Question

我已根据此引用https://www.youtube.com/watch?v=luxE7oEKiic实现了我的应用程序但是，我删除的项目将在重新启动应用程序时自动添加回列表中。知道如何永久删除该项目？

private PackageManager packageManager = null;
private List<ApplicationInfo> applist = null;
private AppAdapter listadapter = null;
ListView list;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    packageManager = getPackageManager();

    new LoadApplications().execute();
   list = (ListView) findViewById(android.R.id.list);

    listadapter = new AppAdapter(this, R.layout.activity_list_app, applist);
    list.setAdapter(listadapter);
    list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);

    list.setMultiChoiceModeListener(new AbsListView.MultiChoiceModeListener() {

        @Override
        public boolean onPrepareActionMode(ActionMode arg0, Menu arg1) {
            // TODO Auto-generated method stub
            return false;
        }

        @Override
        public void onDestroyActionMode(ActionMode arg0) {
            listadapter.removeSelection();
        }

        @Override
        public boolean onCreateActionMode(ActionMode arg0, Menu arg1) {
            arg0.getMenuInflater().inflate(R.menu.menu_main, arg1);
            return true;
        }

        @Override
        public boolean onActionItemClicked(ActionMode arg0, MenuItem arg1) {
            switch (arg1.getItemId()) {
                case R.id.delete:
                    SparseBooleanArray selected = listadapter.getSelectedIds();

                    for(int i = (selected.size() - 1); i >= 0; i--) {
                        if(selected.valueAt(i)) {
                            ApplicationInfo selecteditem = listadapter.getItem(selected.keyAt(i));
                            listadapter.remove(selecteditem);
                        }
                    }
                    arg0.finish();
                    return true;

                default:
                    return false;
            }
        }

        @Override
        public void onItemCheckedStateChanged(ActionMode mode, int position,
                                              long id, boolean checked) {
            final int checkedCount = list.getCheckedItemCount();
            mode.setTitle(checkedCount + " Selected");
            listadapter.toggleSelection(position);

        }

        public void onItemClick(AdapterView<?> parent, View view, int position, long id)
        {
            view.setSelected(true);
        }
    });
}

protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
}

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(intent != null){
            startActivity(intent);
        }
    }catch(ActivityNotFoundException e){
        Toast.makeText(MainActivity.this,e.getMessage(), Toast.LENGTH_LONG).show();
    }catch(Exception e){
        Toast.makeText(MainActivity.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(packageManager.getLaunchIntentForPackage(info.packageName)!=null){
                appList.add(info);
            }
        }catch(Exception e){
            e.printStackTrace();
        }
    }
    return appList;
}

private class LoadApplications extends AsyncTask<Void, Void, Void>{
    private ProgressDialog progress = null;

    protected Void doInBackground(Void... params){
        applist = checkForLaunchIntent(packageManager.getInstalledApplications(PackageManager.GET_META_DATA));
        listadapter = new AppAdapter(MainActivity.this, R.layout.activity_list_app, applist);
        return null;
    }
    protected void onPostExecute(Void result){
        setListAdapter(listadapter);
        progress.dismiss();
        super.onPostExecute(result);
    }
    protected void onPreExecute(){
        progress = ProgressDialog.show(MainActivity.this, null, "Loading apps info...");
        super.onPreExecute();
    }
}

Answer 1

当您致电new LoadApplications().execute();时，您的数据来自来源。

此任务从源列表中获取所有项目。为了完全删除项目（即使应用程序关闭并重新打开后也是如此）您需要在数据库或共享首选项中保存用户删除的项目列表。

    @Override
    public boolean onActionItemClicked(ActionMode arg0, MenuItem arg1) {
        switch (arg1.getItemId()) {
            case R.id.delete:
                SparseBooleanArray selected = listadapter.getSelectedIds();

                for(int i = (selected.size() - 1); i >= 0; i--) {
                    if(selected.valueAt(i)) {
                        ApplicationInfo selecteditem = listadapter.getItem(selected.keyAt(i));
                        listadapter.remove(selecteditem);

                        // Save the selected item in a Content Provider/Shared Pref 
                    }
                }
                arg0.finish();
                return true;

            default:
                return false;
        }
    }

在postExecute类的LoadApplications方法中，在调用notifyDataSetChanged之前，从源代码返回的列表中删除存储在数据库或共享首选项中的项目。

private class LoadApplications extends AsyncTask<Void, Void, Void>{
    private ProgressDialog progress = null;

    protected Void doInBackground(Void... params){
        applist = checkForLaunchIntent(packageManager.getInstalledApplications(PackageManager.GET_META_DATA));

        // Remove the items me stored in the removedList

        listadapter = new AppAdapter(MainActivity.this, R.layout.activity_list_app, applist);
        return null;
    }
    protected void onPostExecute(Void result){
        setListAdapter(listadapter);
        progress.dismiss();
        super.onPostExecute(result);
    }
    protected void onPreExecute(){
        progress = ProgressDialog.show(MainActivity.this, null, "Loading apps info...");
        super.onPreExecute();
    }
}

为您提供快速入门。您可以使用这个非常容易使用的班级TinyDB来保存您的列表。但我建议您详细介绍Content Providers和SharedPrefs。

Answer 2

您应该将修改后的数据存储在onSaveInstanceState中。当您“重新启动”活动时，请先检查savedInstanceState捆绑包。如果它不为空，则从Bundle恢复数据，而不是从原始源获取数据。

如果您的意思是没有savedInstanceState的开始，则必须修改数据源。如果不能，您可以将操作或修改后的数据记录在自己的存储中。

Android：如何在列表视图中永久删除项目？

2 个答案: