現在很多程式要求back鍵不是退出程式而是像home鍵一樣讓Acitivty退至後臺時不被系統銷燬，查到的資料大多說都是繼承activity的沒有繼承TabActivity，

TabActivity和activity不能一樣處理，廢話不多說了上程式碼。

繼承activity的

/**
	 * 返回監聽
	 */
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		// TODO 監聽返回鍵，相當於點選home鍵
		PackageManager pm = getPackageManager();
		ResolveInfo homeInfo = pm.resolveActivity(
				new Intent(Intent.ACTION_MAIN)
						.addCategory(Intent.CATEGORY_HOME), 0);
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			ActivityInfo ai = homeInfo.activityInfo;
			Intent startIntent = new Intent(Intent.ACTION_MAIN);
			startIntent.addCategory(Intent.CATEGORY_LAUNCHER);
			startIntent
					.setComponent(new ComponentName(ai.packageName, ai.name));
			startActivitySafely(startIntent);
			return true;
		} else
			return super.onKeyDown(keyCode, event);
	}
 

@Override
	public boolean dispatchKeyEvent(KeyEvent event) {
		PackageManager pm = getPackageManager();
		ResolveInfo homeInfo = pm.resolveActivity(
				new Intent(Intent.ACTION_MAIN)
						.addCategory(Intent.CATEGORY_HOME), 0);
		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK
				&& event.getAction() == KeyEvent.ACTION_DOWN) {
			ActivityInfo ai = homeInfo.activityInfo;
			Intent startIntent = new Intent(Intent.ACTION_MAIN);
			startIntent.addCategory(Intent.CATEGORY_LAUNCHER);
			startIntent
					.setComponent(new ComponentName(ai.packageName, ai.name));
			startActivitySafely(startIntent);
			return false;
		}
		return super.dispatchKeyEvent(event);
	}
 

private void startActivitySafely(Intent intent) {
		intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
		try {
			startActivity(intent);
		} catch (ActivityNotFoundException e) {
			Toast.makeText(this, "ActivityNotFoundExceptionnull",
					Toast.LENGTH_SHORT).show();
		} catch (SecurityException e) {
			Toast.makeText(this, "SecurityExceptionnull", Toast.LENGTH_SHORT)
					.show();
		}
	}