Android使用UncaughtExceptionHandler捕获异常－－并非如此

1. UncaughtExceptionHandler简介

网上搜索Android崩溃处理之类的，能看到很多关于UncaughtExceptionHandler的文章，包括常用的一些处理方式。

但是，只有很小一部分文章提到这个问题：UncauchtExceptionHandler的对象是线程，而不是进程或app。

2. UncaughtExceptionHandler解析

    /**     * Interface for handlers invoked when a <strong><span style="color:#ff0000;"><tt>Thread</tt> abruptly</span></strong>     * <strong><span style="color:#ff0000;">terminates</span></strong> due to an uncaught exception.     * <p>When a thread is about to terminate due to an uncaught exception     * the Java Virtual Machine will query the thread for its     * <tt>UncaughtExceptionHandler</tt> using     * {@link #getUncaughtExceptionHandler} and will invoke the handler's     * <tt>uncaughtException</tt> method, passing the thread and the     * exception as arguments.     * If a thread has not had its <tt>UncaughtExceptionHandler</tt>     * explicitly set, then its <tt>ThreadGroup</tt> object acts as its     * <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object     * has no     * special requirements for dealing with the exception, it can forward     * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler     * default uncaught exception handler}.     *     * @see #setDefaultUncaughtExceptionHandler     * @see #setUncaughtExceptionHandler     * @see ThreadGroup#uncaughtException     * @since 1.5     */    public interface UncaughtExceptionHandler {        /**         * Method invoked when <strong><span style="color:#ff0000;">the given thread</span></strong> terminates due to the         * given uncaught exception.         * <p>Any exception thrown by this method will be ignored by the         * Java Virtual Machine.         * @param t the thread         * @param e the exception         */        void uncaughtException(Thread t, Throwable e);    }

从源码中可以看出，UncaughtExceptionHandler自JDK1.5开始可用，处理对象为相关线程

3. UncaughtExceptionHandler使用

这里只介绍使用框架，不引入业务逻辑：

CrashHandler的单例模式简单实现：（单例模式选了一种最易理解的写法，因为单例模式不在这篇博客的讨论范围之内）

public class CrashHandler implements UncaughtExceptionHandler {// Singleton Instanceprivate static CrashHandler gInstance = null;private CrashHandler() {}private static class InstanceHolder {static CrashHandler instance = new CrashHandler();}public static CrashHandler getInstance() {if (gInstance == null) {gInstance = new CrashHandler();}return InstanceHolder.instance;}public void init() {Thread.setDefaultUncaughtExceptionHandler(this);}@Overridepublic void uncaughtException(Thread t, Throwable e) {// TODO}}

MyApplication绑定UI主线程与CrashHandler。

public class MyApplication extends Application {@Overridepublic void onCreate() {super.onCreate();CrashHandler.getInstance().init();}}

4. 注意

1. 如果CrashHandler中未调用Systen.exit(int)之类的方法，整个app就会僵死：不会崩溃，但对于任何触摸等动作也无响应。

2. 如果把以下这段异常代码加入UI线程，CrashHandler可以捕获java.lang.ArithmeticException: divide by zero；

    但是，如果把这段异常代码加入非UI线程中，CrashHandler无法捕获异常。但是，app还是会崩溃。

int x = 1/0;