java - 如何在MainActivity中实现导航Activity和Recyclerview

Question

我从抽屉导航 Activity 开始，并将 recyclerView 添加到 content_main.xml 中，但我无法将 RecyclerView 实现到 ManiActivity.java 文件中。

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_camera) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}
}

当我不仅实现了 NavigationView Activity 时，这就是我的 MainAcitity.java 的样子。

public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {

MyRecyclerViewAdapter adapter;

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

    // data to populate the RecyclerView with
    ArrayList<String> animalNames = new ArrayList<>();
    animalNames.add("Horse");
    animalNames.add("Cow");
    animalNames.add("Camel");
    animalNames.add("Sheep");
    animalNames.add("Goat");

    // set up the RecyclerView
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvAnimals);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    adapter = new MyRecyclerViewAdapter(this, animalNames);
    adapter.setClickListener(this);
    recyclerView.setAdapter(adapter);
}

@Override
public void onItemClick(View view, int position) {
    Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
}
}

我还需要这个(recyclerview)到我的 MainActivity.java 中，两者都没有空间

下面的代码是我的适配器类，整个工作就是将其添加到 MainActivity.java

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {

private List<String> mData = Collections.emptyList();
private LayoutInflater mInflater;
private ItemClickListener mClickListener;

// data is passed into the constructor
public MyRecyclerViewAdapter(Context context, List<String> data) {
    this.mInflater = LayoutInflater.from(context);
    this.mData = data;
}

// inflates the row layout from xml when needed
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = mInflater.inflate(R.layout.recyclerview_row, parent, false);
    ViewHolder viewHolder = new ViewHolder(view);
    return viewHolder;
}

// binds the data to the textview in each row
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    String animal = mData.get(position);
    holder.myTextView.setText(animal);
}

// total number of rows
@Override
public int getItemCount() {
    return mData.size();
}


// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    public TextView myTextView;

    public ViewHolder(View itemView) {
        super(itemView);
        myTextView = (TextView) itemView.findViewById(R.id.tvAnimalName);
        itemView.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
    }
}

// convenience method for getting data at click position
public String getItem(int id) {
    return mData.get(id);
}

// allows clicks events to be caught
public void setClickListener(ItemClickListener itemClickListener) {
    this.mClickListener = itemClickListener;
}

// parent activity will implement this method to respond to click events
public interface ItemClickListener {
    void onItemClick(View view, int position);
}

}

Answer 1

您需要在 MainActivity 类上实现 NavigationView.OnNavigationItemSelectedListener 和 MyRecyclerViewAdapter.ItemClickListener 接口(interface)。这样您就可以调用 Recycler View 的适配器类。您的代码应如下所示:

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener, MyRecyclerViewAdapter.ItemClickListener {

  MyRecyclerViewAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

// data to populate the RecyclerView with
ArrayList<String> animalNames = new ArrayList<>();
animalNames.add("Horse");
animalNames.add("Cow");
animalNames.add("Camel");
animalNames.add("Sheep");
animalNames.add("Goat");

// set up the RecyclerView
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvAnimals);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new MyRecyclerViewAdapter(this, animalNames);
adapter.setClickListener(this);
recyclerView.setAdapter(adapter);

}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_camera) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}  

@Override
public void onItemClick(View view, int position) {
    Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
 }
}

在 Java 中，一个类可以实现多个接口(interface)，并且一个类只能从一个父类扩展。多个接口(interface)的实现消除了 Java 中不允许的多重继承。

例如: ClassA 实现 ClassB、ClassC

您编辑的代码可以在 here 找到