用eclipse移动应用开发设计一个计时器，包括main文件和java文件

以下是一个基本的计时器应用程序的main文件和java文件示例，使用Eclipse开发，希望可以帮助您入门移动应用程序开发：

Main文件：

package com.example.timer;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

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

Java文件：

package com.example.timer;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {

    private int seconds = 0;
    private boolean running;
    private boolean wasRunning;

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

        if (savedInstanceState != null) {
            seconds = savedInstanceState.getInt("seconds");
            running = savedInstanceState.getBoolean("running");
            wasRunning = savedInstanceState.getBoolean("wasRunning");
        }

        runTimer();

        Button startButton = findViewById(R.id.start_button);
        startButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                running = true;
            }
        });

        Button stopButton = findViewById(R.id.stop_button);
        stopButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                running = false;
            }
        });

        Button resetButton = findViewById(R.id.reset_button);
        resetButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                running = false;
                seconds = 0;
            }
        });
    }

    private void runTimer() {
        final TextView timeView = findViewById(R.id.time_view);
        final Handler handler = new Handler();

        handler.post(new Runnable() {
            @Override
            public void run() {
                int hours = seconds / 3600;
                int minutes = (seconds % 3600) / 60;
                int secs = seconds % 60;

                String time = String.format("%d:%02d:%02d", hours, minutes, secs);
                timeView.setText(time);

                if (running) {
                    seconds++;
                }

                handler.postDelayed(this, 1000);
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (wasRunning) {
            running = true;
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        wasRunning = running;
        running = false;
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt("seconds", seconds);
        outState.putBoolean("running", running);
        outState.putBoolean("wasRunning", wasRunning);
    }
}

请注意，此示例仅包括计时器应用程序的基本功能，并且还可以进行许多其他改进和自定义，具体取决于您的需求和偏好。