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/*
* Copyright (C) 2014 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 android.hardware.camera2.dispatch;
import android.hardware.camera2.utils.UncheckedThrow;
import android.os.Handler;
import android.util.Log;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import static com.android.internal.util.Preconditions.*;
/**
* Forward all interface calls into a handler by posting it as a {@code Runnable}.
*
* <p>All calls will return immediately; functions with return values will return a default
* value of {@code null}, {@code 0}, or {@code false} where that value is legal.</p>
*
* <p>Any exceptions thrown on the handler while trying to invoke a method
* will be re-thrown. Throwing checked exceptions on a handler which doesn't expect any
* checked exceptions to be thrown will result in "undefined" behavior
* (although in practice it is usually thrown as normal).</p>
*/
public class HandlerDispatcher<T> implements Dispatchable<T> {
private static final String TAG = "HandlerDispatcher";
private final Dispatchable<T> mDispatchTarget;
private final Handler mHandler;
/**
* Create a dispatcher that forwards it's dispatch calls by posting
* them onto the {@code handler} as a {@code Runnable}.
*
* @param dispatchTarget the destination whose method calls will be redirected into the handler
* @param handler all calls into {@code dispatchTarget} will be posted onto this handler
* @param <T> the type of the element you want to wrap.
* @return a dispatcher that will forward it's dispatch calls to a handler
*/
public HandlerDispatcher(Dispatchable<T> dispatchTarget, Handler handler) {
mDispatchTarget = checkNotNull(dispatchTarget, "dispatchTarget must not be null");
mHandler = checkNotNull(handler, "handler must not be null");
}
@Override
public Object dispatch(final Method method, final Object[] args) throws Throwable {
mHandler.post(new Runnable() {
@Override
public void run() {
try {
mDispatchTarget.dispatch(method, args);
} catch (InvocationTargetException e) {
Throwable t = e.getTargetException();
// Potential UB. Hopefully 't' is a runtime exception.
UncheckedThrow.throwAnyException(t);
} catch (IllegalAccessException e) {
// Impossible
Log.wtf(TAG, "IllegalAccessException while invoking " + method, e);
} catch (IllegalArgumentException e) {
// Impossible
Log.wtf(TAG, "IllegalArgumentException while invoking " + method, e);
} catch (Throwable e) {
UncheckedThrow.throwAnyException(e);
}
}
});
// TODO handle primitive return values that would avoid NPE if unboxed
return null;
}
}
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