Question

我正在尝试为简单和科学的计算器创建一个带有两个片段的计算器。但是Viewpager是空的，虽然在两个片段之间可以滚动，但片段的内容是不可见的。此外，如果我将IsViewFromObject更改为true，则两个片段都可以在彼此之上显示。

这是viewpager：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    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.root.calculatorui.Science">
    <EditText
        android:inputType="none"
        android:textIsSelectable="true"
        android:gravity="right|bottom"
        android:textSize="50sp"
        android:background="#FFFFFF"
        android:id="@+id/txtResult"
        android:layout_width="match_parent"
        android:layout_height="180dp" />
<android.support.v4.view.ViewPager
    android:layout_below="@id/txtResult"
    android:id="@+id/viewPager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />
    </RelativeLayout>

这里是用于初始化ViewPager的fragmentActivity代码：

package com.example.root.calculatorui;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;

public class Science extends FragmentActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_for_calculator);
        ViewPager viewPager=(ViewPager)findViewById(R.id.viewPager);
        viewPager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));

    }

    private class MyPagerAdapter extends FragmentStatePagerAdapter {
        public MyPagerAdapter(FragmentManager supportFragmentManager) {
            super(supportFragmentManager);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    Log.d("Load", "Started Science");
                    return new ScienceFragment();
                case 1:
                    Log.d("Load", "Back to Simple");
                    return new SimpleFragment();
                default:
                    return new SimpleFragment();
            }
        }

        @Override
        public int getCount() {
            return 2;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return false;
        }
    }
}

这是simpleFragment：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    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.root.calculatorui.Science">

    <Button
        android:text="C"
        android:textColor="@android:color/holo_orange_dark"
        android:layout_below="@+id/txtResult"
        style="@style/Button"
        android:id="@+id/buttonClear" />

    <Button
        android:text="←"
        style="@style/Button"
        android:id="@+id/buttonDel"
        android:layout_below="@+id/txtResult"
        android:layout_toRightOf="@+id/buttonClear"
        android:layout_toEndOf="@+id/buttonClear" />

    <Button
        android:text="÷"
        style="@style/Button"
        android:id="@+id/buttonDiv"
        android:layout_below="@+id/txtResult"
        android:layout_toRightOf="@+id/buttonDel"
        android:layout_toEndOf="@+id/buttonDel" />

    <Button
        android:text="x"
        style="@style/Button"
        android:id="@+id/buttonMul"
        android:layout_toRightOf="@+id/buttonDiv"
        android:layout_below="@+id/txtResult" />

    <Button
        android:text="7"
        style="@style/Button"
        android:id="@+id/button7"
        android:layout_below="@+id/buttonClear"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:text="8"
        style="@style/Button"
        android:id="@+id/button8"
        android:layout_below="@+id/buttonDel"
        android:layout_toRightOf="@+id/button7"
        android:layout_toEndOf="@+id/button7" />

    <Button
        android:text="9"
        style="@style/Button"
        android:layout_below="@+id/buttonDiv"
        android:layout_toRightOf="@+id/button8"
        android:layout_toEndOf="@+id/button8"
        android:id="@+id/button9" />

    <Button
        android:text="-"
        android:textSize="30sp"
        style="@style/Button"
        android:layout_toRightOf="@+id/button9"
        android:layout_toEndOf="@+id/button9"
        android:id="@+id/buttonSub"
        android:layout_below="@+id/buttonDiv" />

    <Button
        android:text="5"
        android:id="@+id/btn5"
        style="@style/Button"
        android:layout_alignBottom="@+id/btn4"
        android:layout_toRightOf="@+id/button7"
        android:layout_toEndOf="@+id/button7"
        android:layout_below="@+id/button7" />

    <Button
        android:text="4"
        android:id="@+id/btn4"
        style="@style/Button"
        android:layout_below="@+id/button7"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:id="@+id/btn6"
        android:text="6"
        style="@style/Button"
        android:layout_below="@+id/button8"
        android:layout_toRightOf="@+id/btn5"
        android:layout_toEndOf="@+id/btn5" />

    <Button
        android:text="+"
        android:id="@+id/btnPlus"
        style="@style/Button"
        android:layout_below="@+id/buttonSub"
        android:layout_toRightOf="@+id/btn6"
        android:layout_toEndOf="@+id/btn6" />

    <Button
        android:text="1"
        android:id="@+id/btn1"
        style="@style/Button"
        android:layout_below="@+id/btn5"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:text="2"
        android:id="@+id/btn2"
        style="@style/Button"
        android:layout_below="@+id/btn5"
        android:layout_toRightOf="@+id/btn4"
        android:layout_toEndOf="@+id/btn4" />

    <Button
        android:text="3"
        android:id="@+id/btn3"
        style="@style/Button"
        android:layout_below="@+id/btn6"
        android:layout_toRightOf="@+id/btn2"
        android:layout_toEndOf="@+id/btn2" />

    <Button
        android:text="%"
        android:id="@+id/btnPercentage"
        style="@style/Button"
        android:layout_below="@+id/btn1"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:text="0"
        android:id="@+id/btn0"
        style="@style/Button"
        android:layout_below="@+id/btn2"
        android:layout_toRightOf="@+id/btnPercentage"
        android:layout_toEndOf="@+id/btnPercentage" />

    <Button
        android:text="."
        android:textSize="40sp"
        android:id="@+id/btnDot"
        style="@style/Button"
        android:layout_below="@+id/btn2"
        android:layout_toRightOf="@+id/btn0"
        android:layout_toEndOf="@+id/btn0" />

    <Button
        android:text="="
        style="@style/Button"
        android:background="@android:color/holo_orange_light"
        android:id="@+id/buttonEquals"
        android:layout_toRightOf="@+id/btn3"
        android:layout_alignBottom="@+id/btnDot"
        android:layout_below="@+id/btn6" />
</RelativeLayout>

这是SimpleFragment.Java

package com.example.root.calculatorui;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by root on 14/1/17.
 */

public class SimpleFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.activity_main,container,false);
        return view;
    }

    public SimpleFragment(){}

    public Fragment newInstance(int s, String title) {
        SimpleFragment sfrag=new SimpleFragment();
        Bundle args = new Bundle();
        args.putInt("someInt", s);
        args.putString("someTitle",title);
        sfrag.setArguments(args);
        return sfrag;
    }
}

Answer 1

您没有在getItem(int position)方法中创建片段的实例。

根据以下内容进行更改，它应该有效： -

 @Override
            public Fragment getItem(int position) {
                switch (position) {
                    case 0:
                        Log.d("Load", "Started Science");
                        return new ScienceFragment.newInstance("FirstFragment, Instance 1");

                    case 1:
                        Log.d("Load", "Back to Simple");
                        return new SimpleFragment.newInstance("SecondFragment, Instance 2");

                    default:
                        return new SimpleFragment.newInstance("DdefaultFragment, Instance default");
            }
        }

Answer 2

我正在尝试使用两个片段创建一个简单的计算器科学计算器

Fragment s无法容纳其他片段： https://stackoverflow.com/a/6672688/4409113

如果您要创建两个Fragment，请创建一个名为MyPagerAdapter的单个类，然后找到MainActivity （可以通过在Manifest中搜索来完成）< / em>初始化ViewPager中的Activity（例如MainActivity 中的），而不是Fragment ，然后将ViewPager xml代码粘贴到Activity布局中，而不是Fragment。

请注意，您可以在MyPagerAdapter内创建Activity，但您需要更改代码...

（扩展到AppCompatActivity等）。

然后你会好起来的！

Answer 3

使用FragmentPagerAdapter

class ViewPagerAdapter extends FragmentPagerAdapter{
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();

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

@Override
public Fragment getItem(int position) {
        return mFragmentList.get(position);
}

@Override
public int getCount() {
        return mFragmentList.size();
    }
public void addFragment(Fragment fragment, String title) {
    mFragmentList.add(fragment);
    mFragmentTitleList.add(title);
}

@Override
public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
}}

并像这样设置viewpager

    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new ScienceFragment(), "Science");
    adapter.addFragment(new SimpleFragment(), "Simple");
    viewPager.setAdapter(adapter);

Answer 4

在ScienceFragment中使用它，

public static ScienceFragment newInstance(int page, String title) {
    ScienceFragment fragmentFirst = new ScienceFragment();
    Bundle args = new Bundle();
    args.putInt("someInt", page);
    args.putString("someTitle", title);
    fragmentFirst.setArguments(args);
    return fragmentFirst;
}

同样在SimpleFragment中，并在MainActivity中使用它。

private class MyPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int pos) {
            switch(pos) {

                case 0: return ScienceFragment.newInstance(0, "Instance 1");
                case 1: return SimpleFragment.newInstance(1, "Instance 2");
                default: return ScienceFragment.newInstance(0, "Default");
            }
        }

        @Override
        public int getCount() {
            return 2;
        }
    }

Answer 5

这是MainActivity Class。

public class MainActivity extends FragmentActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ViewPager viewPager=(ViewPager)findViewById(R.id.vpPager);
        viewPager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));

    }
    private class MyPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int pos) {
            switch(pos) {

                case 0: return ScienceFragment.newInstance(0, "Science");
                case 1: return SimpleFragment.newInstance(1, "Simple");
                default: return ScienceFragment.newInstance(0, "Default");
            }
        }

        @Override
        public int getCount() {
            return 2;
        }
    }
}

This is ScienceFragment
/**
 * Created by Techno Blogger on 15/1/17.
 */

public class ScienceFragment extends Fragment {
    private String title;
    private int page;

    // newInstance constructor for creating fragment with arguments
    public static ScienceFragment newInstance(int page, String title) {
        ScienceFragment fragmentFirst = new ScienceFragment();
        Bundle args = new Bundle();
        args.putInt("someInt", page);
        args.putString("someTitle", title);
        fragmentFirst.setArguments(args);
        return fragmentFirst;
    }

    // Inflate the view for the fragment based on layout XML
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_science, container, false);
        TextView tvLabel = (TextView) view.findViewById(R.id.textScience);
        tvLabel.setText(page + " -- " + title);
        return view;
    }
}

这是SimpleFragment

public class SimpleFragment extends Fragment {

    // newInstance constructor for creating fragment with arguments
    public static SimpleFragment newInstance(int page, String title) {
        SimpleFragment fragmentFirst = new SimpleFragment();
        Bundle args = new Bundle();
        args.putInt("someInt", page);
        args.putString("someTitle", title);
        fragmentFirst.setArguments(args);
        return fragmentFirst;
    }

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

ViewPager显示空内容

5 个答案: