將ArrayList的點存儲到Java中的Android文件中

Question

我無法將ArrayList寫入文件。我在做以下事情，正確的方法是什麼？
如果我沒有將「pt」添加到arraylist中，過程就會正常進行並保存。
os.writeObject（arr）; - 此行調試器進入IOException後。代碼：

//holder class implements Serializable 
transient ArrayList<Point> arr; 
transient Point pt; 
//I've tried without transient, same result 
// 
arr = new ArrayList<Point>(); 
pt = new Point(); 
p.x = 10; 
p.y = 20; 
arr.add(pt); 
//If I don't add 'pt' into arraylist, process goes fine and it gets saved. 
// 
String strStorageDirectory = this.getFilesDir() + "/DataFiles"; 
final File DataStorageDirectory = new File(strStorageDirectory); 
File lfile = new File(DataStorageDirectory, "samplefile.bin"); 
FileOutputStream fos; 
    try { 
     fos = new FileOutputStream(lfile); 
     ObjectOutputStream os = new ObjectOutputStream(fos); 
     os.writeObject(arr);//after this line debugger goes to IOException 
     //I've tried with os.writeObject((Serializable)arr), same result; 
     os.flush();//I've tried removing it, same result 
     os.close(); 
     fos.close(); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

Answer 1

除了在ArrayList中保留Point之外，您還可以爲每個點添加兩個Integer。整數支持Serializable,Point不支持。

Answer 2

要seralize的List<Point>，你Point類必須serializable。

public class Point implements Serializable {...} 

我建議使用JSON（gson）API來直接讀寫對象。

Answer 3

android.graphics.Point不是Serializable。

創建一個新的類PointSerializable將在複製android.graphics.Point定製Point類

class Point implements Serializable 
{ 
    private static final long serialVersionUID = 1L; 

    private int x; 
    private int y; 

    Point(android.graphics.Point point) 
    { 
     this.x = point.x; 
     this.y= point.y; 
    } 
}