handler以及AnyscTask处理机制

时间：2023-03-09 20:04:17
handler以及AnyscTask处理机制

1、Handler

主文件：MainActivity.java

package com.example.asynctaskdownload;

import java.io.IOException;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.StatusLine;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class MainActivity extends Activity {

 protected static final int SHOW_RESPONSE = 0;

/** Called when the activity is first created. */

    private TextView textView;

    private String result = "";

/////////////////////////////////////////////////////////

    private Handler handler = new Handler(){

        public void handleMessage(Message msg)

        {

            switch(msg.what){

            case SHOW_RESPONSE:

                String result = (String)msg.obj;

                //注意是在此处进行UI操作

                textView.setText(result);

            }

        }

    };

/////////////////////////////////////////////////////

@Override

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    textView = (TextView) findViewById(R.id.TextView01);

    Button button = (Button) findViewById(R.id.readWebpage);

    button.setOnClickListener(new OnClickListener()

    {

        @Override

        public void onClick(View v) {

            //

            //textView.setText(result);

            if(v.getId() == R.id.readWebpage)

            {

                sendRequestHttpUrl();

            }

        }

    });

}

////////////////////////////////////////////////////////

protected void sendRequestHttpUrl() {

    // TODO Auto-generated method stub

    //

    new Thread(new Runnable()

    {

        @Override

        public void run() {

            // 

            try

            {

                HttpClient client = new DefaultHttpClient();

                HttpGet httpGet = new HttpGet("http://10.0.2.2:8080/mp3/a1.lrc");

                HttpResponse response = client.execute(httpGet);

                StatusLine statusLine = response.getStatusLine();

                int statusCode = statusLine.getStatusCode();

                if (statusCode == 200) {

                    HttpEntity entity = response.getEntity();

                    //关于此处中文乱码问题解决？文本文件保存时，文本文档默认为ANSI编码格式，另存为时手动改为utf-8格式即可

                    result = EntityUtils.toString(entity, "utf-8");

                }

                Message message = new Message();

                message.what = SHOW_RESPONSE;

                message.obj = result.toString();

                handler.sendMessage(message);

            }catch(Exception ex)

            {

                ex.printStackTrace();

            }

        }

    }

    ).start();

}

}

activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <Button

        android:id="@+id/readWebpage"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:onClick="onClick"

        android:text="Load Webpage" >

    </Button>

    <ScrollView

        android:layout_width="match_parent"

        android:layout_height="match_parent">

        <TextView

        android:id="@+id/TextView01"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:text="Placeholder" >

        </TextView>

    </ScrollView>

</LinearLayout>

运行结果：

handler以及AnyscTask处理机制

2、AnyscTask

主代码：

package com.example.asynctaskdownload;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import android.app.Activity;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Environment;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends Activity {

  private TextView textView;

  private final String fileName = "a1.lrc";

  //private final String fileUrl = "http://10.0.2.2:8080/mp3/a1.lrc";

  private int result = Activity.RESULT_CANCELED;

  private String response = "";

  @Override

  public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    textView = (TextView) findViewById(R.id.TextView01);

    Button button = (Button) findViewById(R.id.readWebpage);

    button.setOnClickListener(new OnClickListener()

    {

        @Override

        public void onClick(View v) {

            // 

            DownloadWebPageTask task = new DownloadWebPageTask();

            //task.execute(new String[] { "http://www.vogella.com" });

            task.execute(new String[] { "http://10.0.2.2:8080/mp3/a1.lrc" });

            Toast.makeText(MainActivity.this, "Download Success!", Toast.LENGTH_LONG).show();

//            textView.setText(response);

        }

    });

  }

  private class DownloadWebPageTask extends AsyncTask<String, Void, Integer> {

    @Override

    protected Integer doInBackground(String... urls) {

      //获取sdcard的路径，以及设置保存的文件名

      File output = new File(Environment.getExternalStorageDirectory(), fileName);

      if(output.exists())

      {

          output.delete();//若同名文件已存在则删除

      }

//      String response = "";

      InputStream content = null;

      FileOutputStream fos = null;

      //遍历url数组中的url，采用HttpClient(接口)的方式访问网络

      for (String url : urls) {

        //首先创建一个DefaultHttpClient实例

        DefaultHttpClient client = new DefaultHttpClient();

        HttpGet httpGet = new HttpGet(url);//发起一个GET请求，创建一个HttpGet对象，并传入目标网络地址

        try {

          HttpResponse execute = client.execute(httpGet);//调用execute执行访问请求并返回一个HttpResponse对象

          if(execute.getStatusLine().getStatusCode() == 200)

          {

              //注:下面两行code只能使用其中一个：content will be consume only once

              //execute.getEntity()调用了两次

 //             content = execute.getEntity().getContent();//获取服务返回的具体内容

              //调用EntityUtils.toString该静态方法将HttpEntity转换成字符串,为避免中文字符乱码，添加utf-8字符集参数

//              response = EntityUtils.toString(execute.getEntity(), "utf-8");

//////////////////////////////////////////////////////////////////////////////

              HttpEntity entity = execute.getEntity();

 //             response = EntityUtils.toString(entity, "utf-8");

              content = entity.getContent();

          }

          //利用管道 inputstream-->reader

          InputStreamReader reader = new InputStreamReader(content);

          fos = new FileOutputStream(output.getPath());

          int next = -1;

          while ((next = reader.read()) != -1) {

            fos.write(next);

          }

          result = Activity.RESULT_OK;

//          BufferedReader buffer = new BufferedReader(new InputStreamReader(content));

//          String s = "";

//          while ((s = buffer.readLine()) != null) {

//            response += s;

//          }

        } catch (Exception e) {

          e.printStackTrace();

        }finally {

            if (content != null) {

                try {

                  content.close();

                } catch (IOException e) {

                  e.printStackTrace();

                }

              }

              if (fos != null) {

                try {

                  fos.close();

                } catch (IOException e) {

                  e.printStackTrace();

                }

              }

      }

    }

    return result;

  }

    protected void onPostExecute(Integer result) {

    //此处可以根据后台任务完成后返回的结果进行一些UI操作

        if(result == Activity.RESULT_OK)

        {

            textView.setText("mp3 file download success!!");

        }

    }

 /* public void onClick(View view) {

    DownloadWebPageTask task = new DownloadWebPageTask();

    //task.execute(new String[] { "http://www.vogella.com" });

    task.execute(new String[] { "http://10.0.2.2:8080/mp3/a1.lrc" });

  }*/

  }

}

activity_main.xml文件同上

运行结果：成功下载文件a1.lrc到sdcard中

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