程式小試身手

public class Comment {
     private long id;
     private String comment;

     public long getId() {
       return id;
     }

     public void setId(long id) {
       this.id = id;
     }

     public String getComment() {
       return comment;
     }

     public void setComment(String comment) {
       this.comment = comment;
     }

     // Will be used by the ArrayAdapter in the ListView
     @Override
     public String toString() {
       return comment;
     }
   } 

package com.example.ex_sqlite01;

import java.util.ArrayList;
import java.util.List;

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

public class CommentsDataSource {

  // Database fields
  private SQLiteDatabase database;
  private MySQLiteHelper dbHelper;
  private String[] allColumns = { 
        MySQLiteHelper.COLUMN_ID,
      MySQLiteHelper.COLUMN_COMMENT };

  public CommentsDataSource(Context context) {
    dbHelper = new MySQLiteHelper(context);
  }

  public void open() throws SQLException {
    database = dbHelper.getWritableDatabase();
  }

  public void close() {
    dbHelper.close();
  }

  public Comment createComment(String comment) {
    ContentValues values = new ContentValues();
    values.put(MySQLiteHelper.COLUMN_COMMENT, comment);
    long insertId = database.
          insert(MySQLiteHelper.TABLE_COMMENTS, null,values);
    
    Cursor cursor = database.query
          (MySQLiteHelper.TABLE_COMMENTS,
        allColumns, MySQLiteHelper.
        COLUMN_ID + " = " + insertId, null,
        null, null, null);
    cursor.moveToFirst();
    Comment newComment = cursorToComment(cursor);
    cursor.close();
    return newComment;
  }

  public void deleteComment(Comment comment) {
    long id = comment.getId();
    System.out.println("Comment deleted with id: " + id);
    database.delete(MySQLiteHelper.TABLE_COMMENTS, MySQLiteHelper.COLUMN_ID
        + " = " + id, null);
  }

  public List<Comment> getAllComments() {
    List<Comment> comments = new ArrayList<Comment>();

    Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
        allColumns, null, null, null, null, null);

    cursor.moveToFirst();
    while (!cursor.isAfterLast()) {
      Comment comment = cursorToComment(cursor);
      comments.add(comment);
      cursor.moveToNext();
    }
    // make sure to close the cursor
    cursor.close();
    return comments;
  }

  private Comment cursorToComment(Cursor cursor) {
    Comment comment = new Comment();
    comment.setId(cursor.getLong(0));
    comment.setComment(cursor.getString(1));
    return comment;
  }
} 

package com.example.ex_sqlite01;

import java.util.List;
import java.util.Random;

import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;

public class MainActivity extends ListActivity {
        private CommentsDataSource datasource;

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

          datasource = new CommentsDataSource(this);
          datasource.open();

          List<Comment> values = datasource.getAllComments();

          // use the SimpleCursorAdapter to show the
          // elements in a ListView
          ArrayAdapter<Comment> adapter = new ArrayAdapter<Comment>(this,
              android.R.layout.simple_list_item_1, values);
              setListAdapter(adapter);

        }

        // Will be called via the onClick attribute
        // of the buttons in main.xml
        public void onClick(View view) {
          @SuppressWarnings("unchecked")
          ArrayAdapter<Comment> adapter = (ArrayAdapter<Comment>) getListAdapter();
          Comment comment = null;
          switch (view.getId()) {
          case R.id.add:
            String[] comments = new String[] { "Cool", "Very nice", "Hate it" };
            int nextInt = new Random().nextInt(3);
            // save the new comment to the database
            comment = datasource.createComment(comments[nextInt]);
            adapter.add(comment);
            break;
          case R.id.delete:
            if (getListAdapter().getCount() > 0) {
              comment = (Comment) getListAdapter().getItem(0);
              datasource.deleteComment(comment);
              adapter.remove(comment);
            }
            break;
          }
          adapter.notifyDataSetChanged();
        }

        @Override
        protected void onResume() {
          datasource.open();
          super.onResume();
        }

        @Override
        protected void onPause() {
          datasource.close();
          super.onPause();
        }

      } 

package com.example.ex_sqlite01;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MySQLiteHelper extends SQLiteOpenHelper {

  public static final String TABLE_COMMENTS = "comments";
  public static final String COLUMN_ID = "_id";
  public static final String COLUMN_COMMENT = "comment";

  private static final String DATABASE_NAME = "commments.db";
  private static final int DATABASE_VERSION = 2;

  // Database creation sql statement
  private static final String DATABASE_CREATE = "create table "
      + TABLE_COMMENTS + "(" + COLUMN_ID
      + " integer primary key autoincrement, " + COLUMN_COMMENT
      + " text not null);";

  public MySQLiteHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
  }

  @Override
  public void onCreate(SQLiteDatabase database) {
    database.execSQL(DATABASE_CREATE);
  }

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    Log.w(MySQLiteHelper.class.getName(),
        "Upgrading database from version " + oldVersion + " to "
            + newVersion + ", which will destroy all old data");
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
    onCreate(db);
  }

}