吴小龙同學

Android之SqliteSample

原文:https://developer.android.com/training/basics/data-storage/databases.html

  • Define a Schema and Contract
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package com.xiaomolong.sqlitesample;
import android.provider.BaseColumns;
public final class FeedReaderContract {
public FeedReaderContract() {
}
public static abstract class FeedEntry implements BaseColumns {
public static final String TABLE_NAME = "entry";
public static final String COLUMN_NAME_ENTRY_ID = "entryid";
public static final String COLUMN_NAME_TITLE = "title";
public static final String COLUMN_NAME_SUBTITLE = "subtitle";
}
}
  • FeedEntryDb
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package com.xiaomolong.sqlitesample;
public class FeedEntryDb {
public String entryid;
public String title;
public String subtitle;
public String getEntryid() {
return entryid;
}
public void setEntryid(String entryid) {
this.entryid = entryid;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getSubtitle() {
return subtitle;
}
public void setSubtitle(String subtitle) {
this.subtitle = subtitle;
}
}
  • Create a Database Using a SQL Helper
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package com.xiaomolong.sqlitesample;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import com.xiaomolong.sqlitesample.FeedReaderContract.FeedEntry;
public class FeedReaderDbHelper extends SQLiteOpenHelper {
public static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "FeedReader.db";
private static final String TEXT_TYPE = " TEXT";
private static final String COMMA_SEP = ",";
private static final String SQL_CREATE_ENTRIES = "CREATE TABLE "
+ FeedEntry.TABLE_NAME + " (" + FeedEntry._ID
+ " INTEGER PRIMARY KEY," + FeedEntry.COLUMN_NAME_ENTRY_ID
+ TEXT_TYPE + COMMA_SEP + FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE
+ COMMA_SEP + FeedEntry.COLUMN_NAME_SUBTITLE + TEXT_TYPE +
// Any other options for the CREATE command
" )";
private static final String SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS "
+ FeedEntry.TABLE_NAME;
public FeedReaderDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public FeedReaderDbHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE_ENTRIES);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(SQL_DELETE_ENTRIES);
onCreate(db);
}
}
  • DatabaseManger,包括增删改查

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    package com.xiaomolong.sqlitesample;
    import java.util.ArrayList;
    import java.util.List;
    import android.content.ContentValues;
    import android.content.Context;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import com.xiaomolong.sqlitesample.FeedReaderContract.FeedEntry;
    public class DatabaseManger {
    private static FeedReaderDbHelper mFeedReaderDbHelper = null;
    DatabaseManger(Context context) {
    getInstance(context);
    }
    public static void getInstance(Context context) {
    if (mFeedReaderDbHelper == null) {
    mFeedReaderDbHelper = new FeedReaderDbHelper(context);
    }
    }
    /**
    * 插入
    *
    * @return the row ID of the newly inserted row, or -1 if an error occurred
    */
    public long insert(FeedEntryDb feedEntry) {
    // Gets the data repository in write mode
    SQLiteDatabase db = mFeedReaderDbHelper.getWritableDatabase();
    // Create a new map of values, where column names are the keys
    ContentValues values = new ContentValues();
    values.put(FeedEntry.COLUMN_NAME_ENTRY_ID, feedEntry.getEntryid());
    values.put(FeedEntry.COLUMN_NAME_TITLE, feedEntry.getTitle());
    values.put(FeedEntry.COLUMN_NAME_SUBTITLE, feedEntry.getSubtitle());
    // Insert the new row, returning the primary key value of the new row
    long newRowId;
    newRowId = db.insert(FeedEntry.TABLE_NAME, null, values);
    db.close();
    return newRowId;
    }
    /**
    * 查询或通过条件查询
    *
    * @param rowId
    * @return
    */
    public List<FeedEntryDb> query(int rowId) {
    SQLiteDatabase db = mFeedReaderDbHelper.getReadableDatabase();
    // Define a projection that specifies which columns from the database
    // you will actually use after this query.
    String[] projection = { FeedEntry._ID, FeedEntry.COLUMN_NAME_ENTRY_ID,
    FeedEntry.COLUMN_NAME_TITLE, FeedEntry.COLUMN_NAME_SUBTITLE };
    String selection = null;
    String[] selectionArgs = { String.valueOf(rowId) };
    if (rowId != -1) {// 通过条件查询
    selection = FeedEntry._ID + " = ?";
    } else {
    selectionArgs = null;
    }
    // How you want the results sorted in the resulting Cursor
    String sortOrder = FeedEntry.COLUMN_NAME_TITLE + " DESC";
    Cursor cursor = db.query(FeedEntry.TABLE_NAME, // The table to query
    projection, // The columns to return
    selection, // The columns for the WHERE clause
    selectionArgs, // The values for the WHERE clause
    null, // don't group the rows
    null, // don't filter by row groups
    sortOrder // The sort order
    );
    List<FeedEntryDb> feedEntryDbList = new ArrayList<FeedEntryDb>();
    while (cursor.moveToNext()) {
    FeedEntryDb feedEntryDb = new FeedEntryDb();
    long itemId = cursor.getLong(cursor
    .getColumnIndexOrThrow(FeedEntry._ID));
    feedEntryDb.setEntryid(cursor.getString(cursor
    .getColumnIndexOrThrow(FeedEntry.COLUMN_NAME_ENTRY_ID)));
    feedEntryDb.setTitle(cursor.getString(cursor
    .getColumnIndexOrThrow(FeedEntry.COLUMN_NAME_TITLE)));
    feedEntryDb.setSubtitle(cursor.getString(cursor
    .getColumnIndexOrThrow(FeedEntry.COLUMN_NAME_SUBTITLE)));
    feedEntryDbList.add(feedEntryDb);
    }
    cursor.close();
    db.close();
    return feedEntryDbList;
    }
    /**
    * 更新
    *
    * @param feedEntry
    * @param rowId
    * @return
    */
    public int update(FeedEntryDb feedEntryDb, int rowId) {
    SQLiteDatabase db = mFeedReaderDbHelper.getReadableDatabase();
    // New value for one column
    ContentValues values = new ContentValues();
    values.put(FeedEntry.COLUMN_NAME_TITLE, feedEntryDb.getTitle()
    .toString());
    // Which row to update, based on the ID
    String selection = FeedEntry._ID + " = ?";
    String[] selectionArgs = { String.valueOf(rowId) };
    int count = db.update(FeedEntry.TABLE_NAME, values, selection,
    selectionArgs);
    db.close();
    return count;
    }
    /**
    * 删除
    *
    * @param rowId
    * @return
    */
    public int delete(int rowId) {
    SQLiteDatabase db = mFeedReaderDbHelper.getReadableDatabase();
    // Define 'where' part of query.
    String selection = FeedEntry._ID + " = ?";
    // Specify arguments in placeholder order.
    String[] selectionArgs = { String.valueOf(rowId) };
    // Issue SQL statement.
    int count = db.delete(FeedEntry.TABLE_NAME, selection, selectionArgs);
    db.close();
    return count;
    }
    }
  • 方法调用

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    package com.xiaomolong.sqlitesample;
    import java.util.List;
    import android.app.Activity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.TextView;
    public class MainActivity extends Activity implements OnClickListener {
    DatabaseManger mDatabaseManger;
    TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textView = (TextView) findViewById(R.id.textView);
    findViewById(R.id.btnAdd).setOnClickListener(this);
    findViewById(R.id.btnQuery).setOnClickListener(this);
    findViewById(R.id.btnUpdate).setOnClickListener(this);
    findViewById(R.id.btnDelete).setOnClickListener(this);
    mDatabaseManger = new DatabaseManger(this);
    }
    @Override
    public void onClick(View v) {
    switch (v.getId()) {
    case R.id.btnAdd:
    for (int i = 0; i < 5; i++) {
    FeedEntryDb feedEntryDb = new FeedEntryDb();
    feedEntryDb.setEntryid(i + "");
    feedEntryDb.setTitle("title" + i + "");
    feedEntryDb.setSubtitle("subtitle" + i + "");
    mDatabaseManger.insert(feedEntryDb);
    }
    break;
    case R.id.btnQuery:
    List<FeedEntryDb> feedEntryDbList = mDatabaseManger.query(-1);
    String t = "";
    for (int i = 0; i < feedEntryDbList.size(); i++) {
    t = t + feedEntryDbList.get(i).getTitle() + "\n"
    + feedEntryDbList.get(i).getSubtitle() + "\n\n";
    }
    textView.setText(t);
    break;
    case R.id.btnUpdate:
    FeedEntryDb feedEntryDb = new FeedEntryDb();
    feedEntryDb.setTitle("修改");
    Log.d("wxl", "count=" + mDatabaseManger.update(feedEntryDb, 1));
    break;
    case R.id.btnDelete:
    Log.d("wxl", "count=" + mDatabaseManger.delete(1));
    break;
    default:
    break;
    }
    }
    @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();
    if (id == R.id.action_settings) {
    return true;
    }
    return super.onOptionsItemSelected(item);
    }
    }

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