Question

我有一些结果，我将它们存储在ArrayList中。我想将这些txt文件保存（输出）到我的SD卡。但我不知道。我尝试了一个代码，但文件还没有制作完成。如果文件生成，我会写入下一个活动。我想知道如何将ArrayList写入下一个Activity。

点数：列表，存储谷歌地图标记位置 szoveg：一个String ArrayList。

if(points.size()>1  ) { 

                for(int i=0;i<points.size();i++){
                    for(int j=i+1;j<points.size();j++){
                        Location LocA = new Location("A");
                        LocA.setLatitude(points.get(i).latitude);
                        LocA.setLongitude(points.get(i).longitude);

                        Location LocB= new Location("B");
                        LocB.setLatitude(points.get(j).latitude);
                        LocB.setLongitude(points.get(j).longitude);

                        double distance = LocA.distanceTo(LocB);

                        String rad = "";
                        rad=sharedPreferences.getString("rad"+i, "0");
                        double radius=Double.parseDouble(rad);

                        String rad2 = "";
                        rad2=sharedPreferences.getString("rad"+j, "0");
                        double radius2=Double.parseDouble(rad2);

                        if(distance<radius && distance < radius2)
                        {
                            szoveg.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m");
                            Toast.makeText(getBaseContext(), "Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m" , Toast.LENGTH_SHORT).show();
                            // Drawing Polyline on the map
                            //drawPolyline(point);                                     

                        }
                        else if (distance>radius && distance<radius2)
                        {
                            szoveg.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m");
                            Toast.makeText(getBaseContext(), "Kommunikál: " + (j+1) + " -> " + (i+1)+ " - " + distance + " m" , Toast.LENGTH_SHORT).show();
                            // Drawing Polyline on the map
                            //drawPolyline(point);
                        }
                        else if (distance<radius && distance>radius2)
                        {
                            szoveg.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m");
                            Toast.makeText(getBaseContext(), "Kommunikál: " +(i+1)+ " -> " +(j+1)+ " - " + distance + " m" , Toast.LENGTH_SHORT).show();
                            // Drawing Polyline on the map
                            //drawPolyline(point);
                        }
                        //else Toast.makeText(getBaseContext(), "Nem kommunikál -  " + distance + " m" , Toast.LENGTH_SHORT).show();
                    }
                }
            }
            else  Toast.makeText(getBaseContext(), "Marker is added to the Map", Toast.LENGTH_SHORT).show();

        }

我尝试了另一个应用程序但是没有用（我在onCreate中使用writeTest（））：

@SuppressLint("SdCardPath")
private void writeTest() {
    lista = new ArrayList<String>();
    int i= 0;
    int j=0;
    int distance = 100;
    lista.add(("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m"));
    lista.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m");

    try {
        FileOutputStream fileOut = new FileOutputStream("/mnt/sdcard/elso.txt");  
        ObjectOutputStream oos = new ObjectOutputStream (fileOut);  
        oos.writeObject(lista);
        fileOut.close();
    } catch (Exception e) {
        System.err.println(e.getMessage());
    }
}

Answer 1

如果您需要将List保存为文本，请使用ForEach循环或Iterator，运行所有Elements并将每个String提供给FileWriter并将其另存为SD卡上的Text。

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ListDemo {

    public static void main(String[] args) {
        FileWriter fileWriter = null;
        try {
            List<String> lista = new ArrayList<>();
            int i= 0;
            int j=0;
            int distance = 100;
            lista.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m\n");
            lista.add("Kommunikál: " +(i+1)+ " -> " +(j+1)+ " && " +(j+1)+ " -> " +(i+1)+ " - " + distance + " m");

            fileWriter = new FileWriter(new File("listOutput.txt"));
            for(String s : lista) 
                fileWriter.write(s);

            fileWriter.flush();
        } catch (IOException ex) {
            Logger.getLogger(ListDemo.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            try {
                fileWriter.close();
            } catch (IOException ex) {
                Logger.getLogger(ListDemo.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }
}

如果使用ObjectOutputStream，则可以将原始类型和复杂的Java对象写入文件，然后可以从文件中读取此对象并重新构建它。

帕特里克

如何写一个txt文件我的ArrayList？

1 个答案: