【读书笔记】安卓异步任务

来源：互联网发布：stc12c5a32s2数据手册编辑：程序博客网时间：2024/05/19 12:13

首先是页面中的内容，大致如下：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"        xmlns:tools="http://schemas.android.com/tools"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:paddingLeft="@dimen/activity_horizontal_margin"        android:paddingRight="@dimen/activity_horizontal_margin"        android:paddingTop="@dimen/activity_vertical_margin"        android:paddingBottom="@dimen/activity_vertical_margin"        tools:context="com.terry.code0333.AsyncTaskTest"><TextViewandroid:id="@+id/show"        android:text="@string/hello_world"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /><Buttonandroid:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="New Button"        android:id="@+id/button"        android:layout_below="@+id/show"        android:layout_toRightOf="@+id/show"        android:layout_toEndOf="@+id/show"        android:layout_marginTop="149dp" /></RelativeLayout>

后台Activity内容如下：

import android.app.Activity;import android.app.ProgressDialog;import android.content.Context;import android.os.AsyncTask;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;public class AsyncTaskTest extends Activity {    private TextView show;    private Button loadData;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_async_task_test);        show = (TextView) findViewById(R.id.show);        loadData = (Button) findViewById(R.id.button);        loadData.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                DownTask task = new DownTask(AsyncTaskTest.this);                try {                    task.execute(new URL("https://github.com/onecoders/AndroidBook"));                } catch (MalformedURLException e) {                    e.printStackTrace();                }            }        });    }    class DownTask extends AsyncTask<URL, Integer, String> {        ProgressDialog pDialog;        int hasRead = 0;        Context mContext;        public DownTask(Context context) {            mContext = context;        }        @Override        protected String doInBackground(URL... params) {            StringBuilder sb = new StringBuilder();            try {                URLConnection conn = params[0].openConnection();                //打开conn连接对应的输入流，并将它包装成BufferedReader;                BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(), "utf-8"));                String line = null;                while ((line = br.readLine()) != null) {                    sb.append(line).append("\n");                    hasRead++;                    publishProgress(hasRead);                }                return sb.toString();            } catch (IOException ex) {                ex.printStackTrace();            }            return null;        }        @Override        protected void onPostExecute(String result) {            show.setText(result);            pDialog.dismiss();        }        @Override        protected void onPreExecute() {            pDialog = new ProgressDialog(mContext);            pDialog.setTitle("任务正在执行中...");            pDialog.setMessage("任务正在执行中，请稍等...");            pDialog.setCancelable(false);            pDialog.setMax(202);            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);            pDialog.setIndeterminate(false);            pDialog.show();        }        @Override        protected void onProgressUpdate(Integer... values) {            show.setText("已经读取了" + values[0] + "行!");            pDialog.setProgress(values[0]);        }    }}

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