如何将我的主线程与创建的工作线程连接

Question

嘿，我在Android Studio java上使用房间数据库时遇到了麻烦。当我单击保存按钮时，我正在尝试保存类的组件。但问题是在主线程上使用保存或下载调用是一件坏事，所以我正在创建自己的线程，但我如何在该线程之外使用数据？我正在做的班级看起来像这样...

更新：那这应该有效吗？

package com.example.jenso.paperseller;
import android.arch.persistence.room.Room;
import android.content.Intent;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class CreateCustomer extends AppCompatActivity {
    EditText name;
    EditText address;
    EditText phonenumber;
    EditText email;
    Button saveCustomer;
    PapperSellerDatabase pd;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.create_customer);
        name = findViewById(R.id.nameInput);
        address = findViewById(R.id.addressInput);
        phonenumber = findViewById(R.id.phonenumberInput);
        email = findViewById(R.id.emailInput);
        saveCustomer = findViewById(R.id.saveInput);
        setTheDataBase();

        saveCustomer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(CreateCustomer.this, MainActivity.class));
                pd.customerDao().insertAll(new Customer(name.getText().toString(),address.getText().toString(),phonenumber.getText().toString(),email.getText().toString()));
            }
        });


    }
    public void setTheDataBase(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                //here you obtain data from async source
                PapperSellerDatabase pd = Room.databaseBuilder(getApplicationContext(),PapperSellerDatabase.class,"production")
                        .fallbackToDestructiveMigration()
                        .build();

            }
        }).start();

    }
}

在负载方面我这样做？

package com.example.jenso.paperseller;
import android.arch.persistence.room.Room;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.ThemedSpinnerAdapter;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
    RecyclerView recyclerView;
    RecyclerView.Adapter adapter;
    List<Customer> customers;
    PapperSellerDatabase database;

    FloatingActionButton fab;
    private static final  String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        recyclerView = findViewById(R.id.recycler);
        customers = new ArrayList<>();

        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        adapter = new PapperRecyclerAdapter(customers,this);
        recyclerView.setAdapter(adapter);
        downloadTheData();
        fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d(TAG, "onClick: Do this when you click");
                startActivity(new Intent(MainActivity.this, CreateCustomer.class));
            }
        });

    }
    private void downloadTheData(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                //here you obtain data from async source
                PapperSellerDatabase pd = Room.databaseBuilder(getApplicationContext(),PapperSellerDatabase.class,"production")
                        .fallbackToDestructiveMigration()
                        .build();

                customers = pd.customerDao().getAllCustomers();
            }
        }).start();


    }


}

那么，如果我单击"我要将数据保存到房间数据库"然后离开视图的按钮，我将如何进一步呢？

Answer 1

每当你使用前提时，例如在JavaScript中，你不确定前提何时会实现，或者换句话说，你的日期何时可用。因此，通常要做的是在更高的范围内声明变量，这将使它既可用于应该设置它的线程(worker(，也可以提供给应该使用它的线程(main(。

更新

public class Example {
  //here you initialize your variable that will contain data
  List <RemoteData> remoteData = null;
  ....
  public void hereRemoteDataIsUsed(){
     if(remoteData != null){ 
        //use remoteData here
        ...
     }
  }
  ....
  public void hereRemoteDataIsSet(){
      new Thread(new Runnable() {
          @Override
          public void run() {
            //here you obtain data from async source     
            remoteData = getDataFromSomeAsyncSource();
          }
    }).start();
  }
}

您可以注意到，在获取数据的方法中，不返回任何内容。由于这是一个异步操作，您不知道何时会完成它。你只知道它最终会。所以你只是等到它可用(remoteData != null(。