我有一个包含自定义服务对象的ArrayList.我想将整个ArrayList写入一个文件,然后可以读取它.

我为此尝试了Gson,但它给了我一个IllegalStateException：预期为BEGIN_ARRAY,但为STRING.我让它记录了应该是JSON的Strings,并在其中表示了很多异常(作为String中的文本..也许转换出错了吗？).

public int saveListToFile(){

String filename = "service_entries";

File file = new File(getFilesDir(), filename);

try {

BufferedWriter buffWriter = new BufferedWriter(new FileWriter(file, true));

Gson gson = new Gson();

String json = gson.toJson(services); //this is the ArrayList

buffWriter.append(json);

buffWriter.newLine();

buffWriter.close();

} catch (IOException e) {

return -1;

}

return 0;

}

public int readCurrentList(){

String filename = "service_entries";

File file = new File(getFilesDir(), filename);

try {

BufferedReader buffReader = new BufferedReader(new FileReader(file));

String line1, line2;

Gson gson = new Gson();

line1 = buffReader.readLine();

line2 = buffReader.readLine();

if(line1 == null){

buffReader.close();

return 0;

}

Type type = new TypeToken>(){}.getType();

services = gson.fromJson(line1, type);

ArrayList list2;

if(line2 != null){

list2 = gson.fromJson(line2, type);

services.addAll(list2);

list2 = null;

}

buffReader.close();

} catch(IOException e){

return -1;

}

return 0;

}

public class Service {

private double quantity;

private String description;

public Service(){

quantity = 0.0;

description = null;

}

}