Android：等待用户界面在AsyncTask中完成

Question

In my AsyncTask's doInBackground function, I am calling this to display a confirmation dialog:

void CreateOKDialog(final String message)
{
    runOnUiThread(new Runnable() {
        @Override
        public void run()
        {
            AlertDialog.Builder builder = new AlertDialog.Builder(trip.this);
            builder.setTitle(message);
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }
            });
            AlertDialog alert = builder.create();
            alert.show();
        }
    });
}

After calling the above function in doInBackground() I Start a new activity. The problem is that since its asynchronous, it does not wait for the above function to complete. I can just see a popup and it closes. How to solve this ?

        CreateOKDialog("Trip cancelled");
        startActivity(new Intent(trip.this, login.class));

Edit:

void CreateOKDialog( String message)
{
    AlertDialog.Builder builder = new AlertDialog.Builder(trip.this);
    builder.setTitle(message);
    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });
    AlertDialog alert = builder.create();
    alert.show();
}

I am calling this function:

protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);

    if(isError)
        CreateOKDialog("Error cancelling trip");
    else {
        CreateOKDialog("Trip cancelled");
        startActivity(new Intent(trip.this, login.class));
    }
}

It still does not wait for me to press OK, just pops up and disappears.

Answer 1

在异步任务中覆盖onPostExecute并在其中编写对话框和意图代码

Answer 2

Do something like this with your AsyncTask

public YourAsyncTask extends <X, Y, Z>{

    public interface TaskDoneCallback{
        void onTaskDone();
    }

    private TaskDoneCallback mCallback;

    public YourAsyncTask(TaskDoneCallback callback){
        mCallback = callback;
    }

    @Override
    public Z doInBackground(X... params){
        // your stuff
    }

    @Override
    protected void onPostExecute(Z result){
        if(mCallback != null)
            mCallback.onTaskDone();
    }

}

Then from your activity

new YourAsyncTask(new TaskDoneCallback(){

    @Override
    public void onTaskDone(){
        AlertDialog.Builder builder = new AlertDialog.Builder(trip.this);
        builder.setTitle(message);
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                startActivity(new Intent(trip.this, login.class));
            }
        });
        AlertDialog alert = builder.create();
        alert.show();
}).execute(x);

What is happening is the AsyncTask will execute, and onPostExecute it will trigger the callback that you pass to the constructor for your Activity. This will, in turn, build the dialog from within the activity. Then in a positive onClick response, the new activity will be triggered.

Last, you will want to look into naming conventions. Classes should very much so be UpperCamelCase, they are important, make sure people don't get them confused with variables :)