Question

昨天我试图创建一个导航抽屉。在我的源代码中，“R.id.content_frame”和“.commit”总是用红色下划线。有谁可以帮助我？

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentManager;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @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;
    }

    @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);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        android.app.FragmentManager fragmentManager = getFragmentManager();|

        if (id == R.id.nav_first_layout) {
           fragmentManager.beginTransaction()
                   .replace(R.id.content_frame)
                            , new FirstFragment()
            .commit();
        } else if (id == R.id.nav_second_layout ) {
            fragmentManager.beginTransaction()
                    .replace(R.id.content_frame)
                    , new SecondFragment())
            .commit();
        } else if (id == R.id.nav_third_layout) {
            fragmentManager.beginTransaction()
                    .replace(R.id.content_frame)
                    , new ThirdFragment()
                    .commit();
        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
    }

Answer 1

您对括号有疑问：

而不是

fragmentManager.beginTransaction()
                   .replace(R.id.content_frame)
                            , new FirstFragment()
            .commit();

你应该

fragmentManager.beginTransaction()
            .replace(R.id.content_frame, new FirstFragment())
            .commit();

Here is reference to FragmentTransaction#replace method

Fragment是替换方法的一个参数。

Answer 2

试试这个：

FragmentTransaction fragmentManager = 。getSupportFragmentManager（）的BeginTransaction（）;

fragmentManager.replace（R.id.content_frame，new SecondFragment（））; fragmentManager.commit（）;

Android导航抽屉.commit问题

2 个答案: