java在哪里声明RecyclerView，RecyclerView。适配器和回收视图。布局经理？

1 周，5 日 Questions & Answers 41

我有两个recycleView的例子，一个是在onCreate方法中声明上述内容，另一个是在MainActivity中。有什么区别吗？一个是对的还是错的？我猜这不是安卓的概念，而是java的概念。这是密码

package com.commonsware.jetpack.samplerj.recyclerview;

import 安卓.os.Bundle;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import 安卓x.appcompat.app.AppCompatActivity;
import 安卓x.recyclerview.widget.DividerItemDecoration;
import 安卓x.recyclerview.widget.LinearLayoutManager;
import 安卓x.recyclerview.widget.RecyclerView;

public class MainActivity extends AppCompatActivity {
  private final Random random = new Random();

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RecyclerView items = findViewById(R.id.items);
    ColorAdapter adapter = new ColorAdapter(getLayoutInflater());

    adapter.submitList(buildItems());
    items.setLayoutManager(new LinearLayoutManager(this));
    items.addItemDecoration(
      new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
    items.setAdapter(adapter);
  }

  private List<Integer> buildItems() {
    ArrayList<Integer> result = new ArrayList<>(25);

    for (int i = 0; i < 25; i++) {
      result.add(random.nextInt());
    }

    return result;
  }
}

另一个例子

public class MyActivity extends Activity {
    private RecyclerView recyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager layoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);
        recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        recyclerView.setHasFixedSize(true);

        // use a linear layout manager
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        // specify an adapter (see also next example)
        mAdapter = new MyAdapter(myDataset);
        recyclerView.setAdapter(mAdapter);
    }
    // ...
}

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java在哪里声明RecyclerView，RecyclerView。适配器和回收视图。布局经理？

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