Question

我需要一些帮助，我正在从主要活动的数据库表中检索项目（类别）列表，这些都运行良好。问题是用户应该单击其中一个项目，这将导致数据库中的另一个表被查询但在另一个活动（workbook.java）中。那么如何将点击的类别的ID带到下一个活动中，并且还确切地知道单击了哪个项目以便查询正确的表格？

从一个db表中检索类别并在列表视图中显示它们的代码，以及处理列表项的点击的方法： MainActivity.java

@SuppressLint("NewApi")
public void displayCategories(){
    cursor = dbhelper.getCategories();
    String[] FROM = { FeedReaderDbHelper.KEY_CATEGORY_NAME};
    int[] TO = {R.id.textView1};
    adapter = new SimpleCursorAdapter(this, R.layout.row_item, cursor, FROM, TO, 0);
    categories = (ListView) findViewById(android.R.id.list); 
    categories.setAdapter(adapter);
    categories.setOnItemClickListener(new ListClickHandler());
}

public class ListClickHandler implements OnItemClickListener{
@Override
public void onItemClick(AdapterView<?> adapter, View view, int position, long arg3) {
    // TODO Auto-generated method stub
    TextView category_text = (TextView) view.findViewById(R.id.textView1);
    String category = category_text.getText().toString();
    Intent intent = new Intent(MainActivity.this, WorkBook.class);
    intent.putExtra("selected-item", category);
    intent.putExtra("item-ID", position);
    startActivity(intent);
}
}

下面的代码在WorkBook.java中，它应该根据前一个活动中选择的类别（MainActivity.java）查询另一个表：

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.work_book);
    text = (TextView) findViewById(R.id.text);

    //get the intent from which this activity is called
    Intent intent = getIntent();
    //fetch value from key-value pair and make it visible on textView
    String category = intent.getStringExtra("selected-item");
            text.setText("You are here: "+category);

}

我的数据库代码。类别表是在主活动中查询的类别列表。然后，如果用户选择“问候语”类别，则应在下一个活动中查询表格问候语。

package database;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.ateso.learnateso.Category;

public class FeedReaderDbHelper extends SQLiteOpenHelper {

public static final String DATABASE_NAME = "LearnAteso.db";
public static final int DATABASE_VERSION = 1;

//Table Names
public static final String CATEGORIES_TABLE = "categories";
public static final String GREETINGS_TABLE = "greetings";

//Common column name
public static final String KEY_ID = "_id";

//Categories table column names
public static final String KEY_CATEGORY_NAME = "catname";

//greetings table column names
public static final String KEY_GREETING = "greeting";
public static final String KEY_HINT = "hint";
public static final String KEY_AUDIO = "audio";
public static final String KEY_ANSWER = "answer";
public static final String KEY_OPTION_1 = "option_1";
public static final String KEY_OPTION_2 = "option_2";
public static final String KEY_OPTION_3 = "option_3";

//Table create statements
    //categories table create statement
    private static final String CREATE_TABLE_CATEGORIES = 
            "create table " + CATEGORIES_TABLE + "(" + KEY_ID + " integer primary key, "
                    + KEY_CATEGORY_NAME + " text);";

    //greetings create statement
    private static final String CREATE_TABLE_GREETINGS = 
            "create table " + GREETINGS_TABLE + "(" + KEY_ID + " integer primary key, "
            + KEY_GREETING+ " text, " + KEY_HINT + " text, " + KEY_AUDIO + " text, " + KEY_ANSWER + " text, "   
            + KEY_OPTION_1 + " text, " + KEY_OPTION_2 + " text, " + KEY_OPTION_3 + " text);";


  //constructor
    public FeedReaderDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

  //  @Override
    public void onCreate(SQLiteDatabase db) {
        //creating the tables
        db.execSQL(CREATE_TABLE_CATEGORIES);
        db.execSQL(CREATE_TABLE_GREETINGS);
    }

   // @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //on upgrade drop old tables
        db.execSQL("DROP TABLE IF EXISTS " + CATEGORIES_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + GREETINGS_TABLE);
        //create new tables
        onCreate(db);
    }
  //-----------------categories table methods---------------//
 //getting the categories out of the db
 public  Cursor getCategories(){
    SQLiteDatabase db = this.getReadableDatabase();
    String sql = "SELECT * FROM categories;";
    Cursor c =db.rawQuery(sql, null);
    return c;   
}   
//getting greetings table content from the db
public Cursor getAteso(){
    SQLiteDatabase db = this.getReadableDatabase();

    String sql = "SELECT * FROM " + GREETINGS_TABLE + ";";

    Cursor c = db.rawQuery(sql, null);
    if (c != null && c.getCount()>0){
        c.moveToFirst();
        do{
            String audio = c.getString(c.getColumnIndex(KEY_AUDIO));
            String greeting = c.getString(c.getColumnIndex(KEY_GREETING));
            String hint = c.getString(c.getColumnIndex(KEY_HINT));
            String answer = c.getString(c.getColumnIndex(KEY_ANSWER));
            String opt_1 = c.getString(c.getColumnIndex(KEY_OPTION_1));
            String opt_2 = c.getString(c.getColumnIndex(KEY_OPTION_2));
            String opt_3 = c.getString(c.getColumnIndex(KEY_OPTION_3));
        } while (c.moveToNext());
    }
    return c;
}

}

那么如何跟踪用户在MainActivity.java中选择哪个类别以查询WorkBook.java中的相应表。

感谢您的帮助

Answer 1

Hye，我最近也在我的App中使用了这种模式，用户点击了list-Item，然后在其他活动中处理了有关该项目点击的信息。来自 MainActivity 从任意点击的List-Item的类别列表中获取ID，

listView.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, 
            View view, int position, long time) {

                Intent i = new Intent(Categories.this,WorkBook.class);
                i.putExtra("category",YourArrayLIST.get(position).Category);
                startActivity(i);
          }
     });
}

<强> YourArrayLIST.get（位置）.Category

此处 YourArrayLIST 是您已映射所有API元素的类的实例，例如;您从JSON / XML响应获得的BookName，Author等。类别是列表项中的视图，您将获得在下一个活动中处理的参考。

现在在您的接收活动中，即WorkBook，请在您的onCreate方法中执行此操作。

bundle = getIntent().getExtras();
    if (bundle != null) {
        String strName = bundle.getString("category");
        String url = "http://192.168.0.100:7001/XYZ/abc/Info/"  + strName + "/"; 
//now you have the URL to send it to the DB to get info from respective table.
        String URL = Uri.encode(url, "@#&=*+-_.,:!?()/~'%");    //this is for the case if 
there is any space between your Category Name so API  will not process it       
}

如何从上一个活动中的db表中选择列表项，从新活动中的特定db表中检索数据

1 个答案: