Android BadTokenException 问题解决

前言

今天测试过程中发现了“android.view.WindowManager$BadTokenException”问题，这里记录一下解决方法。（PS：第一款应用上线了，感觉BUG还是比较多，感觉因为这个应用，能不能过试用期都是问题了，只能坚持加油了）。

问题分析

这种问题其实在错误日志中都能给出很好的提示，下面贴一下部分有用的错误日志，如下所示：

android.view.WindowManager$BadTokenException,ViewRootImpl.java,android.view.ViewRootImpl,setView,640,android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@444628b8 is not valid, is your activity running? 

通过日志，可以知道，这种问题一般是因为在AsyncTask中的onPostExecute中执行了启动Dialog操作，但是当前的Activity已经被销毁了，写一个错误代码复现一下该问题：

package com.example.testlibrary;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.DialogInterface.OnClickListener;import android.os.AsyncTask;import android.os.Bundle;public class MainActivity extends Activity {private UpdateUIAsyncTask asyncTask;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);updateUIProcess();}private void updateUIProcess() {asyncTask = new UpdateUIAsyncTask();asyncTask.execute();}private class UpdateUIAsyncTask extends AsyncTask<Void, Void, Boolean> {@Overrideprotected void onPostExecute(Boolean result) {if (!isCancelled() && result) {AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this).setTitle("标题").setMessage("这是内容").setPositiveButton("确定", new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}}).setNegativeButton("取消", new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}});AlertDialog dialog = builder.create();dialog.show();}}@Overrideprotected Boolean doInBackground(Void... params) {if (!isCancelled()) {try {Thread.sleep(6000);} catch (InterruptedException e) {return false;}return true;}return true;}}}

启动应用程序，并且在6s以内退出应用程序，返回建即可，就会发现应用程序出现了异常：

解决方案

如果当前Activity已经被销毁（无论是调用finish()或者按back、home键），但是Activity中的AsyncTask异步任务并没有结束，并且在onPostExecute中调用了alertDialog.show()就会出现：

android.view.WindowManager$BadTokenException: Unable to add window — token android.os.BinderProxy@4272a800 is not valid; is your activity running?.

解决方法也很简单：在alertDialog.show()执行之前，判断当前的Activity是否已经销毁了，可以使用android提供的isFinishing()方法。同时，在Activity中也应该增加清理AsyncTask的操作，示例代码如下：

package com.example.testlibrary;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.DialogInterface.OnClickListener;import android.os.AsyncTask;import android.os.Bundle;public class MainActivity extends Activity {private UpdateUIAsyncTask asyncTask;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);updateUIProcess();}@Overrideprotected void onDestroy() {// 增加清理AysncTask操作if (asyncTask != null && asyncTask.getStatus() != AsyncTask.Status.FINISHED) {asyncTask.cancel(true);}super.onDestroy();}private void updateUIProcess() {asyncTask = new UpdateUIAsyncTask();asyncTask.execute();}private class UpdateUIAsyncTask extends AsyncTask<Void, Void, Boolean> {@Overrideprotected void onPostExecute(Boolean result) {// show dialog之前增加判断当前Activity是否finish操作if (!isCancelled() && result && MainActivity.this != null && !MainActivity.this.isFinishing()) {AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this).setTitle("标题").setMessage("这是内容").setPositiveButton("确定", new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}}).setNegativeButton("取消", new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}});AlertDialog dialog = builder.create();dialog.show();}}@Overrideprotected Boolean doInBackground(Void... params) {if (!isCancelled()) {try {Thread.sleep(6000);} catch (InterruptedException e) {return false;}return true;}return true;}}}