Android之Handler 最简单的代码实现Handler

快来打我* 2022-02-14 05:40 200阅读 0赞

首先先写一个简单的布局

<?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:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".MainActivity">
    
    
        <Button
            android:id="@+id/btn_1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="Button"/>
    
        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="Hello World!" />
    
    </LinearLayout>

之后就是编写主代码了

package com.example.handlepro;
    
    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 {
        private static final String TAG = "MainActivity";
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            final TextView textView;
            super.onCreate (savedInstanceState);
            setContentView (R.layout.activity_main);
            textView = findViewById (R.id.textView);
             final Handler handler = new Handler (){   //创建Handler
                @Override
                public void handleMessage(Message msg) {
                    super.handleMessage (msg);
                    Log.d (TAG, "handleMessage: "+msg.what);
                    if(msg.what == 1001){
                        textView.setText ("Fuck");
                    }
                }
            };
             findViewById (R.id.btn_1).setOnClickListener (new View.OnClickListener () {
                 @Override
                 public void onClick(View v) {
                    new Thread (new Runnable () {       //子线程
                        @Override
                        public void run() {
                            handler.sendEmptyMessage (1001);
                        }
                    }).start ();   //启动线程
                 }
             });
    
        }
    }

主线程接收到子线程的消息，然后去处理，就可以实现文本的改变了

其实最简单简洁的代码是这样的

package com.example.handlepro;
    
    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 {
        private static final String TAG = "MainActivity";
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            final TextView textView;
            super.onCreate (savedInstanceState);
            setContentView (R.layout.activity_main);
             Handler handler = new Handler (){
                @Override
                public void handleMessage(Message msg) {
                    super.handleMessage (msg);
                    Log.d (TAG, "handleMessage: "+msg.what);
                }
            };
             textView = findViewById (R.id.textView);
             findViewById (R.id.btn_1).setOnClickListener (new View.OnClickListener () {
                 @Override
                 public void onClick(View v) {
                    new Thread (new Runnable () {
                        @Override
                        public void run() {
                            textView.setText ("Fuck");
                        }
                    }).start ();
                 }
             });
    
        }
    }

直接就可以运行啦