替換導航抽屜中的片段視圖的問題

Question

我正在使用android導航抽屜模板和片段來顯示不同的視圖。

正常情況下，會自動生成MainActivity，activity_main.xml和content_main.xml。

我創建了兩個java類； MusicFragment和MainFragment，當然還有其中包含內容的布局文件。

當我運行該應用程序時，activity_main是啟動的默認布局，並顯示了我喜歡的內容，我正在使用導航抽屜導航到我的MusicFragment和MainFragment，用於替換onNavigationItemSelected方法中當前視圖的這段代碼是；

 if (id == R.id.nav_camara) {

        fm.beginTransaction().replace(R.id.content_frame, new MainFragment()).commit();


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

        fm.beginTransaction().replace(R.id.content_frame, new MusicFragment()).commit();

盡管我有一個很大的問題，但兩者都可以很好地替換，當我選擇導航抽屜並單擊camera選項時，它們顯示片段視圖，但不替換來自activity_main的內容，而是在content_main頂部顯示片段內容，並且不取代它。

這是我的MainActivity：

package com.justmikey.justmik;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentManager;
import android.support.v7.internal.widget.ButtonBarLayout;
import android.text.method.ScrollingMovementMethod;
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.Button;
import android.widget.TextView;
import JustMikey.Fragments.MainFragment;
import JustMikey.Fragments.MusicFragment;

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

//create a media player object called mp
MediaPlayer mp;
//declare my buttons play, pause and stop
Button play, pause,stop;

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

    //Set the textView scrollMain to scrollable
    TextView tv = (TextView) findViewById(R.id.scrollMain);
    tv.setMovementMethod(new ScrollingMovementMethod());

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    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) {
    android.app.FragmentManager fm = getFragmentManager();

    int id = item.getItemId();

    if (id == R.id.nav_camara) {

        fm.beginTransaction().replace(R.id.content_frame, new MainFragment()).commit();


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

        fm.beginTransaction().replace(R.id.content_frame, new MusicFragment()).commit();


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

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

    } 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;
}
}

content_main.xml：

<?xml version="1.0" encoding="utf-8"?>



<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"     android:layout_width="match_parent"
android:layout_height="match_parent"         android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:showIn="@layout/app_bar_main"
tools:context=".MainActivity"
android:background="#dbe4eb">



<FrameLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/content_frame">

    <ImageView
        android:layout_width="355dp"
        android:layout_height="wrap_content"
        android:src="@drawable/jmmain"
        android:id="@+id/imageView2"
        android:layout_gravity="center_horizontal|top"
        android:layout_alignRight="@+id/content_frame"
        android:layout_alignEnd="@+id/content_frame" />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="274dp"
        android:text="hello hello hello hello hello hello hello hello"
        android:id="@+id/scrollMain"
        android:layout_gravity="center_horizontal|bottom"
        android:layout_alignBottom="@+id/scrollView"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="28dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:background="#ffffff"
        android:padding="10dp"
        />

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/scrollView"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_gravity="center">

    </ScrollView>


</FrameLayout>

</RelativeLayout>

Answer 1

FragmentTransaction只能處理Fragment 。 他們不會替換/刪除Fragment沒有的任何東西。 由於僅在啟動時才需要content_frame FrameLayout中包含的View ，因此我們可以在第一個FragmentTransaction FrameLayout其刪除。

為此，我們將創建一個成員boolean標志isStartup ，將其初始化為true 。 在onNavigationItemSelected()方法中，我們將檢查該標志，如果為true ，則刪除View並將其更改為false 。

在任何方法之外聲明並初始化布爾值：

private boolean isStartup = true;

然后在onNavigationItemSelected()方法中進行檢查和刪除。

public boolean onNavigationItemSelected(MenuItem item) {
    android.app.FragmentManager fm = getFragmentManager();
    int id = item.getItemId();

    if(isStartup) {
        ((FrameLayout) findViewById(R.id.content_frame)).removeAllViews();
        isStartup = false;
    }

    if (id == R.id.nav_camara) {
        ...

}

Answer 2

我有同樣的問題。 用上述解決方案無法解決我的問題。 但是我發現了兩種解決方案！

1-您可以將主頁的內容顯示到另一個視圖組中。 並將其隱藏在onNavigationItemSelected中的正確位置：

content_main.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#dbe4eb"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:showIn="@layout/app_bar_main">

<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<LinearLayout
    android:id="@+id/my_linearLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="355dp"
        android:layout_height="wrap_content"
        android:layout_alignEnd="@+id/content_frame"
        android:layout_alignRight="@+id/content_frame"
        android:layout_gravity="center_horizontal|top"
        android:src="@drawable/jmmain" />

    <TextView
        android:id="@+id/scrollMain"
        android:layout_width="fill_parent"
        android:layout_height="274dp"
        android:layout_alignBottom="@+id/scrollView"
        android:layout_alignParentEnd="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentStart="true"
        android:layout_gravity="center_horizontal|bottom"
        android:layout_marginBottom="28dp"
        android:background="#ffffff"
        android:padding="10dp"
        android:text="hello hello hello hello hello hello hello hello" />

    <ScrollView
        android:id="@+id/scrollView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_gravity="center"></ScrollView>
</LinearLayout>
</RelativeLayout>

MainActivity.java中的onNavigationItemSelected方法：

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

    if (id == R.id.main) {
        findViewById(R.id.my_linearLayout).setVisibility(View.VISIBLE);
        fragmentManager.popBackStack("fragment", POP_BACK_STACK_INCLUSIVE);
    } else if (id == R.id.one) {
        findViewById(R.id.my_linearLayout).setVisibility(View.GONE);
        fragmentManager.beginTransaction().replace(R.id.content_frame, new OneFragment()).addToBackStack("fragment").commit();
    } else if (id == R.id.tow) {
        findViewById(R.id.my_linearLayout).setVisibility(View.GONE);
        fragmentManager.beginTransaction().replace(R.id.content_frame, new SecondFragment()).addToBackStack("fragment").commit();
    }

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

2-第二種方法是也考慮主頁內容的片段。 然后在onNavigationItemSelected方法中，將其與其余片段一樣對待：

MainActivity.java中的onNavigationItemSelected方法：

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

    if (id == R.id.main) {
        fragmentManager.beginTransaction().replace(R.id.content_frame, new HomeFragment()).addToBackStack("fragment").commit();
    } else if (id == R.id.one) {
        fragmentManager.beginTransaction().replace(R.id.content_frame, new OneFragment()).addToBackStack("fragment").commit();
    } else if (id == R.id.tow) {
        fragmentManager.beginTransaction().replace(R.id.content_frame, new SecondFragment()).addToBackStack("fragment").commit();
    }

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

注意：要在打開程序時顯示主頁的內容，請在MainActivity的onCreate（）中輸入以下代碼：

        fragmentManager.beginTransaction().replace(R.id.content_frame, new HomeFragment()).addToBackStack("fragment").commit();