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我一直在关注 commonsware 的数据库教程，这是午餐列表示例，但是我很想知道如何添加删除按钮，以便在创建午餐项目后删除它。

我四处搜索并找到了这个答案，但我只是不确定如何实现它，请有人告诉我如何

向 RestaurantHelper 类添加一个 delete() 方法，并从 DetailForm 活动的选项菜单项中调用它。

谢谢露西

ResaurantHelper.java

import android.content.Context;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;

class RestaurantHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME="Lunchlist.db";
private static final int SCHEMA_VERSION=1;

public RestaurantHelper(Context context) {
super(context, DATABASE_NAME, null, SCHEMA_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE restaurants (_id INTEGER PRIMARY KEY AUTOINCREMENT, name    TEXT, address TEXT, type TEXT, notes TEXT);");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// no-op, since will not be called until 2nd schema
// version exists
}

public Cursor getAll() {
return(getReadableDatabase()
        .rawQuery("SELECT _id, name, address, type, notes FROM restaurants ORDER BY  name",
                  null));
}

public void insert(String name, String address,
                 String type, String notes) {
ContentValues cv=new ContentValues();

cv.put("name", name);
cv.put("address", address);
cv.put("type", type);
cv.put("notes", notes);

getWritableDatabase().insert("restaurants", "name", cv);
}

public String getName(Cursor c) {
return(c.getString(1));
}

public String getAddress(Cursor c) {
return(c.getString(2));
}

public String getType(Cursor c) {
return(c.getString(3));
}

public String getNotes(Cursor c) {
return(c.getString(4));
}
}

午餐清单.java

package apt.tutorial;

import android.app.TabActivity;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import android.widget.AdapterView;
import android.widget.CursorAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RadioGroup;
import android.widget.TabHost;
import android.widget.TextView;

public class LunchList extends TabActivity {
Cursor model=null;
RestaurantAdapter adapter=null;
EditText name=null;
EditText address=null;
EditText notes=null;
RadioGroup types=null;
RestaurantHelper helper=null;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

helper=new RestaurantHelper(this);

name=(EditText)findViewById(R.id.name);
address=(EditText)findViewById(R.id.addr);
notes=(EditText)findViewById(R.id.notes);
types=(RadioGroup)findViewById(R.id.types);

address.setVisibility(View.GONE);
notes.setVisibility(View.GONE);

Button save=(Button)findViewById(R.id.save);

save.setOnClickListener(onSave);

ListView list=(ListView)findViewById(R.id.restaurants);

model=helper.getAll();
startManagingCursor(model);
adapter=new RestaurantAdapter(model);
list.setAdapter(adapter);

TabHost.TabSpec spec=getTabHost().newTabSpec("tag1");

spec.setContent(R.id.restaurants);
spec.setIndicator("My Reasons", getResources()
                            .getDrawable(R.drawable.list));
getTabHost().addTab(spec);

spec=getTabHost().newTabSpec("tag2");
spec.setContent(R.id.details);
spec.setIndicator("Add Reason", getResources()
                              .getDrawable(R.drawable.restaurant));
getTabHost().addTab(spec);

getTabHost().setCurrentTab(0);

list.setOnItemClickListener(onListClick);
}

@Override
public void onDestroy() {
super.onDestroy();

helper.close();
}

private View.OnClickListener onSave=new View.OnClickListener() {
public void onClick(View v) {
  String type=null;

  switch (types.getCheckedRadioButtonId()) {
    case R.id.sit_down:
      type="sit_down";
      break;
    case R.id.take_out:
      type="take_out";
      break;
    case R.id.delivery:
      type="delivery";
      break;
  }

  helper.insert(name.getText().toString(),
                address.getText().toString(), type,
                notes.getText().toString());
  model.requery();
  }
};

private AdapterView.OnItemClickListener onListClick=new   AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent,
                          View view, int position,
                          long id) {
  model.moveToPosition(position);
  name.setText(helper.getName(model));
  address.setText(helper.getAddress(model));
  notes.setText(helper.getNotes(model));

  if (helper.getType(model).equals("sit_down")) {
    types.check(R.id.sit_down);
  }
  else if (helper.getType(model).equals("take_out")) {
    types.check(R.id.take_out);
  }
  else {
    types.check(R.id.delivery);
  }

  getTabHost().setCurrentTab(1);
}
};

class RestaurantAdapter extends CursorAdapter {
RestaurantAdapter(Cursor c) {
  super(LunchList.this, c);
}

@Override
public void bindView(View row, Context ctxt,
                     Cursor c) {
  RestaurantHolder holder=(RestaurantHolder)row.getTag();

  holder.populateFrom(c, helper);
}

@Override
public View newView(Context ctxt, Cursor c,
                     ViewGroup parent) {
  LayoutInflater inflater=getLayoutInflater();
  View row=inflater.inflate(R.layout.row, parent, false);
  RestaurantHolder holder=new RestaurantHolder(row);

  row.setTag(holder);

  return(row);
  }
}

static class RestaurantHolder {
private TextView name=null;
private TextView address=null;
private ImageView icon=null;

RestaurantHolder(View row) {
  name=(TextView)row.findViewById(R.id.title);
  address=(TextView)row.findViewById(R.id.address);
  icon=(ImageView)row.findViewById(R.id.icon);
}

void populateFrom(Cursor c, RestaurantHelper helper) {
  name.setText(helper.getName(c));
  address.setText(helper.getAddress(c));

  if (helper.getType(c).equals("sit_down")) {
    icon.setImageResource(R.drawable.ball_red);
  }
  else if (helper.getType(c).equals("take_out")) {
    icon.setImageResource(R.drawable.ball_yellow);
  }
  else {
    icon.setImageResource(R.drawable.ball_green);
    }
  }
}
}
4

4 回答 4

1

如果您可以检查匹配的 ID，这可能会起作用

db.execSQL("DELETE FROM restaurants WHERE id = '+" idToDelete "+' ;");
于 2012-06-06T13:54:57.370 回答
1

将新按钮 (btnDelete) 添加到您的 layout-xml

Button btnDel =(Button)findViewById(R.id.btnDelete); 使用Add a clickListener将其安装在您的代码中，使用：

btnDel.setOnClickListener)new OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                                //add SQL deletion code here
            }
        });

并最终在 onClickListener 中执行 SQL 删除语句；）

于 2012-06-06T13:32:45.070 回答
0

而不是使用execSQL()删除，使用以下：

到delete整个表：

db.delete(DATABASE_TABLE, null, null);

对于delete表中的特定记录：

db.delete(DATABASE_TABLE, whereCondition, null);

例如：
db.delete(restaurants, "id = '"+ IdToBeDeleted +"'", null);

于 2012-06-07T10:59:42.207 回答
0

我相当肯定你需要继续学习这些教程。在网站上观看了 Commons_Ware（这本书的作者和非常活跃的成员）后，我怀疑他会让你悬而未决。我很确定他会一步一步教授完整的 CRUD 模型。

作为旁注，如果您还没有购买他的书的订阅，我强烈推荐它。它们会经常更新以包含最新信息。

于 2012-06-06T13:52:56.533 回答