Question

在我的代码中，我使用Async Task加载了一个微调器适配器在我的情况下，ProgressDialog并没有消失这是我的代码。我想在适配器加载后显示该项目，并且将解除progressDialog 请帮助我，谢谢

private class LoadMoreVehicals extends AsyncTask<Object, Integer, Object> {

        @Override
        protected void onPreExecute() {

            progressBar = ProgressDialog.show(RegistrationScreen.this, "",
                    "Loading...");
            progressBar.setIndeterminate(true);
            progressBar.setIndeterminateDrawable(getResources().getDrawable(
                    R.anim.progressbar_handler));
            super.onPreExecute();
        }

        @Override
        protected Object doInBackground(Object... params) {
            String countryUrl = ConstantURL.COUNTRY_URL;
            getCounty(countryUrl);

            countrySpinner
            .setAdapter(new MyCustomSpinnerAdapter(
                    RegistrationScreen.this,
                    R.layout.spinner_dropdown,
                    countyList));

                                return null;
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            progressBar.getProgress();

        }

        @Override
        protected void onPostExecute(Object result) {

            progressBar.dismiss();

             Log.e("Im in onPostExecute", "");
            super.onPostExecute(result);
        }
    }

Answer 1

在Android中编程时，您应该记住，在主线程上执行任何在屏幕上绘制内容的任务。当你设置适配器然后android调用适配器的getView（）方法并在屏幕上绘制视图。因此，您应该在postExecute（）方法中设置适配器，而不是在doInBackground（）方法中。
这是一个清楚我的观点的小样本：

class MyTask extends AsyncTask<Void, Void, Void> {
    ProgressDialog pd = new ProgressDialog(MainActivity.this);

    @Override
    protected void onPreExecute ( )
    {
        //starting the progress dialogue
        pd.show();
    }

    @Override
    protected Void doInBackground (Void... params)
    {
        //fetch data here
        ...
        ... 
        return null;
    }

            @Override
    protected void onPostExecute (Void result)
    {
        //set adapter here
        ...
        ...
        //dismissing the progress dialogue
        pd.dismiss();
    }

}

Answer 2

首先，您无法在doInBackground中设置适配器遵循这个设计：

private class LoadMoreVehicals extends AsyncTask<Object, Integer, Object> 
{
    private ArrayList<Country> countries;
    @Override
    protected void onPreExecute() {
         progressBar = ProgressDialog.show(RegistrationScreen.this, "","Loading...");
         progressBar.setIndeterminate(true);
         progressBar.setIndeterminateDrawable(getResources().getDrawable(R.anim.progressbar_handler));              
         super.onPreExecute();
    }

    @Override
    protected Object doInBackground(Object... params) {
        String countryUrl = ConstantURL.COUNTRY_URL;
        countries = getCounty(countryUrl);
        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        progressBar.getProgress();

    }

    @Override
    protected void onPostExecute(Object result) {
        countrySpinner.setAdapter(new MyCustomSpinnerAdapter(RegistrationScreen.this,R.layout.spinner_dropdown,countries));
        progressBar.dismiss();
        Log.e("Im in onPostExecute", "");
        super.onPostExecute(result);
    }
}

Answer 3

根据我的经验，我在异步运行和UI方面遇到了很多问题，所以现在总是将试图在每个地方放置“责任”的东西分开。所以我做这样的事情：

使用我想要执行的流程创建我的Async类，并且不改变其中的UI
在UI线程中创建一个函数，在异步任务完成时修改UI，如OnAsyncTaskComplete（对象响应）

保持沟通线程

public class MyActivity extends Activity {

private static MyAsyncClass backgroundTask;
private static ProgressDialog pleaseWaitDialog; 

//......activity stuff.......

@Override
public void onPause()
{
    super.onPause();
    //Get rid of progress dialog in the event of a screen rotation or other state change. Prevents a crash.
    if (pleaseWaitDialog != null)
        pleaseWaitDialog.dismiss();
}
//Function to avoid lose the async thread if the app interrupts (phone rotation, incoming call, etc) RECOMENDED TO HANDLE THIS!!
//Sets the current state after app resume
@Override
public void onResume()
{

    super.onResume();
    //If there is a background task set it to the new activity
    if ((backgroundTask != null) && (backgroundTask.getStatus() == Status.RUNNING))
    {
       if (pleaseWaitDialog != null)
         pleaseWaitDialog.show();

       backgroundTask.setActivity(this);
    }
    }
}

    //Logic business after the web service complete here
//Do the thing that modify the UI in a function like this
private void onTaskCompleted(Object _response) 
{ 
    //For example _response can be a new adapter
MyList.setAdapter((BaseAdapter)_response);
//or can be a list to create the new adapter
MyList.setAdapter(new MyAdapter(this, (ArrayList<String>)_response));
//or can be anything you want, just try to make here the things that you need to change the UI
}

/**
 * Class that handle the async task
 */
public class MyAsyncClass extends AsyncTask<Void, Void, Object>
{
    //Maintain attached activity for states change propose 
     private MyActivity activity;
     //Keep the response of the async task
     private Object _response;
     //Flag that keep async task completed status
     private boolean completed; 

     //Constructor
     private MyAsyncClass(MyActivity activity) { 
             this.activity = activity;
     } 

     //Pre execution actions
     @Override 
     protected void onPreExecute() {
             //Start the splash screen dialog
             if (pleaseWaitDialog == null)
                 pleaseWaitDialog= ProgressDialog.show(activity.this, 
                                                        "PLEASE WAIT", 
                                                        "Getting results...", 
                                                        false);

     } 

     //Execution of the async task
    protected Object doInBackground(Object...params)
    {
        //return the thing you want or do want you want
        return new ArrayList();
    }

    //Post execution actions
    @Override 
    protected void onPostExecute(Object response) 
    {
        //Set task completed and notify the activity
            completed = true;
            _response = response;
            notifyActivityTaskCompleted();
        //Close the splash screen
        if (pleaseWaitDialog != null)
        {
            pleaseWaitDialog.dismiss();
            pleaseWaitDialog = null;
        }
    } 

    //Notify activity of async task completion
    private void notifyActivityTaskCompleted() 
    { 
        if ( null != activity ) { 
            activity.onTaskCompleted(_response); 
        } 
    } 

//for maintain attached the async task to the activity in phone states changes
    //Sets the current activity to the async task
    public void setActivity(MyActivity activity) 
    { 
        this.activity = activity; 
        if ( completed ) { 
            notifyActivityTaskCompleted(); 
        } 
    } 

}
}

希望对你有所帮助

如何使用Async Task Class设置微调器的适配器

3 个答案: