Android消息机制——时钟显示和异步处理工具类（AsyncTask)

1. 时钟显示

定义布局文件——activity_my_analog_clock_thread_demo.xml

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

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

    xmlns:tools="http://schemas.android.com/tools"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.contactsdemo.MyAnalogClockThreadDemo" >



    <AnalogClock 

        android:id="@+id/myAnalogClock"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"/>

    <TextView

        android:id="@+id/info"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content" />



</LinearLayout>

定义Activity程序，进行操作

package com.example.contactsdemo;



import java.text.SimpleDateFormat;

import java.util.Date;



import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.TextView;



public class MyAnalogClockThreadDemo extends ActionBarActivity {

    private TextView info = null;    //文本显示组件

    private static final int SET = 1;  //线程标记

    private Handler handler = new Handler(){



        @Override

        public void handleMessage(Message msg) {

            switch(msg.what){

            case SET:    //判断标志位

                MyAnalogClockThreadDemo.this.info.

                setText("当前时间为："+msg.obj.toString());  //设置显示信息

            }

        }

        

    };

    private class ClockThread implements Runnable{



        @Override

        public void run() {

            while(true){

                Message msg = MyAnalogClockThreadDemo.this.handler

                        .obtainMessage(MyAnalogClockThreadDemo.SET,

                                new SimpleDateFormat("yyyy-MM-dd HH-mm-ss").format(new Date())); //实例化Message

                MyAnalogClockThreadDemo.this.handler.sendMessage(msg);  //发送消息

                try {

                    Thread.sleep(1000);     //延迟1秒

                } catch (InterruptedException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                } 

            }            

        }

        

    }

    

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_my_analog_clock_thread_demo);

        this.info = (TextView) super.findViewById(R.id.info);  //取得组件

        new Thread(new ClockThread()).start();    //启动线程

    }



    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.my_analog_clock_thread_demo, menu);

        return true;

    }



    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        int id = item.getItemId();

        if (id == R.id.action_settings) {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }

}

2. 异步处理工具类：AsyncTask——实现进度条

定义布局文件——activity_my_async_task_demo.xml

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

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

    xmlns:tools="http://schemas.android.com/tools"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.contactsdemo.MyAsyncTaskDemo" >



    <ProgressBar 

        android:id="@+id/bar"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        style="?android:attr/progressBarStyleHorizontal"/>

    <TextView

        android:id="@+id/info"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content" />



</LinearLayout>

定义Activity程序，显示进度条

package com.example.contactsdemo;



import android.support.v7.app.ActionBarActivity;

import android.os.AsyncTask;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.ProgressBar;

import android.widget.TextView;



public class MyAsyncTaskDemo extends ActionBarActivity {

    private ProgressBar bar = null;    //进度条组件

    private TextView info = null;    //文本显示组件

    

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_my_async_task_demo);

        this.bar = (ProgressBar) super.findViewById(R.id.bar);

        this.info = (TextView) super.findViewById(R.id.info);

        ChildUpdate child = new ChildUpdate();  //子任务对象

        child.execute(100);  //休眠时间

    }



    private class ChildUpdate extends AsyncTask<Integer, Integer, String>{



        @Override

        protected void onPostExecute(String result) {  //任务执行完后执行

            MyAsyncTaskDemo.this.info.setText(result); //设置文本

        }



        @Override

        protected void onProgressUpdate(Integer... values) { //每次更新后的数值

            MyAsyncTaskDemo.this.info.setText("当前进度是："+values[0]); //更新文本信息

        }



        @Override

        protected String doInBackground(Integer... arg0) {  //处理后台任务

            for(int i=0;i<100;i++){                            //进度条累加

                MyAsyncTaskDemo.this.bar.setProgress(i);  //设置进度

                this.publishProgress(i);  //传递每次更新的内容

                try {

                    Thread.sleep(arg0[0]);  //延缓执行

                } catch (InterruptedException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                }

            }

            return "执行完毕！";

        }

        

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.my_async_task_demo, menu);

        return true;

    }



    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        int id = item.getItemId();

        if (id == R.id.action_settings) {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }

}