Handler实现计数器

xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/tv_demo_number"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="10"
        android:textColor="#ff0000"
        android:textSize="20sp"/>

    <Button
        android:id="@+id/btn_demo_increase"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="自动增加" />

    <Button
        android:id="@+id/btn_demo_decrease"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="自动减少" />

    <Button
        android:id="@+id/btn_demo_pause"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="暂停"
        android:enabled="false"/>

</LinearLayout>

activity

package com.example.handlerdemo;

import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class HandlerDemo extends AppCompatActivity implements View.OnClickListener {
    TextView tv_demo_number;
    Button btn_demo_increase;
    Button btn_demo_decrease;
    Button btn_demo_pause;

    private Handler handler = new Handler(Looper.myLooper()) {
        @Override
        public void handleMessage(Message msg) {
            //要得到当前显示的数值
            int number = Integer.parseInt(tv_demo_number.getText().toString());
            switch (msg.what) {
                case 1:
                    if (number == 20) {
                        //设置暂停不可操作
                        btn_demo_pause.setEnabled(false);
                        Toast.makeText(HandlerDemo.this, "已经达到最大值", Toast.LENGTH_SHORT).show();
                        return;
                    }
                    number++;
                    tv_demo_number.setText(number + "");
                    //发送延迟消息
                    handler.sendEmptyMessageDelayed(1, 1000);
                    break;
                case 2:
                    if (number == 1) {
                        btn_demo_pause.setEnabled(false);
                        Toast.makeText(HandlerDemo.this, "已经达到最小值", Toast.LENGTH_SHORT).show();
                        return;
                    }
                    number--;
                    tv_demo_number.setText(number + "");
                    handler.sendEmptyMessageDelayed(2, 1000);
                    break;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_handler_demo);
        init();
    }

    private void init() {
        tv_demo_number = findViewById(R.id.tv_demo_number);
        btn_demo_increase = findViewById(R.id.btn_demo_increase);
        btn_demo_decrease = findViewById(R.id.btn_demo_decrease);
        btn_demo_pause = findViewById(R.id.btn_demo_pause);
        btn_demo_increase.setOnClickListener(this);
        btn_demo_decrease.setOnClickListener(this);
        btn_demo_pause.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view == btn_demo_increase) {
            btn_demo_increase.setEnabled(false);
            btn_demo_decrease.setEnabled(true);
            btn_demo_pause.setEnabled(true);
            //停止减少 移除未处理的减少的消息
            handler.removeMessages(2);
            handler.sendEmptyMessage(1);
        } else if (view == btn_demo_decrease) {
            btn_demo_decrease.setEnabled(false);
            btn_demo_increase.setEnabled(true);
            btn_demo_pause.setEnabled(true);
            handler.removeMessages(1);
            handler.sendEmptyMessage(2);
        } else if (view == btn_demo_pause) {
            //移除未处理的减少或者增加的消息
            handler.removeMessages(1);
            handler.removeMessages(2);
            btn_demo_decrease.setEnabled(true);
            btn_demo_increase.setEnabled(true);
            btn_demo_pause.setEnabled(false);
        }
    }
}

效果图