java - 无法在 Snackbar 中设置计时器

Question

我正在尝试在我的 Snackbar 中设置一个计时器，到目前为止我已经尝试过并让计时器工作但不是在 getTime() 方法中，我认为可能是这种情况为什么这不起作用。

如果这个问题太糟糕了，我很抱歉，我只将 Android 作为一个副项目。

public class MainActivity extends AppCompatActivity {

private static final String AUDIO_RECORDER_FILE_EXT = ".3gp";
private static final String AUDIO_RECORDER_FOLDER = "VRemind";
private MediaRecorder recorder = null;
private int currentFormat = 0;
private int output_format = MediaRecorder.OutputFormat.THREE_GPP;
private String file_ext = AUDIO_RECORDER_FILE_EXT;

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

   final CountDownTimer t;


    t = new CountDownTimer( Long.MAX_VALUE , 1000) {

        int cnt=0;

        @Override
        public void onTick(long millisUntilFinished) {

            cnt++;
            long millis = cnt;
            int seconds = (int) (millis / 60);

            setTime(cnt);
            Log.d("Count:", ""+cnt);
        }

        @Override
        public void onFinish() {

        }
    };

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    final Snackbar snackbar = Snackbar.make(findViewById(R.id.root_layout), getTime(), Snackbar.LENGTH_INDEFINITE);

    final FloatingActionButton fabAdd = (FloatingActionButton) findViewById(R.id.fabAdd);
    final FloatingActionButton fabStop = (FloatingActionButton) findViewById(R.id.fabStop);

    fabAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            t.start();
            fabAdd.setVisibility(View.GONE);
            fabStop.setVisibility(View.VISIBLE);
            snackbar.show();
            snackbar.setAction("CANCEL", new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    snackbar.dismiss();
                    fabAdd.setVisibility(View.VISIBLE);
                    fabStop.setVisibility(View.GONE);
                }
            });

        }
    });

    fabStop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            t.cancel();
            snackbar.dismiss();
            fabStop.setVisibility(View.GONE);
            fabAdd.setVisibility(View.VISIBLE);
        }
    });




}




private String display;

public void setTime(int rawCount) {

    int rc = rawCount;

    int minutes = (rc - (rc % 60)) / 60;
    int seconds = (rc % 60);

    String mins = String.format(Locale.ENGLISH, "%02d", minutes);
    String secs = String.format(Locale.ENGLISH, "%02d", seconds);
    display = mins+ ":" +secs;

    Log.d("CountTwo:",display);
    getTime();

}

public String getTime() {

    Log.d("Count getTime:", display);
    return display;
}

Answer 1

你收到这条消息了吗？

java.lang.NullPointerException: println needs a message

如果是，那是因为您尝试像这样记录一条空消息:

Log.d("Count getTime:", display);

您必须初始化显示变量以在第一次运行时具有值。

private String display = "";