我有一个 DialogFragment，它显示一个简单的是/否问题。当用户按下“是”时，我执行一个数据库请求（基本上删除一个条目）。然后我举杯向用户报告成功或失败的消息。
我尽量避免从 UI 线程调用数据库，因此我创建了一个将删除条目的线程，并从该线程调用 DialogFragment 中的处理程序以显示 toast 消息。
我的问题是当用户按下按钮时，线程启动并关闭对话框。当线程启动时，数据会从数据库中删除。但是当我从处理程序吐司消息时，DialogFragment 已经与父 Activity 分离，因此我不再有上下文来调用 Toast.makeText()。
我的问题是我怎样才能敬酒？
我知道我可以创建一个服务来处理数据库操作，但这不会太麻烦吗？有没有更简单的方法？
谢谢 ！
编辑：这是我的代码，以帮助您理解我的问题：
public class EraseHistoryDialogFragment extends DialogFragment {
private HistoryDatabaseHandler mHistoryDbHandler;
private final static int MSG_NOTIFY_EMPTYDB = 1;
private final static int MSG_NOTIFY_DELENTRY = 2;
private final static int MSG_NOTIFY_NODELETION = 3;
private Context mContext;
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_NOTIFY_DELENTRY:
Toast.makeText(mContext,
getS tring(R.string.historytab_erased_entry),
Toast.LENGTH_SHORT).show();
break;
case MSG_NOTIFY_EMPTYDB:
Toast.makeText(mContext,
getS tring(R.string.historytab_history_cleared),
Toast.LENGTH_SHORT).show();
break;
case MSG_NOTIFY_NODELETION:
Toast.makeText(mContext,
getS tring(R.string.historytab_erase_failed),
Toast.LENGTH_SHORT).show();
break;
}
};
};
private Runnable mEraseHistoryRunnable = new Runnable() {
@Override
public void run() {
if (mHistoryDbHandler.clearAllTables()) {
mHandler.sendEmptyMessage(MSG_NOTIFY_EMPTYDB);
} else {
mHandler.sendEmptyMessage(MSG_NOTIFY_NODELETION);
}
}
};
private class EraseEntryRunnable implements Runnable {
private String mEntryId;
public EraseEntryRunnable(String entryID) {
mEntryId = entryID;
}
@Override
public void run() {
if (mHistoryDbHandler.deleteEntry(mEntryId)) {
mHandler.sendEmptyMessage(MSG_NOTIFY_DELENTRY);
} else {
mHandler.sendEmptyMessage(MSG_NOTIFY_NODELETION);
}
}
};
public static EraseHistoryDialogFragment newInstance(String message,
String entryID, boolean eraseAll) {
EraseHistoryDialogFragment frag = new EraseHistoryDialogFragment();
Bundle args = new Bundle();
args.putString("message", message);
args.putString("entryid", entryID);
args.putBoolean("eraseall", eraseAll);
frag.setArguments(args);
return frag;
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
mHistoryDbHandler = HistoryDatabaseHandler.getInstance(getActivity());
mContext = getActivity().getApplicationContext();
String message = getArguments().getString("message");
final String entryID = getArguments().getString("entryid");
final boolean eraseAll = getArguments().getBoolean("eraseall");
return new AlertDialog.Builder(getActivity())
.setMessage(message)
.setPositiveButton(R.string.groupstab_yes,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int whichButton) {
if (eraseAll) {
Thread emptyDbT = new Thread(
mEraseHistoryRunnable);
emptyDbT.start();
} else {
Thread deleteEntryT = new Thread(
new EraseEntryRunnable(entryID));
deleteEntryT.start();
}
}
})
.setNegativeButton(R.string.groupstab_no,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int whichButton) {
getDialog().dismiss();
}
}).create();
}
}