如何将参数从 Activity 传递给 Fragment

Question

我有一个通过采用者类实例化和填充片段的活动。我想将值/对象传递给这个 Fragment 采用者类，以便我可以指定布局等。

我曾尝试使用 setArgument 方法传递捆绑包，但我的代码失败了，不知道为什么。据我了解，我可以在采用者类的 onCreate 方法中收集捆绑包。我看到在注释代码之后立即正确设置了参数，但可惜在那之后它崩溃了，我不明白为什么。如果我删除捆绑代码，它不会崩溃。 :(

下面是我的代码，有人知道我应该把捆绑代码放在哪里，注释掉吗？

public class LoginScreen extends ActionBarActivity {
    private final String ARG_SELECTED_LAYOUT_ID = "selectedLayoutId";
private final int DEFAULT_LAYOUT = R.layout.layout_list;

private int mSelectedLayoutId;

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

    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    actionBar.setDisplayShowTitleEnabled(false);
    actionBar.setDisplayShowHomeEnabled(false);

    mSelectedLayoutId = DEFAULT_LAYOUT;
    if (savedInstanceState != null) {
        mSelectedLayoutId = savedInstanceState.getInt(ARG_SELECTED_LAYOUT_ID);
    }

    addLayoutTab(
            actionBar, R.layout.layout_list, R.drawable.ic_list, "list");
    addLayoutTab(
            actionBar, R.layout.layout_grid, R.drawable.ic_grid, "grid");
    addLayoutTab(
            actionBar, R.layout.layout_staggered_grid, R.drawable.ic_staggered, "staggered");
    addLayoutTab(
            actionBar, R.layout.layout_spannable_grid, R.drawable.ic_spannable, "spannable");
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt(ARG_SELECTED_LAYOUT_ID, mSelectedLayoutId);
}

private void addLayoutTab(ActionBar actionBar, int layoutId, int iconId, String tag) {
    ActionBar.Tab tab = actionBar.newTab()
            .setText("")
            .setIcon(iconId)
            .setTabListener(new TabListener(layoutId, tag));
    actionBar.addTab(tab, layoutId == mSelectedLayoutId);
}

public class TabListener implements ActionBar.TabListener {
    private LayoutFragment mFragment;
    private final int mLayoutId;
    private final String mTag;


    public TabListener(int layoutId, String tag) {
        mLayoutId = layoutId;
        mTag = tag;
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
        mFragment = (LayoutFragment) getSupportFragmentManager().findFragmentByTag(mTag);



        if (mFragment == null) {
            mFragment = (LayoutFragment) LayoutFragment.newInstance(mLayoutId);
            ft.add(R.id.content, mFragment, mTag);

        } else {
            ft.attach(mFragment);
        }


        /*
            Bundle bundle = new Bundle();
            bundle.putInt("noTiles", 4);
            mFragment.setArguments(bundle);           
        */

        mSelectedLayoutId = mFragment.getLayoutId();
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            ft.detach(mFragment);
        }
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
    }
}

}

Logcat

03-03 11:56:53.675  32507-32507/weebuns.predictionking E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: weebuns.predictionking, PID: 32507
    java.lang.RuntimeException: Unable to start activity ComponentInfo{weebuns.predictionking/weebuns.predictionking.LoginScreen}: java.lang.NullPointerException: Attempt to invoke virtual method 'void weebuns.predictionking.LayoutFragment.setArguments(android.os.Bundle)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void weebuns.predictionking.LayoutFragment.setArguments(android.os.Bundle)' on a null object reference

Answer 1

要将参数传递给您的片段，建议创建一个公共静态方法来实例化您的片段，例如：

public static MyFragment newInstance(String firstArg) {
        MyFragment f = new MyFragment ();
        Bundle args = new Bundle();
        args.putString("ARG1", firstArg);
        f.setArguments(args);
        return f;
    }

然后在onCreateView() 方法中检索您的参数，例如：

String arg = getArguments().getString("ARG1");

使用静态方法在其他片段或活动中使用您的参数实例化一个新片段，例如：

MyFragment f = MyFragment.newInstance(myArg);

Answer 2

没有看到logcat很难说，但你肯定错过了在FragmentTransaction上调用commit()方法。还记得在调用ft.commit()之前为片段设置参数。

@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    mFragment = (LayoutFragment) getSupportFragmentManager().findFragmentByTag(mTag);

    if (mFragment == null) {
        Bundle bundle = new Bundle();
        bundle.putInt("noTiles", 4);
        mFragment = (LayoutFragment) LayoutFragment.newInstance(mLayoutId);
        mFragment.setArguments(bundle);
        //ft.add(R.id.content, mFragment, mTag).commit();
        ft.add(R.id.content, mFragment, mTag);

    } else {
        ft.attach(mFragment);
    }

    mSelectedLayoutId = mFragment.getLayoutId();
}

Answer 3

在你的活动中

Bundle args = new Bundle();
args.putString("Menu", "Your String");
Fragment detail = new FragmeantOne();
detail.setArguments(args);
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, detail).commit();

在你的 Fragment.. 在 onCreateView()

String menu = getArguments().getString("Menu");
someTextView.setText(menu);

Answer 4

您可以使用 Bundle 将数据从 Activity 传输到 Fragment，或者将数据从 Fragment 传输到 Fragment。

Bundle bundle = new Bundle();
DisplayDataList fragment = new DisplayDataList();
bundle.putString("listitem", "Buyer,Seller");
            fragment.setArguments(bundle);

            getFragmentManager().beginTransaction().replace(
                    R.id.frame_container, fragment).addToBackStack(null).commit();

您想在DisplayDataList Fragment 类中接收该捆绑包 i.w 的位置。你必须使用getArguments() 方法。

显示数据列表

 Bundle bundle = getArguments();
            String getdata = bundle.getString("listitem");
            System.out.println("Data got-->>> " + getdata);

希望这会对你有所帮助。

Answer 5

您可以使用 Bundle 在 Activity 和 Fragment/Dialog Fragment 之间传输数据

将数据从您的 Activity 发送到 Fragment() -> onClickBtn()

val f = PaymentBottomSheet()
            val bundle = Bundle()
            bundle.putString("coins", walletBinding.edCoins.text.toString())
            bundle.putString("method", getJsonData()[adapter.selected].method)
            bundle.putString("name", walletBinding.edNickName.text.toString())
            bundle.putString("acc", walletBinding.edAccountId.text.toString())
            f.arguments = bundle
            f.show(supportFragmentManager, f.tag)

从您的活动中检索数据（您的片段代码如下所示）onCreateView()

 val bundle = Bundle(arguments)
    coins = bundle.getString("coins")
    method = bundle.getString("method")
    name = bundle.getString("name")
    id = bundle.getString("acc")

    Timber.d("Coins $coins, Method $method, Name $name, ID $id")

谢谢