diff --git a/camera2/public/src/com/android/ex/camera2/blocking/BlockingOfflineSessionCallback.java b/camera2/public/src/com/android/ex/camera2/blocking/BlockingOfflineSessionCallback.java
new file mode 100644
index 0000000..021dcd7
--- /dev/null
+++ b/camera2/public/src/com/android/ex/camera2/blocking/BlockingOfflineSessionCallback.java
@@ -0,0 +1,254 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * 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 com.android.ex.camera2.blocking;
+
+import android.hardware.camera2.CameraDevice;
+import android.hardware.camera2.CameraOfflineSession;
+import android.hardware.camera2.CameraOfflineSession.CameraOfflineSessionCallback;
+import android.os.Handler;
+import android.os.SystemClock;
+import android.util.Log;
+
+import com.android.ex.camera2.exceptions.TimeoutRuntimeException;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A camera offline session listener that implements blocking operations on state changes.
+ *
+ * <p>Provides wait calls that block until the next unobserved state of the
+ * requested type arrives. Unobserved states are states that have occurred since
+ * the last wait, or that will be received from the camera device in the
+ * future.</p>
+ *
+ * <p>Pass-through all offline callbacks to the proxy.</p>
+ *
+ */
+public class BlockingOfflineSessionCallback
+        extends CameraOfflineSession.CameraOfflineSessionCallback {
+    private static final String TAG = "BlockingOfflineSessionCallback";
+    private static final boolean VERBOSE = Log.isLoggable(TAG, Log.VERBOSE);
+
+    private final CameraOfflineSession.CameraOfflineSessionCallback mProxy;
+
+    // Guards mWaiting
+    private final Object mLock = new Object();
+    private boolean mWaiting = false;
+
+    private final LinkedBlockingQueue<Integer> mRecentStates =
+            new LinkedBlockingQueue<Integer>();
+
+    private void setCurrentState(int state) {
+        if (VERBOSE) Log.v(TAG, "Offline session state now " + stateToString(state));
+        try {
+            mRecentStates.put(state);
+        } catch (InterruptedException e) {
+            throw new RuntimeException("Unable to set offline session state", e);
+        }
+    }
+
+    private static final String[] mStateNames = {
+        "STATE_UNINITIALIZED",
+        "STATE_READY",
+        "STATE_IDLE",
+        "STATE_CLOSED",
+        "STATE_ERROR",
+        "STATE_SWITCH_FAILED",
+    };
+
+    /**
+     * Offline session has not reported any state yet
+     */
+    public static final int STATE_UNINITIALIZED = -1;
+
+    /**
+     * The offline session moves to ready state in case of successful offline switch
+     */
+    public static final int STATE_READY = 0;
+
+    /**
+     * The offline session moves to idle state once all offline capture requests complete
+     */
+    public static final int STATE_IDLE = 1;
+
+    /**
+     * The offline session is closed
+     */
+    public static final int STATE_CLOSED = 2;
+
+    /**
+     * The offline session has encountered a fatal error
+     */
+    public static final int STATE_ERROR = 3;
+
+    /**
+     * The offline session failed during the offline switch
+     */
+    public static final int STATE_SWITCH_FAILED = 4;
+
+    /**
+     * Total number of reachable states
+     */
+    private static final int NUM_STATES = 5;
+
+    public BlockingOfflineSessionCallback() {
+        mProxy = null;
+    }
+
+    public BlockingOfflineSessionCallback(
+            CameraOfflineSession.CameraOfflineSessionCallback listener) {
+        mProxy = listener;
+    }
+
+    @Override
+    public void onReady(CameraOfflineSession session) {
+        if (mProxy != null) {
+            mProxy.onReady(session);
+        }
+        setCurrentState(STATE_READY);
+    }
+
+    @Override
+    public void onSwitchFailed(CameraOfflineSession session) {
+        if (mProxy != null) {
+            mProxy.onSwitchFailed(session);
+        }
+        setCurrentState(STATE_SWITCH_FAILED);
+    }
+
+    @Override
+    public void onIdle(CameraOfflineSession session) {
+        if (mProxy != null) {
+            mProxy.onIdle(session);
+        }
+        setCurrentState(STATE_IDLE);
+    }
+
+    @Override
+    public void onError(CameraOfflineSession session, int error) {
+        if (mProxy != null) {
+            mProxy.onError(session, error);
+        }
+        setCurrentState(STATE_ERROR);
+    }
+
+    @Override
+    public void onClosed(CameraOfflineSession session) {
+        if (mProxy != null) {
+            mProxy.onClosed(session);
+        }
+        setCurrentState(STATE_CLOSED);
+    }
+
+    /**
+     * Wait until the desired state is observed, checking all state
+     * transitions since the last state that was waited on.
+     *
+     * <p>Note: Only one waiter allowed at a time!</p>
+     *
+     * @param state state to observe a transition to
+     * @param timeout how long to wait in milliseconds
+     *
+     * @throws TimeoutRuntimeException if the desired state is not observed before timeout.
+     */
+    public void waitForState(int state, long timeout) {
+        Integer[] stateArray = { state };
+
+        waitForAnyOfStates(Arrays.asList(stateArray), timeout);
+    }
+
+    /**
+     * Wait until the one of the desired states is observed, checking all
+     * state transitions since the last state that was waited on.
+     *
+     * <p>Note: Only one waiter allowed at a time!</p>
+     *
+     * @param states Set of desired states to observe a transition to.
+     * @param timeout how long to wait in milliseconds
+     *
+     * @return the state reached
+     * @throws TimeoutRuntimeException if none of the states is observed before timeout.
+     *
+     */
+    public int waitForAnyOfStates(Collection<Integer> states, final long timeout) {
+        synchronized (mLock) {
+            if (mWaiting) {
+                throw new IllegalStateException("Only one waiter allowed at a time");
+            }
+            mWaiting = true;
+        }
+        if (VERBOSE) {
+            StringBuilder s = new StringBuilder("Waiting for state(s) ");
+            appendStates(s, states);
+            Log.v(TAG, s.toString());
+        }
+
+        Integer nextState = null;
+        long timeoutLeft = timeout;
+        long startMs = SystemClock.elapsedRealtime();
+        try {
+            while ((nextState = mRecentStates.poll(timeoutLeft, TimeUnit.MILLISECONDS))
+                    != null) {
+                if (VERBOSE) {
+                    Log.v(TAG, "  Saw transition to " + stateToString(nextState));
+                }
+                if (states.contains(nextState)) break;
+                long endMs = SystemClock.elapsedRealtime();
+                timeoutLeft -= (endMs - startMs);
+                startMs = endMs;
+            }
+        } catch (InterruptedException e) {
+            throw new UnsupportedOperationException("Does not support interrupts on waits", e);
+        }
+
+        synchronized (mLock) {
+            mWaiting = false;
+        }
+
+        if (!states.contains(nextState)) {
+            StringBuilder s = new StringBuilder("Timed out after ");
+            s.append(timeout);
+            s.append(" ms waiting for state(s) ");
+            appendStates(s, states);
+
+            throw new TimeoutRuntimeException(s.toString());
+        }
+
+        return nextState;
+    }
+
+    /**
+     * Convert state integer to a String
+     */
+    public static String stateToString(int state) {
+        return mStateNames[state + 1];
+    }
+
+    /**
+     * Append all states to string
+     */
+    public static void appendStates(StringBuilder s, Collection<Integer> states) {
+        boolean start = true;
+        for (Integer state : states) {
+            if (!start) s.append(" ");
+            s.append(stateToString(state));
+            start = false;
+        }
+    }
+}