進度對話框未在全局AsyncTask類中顯示

Question

這是我的MainActivity ...我把一個按鈕，在按鈕onclick我調用asyncTask

package com.example.asnytaskpro;

import java.util.concurrent.ExecutionException;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class AsyncMainActivity extends Activity implements OnClickListener {

Button button ; 
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_async);

    button = (Button) findViewById(R.id.button1);
    button.setOnClickListener(this);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_async, menu);
    return true;
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    System.err.println("1");
    try {
        new AllPrinterClass(AsyncMainActivity.this, "123456789123456789", "123").execute().get();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    };
}

}

這是我的AsyncTaskClass

import java.text.SimpleDateFormat;
import java.util.Calendar;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.os.SystemClock;
import android.widget.Toast;

public class AllPrinterClass extends AsyncTask<Integer, Integer, Integer>{

public static String ServerData = "";
private ProgressDialog prgDialog;
private Context context;
String TransNo = "" ,IMEINo = "";

int iRetValue = 0;

String  CurrentDate = null, CurrentTime= null;
SimpleDateFormat df,tf;


public AllPrinterClass(Context context1, String imeiNo,String transno2) 
{
        this.context        = context1;
        this.IMEINo         = imeiNo;
        this.TransNo        = transno2;

        Calendar c = Calendar.getInstance();
        df = new SimpleDateFormat("dd/M/yyyy");
        CurrentDate = df.format(c.getTime());
        tf = new SimpleDateFormat("hh:mm:ss");
        CurrentTime = tf.format(c.getTime());

        System.err.println(CurrentDate);
        System.err.println(CurrentTime);


}

@Override
protected void onPreExecute() {
    super.onPreExecute();
    this.prgDialog = new ProgressDialog(context);
    this.prgDialog.setMessage("Place your finger on FPS ...");
    this.prgDialog.setIndeterminate(true);
    this.prgDialog.setCancelable(false);
    this.prgDialog.show();

}

@Override
protected Integer doInBackground(Integer... params) {

//////////////////Doing my Code///////////////////

    for (int i = 0; i < 10; i++) {
        System.err.println("i :-" + i);
        SystemClock.sleep(500);
    }
/////////////////////////////////////////////////////

    return iRetValue;
}

@Override
protected void onPostExecute(Integer result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    prgDialog.dismiss();
    Toast.makeText(context, "Done", Toast.LENGTH_SHORT).show();

}

}

這段代碼為我工作，但我的ProgressDialog沒有顯示（可能是運行后台）。

在我刪除prgDialog.dismiss（）; 在onPostExecute（）方法然后我的對話框顯示在doInBackground（）方法之后。

我想在onPreExecute（）方法中顯示對話框，並在onPostExecute（）方法中解除。

Answer 1

這里：

...execute().get();

調用get方法將阻止主ui線程，直到doInBackground執行未完成。 這就是ProgressDialog沒有顯示的原因。

僅使用execute()方法啟動AsyncTask ，它在doInBackground方法執行期間顯示Progress Dialog：

    new AllPrinterClass(AsyncMainActivity.this,
                     "123456789123456789", "123").execute();