Question

7.2. 使用 Runnable 和 Handler 实现定时执行

原理是使用 handler.postDelayed 延迟 Runnable 的运行时间

		
package cn.netkiller.okhttp;

import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class RunnableActivity extends AppCompatActivity {

    private Handler handler = new Handler();
    private Runnable runnable = new Runnable() {
        public void run() {
            this.update();
            handler.postDelayed(this, 1000);// 1000 ms = 1s 间隔1秒
        }

        void update() {
            DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            time.setText(dateFormat.format(new Date()));
        }
    };
    private TextView time;

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

        time = (TextView) findViewById(R.id.time);
        time.setText("Start...");

        handler.postDelayed(runnable, 1000 * 5); // 5 秒后开始
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        handler.removeCallbacks(runnable);
    }

}