AndroidStudio项目制作倒计时模块的方法

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package cn.edu.gdmec.android.counttime;

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.EditText;
import android.widget.TextView;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
  private EditText inputet;
  private Button get, startTime, stopTime;
  private TextView time;
  private int i = 0;
  private Timer timer = null;
  private TimerTask task = null;

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

  private void initView() {
    inputet = findViewById(R.id.input);
    get = findViewById(R.id.get);
    startTime = findViewById(R.id.starttime);
    stopTime = findViewById(R.id.stoptime);
    time = findViewById(R.id.time);
    getTime.setOnClickListener(this);
    startTime.setOnClickListener(this);
    stopTime.setOnClickListener(this);
  }

  @Override
  public void onClick(View v) {
    switch (v.getId()) {
      case R.id.get:
        time.setText(inputet.getText().toString());
        i = Integer.parseInt(inputet.getText().toString());
        break;
      case R.id.starttime:
        startTime();
        break;
      case R.id.stoptime:
        stopTime();
        break;
      default:
        break;
    }
  }

  private Handler mHandler = new Handler() {
    public void handleMessage(Message msg) {
      time.setText(msg.arg1 + "");
      startTime();
    };
  };

  public void startTime() {
    timer = new Timer();
    task = new TimerTask() {

      @Override
      public void run() {
        if (i > 0) {  //加入判断不能小于0
          i--;
          Message message = mHandler.obtainMessage();
          message.arg1 = i;
          mHandler.sendMessage(message);
        }
      }
    };
    timer.schedule(task, 1000);
  }

  public void stopTime(){
    timer.cancel();
  }
}

//获取的按钮实现：
time.setText(inputet.getText().toString());
i = Integer.parseInt(inputet.getText().toString());
//Handler的加入
private Handler mHandler = new Handler() {
    public void handleMessage(Message msg) {
      time.setText(msg.arg1 + "");
      startTime();
    };
  };
//倒计时主要核心
public void startTime() {
    timer = new Timer();
    task = new TimerTask() {

      @Override
      public void run() {
        if (i > 0) {  //加入判断不能小于0
          i--;
          Message message = mHandler.obtainMessage();
          message.arg1 = i;
          mHandler.sendMessage(message);
        }
      }
    };
    timer.schedule(task, 1000);
  }