Android BadTokenException 問題解決

標籤：android   des   blog   http   java   使用   os   io   

前言今天測試過程中發現了“android.view.WindowManager$BadTokenException”問題，這裡記錄一下解決方案。（PS：第一款應用上線了，感覺BUG還是比較多，感覺因為這個應用，能不能過試用期都是問題了，只能堅持加油了）。
問題分析這種問題其實在錯誤記錄檔中都能給出很好的提示，下面貼一下部分有用的錯誤記錄檔，如下所示：

android.view.WindowManager$BadTokenException,ViewRootImpl.java,android.view.ViewRootImpl,setView,640,android.view.WindowManager$BadTokenException: Unable to add window -- token [email protected] is not valid, is your activity running? 

通過日誌，可以知道，這種問題一般是因為在AsyncTask中的onPostExecute中執行了啟動Dialog操作，但是當前的Activity已經被銷毀了，寫一個錯誤碼複現一下該問題：

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("標題").setMessage("這是內容").setPositiveButton("確定", 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;}}}

啟動應用程式，並且在6s以內退出應用程式，返回建即可，就會發現應用程式出現了異常：
解決方案如果當前Activity已經被銷毀（無論是調用finish()或者按back、home鍵），但是Activity中的AsyncTask非同步任務並沒有結束，並且在onPostExecute中調用了alertDialog.show()就會出現：

android.view.WindowManager$BadTokenException: Unable to add window — token [email protected] is not valid; is your activity running?.

解決方案也很簡單：在alertDialog.show()執行之前，判斷當前的Activity是否已經銷毀了，可以使用android提供的isFinishing()方法。同時，在Activity中也應該增加清理AsyncTask的操作，範例程式碼如下：

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之前增加判斷當前Activity是否finish操作if (!isCancelled() && result && MainActivity.this != null && !MainActivity.this.isFinishing()) {AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this).setTitle("標題").setMessage("這是內容").setPositiveButton("確定", 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;}}}