Java 在片段之间保留数据

我试图使用参数将dataPID从碎片扫描保存到碎片维护

但在my Log.dtag、PID SCAN:+data中，数据始终为空

我的论点有什么问题

这是我的密码

这是我的活动

公共类MainActivity扩展了活动{

private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;

private CharSequence mDrawerTitle;
private CharSequence mTitle;
CustomDrawerAdapter adapter;
SharedPreferences preferences;
String pref;
List<DrawerItem> dataList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    preferences = this.getSharedPreferences(Config.PREFERENCES, MODE_PRIVATE);
    pref = preferences.getString(Config.SESSION,null);
    // Initializing
    dataList = new ArrayList<DrawerItem>();
    mTitle = mDrawerTitle = getTitle();
    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.left_drawer);

    mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow,
            GravityCompat.START);

    // Add Drawer Item to dataList
    dataList.add(new DrawerItem("Scanner", R.drawable.ic_action_email));
    dataList.add(new DrawerItem("Schedule", R.drawable.ic_action_good));
    dataList.add(new DrawerItem("Games", R.drawable.ic_action_gamepad));
    dataList.add(new DrawerItem("Logout", R.drawable.ic_action_about));


    adapter = new CustomDrawerAdapter(this, R.layout.custom_drawer_item,
            dataList);

    mDrawerList.setAdapter(adapter);

    mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

    getActionBar().setDisplayHomeAsUpEnabled(true);
    getActionBar().setHomeButtonEnabled(true);

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
            R.drawable.ic_drawer, R.string.drawer_open,
            R.string.drawer_close) {
        public void onDrawerClosed(View view) {
            getActionBar().setTitle(mTitle);
            invalidateOptionsMenu(); // creates call to
            // onPrepareOptionsMenu()
        }

        public void onDrawerOpened(View drawerView) {
            getActionBar().setTitle(mDrawerTitle);
            invalidateOptionsMenu(); // creates call to
            // onPrepareOptionsMenu()
        }
    };

    mDrawerLayout.setDrawerListener(mDrawerToggle);

    if (savedInstanceState == null) {
        SelectItem(0);
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

public void SelectItem(int possition) {

    Fragment fragment = null;
    Bundle args = new Bundle();
    switch (possition) {
        case 0:
            fragment = new FragmentScan();
            break;
        case 1:
            fragment = new FragmentSchedule();

            break;
        case 2:
            fragment = new FragmentThree();
            args.putString(FragmentThree.ITEM_NAME, dataList.get(possition)
                    .getItemName());
            args.putInt(FragmentThree.IMAGE_RESOURCE_ID, dataList.get(possition)
                    .getImgResID());
            break;
        case 3:
            logout();
            Intent in = new Intent(this, LoginActivity.class);
            startActivity(in);
            finish();
            return;

        default:
            break;
    }

    fragment.setArguments(args);
    FragmentManager frgManager = getFragmentManager();
    frgManager.beginTransaction().replace(R.id.content_frame, fragment)
            .commit();

    mDrawerList.setItemChecked(possition, true);
    setTitle(dataList.get(possition).getItemName());
    mDrawerLayout.closeDrawer(mDrawerList);

}

@Override
public void setTitle(CharSequence title) {
    mTitle = title;
    getActionBar().setTitle(mTitle);
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    // Pass any configuration change to the drawer toggles
    mDrawerToggle.onConfigurationChanged(newConfig);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // The action bar home/up action should open or close the drawer.
    // ActionBarDrawerToggle will take care of this.
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }

    return false;
}

private class DrawerItemClickListener implements
        ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position,
                            long id) {
        SelectItem(position);

    }
}
//In the same activity you’ll need the following to retrieve the results:
private void logout(){
    //TODO delete cookie from db

    SharedPreferences.Editor editor = preferences.edit();
    editor.remove(Config.SESSION);
    editor.remove(Config.USERNAME);
    editor.commit();
}

我希望有人能帮我解决这个问题，

---

之前谢谢。

我认为它应该不为null，也许您只是没有正确检索该值

在日志代码中，您使用了：

Log.d("tag", "PID SCAN: " + data);

但实际上，您使用以下方式存储pid：

data.putString("pid", mPid);

也就是说，您应该使用键pid从包中获取值，如：

Log.d("tag", "PID SCAN: " + data.getString("pid"));

编辑：

如果您试图获取的是进程ID，请查看android.os.process.myPid

如果pid是您自己的预定义变量，包含其他内容， 然后，您需要在创建片段时传递它，如下所示：

fragment = new FragmentScan();
args.putString("pid", YOUR_TV_PID_VALUE);

在FragmentScan的另一端，您可以使用getArguments来获取Bundle，然后使用getStringpid

更新：

在阅读了更多的代码之后，您的循环似乎有点混乱。 但是一个快速的建议是：为什么不像下面这样尝试呢

data.putString("pid", tvPid.getText());

在您的原始代码中，您在savedInstanceState中的pid应该在您执行单击扫描后存在，完成/取消扫描。但是我认为您的代码流有点混乱。 读取调用onSaveInstanceState以在终止活动之前从活动中检索每个实例的状态。

---

=>这意味着，在您打开scanBtn执行的另一个意图之前，将调用onSaveInstanceState并存储tvPid的空值。当主意图恢复时，它将获得包含pid空字符串的捆绑包。但它应该是，而不是null。

是的，我同意。无论如何，我的答案似乎没有帮助。我删除了它。我已将日志d更改为like data.putStringpid，mPid；但我有相同的响应..nullyes，我看到了，并且您尝试过Log.dtag，PID SCAN:+data.getStringpid；？如果它仍然存在，那么您应该显示另一个调用它的代码段FragmentScan@YohanesKhosiawan许先汉 我也有同样的反应

data.putString("pid", tvPid.getText());