Question

我有一个ArrayList()，它存储了一些实时生成的数据。我想得到ArrayList

的连续元素的区别

我试过这个

ArrayList<Long> difference = new ArrayList<>();
difference.add(durationInMs);
//tried to store 
for (int d = 0; d < difference.size()-1; d++){
        time1 = difference.get(d);
        time2 = difference.get(d + 1);
        timeDifference = time2 - time1;
}

此：----------------

ArrayList<Long> difference = new ArrayList<>();
difference.add(durationInMs);

ArrayList<Long> tempArray = new ArrayList<>();
tempArray.add(0, difference.get(0));

for (int d = 0; d < difference.size()-1; d++){
        timeDifference = tempArray.get(d+1) - difference.get(d);
}
Log.d("time", String.valueOf(timeDifference));

也是这个 enter link description here

但是他们似乎没有给我两个连续元素之间的减去值。可能问题是值是实时生成的，这在减去时，尚未生成下一个值。我该怎么做？

更新：方法（如果有帮助）

@Override
public void onPreviewFrame(long startTime, int ySum, int uSum, int vSum, long endTime) {
    begin = startTime;
    img_Y_Avg = ySum;
    img_U_Avg = uSum;
    img_V_Avg = vSum;
    end = endTime;


    //set value of Y on the text view
    TextView valueOfY = (TextView)findViewById(R.id.valueY);
    //valueY = img_Y_Avg;
    valueOfY.setText(Double.toString(img_Y_Avg));

    //set value of U on the text view
    TextView valueOfU = (TextView)findViewById(R.id.valueU);
   // valueU = img_U_Avg;
    valueOfU.setText(Double.toString(img_U_Avg));

    //set value of V on the text view
    TextView valueOfV = (TextView)findViewById(R.id.valueV);
    //valueV = img_V_Avg;
    valueOfV.setText(Double.toString(img_V_Avg));

    //start time in milliseconds
    long StartDurationInMs = TimeUnit.MILLISECONDS.convert(begin, TimeUnit.MILLISECONDS);
    ArrayList<Long> startOfTime = new ArrayList<>();
    startOfTime.add(StartDurationInMs);
    Log.d("time", "start: "+String.valueOf(startOfTime));

    //store value to array list
    ArrayList<Integer> yAverage = new ArrayList<>();
    yAverage.add(img_Y_Avg);
    //Log.d("MyEntryData", String.valueOf(yAverage));

    //store u values to array
    ArrayList<Integer> uAverage = new ArrayList<>();
    uAverage.add(img_U_Avg);
    //Log.d("MyEntryData", String.valueOf(uAverage));

    //store u values to array
    ArrayList<Integer> vAverage = new ArrayList<>();
    vAverage.add(img_V_Avg);
    //Log.d("MyEntryData", String.valueOf(vAverage));
    //time between frames

    //end time in milliseconds
    long EndDurationInMs = TimeUnit.MILLISECONDS.convert(end, TimeUnit.MILLISECONDS);
    ArrayList<Long> endOfTime = new ArrayList<>();
    endOfTime.add(EndDurationInMs);


    Log.d("time", "end: "+String.valueOf(endOfTime));


    ArrayList<Long> getValues = new ArrayList<>();
    for(int i = 0; i < yAverage.size(); i++) {
        getValues.add(startOfTime.get(i));
        getValues.add((long)(yAverage.get(i)));
        getValues.add((long)(uAverage.get(i)));
        getValues.add((long)(vAverage.get(i)));
    }


    String filename = new SimpleDateFormat("yyyyMMddHHmm'.csv'").format(new Date());

    File directoryDownload = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
    File logDir = new File (directoryDownload, "bpReader"); //Creates a new folder in DOWNLOAD directory
    logDir.mkdirs();
    File file = new File(logDir, filename);

    FileOutputStream outputStream = null;
    try {
           outputStream = new FileOutputStream(file, true);
           //outputStream = openFileOutput(filename, Context.MODE_PRIVATE);
           for (int i = 0; i < yAverage.size(); i += 4) {
               outputStream.write((getValues.get(i) + ",").getBytes());
               outputStream.write((getValues.get(i + 1) + ",").getBytes());
               outputStream.write((getValues.get(i + 2) + ",").getBytes());
               outputStream.write((getValues.get(i + 3) + "\n").getBytes());

            }
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    Log.d("MyEntryData", String.valueOf(getValues));


    handler = new Handler();
    final Runnable runnable = new Runnable() {
        @Override
        public void run() {
            readingRemaining = readingRemaining -1;

            if (readingRemaining > 0){
                plotGraph(img_Y_Avg);
            }
        }
    };

    handler.postDelayed(runnable, 100);

    //Log.d("MyEntryData", String.valueOf(img_Y_Avg +" "+ img_U_Avg+" "+img_V_Avg));

}

Answer 1

尝试long delta = difference.get（d + 1） - difference.get（d）;

    ArrayList<Long> difference = new ArrayList<>();
    for (int i = 0; i<10; i++)
        difference.add((long)(Math.random() * 1000));
    for (int d = 0; d < difference.size()-1; d++){
        Log.i("diff", String.format(
                "element %d,%d:%d - %d = %d",
                d+1, d, difference.get(d+1), difference.get(d),
                difference.get(d+1) - difference.get(d)));
    }
    Log.i(TAG, "hello");

输出：

... I/diff: element 1,0:197 - 425 = -228
... I/diff: element 2,1:389 - 197 = 192
... I/diff: element 3,2:947 - 389 = 558
... I/diff: element 4,3:510 - 947 = -437
... I/diff: element 5,4:399 - 510 = -111
... I/diff: element 6,5:971 - 399 = 572
... I/diff: element 7,6:537 - 971 = -434
... I/diff: element 8,7:326 - 537 = -211
... I/diff: element 9,8:897 - 326 = 571

Answer 2

如果您担心在处理数组时实时修改数组，那么

建议1

在生成新数据点时，您是否可以查看先前的数据点并在运行中计算delta，然后将delta（）添加到另一个数组？

  long lastDatum = null;
  ArrayList<long> diffArray = new ArrayList<>();

  void recordDataPoint(long datum)
  { 
      if (lastDatum != null) {
         diffArray.add(datum - lastDatum);
      }
      lastDatum = datum;

      // ... do whatever else you need to do with datum....
   }

建议2
如果阵列稳定，那么我认为你只需要这样做：

  // existing data is in durationInMs[]

  ArrayList<Long> difference = new ArrayList<>();

  for (int d = 0; d < durationInMs.size()-1; d++){
        time1 = durationInMs.get(d);
        time2 = durationInMs.get(d + 1);
        timeDifference = time2 - time1;

        difference.add(timeDifference);
}

ArrayList中两个连续值的差异：Android

2 个答案: