Question

我正在尝试使用Android Studio中预先构建的导航栏，并找到了一些如何使用它的指南，但其中大多数都已过时或因某些原因无效。

我现在使用的那个似乎“工作”但我在newInstance（）上出错了错误代码：

错误：（58,59）错误：类FirstFragment中的方法newInstance不能应用于给定类型; required：String，String 发现：没有争论原因：实际和正式的参数列表长度不同

这是我的代码： `package welovecode.se.outfitted;

import android.app.Activity;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import android.widget.ArrayAdapter;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity
    implements NavigationDrawerFragment.NavigationDrawerCallbacks {

/**
 * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
 */
private NavigationDrawerFragment mNavigationDrawerFragment;

/**
 * Used to store the last screen title. For use in {@link #restoreActionBar()}.
 */
private CharSequence mTitle;

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

    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
    mTitle = getTitle();

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));
}

@Override
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments

    FragmentManager fragmentManager = getSupportFragmentManager();

    if (position == 0) {
        fragmentManager.beginTransaction()
                .replace(R.id.container, FirstFragment.newInstance())
                .commit();
    } else if (position == 1) {
        fragmentManager.beginTransaction()
                .replace(R.id.container, SecondFragment.newInstance())
                .commit();
    } else if (position == 2) {
        fragmentManager.beginTransaction()
                .replace(R.id.container, ThirdFragment.newInstance())
                .commit();
    }

}

public void onSectionAttached(int number) {
    switch (number) {
        case 1:
            mTitle = getString(R.string.title_section1);
            break;
        case 2:
            mTitle = getString(R.string.title_section2);
            break;
        case 3:
            mTitle = getString(R.string.title_section3);
            break;
    }
}

public void restoreActionBar() {
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    if (!mNavigationDrawerFragment.isDrawerOpen()) {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.main, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        ((MainActivity) activity).onSectionAttached(
                getArguments().getInt(ARG_SECTION_NUMBER));
    }
}

}
`

提前非常感谢你！

Answer 1

该错误非常有用。你有类FirstFragment，SecondFragment等定义带有参数的newInstance方法，在本例中是两个字符串。但是，您正在调用那些没有任何参数的方法。所以解决方案应该是显而易见的，要么提供所需的参数，要么修改那些不需要任何参数的类。很难告诉你究竟应该在代码中改变什么，因为1）我不知道你想要完成什么，2）我没有你的片段的代码。

Answer 2

在我看来，您希望为片段传递区号，例如：

int sectNum = 100;
fragmentManager.beginTransaction()
   .replace(R.id.container, FirstFragment.newInstance( sectNum ))

注意：

newInstance方法调用仅需要 int 类型。
您需要确定如何获取部分编号。

使用片段的newInstance（）出错

2 个答案: