Handler常见发送消息方法

原CSDN博客已弃用，文章会逐渐迁移过来。

代码实现最简单的Handler

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:app="http://schemas.android.com/apk/res-auto"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:orientation="vertical"  
    android:layout_height="match_parent"  
    android:gravity="center_horizontal"  
    tools:context="com.administrator.handlerproject.MainActivity">  

    <TextView  
        android:id="@+id/textView"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:text="text"/>  
   <Button  
       android:id="@+id/btn1"  
       android:layout_width="wrap_content"  
       android:layout_height="wrap_content"  
       android:text="按钮"/>  

</LinearLayout>  

MainActivity.java

package com.administrator.handlerproject;  

import android.os.Handler;  
import android.os.Message;  
import android.support.v7.app.AppCompatActivity;  
import android.os.Bundle;  
import android.util.Log;  
import android.view.View;  
import android.widget.TextView;  


public class MainActivity extends AppCompatActivity {  
    /** 
     * UI线程 
     */  
    private static final String TAG = "MainActivity";  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        final TextView textView = findViewById(R.id.textView);  
        //创建一个Handler  
        final Handler handler = new Handler() {  
            @Override  
            public void handleMessage(Message msg) {  
                super.handleMessage(msg);  
                if (msg.what==1001)//得到这个消息标记开始处理消息  
//                //处理消息  
                    textView.setText("weimei");  
//                Log.d(TAG,"handleMessage:" + msg.what);  
            }  
        };  
        findViewById(R.id.btn1).setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                //有可能做大量耗时操作  
                /** 
                 * 子线程 
                 */  
                new Thread(new Runnable() {  
                    @Override  
                    public void run() {  
                        try {  
                            Thread.sleep(2000);  
                        } catch (InterruptedException e) {  
                            e.printStackTrace();  
                        }  
                        handler.sendEmptyMessage(1001);//向消息队列发送一个标记  
                    }  
                }).start();  
            }  
        });  
    }  
}  

Handler的一些常用标记键，以及延时方法。

xml布局同上不变

MainActivity.java

package com.administrator.handlerproject;  

import android.os.Handler;  
import android.os.Message;  
import android.os.SystemClock;  
import android.support.v7.app.AppCompatActivity;  
import android.os.Bundle;  
import android.util.Log;  
import android.view.View;  
import android.widget.TextView;  


public class MainActivity extends AppCompatActivity {  
    /** 
     * UI线程 
     */  
    private static final String TAG = "MainActivity";  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        final TextView textView = findViewById(R.id.textView);  
        //创建一个Handler  
        final Handler handler = new Handler() {  
            @Override  
            public void handleMessage(Message msg) {//接收到完整的包裹  
                super.handleMessage(msg);  
                if (msg.what==1002)//拆解包裹拿值  
//                //处理消息  
                    textView.setText("weimei");  
                Log.d(TAG,"handleMessage:" + msg.arg1);  

            }  
        };  
        findViewById(R.id.btn1).setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                //有可能做大量耗时操作  
                /** 
                 * 子线程 
                 */  
                new Thread(new Runnable() {  
                    @Override  
                    public void run() {  
                        try {  
                            Thread.sleep(2000);  
                        } catch (InterruptedException e) {  
                            e.printStackTrace();  
                        }  
                        handler.sendEmptyMessage(1001);  
                        Message message = Message.obtain();  
                        message.what=1002;  
                        message.arg1=1003;  
                        message.arg2=1004;//将每个消息组装  
                        message.obj=MainActivity.this;//打包发出去  
                        handler.sendMessage(message);  
                        /** 
                         * 定时任务 
                         */  
                        handler.sendMessageAtTime(message, SystemClock.uptimeMillis()+3000);//计时,SystemClock.uptimeMillis()获取当前时间  
                        handler.sendMessageDelayed(message,2000);//上面的是绝对时间，下面的是相对时间，即消息送走时间  

                        final Runnable runnable = new Runnable() {  
                            @Override  
                            public void run() {  
                                int a = 1 + 2 + 3;  
                            }  
                        };  
                        handler.post(runnable);  
                        runnable.run();  

                        handler.postDelayed(runnable,2000);//延迟两秒  
                        }  

                }).start();  
            }  
        });  
    }  
}