android对handler及asynctask的一个例子

来源：互联网发布：linux编程基础编辑：程序博客网时间：2024/06/05 04:18

Android子线程更新UI主线程方法之Handler
Android之多线程工作-AsyncTask与handler
详解Android中AsyncTask的使用
Android线程和Handler基础入门
Android中Handler的机制

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"              android:orientation="vertical"              android:layout_width="match_parent"              android:layout_height="match_parent"><TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="多线程demo。"/>    <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal">        <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="async Task实时更新进度条" android:id="@+id/btn_async_task"/>        <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="取消任务" android:id="@+id/btn_cancel_async_task"/>    </LinearLayout>    <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal">        <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="执行handler任务2" android:id="@+id/btn_handler"/>    </LinearLayout><ProgressBar android:layout_width="fill_parent" android:layout_height="wrap_content" android:progress="0" android:max="100" android:id="@+id/progress_bar_1" style="?android:attr/progressBarStyleHorizontal"/><TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/tips_1"/></LinearLayout>

package com.example.MyStudyAndroid;import android.app.Activity;import android.content.Intent;import android.os.AsyncTask;import android.os.Bundle;import android.os.Handler;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.ProgressBar;import android.widget.TextView;public class ThreadDemo extends Activity {    private static final String TAG="thread demo";    private Button btn_async_task;    private ProgressBar progressBar_1;    private TextView tips_1;    private Button btn_cancel_async_task;    private Task1 myTask;    private Button btn_handler;    private Handler handler=new Handler();    //--耗时的操作。    Runnable longOperation=new Runnable() {        @Override        public void run() {            handler.post(new Runnable() {                @Override                public void run() {                    tips_1.setText("开始执行任务2");                }            });            handler.postDelayed(new Runnable() {                @Override                public void run() {                    tips_1.setText("这里已经任务2完成了。");                }            },5000);        }    };    @Override    public void onCreate(Bundle savedInstanceState){        super.onCreate(savedInstanceState);        setContentView(R.layout.thread_demo);        initUI();        initEvents();    }    private void initUI(){        btn_async_task=(Button)findViewById(R.id.btn_async_task);        progressBar_1=(ProgressBar)findViewById(R.id.progress_bar_1);        tips_1=(TextView)findViewById(R.id.tips_1);        btn_cancel_async_task=(Button)findViewById(R.id.btn_cancel_async_task);        btn_handler=(Button)findViewById(R.id.btn_handler);    }    private void initEvents(){        btn_async_task.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                myTask=new Task1();                myTask.execute("");            }        });        btn_cancel_async_task.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                if(myTask!=null){                    myTask.cancel(true);                }            }        });        btn_handler.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                new Thread(longOperation).start();            }        });    }    class Task1 extends AsyncTask<String,Integer,String>{        //--onPreExecute方法用于在执行后台任务前做一些UI操作        @Override        protected void onPreExecute(){            Log.e(TAG,"task1的onPreExecute开始执行：");            tips_1.setText("开始执行 async task 任务。。。");        }        //--doInBackground方法内部执行后台任务,不可在此方法内修改UI        @Override        protected String doInBackground(String... strings) {            try {                Thread.sleep(500);                publishProgress(10);                Thread.sleep(600);                publishProgress(22);                Thread.sleep(1000);                publishProgress(42);                Thread.sleep(50);                publishProgress(43);;                Thread.sleep(250);                publishProgress(48);                Thread.sleep(1000);                publishProgress(68);                Thread.sleep(500);                publishProgress(78);                Thread.sleep(100);                publishProgress(80);                Thread.sleep(250);                publishProgress(85);                Thread.sleep(500);                publishProgress(95);                Thread.sleep(150);                publishProgress(98);                Thread.sleep(100);                publishProgress(100);            }            catch (Exception ed){                ed.printStackTrace();            }            return "执行完毕了吧？啊啊啊。。";        }        ////onProgressUpdate方法用于更新进度信息        @Override        protected void onProgressUpdate(Integer... values){            progressBar_1.setProgress(values[0]);            tips_1.setText(String.valueOf("加载。。。"+values[0]+"%"));        }        ////onPostExecute方法用于在执行完后台任务后更新UI,显示结果        @Override        protected void onPostExecute(String result){            Log.e(TAG,result);            tips_1.setText(result);        }        //onCancelled方法用于在取消执行中的任务时更改UI        @Override        protected void onCancelled(){            tips_1.setText("取消任务");            progressBar_1.setProgress(0);        }    }}

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