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我是安卓初学者

我是java初学者

然后......我开发没有问题，因为我需要一个应用程序来从 url 下载和解析 xml

然后我写了以下代码：

    package com.aaa.bbb;


import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.util.Base64;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.ProgressBar;

public class Login extends Activity {

    String VA_URL = "MYURL";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
    }

    public void onClick(View v) {
        if ("loginbu".equals(v.getId())){
            new DownloadXml1().execute(VA_URL);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.login, menu);
        return true;
    }
    private class DownloadXml1 extends AsyncTask<String, Void, InputStream> {

        protected void onPreExecute() {
                EditText ET1 = (EditText) findViewById(R.id.editText1);
                EditText ET2 = (EditText) findViewById(R.id.editText2);
                ProgressBar PB1 = (ProgressBar) findViewById(R.id.progressBar1);
                ET1.setVisibility(View.GONE);
                ET2.setVisibility(View.GONE);
                PB1.setVisibility(View.VISIBLE);
            }


            protected InputStream doInBackground(String...f_url) {
                EditText ET1 = (EditText) findViewById(R.id.editText1);
                EditText ET2 = (EditText) findViewById(R.id.editText2);
                String user = ET1.getText().toString();
                String pass = ET2.getText().toString();
                InputStream stream = null;
                try {
                    URL url = new URL(f_url[0]);
                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                    String encoded;
                    encoded = "Basic " + Base64.encodeToString((user + ":" + pass).getBytes(), 0);
                    conn.setRequestProperty("Authorization", encoded);
                conn.setReadTimeout(10000 /* milliseconds */);
                conn.setConnectTimeout(15000 /* milliseconds */);
                conn.setRequestMethod("GET");
                conn.setDoInput(true);
                conn.connect();
                stream = conn.getInputStream();
            } catch (Exception ee) {}
            return stream;
        }

        protected void onPostExecute(InputStream inpStream) {
            // Parse Xml
            try {
                inpStream.close();
            } catch (IOException e) {
            }
        }

    }
}

我在没有按钮和文本框的情况下尝试了它我的意思是删除授权行+预执行功能+获取编辑文本值行...然后在应用程序启动时运行它..但仍然无法正常工作：|

代码有什么问题... ??? 或者如果您知道另一种下载和解析 xml 的方法，请告诉我...

更新：LogCat

    07-26 14:00:33.647: D/gralloc_goldfish(1092): Emulator without GPU emulation detected.
07-26 14:00:34.559: I/Choreographer(1092): Skipped 50 frames!  The application may be doing too much work on its main thread.
07-26 14:00:35.338: I/Choreographer(1092): Skipped 84 frames!  The application may be doing too much work on its main thread.
07-26 14:00:38.008: I/Choreographer(1092): Skipped 37 frames!  The application may be doing too much work on its main thread.
07-26 14:00:43.498: I/Choreographer(1092): Skipped 78 frames!  The application may be doing too much work on its main thread.
07-26 14:00:43.498: D/AndroidRuntime(1092): Shutting down VM
07-26 14:00:43.608: W/dalvikvm(1092): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
07-26 14:00:44.218: E/AndroidRuntime(1092): FATAL EXCEPTION: main
07-26 14:00:44.218: E/AndroidRuntime(1092): java.lang.NullPointerException
07-26 14:00:44.218: E/AndroidRuntime(1092):     at com.aaa.bbb.Login$DownloadXml1.onPostExecute(Login.java:73)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at com.aaa.bbb.Login$DownloadXml1.onPostExecute(Login.java:1)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.os.AsyncTask.finish(AsyncTask.java:631)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.os.Looper.loop(Looper.java:137)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at android.app.ActivityThread.main(ActivityThread.java:5041)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at java.lang.reflect.Method.invokeNative(Native Method)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at java.lang.reflect.Method.invoke(Method.java:511)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-26 14:00:44.218: E/AndroidRuntime(1092):     at dalvik.system.NativeStart.main(Native Method)
07-26 14:01:07.968: I/Process(1092): Sending signal. PID: 1092 SIG: 9
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1 回答 1

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您正在尝试在 onClick 方法中执行 Asynctask 代码，但是您在哪里为 clicklistener 注册了视图？

如果你想执行，DownloadXml1()那么你必须在你的onCreate()方法中编写它。并在onCreate()方法中初始化所有视图，而不是在 AsyncTask 中，如下所示：

       EditText ET1;
         EditText ET2;
       ProgressBar PB1; 
  @Override
 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

     ET1 = (EditText) findViewById(R.id.editText1);
     ET2 = (EditText) findViewById(R.id.editText2);
     PB1 = (ProgressBar) findViewById(R.id.progressBar1);
    if ("loginbu".equals(v.getId())){
        new DownloadXml1().execute(VA_URL);
    }
}

希望你能从中得到想法。试试看，如果有任何问题，请告诉我。

于 2013-07-26T13:50:02.667 回答