我几乎是在为一项 Activity 制作自定义倒数计时器，但在切换 Activity 时我很难不断更新该值。每次更改 Activity 时，我只能更新一次该值。

例子:

Activity A -> B(屏幕上默认为 0，用户将值更新为 10)

B -> A ->(屏幕上显示 10，用户将值更新为 10)

B -> A ->(屏幕上显示 35，用户将值更新为 9000)等

但是，一旦用户设置了时间，它就应该不断更新并倒计时。

我可以通过 Runnable 更新屏幕后面的值并在控制台上打印出这些值，但我不知道为什么它不会不断地将值传回之前的 Activity ， A，(所以它是最新的)然后当用户返回 B 时让 A 将它传回给 B。

我应该注意，当我尝试只更新 run() 而不是 updateTimerButton() 时，屏幕上没有任何变化，默认值在那里，但在幕后，值正在更新(控制台)。

这是我的:

public class CustomTimer extends Activity {

    private final Handler handler = new Handler();

    private Intent intent;
    private Button timerButton;
    private EditText hourValue, minuteValue;

    private long startTime = 0L;
    private long timeInMilliseconds = 0L;
    private long timeSwapBuff = 0L;
    private long updatedTime = 0L;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_custom_timer);

        intent = getIntent();
        hourValue = (EditText) findViewById(R.id.hour_value);
        minuteValue = (EditText) findViewById(R.id.minute_value);
        timerButton = (Button) findViewById(R.id.start_timer_button);

        //avoid grabbing values from hour and minute if they were not passed for some reason
        if(intent.getStringExtra("hourValue") != null)
            hourValue.setText(getIntent().getStringExtra("hourValue"));
        if(intent.getStringExtra("minuteValue") != null)
            minuteValue.setText(getIntent().getStringExtra("minuteValue"));

        setUpHourValue();
        setUpMinuteValue();
        setUpTimerButton();
    }

    private void setUpHourValue(){

        hourValue.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
                hourValue.setText(v.getText().toString());
                return false;
            }
        });
    }

    private void setUpMinuteValue(){

        minuteValue.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
                minuteValue.setText(v.getText().toString());
                return false;
            }
        });
    }

    private void setUpTimerButton(){

        timerButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View view) {

                String hourTime = hourValue.getText().toString();
                String minuteTime = minuteValue.getText().toString();

                //only start the timer if it is not zero
                if (!hourTime.equals("00") || !minuteTime.equals("00")) {
                    System.out.println("starting runnable");
                    startTime = SystemClock.uptimeMillis();
                    handler.postDelayed(updateTimerThread, 0);
                }
                else{
                    System.out.println("time is default\t" + hourTime + "  : " + minuteTime + "************");
                }

                //send the time values back to main
                //this does not constantly update the values, it only updates it once
                intent.putExtra("hourValue", hourTime);
                intent.putExtra("minuteValue", minuteTime);
                setResult(RESULT_OK, intent);
                finish();//go back to the previous page
            }
        });
    }

    private Intent getOuterClassIntent(){
        return intent;
    }

    private Runnable updateTimerThread = new Runnable() {

        //update the time on the screen and constantly pass the values back to main
        public void run() {

            String hourTime = hourValue.getText().toString();
            String minuteTime = minuteValue.getText().toString();

            timeInMilliseconds = SystemClock.uptimeMillis() - startTime;

            updatedTime = timeSwapBuff + timeInMilliseconds;

            int secs = (int) (updatedTime / 1000);
            int mins = secs / 60;
            int hour = mins / 60;
            secs = secs % 60;

            //update the time on screen
            hourValue.setText(Integer.toString(Integer.parseInt(hourTime) - hour));
            minuteValue.setText(Integer.toString(Integer.parseInt(minuteTime) - secs));

            System.out.println("updating time in runnable");
            System.out.println(hourValue.getText().toString()+ " : " + minuteValue.getText().toString());

            //pass the values back to main, but this does NOTHING if I comment out the previous putExtras (above)
            getOuterClassIntent().putExtra("hourValue", hourTime);
            getOuterClassIntent().putExtra("minuteValue", minuteTime);
            setResult(RESULT_OK, getOuterClassIntent());

            handler.postDelayed(this, 0);
        }
    };
}

最佳答案

如果您需要在多个 Activity 之间共享数据，则数据不应由任何一个 Activity 拥有。创建一个服务，让两个 Activity 在启动时绑定(bind)到它，并在需要知道值时查询服务(通过 Binder)。所有值的更新都应该在服务中进行。

关于Android:如何不断更新/将值从一个 Activity 传递到另一个 Activity ？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35547651/