我一直在这里搜索，但似乎无法找到有效的方法。我试图将一个简单的对象列表写入序列化文件，并且似乎无法在android中找到该文件。这是我第一次构建应用程序，我通过指向src / list.ser在netbeans中工作，但是，这在android studio中不起作用。我想我的问题是我在哪里放置ser文件，我如何在代码中指向它？这是我的代码：
ListActivity：
public class ListActivity extends Activity implements Serializable {
private ArrayList<Item> list;
public List() throws Exception {
list = new ArrayList<Item>();
}
public void addItem(String name) {
list.add(new Item(name));
}
public void addCurrentList() throws Exception{
String pathToAppFolder = getExternalFilesDir(null).getAbsolutePath();
String filePath = pathToAppFolder +File.separator + "list.ser";
try {
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(filePath));
os.writeObject(list);
os.close();
}
catch (Exception e) {
System.out.println("NOPE NOPE NOPE NOPE");
}
}
public void addItem(String name, int price) {
list.add(new Item(name, price));
}
public ArrayList<Item> populate() {
return list;
}
public void record() {
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream("src/list.ser"));
ArrayList<Item> list2 = (ArrayList<Item>) in.readObject();
System.out.println(list2);
list = list2;
in.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
MainActivity：
public class MainActivity extends AppCompatActivity {
private List tester;
private ListView lv;
private EditText gg;
private Button button;
private Button clearButton;
private ArrayList list;
String pathToAppFolder = getExternalFilesDir(null).getAbsolutePath();
String filePath = pathToAppFolder + File.separator + "list.ser";
@Override
protected void onDestroy() {
try {
tester.addCurrentList();
} catch (Exception e) {
e.printStackTrace();
}
super.onDestroy();
}
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//create the list
lv = (ListView) findViewById(R.id.listDisplay);
ListView mine = lv;
list = new ArrayList<String>();
try {
tester = new List();
}
catch (Exception e) {
}
for (Item item : tester.populate()) {
list.add(item);
}
final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,list);
lv.setAdapter(arrayAdapter);
final TextView firstTextView = (TextView) findViewById(R.id.textView);
button = (Button) findViewById(R.id.button);
clearButton = (Button) findViewById(R.id.clear);
gg = (EditText) findViewById(R.id.item);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String no = gg.getText().toString();
if (!no.isEmpty()) {
tester.addItem(no);
arrayAdapter.add(no);
arrayAdapter.notifyDataSetChanged();
gg.setText("");
}
}
});
clearButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
arrayAdapter.clear();
arrayAdapter.notifyDataSetChanged();
}
});
lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String item = lv.getItemAtPosition(position).toString();
arrayAdapter.remove(arrayAdapter.getItem(position));
arrayAdapter.notifyDataSetChanged();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
}
答案 0 :(得分：2)
首先确保您有权写入外部存储空间。
如，
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
你可以使用，
public void addCurrentList() throws Exception{
String pathToAppFolder = getExternalFilesDir(null).getAbsolutePath();
String filePath = pathToAppFolder +File.seperator + "list.ser";
try {
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(filePath));
os.writeObject(list);
os.close();
}
catch (Exception e) {
System.out.println("");
}
}
并使用从中创建文件路径，
String filePath = pathToAppFolder +File.seperator + "Test.text";
然后您想要再次阅读此文件，您可以重新创建路径。因为您可以从Android代码
访问context
修改
您无法像在代码中那样访问上下文。您可以在onCreate方法中执行此操作。我只添加了必要的部分。
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pathToAppFolder = getExternalFilesDir(null).getAbsolutePath();
filePath = pathToAppFolder + File.separator + "list.ser";
//create the list
天啊，我不得不竭尽全力回答你的问题。在这里，您的List类不是应用程序中的Activity。这只是一堂课。所以我建议你先删除那些继承。删除此extends Activity。我建议你将List类名更改为其他名称。因为List是一个已定义的关键字，这不是最佳做法。
更改列表活动中的方法，如下所示。
public void addCurrentList(String filePath) throws Exception
try {
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(filePath));
os.writeObject(list);
os.close();
}
catch (Exception e) {
System.out.println(e.getMessage());
}
}
public void record(String filePath) {
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(filePath));
ArrayList<Item> list2 = (ArrayList<Item>) in.readObject();
System.out.println(list2);
list = list2;
in.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
在MainActivity中，onDestroy方法， 将代码更改为，
tester.addCurrentList(filePath);