Question

我在这里阅读了很多问题，但是我没有找到解决问题的正确方法。我有一个MainActivity java类，我有几个活动为我的应用程序。现在，我在Android Studio中自动创建了一个“选项卡式活动”。我有一个Imagebutton，用于打开一个新的片段。这个新片段被称为“Generaldiscription”。我了解到，片段无法像活动那样启动，我需要使用FragmentManagener来打开片段。我的应用程序启动，但是当我点击图像按钮时，实际上我的片段应该从哪里开始，应用程序崩溃了。

在下面，您可以看到我的mainactivity.java，以及java和xml这些片段。谢谢你的期待。

MainActivity.java

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);
    final ImageButton generaldiscriptionbutton = (ImageButton) findViewById(R.id.imageButton);
    setSupportActionBar(toolbar);
    checkFirstRun();



    generaldiscriptionbutton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            FragmentManager fm = getSupportFragmentManager();
            Generaldiscription fragment = new Generaldiscription();
            fm.beginTransaction().add(R.id.main_content, ); // don't know what to write here.



        }
    });

我自动创建的activity_generaldiscription.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
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:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
 >


<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/appbar_padding_top"
    android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/AppTheme.PopupOverlay">

    </android.support.v7.widget.Toolbar>


</android.support.design.widget.AppBarLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

我的fragment_generaldiscription.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.user.myapp.Generaldiscription$PlaceholderFragment">

<TextView
    android:id="@+id/section_label"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:text="fffff" />

编辑我的generaldiscription.java

 import android.support.design.widget.FloatingActionButton;
 import android.support.design.widget.Snackbar;
 import android.support.v7.app.AppCompatActivity;
 import android.support.v7.widget.Toolbar;

 import android.app.Fragment;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.app.FragmentPagerAdapter;
 import android.support.v4.view.ViewPager;
 import android.os.Bundle;
 import android.view.LayoutInflater;
  import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;

import android.widget.TextView;

public class Generaldiscription extends AppCompatActivity {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link FragmentPagerAdapter} derivative, which will keep every
 * loaded fragment in memory. If this becomes too memory intensive, it
 * may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
private SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
private ViewPager mViewPager;

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);


    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();
        }
    });

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_generaldiscription, 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);
}

/**
 * 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";

    public PlaceholderFragment() {
    }

    /**
     * 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;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_generaldiscription, container, false);
        TextView textView = (TextView) rootView.findViewById(R.id.section_label);
        textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
 * one of the sections/tabs/pages.
 */
public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        return PlaceholderFragment.newInstance(position + 1);
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "SECTION 1";
            case 1:
                return "SECTION 2";
            case 2:
                return "SECTION 3";
        }
        return null;
    }
}

}

Answer 1

以这种方式开始你的片段：

            FragmentManager fragmentmanager = getFragmentManager();
            fragmentmanager.beginTransaction()
                .replace(R.id.main_content
                        , new Generaldiscription())
                .commit();

修改

在你的情况下，你应该开始这样的Generaldiscription：

Intent myIntent = new Intent(MainActivity.this, Generaldiscription.class); MainActivity.this.startActivity(myIntent);

此外，您的GeneralDiscription应导入android.support.v4.app.Fragment;而不是android.app.Fragment;

Answer 2

来自Documentation

FragmentTransaction add (int containerViewId, 
                Fragment fragment, 
                String tag)

将片段添加到活动状态。该片段可以任选地   也有它的视图（如果Fragment。onCreateView返回非null）   插入到活动的容器视图中。

参数


containerViewId int：此片段放入的容器的可选标识符。如果为0，则不会放在一个
中   容器。

fragment Fragment：要添加的片段。此片段不得已添加到活动中。


tag String：片段的可选标记名称，以便稍后使用
检索片段
FragmentManager.findFragmentByTag(String).

所以在你的代码中写道：

FragmentManager manager = getSupportFragmentManager();
Generaldiscription fragment = new Generaldiscription();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.main_content,fragment,"Tag");
transaction.addToBackStack(null);
transaction.commit();

在你的Generaldiscription片段中：

import android.support.v4.app.Fragment;  //make sure you import the support package

public class Generaldiscription extends Fragment {

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

Answer 3

像你这样在你的片段中声明

public interface OnClickListener {
    void onClick();
}
private final OnClickListener listener;

在按钮中单击侦听器添加此

if(listener!=null){
      listener.onclick();
}

在您的Activity中，实现此侦听器并将其添加到片段中你可以隐藏当前片段并在Activity

中的onClick方法中显示第二个片段

从mainactivity启动新片段

3 个答案: