Fix some potential NPEs with WeakReference usage

scottkennedy · scottkennedy · commit 43ae497ecf74 · 2017-06-26T10:51:58.000-07:00
Even if the WeakReference field is not null, the contained value may be null.  Additionally, you always need a strong reference to the value to ensure it isn't garbage collected while you're using it.
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/LineChartRenderer.java b/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/LineChartRenderer.java
@@ -76,19 +76,21 @@ public void drawData(Canvas c) {
         int width = (int) mViewPortHandler.getChartWidth();
         int height = (int) mViewPortHandler.getChartHeight();
 
-        if (mDrawBitmap == null
-                || (mDrawBitmap.get().getWidth() != width)
-                || (mDrawBitmap.get().getHeight() != height)) {
+        Bitmap drawBitmap = mDrawBitmap == null ? null : mDrawBitmap.get();
 
-            if (width > 0 && height > 0) {
+        if (drawBitmap == null
+                || (drawBitmap.getWidth() != width)
+                || (drawBitmap.getHeight() != height)) {
 
-                mDrawBitmap = new WeakReference<Bitmap>(Bitmap.createBitmap(width, height, mBitmapConfig));
-                mBitmapCanvas = new Canvas(mDrawBitmap.get());
+            if (width > 0 && height > 0) {
+                drawBitmap = Bitmap.createBitmap(width, height, mBitmapConfig);
+                mDrawBitmap = new WeakReference<>(drawBitmap);
+                mBitmapCanvas = new Canvas(drawBitmap);
             } else
                 return;
         }
 
-        mDrawBitmap.get().eraseColor(Color.TRANSPARENT);
+        drawBitmap.eraseColor(Color.TRANSPARENT);
 
         LineData lineData = mChart.getLineData();
 
@@ -98,7 +100,7 @@ public void drawData(Canvas c) {
                 drawDataSet(c, set);
         }
 
-        c.drawBitmap(mDrawBitmap.get(), 0, 0, mRenderPaint);
+        c.drawBitmap(drawBitmap, 0, 0, mRenderPaint);
     }
 
     protected void drawDataSet(Canvas c, ILineDataSet dataSet) {
@@ -738,7 +740,10 @@ public void releaseBitmap() {
             mBitmapCanvas = null;
         }
         if (mDrawBitmap != null) {
-            mDrawBitmap.get().recycle();
+            Bitmap drawBitmap = mDrawBitmap.get();
+            if (drawBitmap != null) {
+                drawBitmap.recycle();
+            }
             mDrawBitmap.clear();
             mDrawBitmap = null;
         }
diff --git a/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.java b/MPChartLib/src/main/java/com/github/mikephil/charting/renderer/PieChartRenderer.java
@@ -126,19 +126,21 @@ public void drawData(Canvas c) {
         int width = (int) mViewPortHandler.getChartWidth();
         int height = (int) mViewPortHandler.getChartHeight();
 
-        if (mDrawBitmap == null
-                || (mDrawBitmap.get().getWidth() != width)
-                || (mDrawBitmap.get().getHeight() != height)) {
+        Bitmap drawBitmap = mDrawBitmap == null ? null : mDrawBitmap.get();
 
-            if (width > 0 && height > 0) {
+        if (drawBitmap == null
+                || (drawBitmap.getWidth() != width)
+                || (drawBitmap.getHeight() != height)) {
 
-                mDrawBitmap = new WeakReference<Bitmap>(Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444));
-                mBitmapCanvas = new Canvas(mDrawBitmap.get());
+            if (width > 0 && height > 0) {
+                drawBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444);
+                mDrawBitmap = new WeakReference<>(drawBitmap);
+                mBitmapCanvas = new Canvas(drawBitmap);
             } else
                 return;
         }
 
-        mDrawBitmap.get().eraseColor(Color.TRANSPARENT);
+        drawBitmap.eraseColor(Color.TRANSPARENT);
 
         PieData pieData = mChart.getData();
 
@@ -1010,7 +1012,10 @@ public void releaseBitmap() {
             mBitmapCanvas = null;
         }
         if (mDrawBitmap != null) {
-            mDrawBitmap.get().recycle();
+            Bitmap drawBitmap = mDrawBitmap.get();
+            if (drawBitmap != null) {
+                drawBitmap.recycle();
+            }
             mDrawBitmap.clear();
             mDrawBitmap = null;
         }
