我正在尝试使用MVVM,我试图在Viewodel中获取数据(通常来自服务)并将其设置为我的活动,但是当我尝试仅使用ContractModel的简单ArrayList和将其添加到适配器中,一切正常,但是当我尝试调用ViewModel时,一切都会停止。
我正在上一门与我做的事情相同但结果不同的课程。
这是我的MainActivity:
public class MainActivity extends AppCompatActivity {
ContractsListViewModel contractsListViewModel;
@BindView(R.id.contractList)
RecyclerView contractList;
RecyclerView.Adapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
contractList.setLayoutManager(new LinearLayoutManager(this));
contractsListViewModel = ViewModelProviders.of(this).get(ContractsListViewModel.class);
contractsListViewModel.call();
adapter = new ContractListAdapter(this, contractsListViewModel.contractList.getValue());
contractList.setAdapter(adapter);
}
}
那就是我的ViewModel:
public class ContractsListViewModel extends ViewModel {
public MutableLiveData<List<ContractModel>> contractList;
MutableLiveData<Boolean> isLoading;
MutableLiveData<Boolean> error;
public void call(){
fetchContracts();
}
public void fetchContracts(){
ContractModel contractModel = new ContractModel(1, "hfdfd", "h");
ContractModel contractModel1 = new ContractModel(1, "hfdffddd", "h");
ContractModel contractModel2 = new ContractModel(1, "hdffd", "j");
ContractModel contractModel3 = new ContractModel(1, "hdffdfd", "h");
List<ContractModel> list = new ArrayList<ContractModel>();
list.add(...allofthem);
contractList.setValue(list);
}
}
我的适配器工作正常,因为它可以与上面提到的ArrayList一起使用。但是这里是:
public class ContractListAdapter extends RecyclerView.Adapter<ContractListAdapter.ContractViewHolder> {
List<ContractModel> contracts;
Context context;
public ContractListAdapter(Context context, List<ContractModel> contracts){
this.context = context;
this.contracts = contracts;
}
@NonNull
@Override
public ContractViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.contrat, parent, false);
return new ContractViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ContractViewHolder holder, int position) {
holder.bind(contracts.get(position));
}
@Override
public int getItemCount() {
return this.contracts.size();
}
public class ContractViewHolder extends RecyclerView.ViewHolder {
@BindView(R.id.courtier)
TextView courtier;
public ContractViewHolder(@NonNull View view){
super(view);
ButterKnife.bind(this, view);
}
public void bind(ContractModel contractModel){
courtier.setText(contractModel.getCourtier());
}
}
}
任何帮助将非常感激。
快速解决
public MutableLiveData<List<ContractModel>> contractList=new MutableLiveData<>();
因为您应该先创建一个列表,然后再在此处设置数据 contractList.setValue(list);
更结构化的解决方案
public class ContractsListViewModel extends ViewModel {
public MutableLiveData<List<ContractModel>> contractList=new MutableLiveData<>();
MutableLiveData<Boolean> isLoading;
MutableLiveData<Boolean> error;
public void call(){
fetchContracts();
}
public void fetchContracts(){
ContractModel contractModel = new ContractModel(1, "hfdfd", "h");
ContractModel contractModel1 = new ContractModel(1, "hfdffddd", "h");
ContractModel contractModel2 = new ContractModel(1, "hdffd", "j");
ContractModel contractModel3 = new ContractModel(1, "hdffdfd", "h");
List<ContractModel> list = new ArrayList<ContractModel>();
list.add(contractModel);
list.add(contractModel1);
list.add(contractModel2);
list.add(contractModel3);
contractList.postValue(list);
}
}
MainActivity onCreate()
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
contractList.setLayoutManager(new LinearLayoutManager(this));
contractsListViewModel = ViewModelProviders.of(this).get(ContractsListViewModel.class);
contractsListViewModel.call();
contractsListViewModel.contractList.observe(this,contractModels -> {
adapter = new ContractListAdapter(MainActivity.this, contractModels);
contractList.setAdapter(adapter);
});
}
检查一下以了解setValue和postValue之间的区别
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