Handler常见发送消息方法

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();
            }
        });
    }
}

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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();
            }
        });
    }
}