android studio的Handler简单实例代码

实现：edittext输入消息，通过按钮选择发送给主线程或者子线程；

以下有效果图、mainactivity.java代码和activity_main.xml代码

效果图：

mainactivity.java代码

package huan.san.handleroneapp;

import androidx.annotation.nonnull;
import androidx.appcompat.app.appcompatactivity;

import android.os.bundle;
import android.os.handler;
import android.os.looper;
import android.os.message;
import android.util.log;
import android.view.view;
import android.widget.button;
import android.widget.edittext;
import android.widget.textview;

public class mainactivity extends appcompatactivity {
    public static final string tag = "mainactivity";
    private textview mtextview1;
    private textview mtextview2;
    private button mbutton1;
    private button mbutton2;
    private handler1 msubthreadhandler;
    private handler2 mmainthreadhandler;
    private edittext medittext;
    string smessage;
    private int counter = 0;
    @override
    protected void oncreate(bundle savedinstancestate) {
        super.oncreate(savedinstancestate);
        setcontentview(r.layout.activity_main);
        init();
    }
    public void init() {
        mtextview1 = (textview)findviewbyid(r.id.textview1);
        mtextview2 = (textview)findviewbyid(r.id.textview2);
        mbutton1 = (button) findviewbyid(r.id.button1);
        mbutton2 = (button) findviewbyid(r.id.button2);
        medittext = (edittext)findviewbyid(r.id.edittexttextpersonname) ;

        mbutton1.setonclicklistener(new view.onclicklistener() {
            @override
            public void onclick(view view) {
                smessage=medittext.gettext().tostring();
                //主线程发送消息到子线程
                msubthreadhandler = new handler1(getmainlooper());
                message message = new message();
                message.obj = smessage;
                msubthreadhandler.sendmessage(message);
            }
        });
        mbutton2.setonclicklistener(new view.onclicklistener() {
            @override
            public void onclick(view view) {
                smessage=medittext.gettext().tostring();
                //子线程发送消息到主线程
                mmainthreadhandler = new handler2(getmainlooper());
                message message = new message();
                message.obj = smessage;
                mmainthreadhandler.sendmessage(message);
            }
        });

        new thread(){
            public void run(){
                looper.prepare();
                //looper.mylooper()获取当前线程的looper
                msubthreadhandler = new handler1(looper.mylooper());
                message message = new message();
                message.obj = smessage;
            };
        }.start();
    }
    
    public class handler1 extends handler{
        private handler1(looper looper){
            super(looper);
        }

        @override
        public void handlemessage(@nonnull message msg) {
            super.handlemessage(msg);
            //子线程消息显示
            mtextview2.settext("子线程收到：" + msg.obj);
        }
    }

    public class handler2 extends handler{
        private handler2(looper looper){
            super(looper);
        }

        @override
        public void handlemessage(@nonnull message msg) {
            super.handlemessage(msg);
            //主线程消息显示
            mtextview1.settext("主线程收到：" + msg.obj);

        }
    }
}

activity_main.xml代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.constraintlayout 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:layout_height="match_parent"
    tools:context=".mainactivity">


    <button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="60dp"
        android:layout_margintop="140dp"
        android:text="主线程发送消息"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent" />

    <button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginstart="220dp"
        android:layout_margintop="140dp"
        android:text="子线程发送消息"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent" />

    <textview
        android:id="@+id/textview2"
        android:layout_width="137dp"
        android:layout_height="97dp"
        android:layout_marginstart="220dp"
        android:layout_margintop="216dp"
        android:text="没有收到消息"
        android:textsize="20sp"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent" />

    <textview
        android:id="@+id/textview1"
        android:layout_width="139dp"
        android:layout_height="94dp"
        android:layout_marginstart="60dp"
        android:layout_margintop="216dp"
        android:text="没有收到消息"
        android:textsize="20sp"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent" />

    <edittext
        android:id="@+id/edittexttextpersonname"
        android:layout_width="200dp"
        android:layout_height="51dp"
        android:layout_marginstart="104dp"
        android:layout_margintop="64dp"
        android:ems="10"
        android:inputtype="textpersonname"
        android:text="请输入"
        app:layout_constraintstart_tostartof="parent"
        app:layout_constrainttop_totopof="parent" />


</androidx.constraintlayout.widget.constraintlayout>

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