Androidstudio计时器源代码

以下是一个简单的计时器应用程序的源代码：

MainActivity.java:

public class MainActivity extends AppCompatActivity {

    private TextView timerTextView;
    private Button startButton, pauseButton, resetButton;
    private CountDownTimer countDownTimer;
    private boolean timerRunning;
    private long startTimeInMillis, timeLeftInMillis;

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

        timerTextView = findViewById(R.id.timerTextView);
        startButton = findViewById(R.id.startButton);
        pauseButton = findViewById(R.id.pauseButton);
        resetButton = findViewById(R.id.resetButton);

        startButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!timerRunning) {
                    startTimer();
                }
            }
        });

        pauseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (timerRunning) {
                    pauseTimer();
                }
            }
        });

        resetButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                resetTimer();
            }
        });
    }

    private void startTimer() {
        countDownTimer = new CountDownTimer(timeLeftInMillis, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                timeLeftInMillis = millisUntilFinished;
                updateTimer();
            }

            @Override
            public void onFinish() {
                timerRunning = false;
                updateButtons();
            }
        }.start();

        timerRunning = true;
        updateButtons();
    }

    private void pauseTimer() {
        countDownTimer.cancel();
        timerRunning = false;
        updateButtons();
    }

    private void resetTimer() {
        timeLeftInMillis = startTimeInMillis;
        updateTimer();
        updateButtons();
    }

    private void updateTimer() {
        int minutes = (int) (timeLeftInMillis / 1000) / 60;
        int seconds = (int) (timeLeftInMillis / 1000) % 60;
        String timeLeftFormatted = String.format(Locale.getDefault(), "%02d:%02d", minutes, seconds);
        timerTextView.setText(timeLeftFormatted);
    }

    private void updateButtons() {
        if (timerRunning) {
            startButton.setEnabled(false);
            pauseButton.setEnabled(true);
            resetButton.setEnabled(false);
        } else {
            startButton.setEnabled(true);
            pauseButton.setEnabled(false);
            resetButton.setEnabled(true);
        }
    }
}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.timer.MainActivity">

    <TextView
        android:id="@+id/timerTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="60sp"
        android:text="00:00"
        android:layout_centerInParent="true"/>

    <Button
        android:id="@+id/startButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start"
        android:layout_below="@+id/timerTextView"
        android:layout_marginTop="16dp"
        android:layout_centerHorizontal="true"/>

    <Button
        android:id="@+id/pauseButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pause"
        android:layout_toLeftOf="@+id/resetButton"
        android:layout_below="@+id/timerTextView"
        android:layout_marginTop="16dp"
        android:layout_marginRight="16dp"
        android:enabled="false"/>

    <Button
        android:id="@+id/resetButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Reset"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/timerTextView"
        android:layout_marginTop="16dp"
        android:layout_marginLeft="16dp"
        android:enabled="false"/>

</RelativeLayout>

这个应用程序包含一个 `TextView` 显示剩余时间，以及三个按钮：`Start`，`Pause` 和 `Reset`。当用户点击 `Start` 按钮时，计时器开始倒计时，并且 `Start` 按钮禁用，`Pause` 按钮启用。当用户点击 `Pause` 按钮时，计时器暂停，并且 `Pause` 按钮禁用，`Start` 按钮启用。当用户点击 `Reset` 按钮时，计时器被重置为初始状态，即未开始状态。