphics.Canvas;
+import android.util.Log;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+@Deprecated
+class LegacyCanvasSaveProxy implements CanvasSaveProxy {
+    private static final String TAG = CanvasSaveProxy.class.getSimpleName();
+    private static final String METHOD_NAME = "save";
+    private static final String FIELD_NAME = "CLIP_SAVE_FLAG";
+
+    private final Canvas mCanvas;
+    private final Method mSaveMethod;
+    private final int mClipSaveFlag;
+
+    LegacyCanvasSaveProxy(final Canvas canvas) {
+        Log.d(TAG, "New LegacyCanvasSaveProxy");
+
+        mCanvas = canvas;
+        mSaveMethod = findSaveMethod();
+        mClipSaveFlag = getClipSaveFlagValue();
+    }
+
+    @Override
+    public int save() {
+        return invokeSave();
+    }
+
+    @Override
+    public boolean isFor(final Canvas canvas) {
+        return canvas == mCanvas;
+    }
+
+    private int getClipSaveFlagValue() {
+        final Field constantField;
+        try {
+            constantField = Canvas.class.getDeclaredField(FIELD_NAME);
+            return (int) constantField.get(null);
+        } catch (NoSuchFieldException e) {
+            throw new IllegalStateException("Failed to get value of " + FIELD_NAME + " - NoSuchFieldException", e);
+        } catch (IllegalAccessException e) {
+            throw new IllegalStateException("Failed to get value of " + FIELD_NAME + " - IllegalAccessException", e);
+        }
+    }
+
+    private Method findSaveMethod() {
+        try {
+            return Canvas.class.getMethod(METHOD_NAME, int.class);
+        } catch (NoSuchMethodException e) {
+            throw new IllegalStateException("Canvas does not contain a method with signature save(int)");
+        }
+    }
+
+    private int invokeSave() {
+        try {
+            return (int) mSaveMethod.invoke(mCanvas, mClipSaveFlag);
+        } catch (IllegalAccessException e) {
+            throw new IllegalStateException("Failed to execute save(int) - IllegalAccessException", e);
+        } catch (InvocationTargetException e) {
+            throw new IllegalStateException("Failed to execute save(int) - InvocationTargetException", e);
+        }
+    }
+}