Android:如何保存ArrayList项目，即使应用程序关闭

Question

我正在开发一个应用程序，我必须在一个带有复选框的列表视图中显示所有安装的应用程序。每当用户从列表中选择任何复选框时，应用程序信息对象(对应于选中的复选框)被添加到我的全局类变量(ArrayList added_apps)。我成功地做到了。但问题是，每当i退出应用程序的所有项目，用户添加到added_apps ArrayList不保存。我必须再次添加数组列表中的元素才能继续。我已经尝试到目前为止，这里是我的代码，但它不工作。

显示已安装应用程序并添加到全局类变量added_apps ArrayList的代码

mainactivity.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    tools:context="com.example.pc.fkidshell.Teen3Activity">
    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <Button
        android:id="@+id/btn_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:layout_marginBottom="20dp"
        android:text="Add Selected Apps"
        android:width="170dp"
        android:layout_alignParentBottom="true"
        android:layout_gravity="center_horizontal" />
</LinearLayout>

row.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="fill_parent"
    android:layout_height="match_parent">
    <ImageView
        android:id="@+id/app_icon"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:padding="3dp"
        android:scaleType="centerCrop" />
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:gravity="center_vertical"
        android:orientation="vertical"
        android:paddingLeft="5dp" >
        <TextView
            android:id="@+id/app_name"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            android:textStyle="bold" />
        <TextView
            android:id="@+id/app_paackage"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical" />
    </LinearLayout>
    <CheckBox
        android:id="@+id/cb_app"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

Activitymain.java:

public class Teen3Activity extends ListActivity {
    private PackageManager packageManager = null;
    private List<ApplicationInfo> applist = null;
    private ApplicationAdapter listadaptor = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_teen3);
        //teenadd=(Toolbar) findViewById(R.id.teenaddtb);
        //setSupportActionBar(teenadd);
        //getSupportActionBar().setTitle("Restrict Your APP's");
        Button btn1=(Button)  findViewById(R.id.btn_add);
        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                MyAddedapss.writeList(Teen3Activity.this,MyAddedapss.getAdded_apps()); //here i am storing ArrayList of Added applications to file
                if(MyAddedapss.getAdded_apps().isEmpty())
                {
                    Toast.makeText(getApplicationContext(), "Nothing to ADD!", Toast.LENGTH_LONG).show();
                }
                else
                {
                    Toast.makeText(getApplicationContext(), "Apps Added!", Toast.LENGTH_LONG).show();
                }
            }
        });
        packageManager = getPackageManager();
        new LoadApplications().execute();
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id)
    {
        super.onListItemClick(l, v, position, id);
        ApplicationInfo app = applist.get(position);
        try {
            Intent intent = packageManager.getLaunchIntentForPackage(app.packageName);
            if (null != intent) {
                startActivity(intent);
            }
        } catch (ActivityNotFoundException e) {
            Toast.makeText(Teen3Activity.this, e.getMessage(), Toast.LENGTH_LONG).show();
        } catch (Exception e) {
            Toast.makeText(Teen3Activity.this, e.getMessage(), Toast.LENGTH_LONG).show();
        }
    }
    private List<ApplicationInfo> checkForLaunchIntent(List<ApplicationInfo> list)
    {
        ArrayList<ApplicationInfo> applist = new ArrayList<ApplicationInfo>();
        for (ApplicationInfo info : list) {
            try {
                if (null != packageManager.getLaunchIntentForPackage(info.packageName))
                {
                    applist.add(info);
                }
            } catch (Exception e)
            {
                e.printStackTrace();
            }
        }
        return applist;
    }

    private class LoadApplications extends AsyncTask<Void, Void, Void>
    {
        private ProgressDialog progress = null;
        @Override
        protected Void doInBackground(Void... params)
        {
            applist = checkForLaunchIntent(packageManager.getInstalledApplications(PackageManager.GET_META_DATA));
            listadaptor = new ApplicationAdapter(Teen3Activity.this, R.layout.row, applist);
            return null;
        }
        @Override
        protected void onCancelled()
        {
            super.onCancelled();
        }
        @Override
        protected void onPostExecute(Void result)
        {
            setListAdapter(listadaptor);
            progress.dismiss();
            super.onPostExecute(result);
        }
        @Override
        protected void onPreExecute()
        {
            progress = ProgressDialog.show(Teen3Activity.this, null, "Loading application info...");
            super.onPreExecute();
        }
        @Override
        protected void onProgressUpdate(Void... values)
        {
            super.onProgressUpdate(values);
        }
    }
}

应用程序适配器:

public class ApplicationAdapter extends ArrayAdapter<ApplicationInfo> {
    private List<ApplicationInfo> appsList = null;
    private Context context;
    private PackageManager packageManager;
    private ArrayList<Boolean> checkList = new ArrayList<Boolean>();
    public ApplicationAdapter(Context context, int textViewResourceId, List<ApplicationInfo> appsList)
    {
        super(context, textViewResourceId, appsList);
        this.context = context;
        this.appsList = appsList;
        packageManager = context.getPackageManager();
        for (int i = 0; i < appsList.size(); i++) {
            checkList.add(false);
        }
    }
    @Override
    public int getCount() {
        return ((null != appsList) ? appsList.size() : 0);
    }
    @Override
    public ApplicationInfo getItem(int position) {
        return ((null != appsList) ? appsList.get(position) : null);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if (null == view) {
            LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = layoutInflater.inflate(R.layout.row, null);
        }
        ApplicationInfo data = appsList.get(position);
        if (null != data) {
            TextView appName = (TextView) view.findViewById(R.id.app_name);
            TextView packageName = (TextView) view.findViewById(R.id.app_paackage);
            ImageView iconview = (ImageView) view.findViewById(R.id.app_icon);
            CheckBox checkBox = (CheckBox) view.findViewById(R.id.cb_app);
            checkBox.setTag(Integer.valueOf(position)); // set the tag so we can identify the correct row in the listener
            checkBox.setChecked(checkList.get(position));// set the status as we stored it
            checkBox.setOnCheckedChangeListener(mListener); // set the listener
            appName.setText(data.loadLabel(packageManager));
            packageName.setText(data.packageName);
            iconview.setImageDrawable(data.loadIcon(packageManager));
        }
        return view;
    }
    CompoundButton.OnCheckedChangeListener mListener = new CompoundButton.OnCheckedChangeListener()
    {
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
        {
            checkList.set((Integer)buttonView.getTag(),isChecked); // get the tag so we know the row and store the status
            if(isChecked)
            {
                int addapppos = (Integer) buttonView.getTag();
                ApplicationInfo p=appsList.get(addapppos);
                MyAddedapss.setAdded_apps(p);
                buttonView.setEnabled(false);
            }
        }
    };
}

MyAddedApps.java:(包含写入方法的全局类，以保存数组列表到文件)

public class MyAddedapss extends Application {
    private static ArrayList<ApplicationInfo> added_apps=new ArrayList<ApplicationInfo>();
    public static void setAdded_apps(ApplicationInfo element)
    {
        added_apps.add(element);
    }
    public static ArrayList<ApplicationInfo> getAdded_apps(){
        return added_apps;
    }
    public static boolean remove_app(ApplicationInfo element)
    {
        return added_apps.remove(element);
    }
    public static ArrayList<ApplicationInfo> readList(Context c)
    {
        try
        {
            FileInputStream fis = c.openFileInput("NAME");
            ObjectInputStream is = new ObjectInputStream(fis);
            ArrayList<ApplicationInfo> list = (ArrayList<ApplicationInfo>)is.readObject();
            is.close();
            return list;
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
            return null;
        }
    }
    public static void writeList(Context c, ArrayList<ApplicationInfo> list){
        try
        {
            FileOutputStream fos = c.openFileOutput("NAME", Context.MODE_PRIVATE);
            ObjectOutputStream os = new ObjectOutputStream(fos);
            os.writeObject(list);
            os.close();
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }
    }
}

Answer 1

在应用程序中永久存储值的一种方法是使用SharedPreferences。基本上，您需要做的唯一一件事就是在选中时将值存储在SharedPreferences中，并在取消选中时删除它们。

阅读更多:

https://developer.android.com/reference/android/content/SharedPreferences.html

Answer 2

首先，需要将对象列表转换为JSON字符串。之后，您可以将此字符串保存在共享首选项中。当你的应用程序唤醒时，你可以从共享偏好中检索列表。