如何在片段中使用Parcelable获取数据？ [英] How to use Parcelable in fragment for getting data?

问题描述

我可以在Activity中使用Parcelable，但我不知道如何在Fragment中使用它。

我在FragmentGet中有一个ListFragment来显示ListView中的所有行数据库，我想在单击时在另一个Fragment中获得ListView的详细信息，我使用Parcelable在Fragments之间传递数据。

这是我的Test.java：

  import android.os.Parcel; 
导入android.os.Parcelable; 
 
 public class Test实现Parcelable {
 
 private int studentNumber; 
 private String studentName; 
私人字符串studentFamily; 
 
 public int getStudentNumber（）{
 return studentNumber; 
} 
 
 public void setStudentNumber（int studentNumber）{
 this.studentNumber = studentNumber; 
} 
 
 public String getStudentName（）{
 return studentName; 
} 
 
 public void setStudentName（String studentName）{
 this.studentName = studentName; 
} 
 
 public String getStudentFamily（）{
 return studentFamily; 
} 
 
 public void setStudentFamily（String studentFamily）{
 this.studentFamily = studentFamily; 
 
 $ b $ public Test（）{
} 
 
 public Test（Parcel read）{
 studentNumber = read.readInt（）; 
 studentName = read.readString（）; 
 studentFamily = read.readString（）; 
} 
 
 @Override 
 public int describeContents（）{
 return 0; 
} 
 
 @Override 
 public void writeToParcel（Parcel write，int flags）{
 write.writeInt（studentNumber）; 
 write.writeString（studentName）; 
 write.writeString（studentFamily）; 
} 
 
 public static final Parcelable.Creator< Test> CREATOR = 
 new Parcelable.Creator< Test>（）{
 @Override 
 public Test createFromParcel（Parcel source）{
 return new TestP（source）; 
} 
 @Override 
 public Test [] newArray（int size）{
 return new TestP [size]; 
} 
}; 
 
  

在FragmentSend.java中，我想将数据发送到FragmentGet.java，这是代码：

  public class FragmentSend extends ListFragment {
 
 //类
 TestReadData readData ; 
 TestDataSource dataSource; 
 
私人列表< Test> listTest; 
 
 public FragmentSend（）{
 //必需的空公共构造函数
} 
 
 
 @TargetApi（Build.VERSION_CODES.M）
 @Override 
 public view onCreateView（LayoutInflater inflater，ViewGroup container，
 Bundled savedInstanceState）{
 
 View layout = inflater.inflate（R.layout.fragment_send，container，假）; 
 
 readData = new TestReadData（getContext（））; 
 dataSource = new TestDataSource（getContext（））; 
 
 refreshStudentList（inflater）; 
 
返回布局; 
 
 
 public void refreshStudentList（LayoutInflater inflater）{
 
 listTest = readData.getAllStudentRows（）; 
 ArrayAdapter< Test> testAdapter = new TestFragmentListAdapter（inflater.getContext（），listTest）; 
 setListAdapter（testAdapter）; 
 
 
 
 @Override 
 public void onResume（）{
 super.onResume（）; 
 dataSource.open（）; 
} 
 
 @Override 
 public void onPause（）{
 super.onPause（）; 
 dataSource.close（）; 
 
 $ b @Override 
 public void onListItemClick（ListView l，View v，int position，long id）{
 super.onListItemClick（l，v，position， ID）; 
 
 Test model = listTest.get（position）; 
 
 //这三行代码适用于Activity not Fragment！ 
 Intent intent = new Intent（getContext（），FragmentGet.class）; 
 intent.putExtra（Student，model）; 
 // startActivity（intent）; 
 
 //我使用此代码片段
片段fragmentGet = new FragmentGet（）; 
 fragmentGet.setArguments（intent.getExtras（））; 
 FragmentManager fragmentManager = getActivity（）。getSupportFragmentManager（）; 
 FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction（）; 
 fragmentTransaction.replace（R.id.frame_container，fragmentGet）; 
 fragmentTransaction.addToBackStack（null）; 
 fragmentTransaction.commit（）; 
 
 
 $ / code> 

在FragmentGet.java中，我得到这样的数据：

  public class FragmentGet extends Fragment {
 
 //类
测试模型; 
 
 //变量
私人列表< Test> listTest; 
 
 public FragmentGet（）{
 //必需的空公共构造函数
} 
 
 
 @Override 
 public View onCreateView LayoutInflater inflater，ViewGroup容器，
 Bundled savedInstanceState）{
 //膨胀这个片段的布局
 View layout = inflater.inflate（R.layout.fragment_get，container，false）; 
 
 //关联的类
 model = new Test（Parcel.obtain（））; 
 
 Bundle bundle = getActivity（）。getIntent（）。getExtras（）; 
 model = bundle.getParcelable（Student）; 
 
返回布局; 
} 
  

当我运行该应用程序时，我会收到此错误：

试图调用虚拟方法'android.os.Parcelable
android.os.Bundle.getParcelable（java.lang.String）'空对象
引用

我该如何解决这个错误？

Fragments 是通过使用 Bundles 而不是来传递的。解决方案 code> Intents 。

在 FragmentSend 更改

  Intent intent = new Intent（getContext（），FragmentGet.class）; 
 intent.putExtra（Student，model）; 
 
片段fragmentGet = new FragmentGet（）; 
 fragmentGet.setArguments（intent.getExtras（））; b 
 
 
 
 
 
 code> Fragment fragmentGet = new FragmentGet（）; 
 Bundle bundle = new Bundle（）; 
 bundle.putParcelable（Student，model）; 
 fragmentGet.setArguments（bundle）; 
  

并且接收 FragmentGet 变化中的数据

  Bundle bundle = getActivity（）。getIntent（）。getExtras（）; 
 model = bundle.getParcelable（Student）; 
  

至

  Bundle bundle = this.getArguments（）; 
 if（bundle！= null）{
 model = bundle.getParcelable（Student）; 
} 
  

I can use Parcelable in Activity but I don't know how to use it in Fragment.

I have a ListFragment in FragmentGet to display all rows database in ListView, I want to get details of ListView in another Fragment when it's clicked, I use Parcelable to passing data between Fragments.

This is my Test.java:

import android.os.Parcel;
import android.os.Parcelable;

public class Test implements Parcelable {

    private int studentNumber;
    private String studentName;
    private String studentFamily;

    public int getStudentNumber() {
        return studentNumber;
    }

    public void setStudentNumber(int studentNumber) {
        this.studentNumber = studentNumber;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public String getStudentFamily() {
        return studentFamily;
    }

    public void setStudentFamily(String studentFamily) {
        this.studentFamily = studentFamily;
    }

    public Test() {
    }

    public Test(Parcel read) {
        studentNumber = read.readInt();
        studentName = read.readString();
        studentFamily = read.readString();
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel write, int flags) {
        write.writeInt(studentNumber);
        write.writeString(studentName);
        write.writeString(studentFamily);
    }

    public static final Parcelable.Creator<Test> CREATOR =
            new Parcelable.Creator<Test>() {
                @Override
                public Test createFromParcel(Parcel source) {
                    return new TestP(source);
                }
                @Override
                public Test[] newArray(int size) {
                    return new TestP[size];
                }
            };
}

In FragmentSend.java I want to send data to FragmentGet.java, this is the code:

public class FragmentSend extends ListFragment {

    //    Classes
    TestReadData readData;
    TestDataSource dataSource;

    private List<Test> listTest;       

    public FragmentSend() {
        // Required empty public constructor
    }


    @TargetApi(Build.VERSION_CODES.M)
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View layout = inflater.inflate(R.layout.fragment_send, container, false);

        readData = new TestReadData(getContext());
        dataSource = new TestDataSource(getContext());  

       refreshStudentList(inflater);

    return layout;
}

public void refreshStudentList(LayoutInflater inflater) {

    listTest = readData.getAllStudentRows();
    ArrayAdapter<Test> testAdapter = new TestFragmentListAdapter(inflater.getContext(), listTest);
    setListAdapter(testAdapter);

}

    @Override
    public void onResume() {
        super.onResume();
        dataSource.open();
    }

    @Override
    public void onPause() {
        super.onPause();
        dataSource.close();
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        Test model = listTest.get(position);

        // this three line code is for Activity not Fragment!
        Intent intent = new Intent(getContext(), FragmentGet.class);
        intent.putExtra("Student", model);
       // startActivity(intent);

        // I use this code for fragment
        Fragment fragmentGet = new FragmentGet();
    fragmentGet.setArguments(intent.getExtras());
    FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.replace(R.id.frame_container, fragmentGet);
    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();

    }

In the FragmentGet.java I get data like this:

public class FragmentGet extends Fragment {

    //    Classes
    Test model;    

    //    Variables
    private List<Test> listTest;

    public FragmentGet () {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View layout = inflater.inflate(R.layout.fragment_get, container, false);

        //        Classes Associated
        model = new Test(Parcel.obtain());

        Bundle bundle = getActivity().getIntent().getExtras();
        model = bundle.getParcelable("Student");

        return layout;    
    }

When I run the app, I will get this error:

Attempt to invoke virtual method 'android.os.Parcelable android.os.Bundle.getParcelable(java.lang.String)' on a null object reference

how can I fix this error?

解决方案

Passing data to Fragments is carried by using Bundles but not Intents.

In FragmentSend change

Intent intent = new Intent(getContext(), FragmentGet.class);
intent.putExtra("Student", model);

Fragment fragmentGet = new FragmentGet();
fragmentGet.setArguments(intent.getExtras());

to this

Fragment fragmentGet = new FragmentGet();
Bundle bundle = new Bundle();
bundle.putParcelable("Student", model);
fragmentGet.setArguments(bundle);

And to receive the data in FragmentGet change

Bundle bundle = getActivity().getIntent().getExtras();
model = bundle.getParcelable("Student");

to

Bundle bundle = this.getArguments();
if (bundle != null) {
    model = bundle.getParcelable("Student");
}

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