persist presenters - fight against process death

sample/src/main/java/net/grandcentrix/thirtyinch/sample/HelloWorldPresenter.java

@@ -20,7 +20,9 @@
 import net.grandcentrix.thirtyinch.rx.RxTiPresenterUtils;
 
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 
+import java.math.BigInteger;
 import java.util.concurrent.TimeUnit;
 
 import rx.Observable;
@@ -66,7 +68,16 @@ public void call(final Void aVoid) {
     protected void onCreate() {
         super.onCreate();
 
-        mText.onNext("Hello World!");
+        final byte[] state = getPersistentState();
+        if (state != null) {
+            mCounter = new BigInteger(state).intValue();
+        }
+
+        if (mCounter == 0) {
+            mText.onNext("Click the Button");
+        } else {
+            mText.onNext("Count: " + mCounter);
+        }
 
         rxSubscriptionHelper.manageSubscription(Observable.interval(0, 1, TimeUnit.SECONDS)
                 .compose(RxTiPresenterUtils.<Long>deliverLatestToView(this))
@@ -105,6 +116,13 @@ public void call(final Integer integer) {
                 .subscribe());
     }
 
+    @Nullable
+    @Override
+    protected byte[] onSavePersistentState() {
+        final byte[] bytes = BigInteger.valueOf(mCounter).toByteArray();
+        return bytes;
+    }
+
     /**
      * fake a heavy calculation
      */

sample/src/main/java/net/grandcentrix/thirtyinch/sample/SampleApp.java

@@ -16,7 +16,10 @@
 package net.grandcentrix.thirtyinch.sample;
 
 
+import net.grandcentrix.thirtyinch.TiConfiguration;
 import net.grandcentrix.thirtyinch.TiLog;
+import net.grandcentrix.thirtyinch.TiPresenter;
+import net.grandcentrix.thirtyinch.serialize.PresenterStateSerializer;
 
 import android.app.Application;
 
@@ -28,5 +31,9 @@ public void onCreate() {
 
         // log ThirtyInch output with logcat
         TiLog.setLogger(TiLog.LOGCAT);
+
+        TiPresenter.setDefaultConfig(new TiConfiguration.Builder()
+                .setPresenterSerializer(new PresenterStateSerializer(this))
+                .build());
     }
 }

thirtyinch/src/main/java/net/grandcentrix/thirtyinch/TiConfiguration.java

@@ -23,6 +23,7 @@
 import android.app.Activity;
 import android.app.Application;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatActivity;
 
 /**
@@ -144,6 +145,12 @@ public Builder setDistinctUntilChangedInterceptorEnabled(final boolean enabled)
             return this;
         }
 
+        //TODO documentation
+        public Builder setPresenterSerializer(TiPresenterSerializer serializer) {
+            mConfig.mPresenterSerializer = serializer;
+            return this;
+        }
+
         /**
          * When set to <code>true</code> the {@link TiPresenter} will be restored when the {@link
          * Activity} recreates due to a configuration changes such as the orientation change.
@@ -197,7 +204,6 @@ public Builder setUseStaticSaviorToRetain(final boolean enabled) {
             mConfig.mUseStaticSaviorToRetain = enabled;
             return this;
         }
-
     }
 
     public static final TiConfiguration DEFAULT = new Builder().build();
@@ -206,6 +212,8 @@ public Builder setUseStaticSaviorToRetain(final boolean enabled) {
 
     private boolean mDistinctUntilChangedInterceptorEnabled = true;
 
+    private TiPresenterSerializer mPresenterSerializer;
+
     private boolean mRetainPresenter = true;
 
     private boolean mUseStaticSaviorToRetain = true;
@@ -216,6 +224,11 @@ public Builder setUseStaticSaviorToRetain(final boolean enabled) {
     private TiConfiguration() {
     }
 
+    @Nullable
+    public TiPresenterSerializer getPresenterSerializer() {
+        return mPresenterSerializer;
+    }
+
     public boolean isCallOnMainThreadInterceptorEnabled() {
         return mCallOnMainThreadInterceptorEnabled;
     }

thirtyinch/src/main/java/net/grandcentrix/thirtyinch/TiPresenter.java

@@ -28,6 +28,11 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Queue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.LinkedBlockingQueue;
 
 /**
@@ -85,6 +90,13 @@ public enum State {
 
     private final TiConfiguration mConfig;
 
+    private String mId;
+
+    private final ExecutorService mPersistentStateExecutorService =
+            Executors.newSingleThreadExecutor();
+
+    private Future<byte[]> mPersistentStateFuture;
+
     private LinkedBlockingQueue<ViewAction<V>> mPostponedViewActions = new LinkedBlockingQueue<>();
 
     private State mState = State.INITIALIZED;
@@ -95,11 +107,11 @@ public static void setDefaultConfig(final TiConfiguration config) {
         sDefaultConfig = config;
     }
 
-
     public TiPresenter() {
         this(sDefaultConfig);
     }
 
+
     /**
      * Constructs a presenter with a different configuration then the default one. Change the
      * default configuration with {@link #setDefaultConfig(TiConfiguration)}
@@ -135,7 +147,6 @@ public void onRemove() {
         };
     }
 
-
     /**
      * bind a new view to this presenter.
      *
@@ -237,6 +248,11 @@ public final void destroy() {
 
         // release everything, no new states will be posted
         mLifecycleObservers.clear();
+
+        final TiPresenterSerializer serializer = getConfig().getPresenterSerializer();
+        if (serializer != null) {
+            serializer.free(this);
+        }
     }
 
     /**
@@ -272,6 +288,11 @@ public final void detachView() {
         mView = null;
     }
 
+    public void generatNewId() {
+        final String id = getClass().getSimpleName() + ":" + hashCode() + ":" + System.nanoTime();
+        setId(id);
+    }
+
     /**
      * @return the presenter configuration
      */
@@ -280,6 +301,13 @@ public TiConfiguration getConfig() {
         return mConfig;
     }
 
+    /**
+     * @return A unique id of this instance.
+     */
+    public final String getId() {
+        return mId;
+    }
+
     /**
      * @return the current lifecycle state
      */
@@ -315,6 +343,51 @@ public boolean isViewAttached() {
         return mState == State.VIEW_ATTACHED;
     }
 
+    //TODO documentation
+    public void persistState() {
+        mPersistentStateExecutorService.submit(new Runnable() {
+            @Override
+            public void run() {
+                TiPresenterSerializer serializer = mConfig.getPresenterSerializer();
+                if (serializer != null) {
+                    final byte[] data = onSavePersistentState();
+                    serializer.serialize(TiPresenter.this, data);
+                }
+            }
+        });
+    }
+
+    @NonNull
+    public Future<byte[]> prefetchPersistentState() {
+        mPersistentStateFuture = mPersistentStateExecutorService.submit(new Callable<byte[]>() {
+            @Override
+            public byte[] call() throws Exception {
+                final TiPresenterSerializer serializer = mConfig.getPresenterSerializer();
+                if (serializer != null) {
+                    return serializer.deserialize(TiPresenter.this);
+                }
+                return null;
+            }
+        });
+
+        return mPersistentStateFuture;
+    }
+
+    /**
+     * the id can only be set once
+     */
+    public void setId(@NonNull final String id) {
+        //noinspection ConstantConditions
+        if (id == null) {
+            throw new IllegalArgumentException("the id cannot be null");
+        }
+        if (mId == null) {
+            mId = id;
+        } else {
+            throw new IllegalArgumentException("the id can only be set once");
+        }
+    }
+
     @Override
     public String toString() {
         final String viewName;
@@ -329,6 +402,24 @@ public String toString() {
                 + "{view = " + viewName + "}";
     }
 
+    //TODO documentation
+    @Nullable
+    protected byte[] getPersistentState() {
+        Future<byte[]> future = mPersistentStateFuture;
+        if (future == null) {
+            future = mPersistentStateFuture = prefetchPersistentState();
+        }
+        try {
+            // wait for result even when not prefetched
+            return future.get();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        } catch (ExecutionException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
     /**
      * Gives access to the postponed actions while the view is not attached.
      *
@@ -400,6 +491,12 @@ protected void onDetachView() {
         mCalled = true;
     }
 
+    //TODO documentation
+    @Nullable
+    protected byte[] onSavePersistentState() {
+        return null;
+    }
+
     /**
      * @deprecated use {@link #onDetachView()} instead
      */

thirtyinch/src/main/java/net/grandcentrix/thirtyinch/TiPresenterSerializer.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2016 grandcentrix GmbH
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.grandcentrix.thirtyinch;
+
+import android.support.annotation.NonNull;
+
+public interface TiPresenterSerializer {
+
+    @NonNull
+    byte[] deserialize(@NonNull TiPresenter presenter);
+
+    void free(@NonNull TiPresenter presenter);
+
+    void serialize(@NonNull final TiPresenter presenter, final byte[] data);
+}

thirtyinch/src/main/java/net/grandcentrix/thirtyinch/internal/PresenterSavior.java

@@ -52,7 +52,7 @@ public TiPresenter recover(final String id) {
     }
 
     public String safe(@NonNull final TiPresenter presenter) {
-        final String id = generateId(presenter);
+        final String id = presenter.getId();
         TiLog.v(TAG, "safe presenter with id " + id + " " + presenter);
         mPresenters.put(id, presenter);
         return id;
@@ -62,10 +62,4 @@ public String safe(@NonNull final TiPresenter presenter) {
     void clear() {
         mPresenters.clear();
     }
-
-    private String generateId(@NonNull final TiPresenter presenter) {
-        return presenter.getClass().getSimpleName()
-                + ":" + presenter.hashCode()
-                + ":" + System.nanoTime();
-    }
 }