android - 当我拥有main代码时，为什么不能在导航中添加时间？

Question

我制作了一个单独的演示应用程序来说明时间，我想将其添加到导航窗口(汉堡窗口)中，但是当我将代码放在Main中时，导航栏的代码却崩溃了。

package com.example.user.navigationdrawer;

import android.app.Fragment;
import android.app.FragmentManager;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
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;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

 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();
    //This code
    TextView theTime = (TextView) findViewById(R.id.theT);
    SimpleDateFormat df = new SimpleDateFormat("EEEE, MMMM dd, yyyy", Locale.ENGLISH);
    Date today = Calendar.getInstance().getTime();
    String reportDate = df.format(today);
    theTime.setText(reportDate);
    //This code

    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


    return super.onOptionsItemSelected(item);
}

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

    }

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


 }
 }

这是我的Xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="200dp"
android:background="@drawable/side_nav_bar"
android:gravity="bottom"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:theme="@style/ThemeOverlay.AppCompat.Dark">


<ImageView
    android:id="@+id/imageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true"
    android:layout_gravity="center_vertical"
    android:src="@mipmap/sijny"
    android:contentDescription="" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingTop="7dp"
    android:paddingBottom="2dp"
    android:text="SIJNY Islamic Center"
    android:textAppearance="@style/TextAppearance.AppCompat.Body1"
    android:id="@+id/textView3"
    android:textStyle="normal|bold"
    android:adjustViewBounds="true" />

<TextView
    android:id="@+id/theT"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingBottom="2dp"
    android:textColor="#FFFF"
    android:text="Time" />

<TextView
    android:id="@+id/textView6"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="#FFFF"
    android:text="13 Ramadan 1436" />


 </LinearLayout>

Answer 1

好了，现在解决了这个问题。原来我只需要添加一行代码，因为我想在一个片段中修改textview。

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

    View navHeaderView = navigationView.getHeaderView(0); // this
    TextView theTime = (TextView) navHeaderView.findViewById(R.id.theT);//this

    SimpleDateFormat df = new SimpleDateFormat("EEEE, MMMM dd, yyyy", Locale.ENGLISH);
    Date today = Calendar.getInstance().getTime();
    String reportDate = df.format(today);
    theTime.setText(reportDate);

您的变量/ xml ID可能有所不同。无论如何，感谢您的帮助。