我在使用 Android DataBinding 和 BaseAdapter 为 Spinner 实现 CustomAdapter 时遇到问题。
数据有两个值。我想使用两个 TextView。 CustomAdapter必须继承自BaseAdapter,ArrayAdapter的更简单变体仅支持一个TextView。从长远来看,第二个 TextView 可能是 ImageView,因此将两个值合并到一个 String 中以便能够使用 ArrayAdapter 仍然没有帮助。
我还尝试过:为了确保这个想法和 Spinner 正常工作,我实现了一个没有数据绑定(bind)的版本,并且我的数据绑定(bind)实现基于 chrislizh 的项目 https://github.com/chrislizh/SpinnerTwoWayDataBindingDemo ,它正在使用 ArrayAdapter。
我还尝试调用:binding.executePendingBindings()
,并尝试不使用 ViewHolder 模式。
问题结果详细: 该项目是关于行星的。旋转器允许选择行星。每个行星都有一个名称和距离。两个值都会显示。我使用 DataBinding 实现 CustomAdapter(称为 PlanetAdapter)的结果在选择后显示第一个项目两次。查看屏幕截图。选择除第一个项目之外的任何其他行星,都会随选择“切换”其位置,并保持显示两次。这样,显示的列表中始终会缺少一颗行星。
PlanetAdapter 的代码以及在 MainActivty 的 onCreate 方法中创建它的调用:
行星适配器
public class PlanetAdapter extends BaseAdapter
{
private int itemLayoutResourceId;
private final List<Planet> planets;
private LayoutInflater inflater;
public PlanetAdapter(@NonNull Context context, @LayoutRes int itemLayoutResourceId, List<Planet> planets)
{
inflater = LayoutInflater.from(context);
this.itemLayoutResourceId = itemLayoutResourceId;
this.planets = planets;
}
@Override
public int getCount()
{
return planets.size();
}
@Override
public Object getItem(int position)
{
return planets.get(position);
}
@Override
public long getItemId(int position)
{
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
PlanetViewHolder holder;
if (convertView == null) {
PlanetSpinnerItemBinding itemBinding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()), R.layout.planet_spinner_item, parent, false);
itemBinding.setPlanet(planets.get(position));
holder = new PlanetViewHolder(itemBinding);
holder.view = itemBinding.getRoot();
holder.view.setTag(holder);
}
else {
holder = (PlanetViewHolder) convertView.getTag();
}
return holder.view;
}
private static class PlanetViewHolder
{
private View view;
PlanetViewHolder(PlanetSpinnerItemBinding binding)
{
this.view = binding.getRoot();
}
}}
创建并设置适配器:
public class MainActivity extends AppCompatActivity implements IDataChangeListener
{
private static final String BUNDLE_SELECTED_PLANET = "bundle_selected_planet";
private ActivityMainBinding activityMainBinding_;
private List<Planet> planets_;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
activityMainBinding_ = DataBindingUtil.setContentView(this, R.layout.activity_main);
planets_ = loadPlanets(this, R.array.planetsInSolarSystem);
if (planets_ != null) {
planets_.add(0, new Planet("", 0)); // insert a blank item on the top of the list
PlanetAdapter planetAdapter = new PlanetAdapter(this, R.layout.planet_spinner_item, planets_);
activityMainBinding_.setSpinAdapterPlanet(planetAdapter);
Planet selectedPlanet = savedInstanceState != null ? savedInstanceState.<Planet>getParcelable(BUNDLE_SELECTED_PLANET) : planets_.get(3);//initial selected planet is Earth, 3 is the index of Earth after a blank item inserted
activityMainBinding_.setBindingPlanet(new BindingPlanet(this, selectedPlanet));
}
} // loadPlanets skipped.
}
行星类别:
public class Planet implements Parcelable {
private String name_;
private float distance_; //distance to Sun in AU(Astronomical Unit)
public Planet(String name, float distance) {
name_ = name;
distance_ = distance;
}
protected Planet(Parcel in) {
name_ = in.readString();
distance_ = in.readFloat();
}
public static final Creator<Planet> CREATOR = new Creator<Planet>() {
@Override
public Planet createFromParcel(Parcel in) {
return new Planet(in);
}
@Override
public Planet[] newArray(int size) {
return new Planet[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(name_);
dest.writeFloat(distance_);
}
@Override
public String toString() {
return name_ != null ? name_ : super.toString();
}
public String getName() {
return name_;
}
public void setName(String name) {
name_ = name;
}
public float getDistance() {
return distance_;
}
public void setDistance(float distance) {
distance_ = distance;
}
}
项目布局的 XML:spinner_planet_item.xml `
<data>
<variable
name="planet"
type="au.com.chrisli.spinnertwowaydatabindingdemo.Planet">
</variable>
</data>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/planetName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{planet.name}"
tools:text="Dummy Planet"
android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>
<TextView
android:id="@+id/planetDistance"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="8dp"
android:text="@{String.valueOf(planet.distance)}"
android:textAppearance="@style/TextAppearance.AppCompat.Medium"
tools:text="2393.0 km"/>
</LinearLayout>
在github代码中,我还在文件末尾的类PlanetAdapter中包含了经典案例(没有数据绑定(bind)),但注释掉了。如果您想查看它的工作原理 - 只需在那里切换 getView 和 PlaneViewHolder 实现即可。
完整修改的项目位于我的 github 上:https://github.com/Minsky/SO_Question_SpinnerDataBindingBaseAdapter
我的 BaseAdapter 的 Binding 实现有什么问题?
最佳答案
正如 Commonsware 在评论中所写,回收案例中的 View 绑定(bind)缺失。 PlanetAdapter 中 getView() 方法的工作代码如下所示:
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
PlanetViewHolder holder;
if (convertView == null) {
PlanetSpinnerItemBinding itemBinding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()), R.layout.planet_spinner_item, parent, false);
holder = new PlanetViewHolder(itemBinding);
holder.view = itemBinding.getRoot();
holder.view.setTag(holder);
}
else {
holder = (PlanetViewHolder) convertView.getTag();
}
holder.binding.setPlanet(planets.get(position));
return holder.view;
}
PlanetViewHolder 现在持有绑定(bind):
private static class PlanetViewHolder {
private View view;
private PlanetSpinnerItemBinding binding;
PlanetViewHolder(PlanetSpinnerItemBinding binding) {
this.view = binding.getRoot();
this.binding = binding;
}
}
分支“已解决”中的最终 Github 项目:https://github.com/Minsky/SO_Question_SpinnerDataBindingBaseAdapter/tree/solved
关于android - 如何为 Spinner 继承自 BaseAdapter 的 CustomAdapter 进行 Android 数据绑定(bind)?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43973490/