让ProgressDialog在setCancelable(false)时按返回键可dismiss

package cn.winfirm.examples.base;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnKeyListener;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Window;

/**
* Activity的基类，带一个ProgressDialog，可双击取消其显示
*
* @author savant
*
*/
public class BaseActivity extends Activity {

private ProgressDialog progressDialog = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
}

/**
* show loading progress dialog
*/
public void showDialog() {
if (null == progressDialog) {
progressDialog = ProgressDialog.show(BaseActivity.this, "", "正在加载，请稍候...");
progressDialog.setCancelable(false);
} else {
progressDialog.show();
}
progressDialog.setOnKeyListener(onKeyListener);
}

/**
* add a keylistener for progress dialog
*/
private OnKeyListener onKeyListener = new OnKeyListener() {
@Override
public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
dismissDialog();
}
return false;
}
};

/**
* dismiss dialog
*/
public void dismissDialog() {
if (isFinishing()) {
return;
}
if (null != progressDialog && progressDialog.isShowing()) {
progressDialog.dismiss();
}
}

/**
* cancel progress dialog if nesseary
*/
@Override
public void onBackPressed() {
if (progressDialog != null && progressDialog.isShowing()) {
dismissDialog();
} else {
super.onBackPressed();
}
}
}


最近发现Android4.0系统中ProgressDialog设置为setCancelable(true)时，点击ProgressDialog以外的区域也可以让ProgressDialog dismiss掉。但有时我们不希望是这样的效果，于是将ProgressDialog设置setCancelable(false)，再点击ProgressDialog以外的区域就不会出现前面所说的情况了，然而这样以来再按返回键时就不起作用了，只能等待程序执行到dissmiss处为止。其实，只要为ProgressDialog添加KeyListener来对返回键予以处理就可以解决这个问题了。