android - 如何将 List 从 Activity 传递到 fragment

Question

这是我使用数据库助手类从数据库中检索数据的代码

 public List<Hospitals> getHospitals(Context context){
    Hospitals hospitals = null;
    List<Hospitals> hospitalList = new ArrayList<>();
    openDatabase(context);
    Cursor cursor = database.rawQuery("SELECT * FROM buildings WHERE category_id = 1", null);
    cursor.moveToFirst();
    while(!cursor.isAfterLast()){
        hospitals = new Hospitals(cursor.getInt(0), cursor.getString(1), cursor.getFloat(2), cursor.getFloat(4));
        hospitalList.add(hospitals);
        cursor.moveToNext();
    }
    cursor.close();
    closeDatabase();

    return hospitalList;
}

这是我的类(class)医院

public class Hospitals {
private int id;
private String name;
private Float latitude;
private Float longhitude;

public Hospitals(int id, String name, Float latitude, Float longhitude ){
    this.id = id;
    this.name = name;
    this.latitude = latitude;
    this.longhitude = longhitude;

}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public String getName() {
    return name;
}

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

public Float getLatitude() {
    return latitude;
}

public void setLatitude(Float latitude) {
    this.latitude = latitude;
}

public Float getLonghitude() {
    return longhitude;
}

public void setLonghitude(Float longhitude) {
    this.longhitude = longhitude;
}

这是我在主要 Activity 中将 List<> 传递给 fragment 的代码

List<Hospitals> result = databaseHelper.getHospitals(this);
        Bundle bundle = new Bundle();
        bundle.putParcelableArrayList("valuesArray", result);
        GmapFragment gmapFragment = new GmapFragment();
        gmapFragment.setArguments(bundle);
        fragmentManager.beginTransaction().replace(R.id.mainLayout, gmapFragment).commit();

我在 putParcelableArrayList() 中得到了第二个参数 - 第二个参数类型错误。找到:'java.util.List'，需要:'java.util.ArrayList

如何解决该错误？

Answer 1

Wrong 2nd argument type. Found: 'java.util.List', required: 'java.util.ArrayList

首先将LIST转换为ARRAYLIST。

 List<Hospitals> result = databaseHelper.getHospitals(this);
 ArrayList<Hospitals> al_HOSPITAL = new ArrayList<>(result.size());
 al_HOSPITAL.addAll(result);

然后

Bundle bundle = new Bundle();
bundle.putSerializable("valuesArray", al_HOSPITAL);

你应该使用 Parcelable .

AFAIK 使用 Parcelable 优于 Serializable 。

• Parcelable 是耗时且容易出错的过程。

Interface for classes whose instances can be written to and restored from a Parcel. Classes implementing the Parcelable interface must also have a non-null static field called CREATOR of a type that implements the Parcelable.Creator interface.

public class Hospitals implements Parcelable {

最后 Clean-Rebuild-Run 。希望这会有所帮助。