在我的应用程序中，我根据从数据库中获得的数据计算了一些特征（平均值、最大值、分箱分布等）。但是当我尝试将这些功能写入文件时，它只显示 null 其中特定的功能变量。我看着并试图找到问题的根源，但找不到解决方案。这是我计算在文件上显示 null 的值（它仅在 binz10 上显示 null）：
i=1;
first=minZ;
next=minZ+zInterval;
while(i<=10){
Cursor myCursor2;
if(i==10)
myCursor2=db.rawQuery("SELECT * from Koordinatlar where zKoor>="+first+" AND zKoor<="+next+" AND zaman>="+firstTime+" AND zaman<="+lastTime,null);
else
myCursor2=db.rawQuery("SELECT * from Koordinatlar where zKoor>="+first+" AND zKoor<"+next+" AND zaman>="+firstTime+" AND zaman<="+lastTime,null);
myContentValues.put("binZ"+i, myCursor2.getCount());
i++;
first=next;
next=next+zInterval;
}
这就是我将它写入文件（csv 格式）的地方：
private void dosyayaYaz(){
Cursor dataReader;
File myFile;
myFile= new File("sdcard/"+label+"-features.csv");
try {
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append("ortX;ortY;ortZ;stdX;stdY;stdZ;maxX;maxY;maxZ;aadX;aadY;aadZ;averageResultantAcc;binX1;binX2;binX3;binX4;binX5;binX6;binX7;binX8;binX9;binX10;binY1;binY2;binY3;binY4;binY5;binY6;binY7;binY8;binY9;binY10;binZ1;binZ2;binZ2;binZ3;binZ4;binZ5;binZ6;binZ7;binZ8;binZ9;binZ10;label");
myOutWriter.append("\n");
dataReader=db.rawQuery("SELECT * FROM Features", null);
while(dataReader.moveToNext()){
Float ortX1=(dataReader.getFloat(dataReader.getColumnIndex("ortX")));
Float ortY1=(dataReader.getFloat(dataReader.getColumnIndex("ortY")));
Float ortZ1=(dataReader.getFloat(dataReader.getColumnIndex("ortZ")));
Float maxX1=(dataReader.getFloat(dataReader.getColumnIndex("maxX")));
Float maxY1=(dataReader.getFloat(dataReader.getColumnIndex("maxY")));
Float maxZ1=(dataReader.getFloat(dataReader.getColumnIndex("maxZ")));
Float stdX1=(dataReader.getFloat(dataReader.getColumnIndex("stdX")));
Float stdY1=(dataReader.getFloat(dataReader.getColumnIndex("stdY")));
Float stdZ1=(dataReader.getFloat(dataReader.getColumnIndex("stdZ")));
Float aadX1=(dataReader.getFloat(dataReader.getColumnIndex("aadX")));
Float aadY1=(dataReader.getFloat(dataReader.getColumnIndex("aadY")));
Float aadZ1=(dataReader.getFloat(dataReader.getColumnIndex("aadZ")));
int binX1=(dataReader.getInt(dataReader.getColumnIndex("binX1")));
int binX2=(dataReader.getInt(dataReader.getColumnIndex("binX2")));
int binX3=(dataReader.getInt(dataReader.getColumnIndex("binX3")));
int binX4=(dataReader.getInt(dataReader.getColumnIndex("binX4")));
int binX5=(dataReader.getInt(dataReader.getColumnIndex("binX5")));
int binX6=(dataReader.getInt(dataReader.getColumnIndex("binX6")));
int binX7=(dataReader.getInt(dataReader.getColumnIndex("binX7")));
int binX8=(dataReader.getInt(dataReader.getColumnIndex("binX8")));
int binX9=(dataReader.getInt(dataReader.getColumnIndex("binX9")));
int binX10=(dataReader.getInt(dataReader.getColumnIndex("binX10")));
int binY1=(dataReader.getInt(dataReader.getColumnIndex("binY1")));
int binY2=(dataReader.getInt(dataReader.getColumnIndex("binY2")));
int binY3=(dataReader.getInt(dataReader.getColumnIndex("binY3")));
int binY4=(dataReader.getInt(dataReader.getColumnIndex("binY4")));
int binY5=(dataReader.getInt(dataReader.getColumnIndex("binY5")));
int binY6=(dataReader.getInt(dataReader.getColumnIndex("binY6")));
int binY7=(dataReader.getInt(dataReader.getColumnIndex("binY7")));
int binY8=(dataReader.getInt(dataReader.getColumnIndex("binY8")));
int binY9=(dataReader.getInt(dataReader.getColumnIndex("binY9")));
int binY10=(dataReader.getInt(dataReader.getColumnIndex("binY10")));
int binZ1=(dataReader.getInt(dataReader.getColumnIndex("binZ1")));
int binZ2=(dataReader.getInt(dataReader.getColumnIndex("binZ2")));
int binZ3=(dataReader.getInt(dataReader.getColumnIndex("binZ3")));
int binZ4=(dataReader.getInt(dataReader.getColumnIndex("binZ4")));
int binZ5=(dataReader.getInt(dataReader.getColumnIndex("binZ5")));
int binZ6=(dataReader.getInt(dataReader.getColumnIndex("binZ6")));
int binZ7=(dataReader.getInt(dataReader.getColumnIndex("binZ7")));
int binZ8=(dataReader.getInt(dataReader.getColumnIndex("binZ8")));
int binZ9=(dataReader.getInt(dataReader.getColumnIndex("binZ9")));
int binZ10=(dataReader.getInt(dataReader.getColumnIndex("binZ10")));
String tempLabel=(dataReader.getString(dataReader.getColumnIndex("label")));
Float averageResultantAcc1=(dataReader.getFloat(dataReader.getColumnIndex("averageResultantAcc")));
myOutWriter.append(String.format("%f",ortX1)+";"+String.format("%f",ortY1)+";"+String.format("%f",ortZ1)+";"+String.format("%f",stdX1)+";"+String.format("%f",stdY1)+";"+String.format("%f",stdZ1)+";"+String.format("%f",maxX1)+";"+String.format("%f",maxY1)+";"+String.format("%f",maxZ1)+";"+String.format("%f",aadX1)+";"+String.format("%f",aadY1)+";"+String.format("%f",aadZ1)+";"+String.format("%f",averageResultantAcc1)+";"+String.format("%d",binX1)+";"+String.format("%d",binX2)+";"+String.format("%d",binX3)+";"+String.format("%d",binX4)+";"+String.format("%d",binX5)+";"+String.format("%d",binX6)+";"+String.format("%d",binX7)+";"+String.format("%d",binX8)+";"+String.format("%d",binX9)+";"+String.format("%d",binX10)+";"+String.format("%d",binY1)+";"+String.format("%d",binY2)+";"+String.format("%d",binY3)+";"+String.format("%d",binY4)+";"+String.format("%d",binY5)+";"+String.format("%d",binY6)+";"+String.format("%d",binY7)+";"+String.format("%d",binY8)+";"+String.format("%d",binY9)+";"+String.format("%d",binY10)+";"+String.format("%d",binZ1)+";"+String.format("%d",binZ2)+";"+String.format("%d",binZ3)+";"+String.format("%d",binZ4)+";"+String.format("%d",binZ5)+";"+String.format("%d",binZ6)+";"+String.format("%d",binZ7)+";"+String.format("%d",binZ8)+";"+String.format("%d",binZ9)+";"+String.format("%d",binZ10)+";"+tempLabel);
myOutWriter.append("\n");
}
myOutWriter.close();
fOut.close();
Toast toast=Toast.makeText(this.myContext, "Feature'lar başarıyla üretilip dosyaya yazıldı...",Toast.LENGTH_SHORT);
toast.show();
}
catch(IOException ex){
Toast toast=Toast.makeText(this.myContext, "Dosyaya yazma sırasında bir hata oluştu"+" "+ex.toString(),Toast.LENGTH_LONG);
toast.show();
}
}