如何在异步任务完成加载之前显示加载屏幕

Question

这是 activity 的代码，造成问题的是 while 循环它阻塞了 ui 线程，但它会停止控制直到加载完成，我想要的是显示一些图像直到 asynctask 完成是任务，如果成功则屏幕 1 否则 screen2.what 目前我看到的只是黑屏。请帮助。

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URI;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;
import android.widget.ProgressBar;
import android.widget.Spinner;


public class loadingscreen extends Activity {


public final static String UID_MESSAGE="abe user name hai be";
int al=0,rt=0;

public static Spinner pb;
SharedPreferences save;
TelephonyManager tel;
SharedPreferences.Editor editor;
networker create;

String def=null;
String newt=null;
String imei=null;
String bus="AA";
Context context;
Intent  intent;

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);                    
    save=getSharedPreferences("map",MODE_PRIVATE);
    editor=save.edit(); 
    tel = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);        
    setContentView(R.layout.loading);
    pb=(Spinner)findViewById(R.id.pb);

    def=save.getString("uid","test");
    imei=tel.getDeviceId();       


    if(!(def.equals("true"))){

            Log.e(null," please wait logging in ");         

            new fsnetworker(context,0,0,0,5).executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,imei,def,bus);

            while(fsnetworker.done==0){ Log.e(null,"trying "); }

            if(fsnetworker.done==4 ){                       

                intent = new Intent(getBaseContext(),MapActivity.class);
                intent.putExtra(UID_MESSAGE, def);                                
                startActivity(intent);                                                                                                                                                                                                      
            }       
    }


    intent = new Intent(getBaseContext(),firstScreen.class);
    intent.putExtra(UID_MESSAGE, def);                                
    startActivity(intent);   

}   


public static class fsnetworker extends AsyncTask<String,Void,String>{

Context context;                 
double lat=0f;
double lng=0f;  
float acc=0;
int rt=0;
String imei;
String uid;
String bus;
public static int done;

public fsnetworker(Context context,double lat2,double lng2,float acc2,int rt){

this.context=context;
this.lat=lat2;
this.lng=lng2;
this.acc=acc2;
this.rt=rt;

}
@Override
protected void onPreExecute() {
 super.onPreExecute();


}

@Override
protected void onPostExecute(String success) {
 super.onPostExecute(success);


}


@Override
protected String doInBackground(String... arg0) {
    try{ 
         done=0;
         Log.e(null,"networking");
         imei=(String)arg0[0];
         uid=(String)arg0[1];
         bus=(String)arg0[2];


        HttpClient client=new DefaultHttpClient();
           HttpGet get=new HttpGet();
           get.setURI(new URI("http://*********************?"
                     +"imei="+imei
                     +"&name="+uid
                     +"&lat="+lat
                     +"&lng="+lng
                     +"&acc="+acc
                     +"&bus="+bus
                     +"&rt="+rt));

           HttpResponse response=client.execute(get);
           HttpEntity entity=response.getEntity();

           BufferedReader sread=new BufferedReader(new InputStreamReader(entity.getContent()));
           StringBuilder  sb = new StringBuilder();
           String out=null;
           while((out=sread.readLine())!=null){
               sb.append(out);
               break;
           }

         Log.e(" url", ""+sb.toString());

Answer 1

您似乎没有获取 AsyncTasks。它们并行执行。因此，您不要在调用执行后放置要在其完成后执行的代码。您将它放在 onPostExecute 函数中，该函数在任务完成后在 UI 线程上调用。您永远不会循环、休眠或以其他方式等到 AsyncTask 完成 - 这与整点背道而驰。

Answer 2

您不需要跟踪 AsyncTask 的当前状态。您可以确定 AsyncTask 何时完成，当 AsyncTask 完成其任务时，它将调用 onPostExecute 方法。

您修改后的代码

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URI;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.util.Log;
import android.widget.ProgressBar;
import android.widget.Spinner;


public class loadingscreen extends Activity {


public final static String UID_MESSAGE="abe user name hai be";
int al=0,rt=0;

public static Spinner pb;
SharedPreferences save;
TelephonyManager tel;
SharedPreferences.Editor editor;
networker create;

String def=null;
String newt=null;
String imei=null;
String bus="AA";
Context context;
Intent  intent;

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);                    
    save=getSharedPreferences("map",MODE_PRIVATE);
    editor=save.edit(); 
    tel = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);        
    setContentView(R.layout.loading);
    pb=(Spinner)findViewById(R.id.pb);

    def=save.getString("uid","test");
    imei=tel.getDeviceId();       


    if(!(def.equals("true"))){

            Log.e(null," please wait logging in ");         

            new fsnetworker(context,0,0,0,5).executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,imei,def,bus);
  
    }


    intent = new Intent(getBaseContext(),firstScreen.class);
    intent.putExtra(UID_MESSAGE, def);                                
    startActivity(intent);   

}   


public static class fsnetworker extends AsyncTask<String,Void,String>{

Context context;                 
double lat=0f;
double lng=0f;  
float acc=0;
int rt=0;
String imei;
String uid;
String bus;
public static int done;

public fsnetworker(Context context,double lat2,double lng2,float acc2,int rt){

this.context=context;
this.lat=lat2;
this.lng=lng2;
this.acc=acc2;
this.rt=rt;

}
@Override
protected void onPreExecute() {
 super.onPreExecute();


}

@Override
protected void onPostExecute(String success) {
 super.onPostExecute(success);

intent = new Intent(getBaseContext(),MapActivity.class);
                intent.putExtra(UID_MESSAGE, def);                                
                startActivity(intent);

}


@Override
protected String doInBackground(String... arg0) {
    try{ 
         done=0;
         Log.e(null,"networking");
         imei=(String)arg0[0];
         uid=(String)arg0[1];
         bus=(String)arg0[2];


        HttpClient client=new DefaultHttpClient();
           HttpGet get=new HttpGet();
           get.setURI(new URI("http://*********************?"
                     +"imei="+imei
                     +"&name="+uid
                     +"&lat="+lat
                     +"&lng="+lng
                     +"&acc="+acc
                     +"&bus="+bus
                     +"&rt="+rt));

           HttpResponse response=client.execute(get);
           HttpEntity entity=response.getEntity();

           BufferedReader sread=new BufferedReader(new InputStreamReader(entity.getContent()));
           StringBuilder  sb = new StringBuilder();
           String out=null;
           while((out=sread.readLine())!=null){
               sb.append(out);
               break;
           }

         Log.e(" url", ""+sb.toString());

如何在异步任务完成加载之前显示加载屏幕

how to show loading screen till the asynctask is done loading

android

loading

android-asynctask

android-activity