如何处理输出中三个不同泛型列表类的加载器管理器 onLoadFinished 方法

Question

i 有三个泛型类列表

1 List< Board >
2 List< Class >
3 List< Subject >

在运行时，我可以返回任何类型的列表，我将如何获取特定列表并显示它？

@Override
 public Loader<List<Board>> onCreateLoader(int id, Bundle args) {
    String s=null;
    if (args!=null)
   s = args.getString("string_board_id");
    if (id==1) {
        return new BoardLoader(this, boardUrl);
    }
    if (id==2){
        return new ClassLoader(this, boardUrl,s);
    }
    return null;
 }
@Override
public void onLoadFinished(Loader<List<Board>> loader, List<Board> data) {
    if (data !=null && data.size() != 0){
        boardAdapter.addAll(data);
    }
    else{
        Log.e(LOG_TAG,"problem with board  list ");
    }
  }

提前谢谢。

Answer 1

与其在 Activity 上实现 3 个回调，不如创建 3 个LoaderManager.LoaderCallbacks<Type>对象。在引用活动时使用这些对象。

使用

onLoadFinished() 内部的 loader.getId() 查看哪个加载器已完成，以防您想使用带有 2 个加载器的加载器回调。

像这样：

LoaderManager.LoaderCallbacks<String> mStringCallbacks = new LoaderManager.LoaderCallbacks<String>() {
    @Override
    public Loader<String> onCreateLoader(int id, Bundle args) {
        return null;
    }
    @Override
    public void onLoadFinished(Loader<String> loader, String data) {
    }
    @Override
    public void onLoaderReset(Loader<String> loader) {
    }
};

Answer 2

这是我的家庭活动

package com.directionclasses.directionclasses;

import android.app.LoaderManager;
import android.content.Loader;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class HomeActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<List<Object>> {
public static final String LOG_TAG = HomeActivity.class.getName();
Spinner spinner;
Spinner spinnerClass;
Spinner spinnerSubject;
private static final int mBoardLoaderManager=1;
private static final int mClassLoaderManager=2;
private static final int mSubjectLoaderManager=3;
private static final String boardUrl = "http://directionclasses.com/Android/selectBoard.php";
private static final String classUrl = "http://directionclasses.com/Android/selectClass.php";
private static final String subjectUrl = "http://directionclasses.com/Android/selectSubject.php";
BoardAdapter boardAdapter = null;
ClassAdapter classAdapter = null;
SubjectAdapter subjectAdapter = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);
    Toolbar mToolBar=(Toolbar)findViewById(R.id.toolbar);
    mToolBar.setTitle(getString(R.string.app_name));
    //  mToolBar.setNavigationIcon(R.drawable.ic_launcher);
    mToolBar.inflateMenu(R.menu.menu_main);
    android.app.LoaderManager loaderManager=getLoaderManager();
    loaderManager.initLoader(mBoardLoaderManager,null,this);

    spinner = (Spinner) findViewById(R.id.spinner1);
    spinnerClass = (Spinner) findViewById(R.id.spinner2);
    spinnerSubject = (Spinner) findViewById(R.id.spinner3);
    boardAdapter = new BoardAdapter(this, new ArrayList<Board>());
    classAdapter = new ClassAdapter(this, new ArrayList<Class>());
    subjectAdapter = new SubjectAdapter(this, new ArrayList<Subject>());
    spinner.setAdapter(boardAdapter);

    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            Board board = boardAdapter.getItem(position);
            int board_id = board.getBoard_id();
            if (board_id != 0) {
                Toast.makeText(HomeActivity.this, "jai ho" + board_id, Toast.LENGTH_SHORT).show();
                String string_board_id = String.valueOf(board_id);
                Bundle b = new Bundle();
                b.putString("string_board_id", string_board_id);
                android.app.LoaderManager loaderManager=getLoaderManager();
                loaderManager.initLoader(mClassLoaderManager,b,HomeActivity.this);

            } else {
                Toast.makeText(HomeActivity.this, "jai ho with no id", Toast.LENGTH_SHORT).show();
            }
        }
        @Override
        public void onNothingSelected(AdapterView<?> parent) {
        }
    });
}
@Override
public Loader<List<Object>> onCreateLoader(int id, Bundle args) {
    String s=null;
    if (args!=null) {
        s = args.getString("string_board_id");
    }
    if (id==1) {
        return new BoardLoader(this, boardUrl);
    }
    if (id==2){
        return new ClassLoader(this, classUrl,s);
    }
    return null;
}
@Override
public void onLoadFinished(Loader<List<Object>> loader, List<Object> data) {
    int loader_id=loader.getId();
    if (loader_id==1){
        if (data !=null && data.size() != 0){
            List<Board> mythings = (List<Board>) (Object) data;
            boardAdapter.addAll(mythings);
        }
        else{
            Log.e(LOG_TAG,"problem with board  list ");
        }
    }
    if (loader_id==2){
        if (data !=null && data.size() != 0){
            List<Class> mythings = (List<Class>) (Object) data;
            classAdapter.addAll(mythings);
        }
        else{
            Log.e(LOG_TAG,"problem with class  list ");
        }
    }
    if (loader_id==3){
        if (data !=null && data.size() != 0){
            List<Subject> mythings = (List<Subject>) (Object) data;
            subjectAdapter.addAll(mythings);
        }
        else{
            Log.e(LOG_TAG,"problem with subject  list ");
        }
    }

}
@Override
public void onLoaderReset(Loader<List<Object>> loader) {
    Log.v(LOG_TAG,"this is the on Load Reset method");
   // boardAdapter.clear();
}

}

这是我的装板机.java文件

package com.directionclasses.directionclasses;
import android.content.AsyncTaskLoader;
import android.content.Context;
import android.util.Log;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

public class BoardLoader extends AsyncTaskLoader {
private static final String LOG_TAG = BoardLoader.class.getName();
private String mUrl;
public BoardLoader(Context context, String url) {
    super(context);
    mUrl = url;
}
@Override
public List<Board> loadInBackground() {

    ArrayList<Board> boards1 = new ArrayList<Board>();
    URL url1 = null;
    try {
        url1 = new URL(mUrl);
    } catch (MalformedURLException e) {
        e.printStackTrace();
        Log.e(LOG_TAG, "this is url malformed exception");
    }
    BufferedReader reader = null;
    String text = null;
    try {
        URLConnection conn = url1.openConnection();
        conn.setDoOutput(true);
        OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
        wr.flush();
        reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "n");
        }
        text = sb.toString();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    boards1 = featuresExtractFromJson(text);
    return boards1;
}
@Override
protected void onStartLoading() {
    forceLoad();
}
private ArrayList<Board> featuresExtractFromJson(String JsonResponse) {

    ArrayList<Board> results = new ArrayList<Board>();

    try {
        JSONArray root = new JSONArray(JsonResponse);
        for (int i = 0; i < root.length(); i++) {
            JSONObject jsonObject = root.getJSONObject(i);
            String board_id = jsonObject.getString("board_id");
            String board_name = jsonObject.getString("board_name");
            int parse_board_id = Integer.parseInt(board_id);
            results.add(new Board(parse_board_id, board_name));
        }
    } catch (JSONException e) {
        e.printStackTrace();
        Log.e(LOG_TAG, "Json execption");
    }
    return results;
}
}

这是我的主板适配器.java文件

public class BoardAdapter extends ArrayAdapter<Board> {

public BoardAdapter(Context context, ArrayList<Board> boards) {
    super(context, 0, boards);
}
public BoardAdapter(@NonNull Context context, @LayoutRes int resource, ArrayList<Board> boards) {
    super(context, resource);
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    return getCustomView(position, convertView, parent);
}
 @Override
  public View getDropDownView(int position, @Nullable View convertView,  @NonNull ViewGroup parent) {
    return getCustomView(position, convertView, parent);
}
public View getCustomView(int position, View convertView, ViewGroup parent) {
    View listItemView = convertView;
    if (listItemView == null) {
        listItemView = LayoutInflater.from(getContext()).inflate(R.layout.row, parent, false);
    }
    Board board = getItem(position);
    int board_id = board.getBoard_id();
    String board_name = board.getBoard_name();
    TextView text_name = (TextView) listItemView.findViewById(R.id.tv1);
    text_name.setText(board_name);
  //  TextView text_id = (TextView) listItemView.findViewById(R.id.tv2);
   // text_id.setText(board_id+"");
    return listItemView;

}
}

这是我的类加载器.java文件

public class ClassLoader extends AsyncTaskLoader {
private static final String LOG_TAG = ClassLoader.class.getName();
private String mUrl;
private String borad_id=null;
public ClassLoader(Context context, String url,String borad_id1 ) {
    super(context);
    mUrl = url;
    borad_id=borad_id1;
}
@Override
public Object loadInBackground() {
    String data = null;
    try {
        data = URLEncoder.encode("board_id", "UTF-8") + "=" + URLEncoder.encode(borad_id, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    ArrayList<Class> boards1 = new ArrayList<Class>();
    URL url1 = null;
    try {
        url1 = new URL(mUrl);
    } catch (MalformedURLException e) {
        e.printStackTrace();
        Log.e(LOG_TAG, "this is url malformed exception");
    }
    BufferedReader reader = null;
    String text = null;
    try {
        URLConnection conn = url1.openConnection();
        conn.setDoOutput(true);
        OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
        wr.write(data);
        wr.flush();
        reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "n");
        }
        text = sb.toString();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    boards1 = featuresExtractFromJson(text);
    return boards1;
}
@Override
protected void onStartLoading() {
    forceLoad();
}
private ArrayList<Class> featuresExtractFromJson(String JsonResponse) {

    ArrayList<Class> results = new ArrayList<Class>();

    try {
        JSONArray root = new JSONArray(JsonResponse);
        for (int i = 0; i < root.length(); i++) {
            JSONObject jsonObject = root.getJSONObject(i);
            String calss_id = jsonObject.getString("calss_id");
            String class_name = jsonObject.getString("class_name");
            String board_id = jsonObject.getString("board_id");
            int parse_board_id = Integer.parseInt(board_id);
            int parse_class_id = Integer.parseInt(calss_id);
            results.add(new Class(parse_class_id, class_name, parse_board_id));
        }
    } catch (JSONException e) {
        e.printStackTrace();
        Log.e(LOG_TAG, "Json execption");
    }
    return results;
}
}

这是我的类适配器.java文件

public class ClassAdapter extends ArrayAdapter<Class> {
public static final String LOG_TAG = ClassAdapter.class.getName();
public ClassAdapter(Context context, ArrayList<Class> classes) {
    super(context, 0, classes);
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    return getCustomView(position, convertView, parent);
}
@Override
public View getDropDownView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    return getCustomView(position, convertView, parent);
}
public View getCustomView(int position, View convertView, ViewGroup parent) {
    View listItemView = convertView;
    if (listItemView == null) {
        listItemView = LayoutInflater.from(getContext()).inflate(R.layout.row, parent, false);
    }
    Class classes = getItem(position);
    int class_id = classes.getClass_id();
    String class_name = classes.getClass_name();
    Log.e(LOG_TAG,"string class_name"+class_name);
    TextView text_name = (TextView) listItemView.findViewById(R.id.tv1);
    text_name.setText(class_name);
    //  TextView text_id = (TextView) listItemView.findViewById(R.id.tv2);
    // text_id.setText(board_id+"");
    return listItemView;

}
}

在此代码之后，我的板值来自 sever.u 可以在下面的链接中看到在此处输入图像描述

但是 oniteemclick 我的类值正在从服务器分别获取其板 我已经通过调试我的应用程序看到了它们。 但是我的 CLAS 值没有显示在我的类微调器中。