Question

我正在尝试找到一种方法来动态地将片段添加到活动布局，同时唯一地设置该片段的TextView。假设我在下面有片段类ExampleFragment：

package com.project.testapplication;

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

import com.project.testapplication.R;

public class ExampleFragment extends Fragment {

    TextView Name, Location;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_layout, container, false);
        Name=(TextView)view.findViewById(R.id.name);
        Location=(TextView)view.findViewById(R.id.location);
        return view;
    }

    public void setName(String n)
    {
        Name.setText(n);
    }

    public void setLocation(String loc)
    {
        Location.setText(loc);
    }

}

使用布局fragment_layout.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="56dp"
        android:text="name"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <TextView
        android:id="@+id/location"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/name"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="109dp"
        android:text="location" />
</RelativeLayout>

现在在另一个活动中，我想要为布局添加用户指定数量的这些片段，并为每个片段添加用户指定的名称和位置（设置为TextView）。我正在使用FragmentManager将片段添加到我的活动中。当我不尝试编辑片段中的任何TextView时（使用片段中的setter方法），片段正确添加。但是，如果我尝试从Fragment中为任何TextView设置setText，则应用程序崩溃。我在ExampleActivity类下面的代码（包含导致程序崩溃的行）：

package com.project.testapplication;

import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import com.project.testapplication.ExampleFragment;
import com.project.testapplication.ExampleObject;
import com.project.testapplication.R;

import java.util.ArrayList;

public class ExampleActivity extends AppCompatActivity {

    ArrayList<ExampleObject> list = new ArrayList<ExampleObject>();

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

        //Populate "list" ArrayList with "ExampleObject" objects
        list.add(new ExampleObject("name1", "location1"));
        list.add(new ExampleObject("name2", "location2"));
        list.add(new ExampleObject("name3", "location3"));

        for(ExampleObject o: list)
        {
            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            ExampleFragment fragment = new ExampleFragment();
            fragment.setName(o.getName()); /***line causes crash***/
            fragment.setLocation(o.getLocation()); /***line causes crash (if not for line above)***/
            fragmentTransaction.add(R.id.linear_layout_scroll, fragment);
            fragmentTransaction.commit();
        }

    }
}

ExampleObject定义如下：

package com.project.testapplication;

public class ExampleObject {

    String name, location;
    public ExampleObject(String name, String location)
    {
        this.name=name;
        this.location=location;
    }

    public void setName(String name)
    {
        this.name=name;
    }

    public String getName()
    {
        return name;
    }

    public void setLocation(String location)
    {
        this.location=location;
    }

    public String getLocation()
    {
        return location;
    }
}

在我的activity_example.xml布局中：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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/lin_lay"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.project.testapplication.ExampleActivity">

    <ScrollView
        android:id="@+id/scroll_v"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

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

在ExampleActivity类中，当我删除崩溃应用程序的两行代码时，片段添加正常但没有自定义TextView。我试图找出一种方法来独特地设置TextViews（通过片段中的方法）而不会崩溃应用程序。

任何回复都表示赞赏。谢谢。

编辑：找到了我的问题的解决方案，在下面回答。

Answer 1

我终于通过查看this帖子了解了这一点。我必须先将这些方法添加到我的ExampleFragment类：

     public static ExampleFragment newInstance(String name, String location) {
             ExampleFragment myFragment = new ExampleFragment();
             Bundle args = new Bundle();
             args.putString("name", name);
             args.putString("location", location);
             myFragment.setArguments(args);

             return myFragment;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        String name = getArguments().getString("name");
        String location = getArguments().getString("location");
        Name.setText(name);
        Location.setText(location);

然后在ExampleActivity中，而不是将片段实例化为：

ExampleFragment fragment = new ExampleFragment();

我将其实例化为：

ExampleFragment fragment = ExampleFragment.newInstance(o.getName(), o.getLocation());

除了删除OP中最初导致它崩溃的两行代码。（fragment.setName()和fragment.setLocation()语句。

问题是我在初始化之前尝试在TextView上设置文本（在调用onCreateView之前）。这种实例化片段的方式可确保在创建片段视图之前不会设置TextView。 This帖子也是一个很好的参考，以及Android网站上的documentation。

Answer 2

试试此代码

片段

public class ExampleFragment extends Fragment {
    ArrayList<ExampleObject> list = new ArrayList<ExampleObject>();
    TextView Name, Location;

    public ExampleFragment(ArrayList<ExampleObject> arrayList){
        list=arrayList;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup 
    container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_layout, container, 
    false);
        Name=(TextView)view.findViewById(R.id.name);
        Location=(TextView)view.findViewById(R.id.location);
        for(ExampleObject o: list)
        {
        setName(o.getName()); 
            setLocation(o.getLocation());
        }
        return view;
    }

    public void setName(String n)
    {
        Name.setText(n);
    }

    public void setLocation(String loc)
    {
        Location.setText(loc);
    }
}

活动

public class ExampleActivity extends AppCompatActivity {

    ArrayList<ExampleObject> list = new ArrayList<ExampleObject>();

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

        //Populate "list" ArrayList with "ExampleObject" objects
        list.add(new ExampleObject("name1", "location1"));
        list.add(new ExampleObject("name2", "location2"));
        list.add(new ExampleObject("name3", "location3"));


            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            ExampleFragment fragment = new ExampleFragment(list);
            fragmentTransaction.add(R.id.linear_layout_scroll, fragment);
            fragmentTransaction.commit();

    }
}

尝试在动态添加到布局的片段中设置TextView时Android应用程序崩溃

2 个答案: