Android消息机制—倒计时计数器

最新推荐文章于 2021-06-08 16:01:58 发布

原创最新推荐文章于 2021-06-08 16:01:58 发布 · 440 阅读

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#消息 #android

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本文介绍了三种在Android中实现倒计时的方法：使用Handler和Thread、Looper以及AsyncTask。每种方法都通过实例展示了如何更新UI显示剩余的时间。

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1，普通Handler，Thread；

package com.zdsoft.clock1230;

import android.os.Handler;
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;

public class MainActivity extends AppCompatActivity {
    private Button bt_start;
    private TextView tv_show;
    private int count = 10;

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

        initView();
        bt_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final Handler handler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        if (msg.what == 1) {
                            tv_show.setText(msg.obj + "");
                        }
                    }
                };
                new Thread() {
                    @Override
                    public void run() {
                        while (count >= 0) {
                            Message message = new Message();
                            message.what = 1;
                            message.obj = count;
                            handler.sendMessage(message);
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            count--;
                        }
                    }
                }.start();
            }
        });
    }

    private void initView() {
        bt_start = (Button) findViewById(R.id.bt_start);
        tv_show = (TextView) findViewById(R.id.tv_show);
    }
}

2、Looper

package com.zdsoft.clock1230;

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;

public class MainActivity extends AppCompatActivity {
    private Button bt_start;
    private TextView tv_show;
    private int count = 10;
    private MyHandler handler;

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

        initView();
        handler = new MyHandler();
        bt_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(new MyThread()).start();
            }
        });
    }

    private void initView() {
        bt_start = (Button) findViewById(R.id.bt_start);
        tv_show = (TextView) findViewById(R.id.tv_show);
    }

    private class MyHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            //接受消息处理UI
            if (msg.what == 1) {
                tv_show.setText(msg.obj + "");
            }
        }
    }

    private class MyThread extends Thread {
        @Override
        public void run() {
            //发送消息
            Looper.prepare();
            while (count >= 0) {
                Message message = new Message();
                message.what = 1;
                message.obj = count;
                handler.sendMessage(message);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                count--;
            }
            Looper.loop();
        }
    }
}

3、AsyncTask

package com.zdsoft.clock1230;

import android.os.AsyncTask;
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;

public class MainActivity extends AppCompatActivity {
    private Button bt_start;
    private TextView tv_show;
    private int count = 10;

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

        initView();
        bt_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new MyTask().execute();
            }
        });
    }

    private void initView() {
        bt_start = (Button) findViewById(R.id.bt_start);
        tv_show = (TextView) findViewById(R.id.tv_show);
    }

    private class MyTask extends AsyncTask {

        @Override
        protected Object doInBackground(Object[] params) {
            while (count >= 0) {
                publishProgress(count);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                count--;
            }
            return "结束";
        }

        /**
         * 执行过程中，更新UI
         *
         * @param values
         */
        @Override
        protected void onProgressUpdate(Object[] values) {
            tv_show.setText(values[0].toString());
        }

        /**
         * 执行结束后，更新UI
         *
         * @param o
         */
        @Override
        protected void onPostExecute(Object o) {
            tv_show.setText(o.toString());
        }
    }
}