Android app: build safe AsyncTask behaviour into a derived class

4 files changed, 33 insertions, 26 deletions

diff --git a/android/src/com/artifex/mupdf/MuPDFActivity.java b/android/src/com/artifex/mupdf/MuPDFActivity.java
index da3c024e..bdc1971f 100644
--- a/android/src/com/artifex/mupdf/MuPDFActivity.java
+++ b/android/src/com/artifex/mupdf/MuPDFActivity.java
@@ -10,7 +10,6 @@ import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.graphics.RectF;
 import android.net.Uri;
-import android.os.AsyncTask;
 import android.os.Bundle;
 import android.os.Handler;
 import android.text.Editable;
@@ -93,7 +92,7 @@ public class MuPDFActivity extends Activity
 	private ImageButton  mSearchBack;
 	private ImageButton  mSearchFwd;
 	private EditText     mSearchText;
-	private AsyncTask<Integer,Integer,SearchTaskResult> mSearchTask;
+	private SafeAsyncTask<Integer,Integer,SearchTaskResult> mSearchTask;
 	//private SearchTaskResult mSearchTaskResult;
 	private AlertDialog.Builder mAlertBuilder;
 	private LinkState    mLinkState = LinkState.DEFAULT;
@@ -648,7 +647,7 @@ public class MuPDFActivity extends Activity
 		});
 		progressDialog.setMax(core.countPages());
 
-		mSearchTask = new AsyncTask<Integer,Integer,SearchTaskResult>() {
+		mSearchTask = new SafeAsyncTask<Integer,Integer,SearchTaskResult>() {
 			@Override
 			protected SearchTaskResult doInBackground(Integer... params) {
 				int index;
@@ -712,6 +711,6 @@ public class MuPDFActivity extends Activity
 			}
 		};
 
-		mSearchTask.execute(new Integer(direction));
+		mSearchTask.safeExecute(new Integer(direction));
 	}
 }
diff --git a/android/src/com/artifex/mupdf/MuPDFPageAdapter.java b/android/src/com/artifex/mupdf/MuPDFPageAdapter.java
index 4587e244..e015ceb4 100644
--- a/android/src/com/artifex/mupdf/MuPDFPageAdapter.java
+++ b/android/src/com/artifex/mupdf/MuPDFPageAdapter.java
@@ -48,7 +48,7 @@ public class MuPDFPageAdapter extends BaseAdapter {
 			// Page size as yet unknown. Blank it for now, and
 			// start a background task to find the size
 			pageView.blank(position);
-			AsyncTask<Void,Void,PointF> sizingTask = new AsyncTask<Void,Void,PointF>() {
+			SafeAsyncTask<Void,Void,PointF> sizingTask = new SafeAsyncTask<Void,Void,PointF>() {
 				@Override
 				protected PointF doInBackground(Void... arg0) {
 					return mCore.getPageSize(position);
@@ -65,21 +65,8 @@ public class MuPDFPageAdapter extends BaseAdapter {
 						pageView.setPage(position, result);
 				}
 			};
-			try
-			{
-				sizingTask.execute((Void)null);
-			}
-			catch (java.util.concurrent.RejectedExecutionException e)
-			{
-				// If we can't do it in the background, just
-				// do it in the foreground.
-				PointF result = mCore.getPageSize(position);
-				mPageSizes.put(position, result);
-				// Check that this view hasn't been reused for
-				// another page since we started
-				if (pageView.getPage() == position)
-					pageView.setPage(position, result);
-			}
+
+			sizingTask.safeExecute((Void)null);
 		}
 		return pageView;
 	}
diff --git a/android/src/com/artifex/mupdf/PageView.java b/android/src/com/artifex/mupdf/PageView.java
index b0507182..123d5037 100644
--- a/android/src/com/artifex/mupdf/PageView.java
+++ b/android/src/com/artifex/mupdf/PageView.java
@@ -54,12 +54,12 @@ public abstract class PageView extends ViewGroup {
 
 	private       ImageView mEntire; // Image rendered at minimum zoom
 	private       Bitmap    mEntireBm;
-	private       AsyncTask<Void,Void,LinkInfo[]> mDrawEntire;
+	private       SafeAsyncTask<Void,Void,LinkInfo[]> mDrawEntire;
 
 	private       Point     mPatchViewSize; // View size on the basis of which the patch was created
 	private       Rect      mPatchArea;
 	private       ImageView mPatch;
-	private       AsyncTask<PatchInfo,Void,PatchInfo> mDrawPatch;
+	private       SafeAsyncTask<PatchInfo,Void,PatchInfo> mDrawPatch;
 	private       RectF     mSearchBoxes[];
 	private       LinkInfo  mLinks[];
 	private       View      mSearchView;
@@ -144,7 +144,7 @@ public abstract class PageView extends ViewGroup {
 		}
 
 		// Render the page in the background
-		mDrawEntire = new AsyncTask<Void,Void,LinkInfo[]>() {
+		mDrawEntire = new SafeAsyncTask<Void,Void,LinkInfo[]>() {
 			protected LinkInfo[] doInBackground(Void... v) {
 				drawPage(mEntireBm, mSize.x, mSize.y, 0, 0, mSize.x, mSize.y);
 				return getLinkInfo();
@@ -177,7 +177,7 @@ public abstract class PageView extends ViewGroup {
 			}
 		};
 
-		mDrawEntire.execute();
+		mDrawEntire.safeExecute();
 
 		if (mSearchView == null) {
 			mSearchView = new View(mContext) {
@@ -319,7 +319,7 @@ public abstract class PageView extends ViewGroup {
 
 			Bitmap bm = Bitmap.createBitmap(patchArea.width(), patchArea.height(), Bitmap.Config.ARGB_8888);
 
-			mDrawPatch = new AsyncTask<PatchInfo,Void,PatchInfo>() {
+			mDrawPatch = new SafeAsyncTask<PatchInfo,Void,PatchInfo>() {
 				protected PatchInfo doInBackground(PatchInfo... v) {
 					drawPage(v[0].bm, v[0].patchViewSize.x, v[0].patchViewSize.y,
 									  v[0].patchArea.left, v[0].patchArea.top,
@@ -339,7 +339,7 @@ public abstract class PageView extends ViewGroup {
 				}
 			};
 
-			mDrawPatch.execute(new PatchInfo(bm, patchViewSize, patchArea));
+			mDrawPatch.safeExecute(new PatchInfo(bm, patchViewSize, patchArea));
 		}
 	}
 
diff --git a/android/src/com/artifex/mupdf/SafeAsyncTask.java b/android/src/com/artifex/mupdf/SafeAsyncTask.java
new file mode 100644
index 00000000..fc1aa3cf
--- /dev/null
+++ b/android/src/com/artifex/mupdf/SafeAsyncTask.java
@@ -0,0 +1,21 @@
+package com.artifex.mupdf;
+
+import android.os.AsyncTask;
+import java.util.concurrent.RejectedExecutionException;
+
+
+public abstract class SafeAsyncTask<Params, Progress, Result> extends AsyncTask<Params, Progress, Result> {
+	public void safeExecute(Params... params) {
+		try {
+			execute(params);
+		} catch(RejectedExecutionException e) {
+			// Failed to start in the background, so do it in the foreground
+			onPreExecute();
+			if (isCancelled()) {
+				onCancelled();
+			} else {
+				onPostExecute(doInBackground(params));
+			}
+		}
+	}
+}