我們看下android 在啓動的時候，會設置一個默認的UncaughtExceptionHandler .
名字叫做LoggingHandler 。專門負責打印日誌：
代碼 如下：
/*
* Copyright (C) 2006 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.internal.os;
/**
* Main entry point for runtime initialization. Not for
* public consumption.
* @hide
*/
public class RuntimeInit {
final static String TAG = "AndroidRuntime";
final static boolean DEBUG = false;
/** true if commonInit() has been called */
@UnsupportedAppUsage
private static boolean initialized;
@UnsupportedAppUsage
private static IBinder mApplicationObject;
private static volatile boolean mCrashing = false;
private static final native void nativeFinishInit();
private static final native void nativeSetExitWithoutCleanup(boolean exitWithoutCleanup);
private static int Clog_e(String tag, String msg, Throwable tr) {
return Log.printlns(Log.LOG_ID_CRASH, Log.ERROR, tag, msg, tr);
}
/**
* Logs a message when a thread encounters an uncaught exception. By
* default, {@link KillApplicationHandler} will terminate this process later,
* but apps can override that behavior.
*/
private static class LoggingHandler implements Thread.UncaughtExceptionHandler {
public volatile boolean mTriggered = false;
@Override
public void uncaughtException(Thread t, Throwable e) {
mTriggered = true;
// Don't re-enter if KillApplicationHandler has already run
if (mCrashing) return;
// mApplicationObject is null for non-zygote java programs (e.g. "am")
// There are also apps running with the system UID. We don't want the
// first clause in either of these two cases, only for system_server.
if (mApplicationObject == null && (Process.SYSTEM_UID == Process.myUid())) {
Clog_e(TAG, "*** FATAL EXCEPTION IN SYSTEM PROCESS: " + t.getName(), e);
} else {
StringBuilder message = new StringBuilder();
// The "FATAL EXCEPTION" string is still used on Android even though
// apps can set a custom UncaughtExceptionHandler that renders uncaught
// exceptions non-fatal.
message.append("FATAL EXCEPTION: ").append(t.getName()).append("\n");
final String processName = ActivityThread.currentProcessName();
if (processName != null) {
message.append("Process: ").append(processName).append(", ");
}
message.append("PID: ").append(Process.myPid());
Clog_e(TAG, message.toString(), e);
}
}
}
/**
* Handle application death from an uncaught exception. The framework
* catches these for the main threads, so this should only matter for
* threads created by applications. Before this method runs, the given
* instance of {@link LoggingHandler} should already have logged details
* (and if not it is run first).
*/
private static class KillApplicationHandler implements Thread.UncaughtExceptionHandler {
private final LoggingHandler mLoggingHandler;
/**
* Create a new KillApplicationHandler that follows the given LoggingHandler.
* If {@link #uncaughtException(Thread, Throwable) uncaughtException} is called
* on the created instance without {@code loggingHandler} having been triggered,
* {@link LoggingHandler#uncaughtException(Thread, Throwable)
* loggingHandler.uncaughtException} will be called first.
*
* @param loggingHandler the {@link LoggingHandler} expected to have run before
* this instance's {@link #uncaughtException(Thread, Throwable) uncaughtException}
* is being called.
*/
public KillApplicationHandler(LoggingHandler loggingHandler) {
this.mLoggingHandler = Objects.requireNonNull(loggingHandler);
}
@Override
public void uncaughtException(Thread t, Throwable e) {
try {
ensureLogging(t, e);
// Don't re-enter -- avoid infinite loops if crash-reporting crashes.
if (mCrashing) return;
mCrashing = true;
// Try to end profiling. If a profiler is running at this point, and we kill the
// process (below), the in-memory buffer will be lost. So try to stop, which will
// flush the buffer. (This makes method trace profiling useful to debug crashes.)
if (ActivityThread.currentActivityThread() != null) {
ActivityThread.currentActivityThread().stopProfiling();
}
// Bring up crash dialog, wait for it to be dismissed
ActivityManager.getService().handleApplicationCrash(
mApplicationObject, new ApplicationErrorReport.ParcelableCrashInfo(e));
} catch (Throwable t2) {
if (t2 instanceof DeadObjectException) {
// System process is dead; ignore
} else {
try {
Clog_e(TAG, "Error reporting crash", t2);
} catch (Throwable t3) {
// Even Clog_e() fails! Oh well.
}
}
} finally {
// Try everything to make sure this process goes away.
Process.killProcess(Process.myPid());
System.exit(10);
}
}
/**
* Ensures that the logging handler has been triggered.
*
* See b/73380984. This reinstates the pre-O behavior of
*
* {@code thread.getUncaughtExceptionHandler().uncaughtException(thread, e);}
*
* logging the exception (in addition to killing the app). This behavior
* was never documented / guaranteed but helps in diagnostics of apps
* using the pattern.
*
* If this KillApplicationHandler is invoked the "regular" way (by
* {@link Thread#dispatchUncaughtException(Throwable)
* Thread.dispatchUncaughtException} in case of an uncaught exception)
* then the pre-handler (expected to be {@link #mLoggingHandler}) will already
* have run. Otherwise, we manually invoke it here.
*/
private void ensureLogging(Thread t, Throwable e) {
if (!mLoggingHandler.mTriggered) {
try {
mLoggingHandler.uncaughtException(t, e);
} catch (Throwable loggingThrowable) {
// Ignored.
}
}
}
}
所以，只要是java層崩潰了，就可以搜索AndroidRuntime