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从零开始学android<Message消息机制.四十二.>
ndroid.os.Message的主要功能是进行消息的封装，并且同时可以指定消息的操作形式。
No. | 变量或方法 | 类型 | 描述 |
1 | public int what | 变量 | 用于定义此Message属于何种操作 |
2 | public Object obj | 变量 | 用于定义此Message传递的信息数据 |
3 | public int arg1 | 变量 | 传递一些整型数据时使用，一般很少使用 |
4 | public int arg2 | 变量 | 传递一些整型数据时使用，一般很少使用 |
5 | public Handler getTarget() | 普通 | 取得操作此消息的Handler对象 |
可以使用 Handler 和Message处理后台耗时操作最后更新到前台UI。
使用Hander与Message下载网络图片
<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: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=".MainActivity" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="40dp"
android:src=http://www.mamicode.com/"@drawable/ic_launcher" />>
package com.example.message1;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends Activity {
public static final String URL = "http://www.baidu.com/img/baidu_sylogo1.gif";
public static final int SUCCESS_CODE = 1;
private Button button;
private ImageView imageView;
private Handler handler;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) this.findViewById(R.id.button1);
imageView = (ImageView) this.findViewById(R.id.imageView1);
final ProgressDialog dialog = new ProgressDialog(
MainActivity.this);
dialog.setTitle("加载图片");
dialog.setMessage("正在加载请稍后……");
dialog.setCancelable(false);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new Thread(new MyThread()).start();
dialog.show();
}
});
// 前台UI的更新
handler = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
// 取得Bitmap图片
Bitmap bitmap = (Bitmap) msg.obj;
// 为图片设置资源
imageView.setImageBitmap(bitmap);
// 判断图片是否获得，并关闭对话框
if (msg.what == SUCCESS_CODE) {
dialog.dismiss();
}
}
};
}
//后台线程
class MyThread implements Runnable {
@Override
public void run() {
Bitmap bitmap = null;
// TODO Auto-generated method stub
try {
URL url = new URL(URL);//创建Url对象
InputStream inputStream = url.openStream();//获得输入流
bitmap = BitmapFactory.decodeStream(inputStream);//将输入流转换为Bitmap对象
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// 创建Message对象，返回信息
Message message = Message.obtain();
message.obj = bitmap;
message.what = SUCCESS_CODE;
handler.sendMessage(message);
}
}
}
接下来，我们来从基础开始学习。
<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: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=".MainActivity" >
<TextView
android:id="@+id/info"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="150dp"
android:text="获取数据" />
</RelativeLayout>
package com.example.message2;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.Button;import android.widget.TextView;public class MainActivity extends Activity {<span style="white-space:pre"> </span>private Button button;<span style="white-space:pre"> </span>private TextView textView;<span style="white-space:pre"> </span>private Handler handler;<span style="white-space:pre"> </span>@Override<span style="white-space:pre"> </span>protected void onCreate(Bundle savedInstanceState) {<span style="white-space:pre"> </span>super.onCreate(savedInstanceState);<span style="white-space:pre"> </span>super.setContentView(R.layout.activity_main);<span style="white-space:pre"> </span>button = (Button) this.findViewById(R.id.button1);<span style="white-space:pre"> </span>textView = (TextView) this.findViewById(R.id.info);<span style="white-space:pre"> </span>handler = new Handler() {<span style="white-space:pre"> </span>@Override<span style="white-space:pre"> </span>public void handleMessage(Message msg) {<span style="white-space:pre"> </span>// TODO Auto-generated method stub<span style="white-space:pre"> </span>int what = msg.what;<span style="white-space:pre"> </span>int arg1 = msg.arg1;<span style="white-space:pre"> </span>int arg2 = msg.arg2;<span style="white-space:pre"> </span>Object obj = msg.obj;<span style="white-space:pre"> </span>List<Integer> list = null;<span style="white-space:pre"> </span>Bundle bundle = null;<span style="white-space:pre"> </span>bundle = msg.getData();//接受Bundle数据<span style="white-space:pre"> </span>list =bundle.getIntegerArrayList("num");//解析数据<span style="white-space:pre"> </span>for (Integer num : list) {<span style="white-space:pre"> </span>System.out.print("--list:"+num);<span style="white-space:pre"> </span>}<span style="white-space:pre"> </span>System.out.println("what:" + what + ",arg1:" + arg1 + ",arg2:"<span style="white-space:pre"> </span>+ arg2 + ".obj:" + obj);<span style="white-space:pre"> </span>}<span style="white-space:pre"> </span>};<span style="white-space:pre"> </span>button.setOnClickListener(new View.OnClickListener() {<span style="white-space:pre"> </span>@Override<span style="white-space:pre"> </span>public void onClick(View v) {<span style="white-space:pre"> </span>// TODO Auto-generated method stub<span style="white-space:pre"> </span>new Thread(new MyThread()).start();<span style="white-space:pre"> </span>}<span style="white-space:pre"> </span>});<span style="white-space:pre"> </span>}<span style="white-space:pre"> </span>class MyThread implements Runnable {<span style="white-space:pre"> </span>@Override<span style="white-space:pre"> </span>public void run() {<span style="white-space:pre"> </span>// TODO Auto-generated method stub<span style="white-space:pre"> </span>// Message message=new Message();<span style="white-space:pre"> </span>// message.arg1=1;<span style="white-space:pre"> </span>// message.arg2=2;<span style="white-space:pre"> </span>// message.obj=3;<span style="white-space:pre"> </span>// message.what=4;<span style="white-space:pre"> </span>// handler.sendMessage(message);<span style="white-space:pre"> </span>// 第二种方法<span style="white-space:pre"> </span>// Message message=Message.obtain();<span style="white-space:pre"> </span>// message.what=1;<span style="white-space:pre"> </span>// message.arg1=2;<span style="white-space:pre"> </span>// message.arg2=3;<span style="white-space:pre"> </span>// message.obj=4;<span style="white-space:pre"> </span>// handler.sendMessage(message);<span style="white-space:pre"> </span>// 第三种方法<span style="white-space:pre"> </span>// Message message=Message.obtain(handler);<span style="white-space:pre"> </span>// message.what=1;<span style="white-space:pre"> </span>// message.arg1=2;<span style="white-space:pre"> </span>// message.arg2=3;<span style="white-space:pre"> </span>// message.obj=4;<span style="white-space:pre"> </span>// message.sendToTarget();<span style="white-space:pre"> </span>// 第四种方法<span style="white-space:pre"> </span>// Message message=Message.obtain(handler, 1);<span style="white-space:pre"> </span>// message.arg1=2;<span style="white-space:pre"> </span>// message.arg2=3;<span style="white-space:pre"> </span>// message.obj=4;<span style="white-space:pre"> </span>// message.sendToTarget();<span style="white-space:pre"> </span>// 第五种方法<span style="white-space:pre"> </span>// Message message=Message.obtain(handler, 1, 4);<span style="white-space:pre"> </span>// message.arg1=2;<span style="white-space:pre"> </span>// message.arg2=3;<span style="white-space:pre"> </span>// message.sendToTarget();<span style="white-space:pre"> </span>// 第六种方法<span style="white-space:pre"> </span>// Message message=Message.obtain(handler, 1, 2, 3);<span style="white-space:pre"> </span>// message.obj = 4;<span style="white-space:pre"> </span>// message.sendToTarget();<span style="white-space:pre"> </span>// 第七种方法<span style="white-space:pre"> </span>// Message message=Message.obtain(handler, 1, 2, 3, 4);<span style="white-space:pre"> </span>// message.sendToTarget();<span style="white-space:pre"> </span>// 第八种方法<span style="white-space:pre"> </span>Message message = Message.obtain(handler, 1, 2, 3, 4);<span style="white-space:pre"> </span>Bundle bundle = new Bundle();<span style="white-space:pre"> </span>List<Integer>list=new ArrayList<Integer>();<span style="white-space:pre"> </span>list.add(5);<span style="white-space:pre"> </span>list.add(6);<span style="white-space:pre"> </span>list.add(7);<span style="white-space:pre"> </span>bundle.putIntegerArrayList("num", (ArrayList<Integer>)list);<span style="white-space:pre"> </span>message.setData(bundle);<span style="white-space:pre"> </span>message.sendToTarget();<span style="white-space:pre"> </span>}<span style="white-space:pre"> </span>}}
打开logcat 在System.out的过滤器中显示
使用Send和psot发送消息
点击获取信息后，将在3秒后在控制台输出
DEMO 使用hander 实现应用程序的第一屏
主要使用pos方法进行延时操作
当然，此操作需要实现准备一张图片，作为背景。
第一屏xml
<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: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=".MainActivity" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:src=http://www.mamicode.com/"@drawable/logo" />>
主界面xml<?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" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="主界面" />
</LinearLayout>
第一屏JAVA
package com.example.message4;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.Window;
import android.view.WindowManager;
public class MainActivity extends Activity {
public static final int SIGHT_TIME = 3000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);//设置应用没有标题
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
//以上两个设置都必须放在setContentView之前，不然会出现异常
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
Intent intent = new Intent(MainActivity.this, Two.class);
startActivity(intent);
finish();
}
}, SIGHT_TIME);
}
}
第二屏JAVA文件
package com.example.message4;
import android.app.Activity;
import android.os.Bundle;
public class Two extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
super.setContentView(R.layout.main);
}
}
3秒后自动进入主界面
当然，实现应用的第一屏效果可以使用多种方法实现，在这里知识其中的一种，读者也可以直接使用线程进行操作。
下节预报：Service 服务
从零开始学android<Message消息机制.四十二.>
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