Android疑惑之使用ContentProvider实现数据共享
Anroid疑惑之使用ContentProvider实现数据共享
ContentProvider是我学习安卓这几个月以来碰到最难理解的一块，感觉很难掌握，不知道如何使用这一块内容，有些方法的参数使用起来真的是令人发指，我也不打算一下子把全部内容都运用自如，那是不可能的事情，下面是学习ContentProvider所实现的一个实例：
实例：使用ContentProvider共享生词本数据
这个实例可以简单实现添加生词和查询生词的功能，我原本想扩展一下这个应用程序的功能，但却不知道从何做起，只是简简单单换了了界面背景就是了。
创建项目：DictProvider
项目运行效果：
下面只给出主要代码布局文件和string资源文件均不给出
运行以上项目需要在Menifest文件注册相关信息，和设置相关权限
<activity android:name=".ResultActivity"
android:theme="@android:style/Theme.Dialog"
android:label="找到的单词">
</activity>
<provider android:name=".DictProvider"
android:authorities="org.crazyit.providers.dictprovider"/>
定义的工具类：Words.java
package wwj.dictprovider;
import android.net.Uri;
import android.provider.BaseColumns;
public final class Words
{
// 定义该ContentProvider的Authority
public static final String AUTHORITY
= "org.crazyit.providers.dictprovider";
//定义一个静态内部类
public static final class Word implements BaseColumns
{
// 定义Content所允许操作的3个数据列
public final static String _ID = "_id";
public final static String WORD = "word";
public final static String DETAIL = "detail";
// 定义该Content提供服务的两个Uri
public final static Uri DICT_CONTENT_URI =
Uri.parse("content://" + AUTHORITY + "/words");
public final static Uri WORD_CONTENT_URI =
Uri.parse("content://" + AUTHORITY + "/word");
}
}
因为要用到SQLite数据库，所以需要继承SQLiteOpenHelper类
==>MyDatabaseHelper.java
package wwj.dictprovider;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class MyDatabaseHelper extends SQLiteOpenHelper
{
final String CREATE_TABLE_SQL =
"create table dict(_id integer primary key autoincrement , word , detail)";
/**
* @param context
* @param name
* @param version
*/
public MyDatabaseHelper(Context context, String name, int version)
{
super(context, name, null, version);
}
@Override
public void onCreate(SQLiteDatabase db)
{
// 第一个使用数据库时自动建表
db.execSQL(CREATE_TABLE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
System.out.println("--------onUpdate Called--------"
+ oldVersion + "--->" + newVersion);
}
}
实现ContentProvider类：DictProvider.java
package wwj.dictprovider;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
public class DictProvider extends ContentProvider
{
private static UriMatcher matcher
= new UriMatcher(UriMatcher.NO_MATCH);
private static final int WORDS = 1;
private static final int WORD = 2;
private MyDatabaseHelper dbOpenHelper;
static
{
// 为UriMatcher注册两个Uri
matcher.addURI(Words.AUTHORITY, "words", WORDS);
matcher.addURI(Words.AUTHORITY, "word/#", WORD);
}
// 第一次调用该DictProvider时，系统先创建DictProvider对象，并回调该方法
@Override
public boolean onCreate()
{
dbOpenHelper = new MyDatabaseHelper(this.getContext(), "myDict.db3", 1);
return true;
}
// 插入数据方法
@Override
public Uri insert(Uri uri, ContentValues values)
{
// 获得数据库实例
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
// 插入数据，返回行ID
long rowId = db.insert("dict", Words.Word._ID, values);
// 如果插入成功返回uri
if (rowId > 0)
{
// 在已有的 Uri的后面追加ID数据
Uri wordUri = ContentUris.withAppendedId(uri, rowId);
// 通知数据已经改变
getContext().getContentResolver().notifyChange(wordUri, null);
return wordUri;
}
return null;
}
// 删除数据的方法
@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
// 记录所删除的记录数
int num = 0;
// 对于uri进行匹配。
switch (matcher.match(uri))
{
case WORDS:
num = db.delete("dict", selection, selectionArgs);
break;
case WORD:
// 解析出所需要删除的记录ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原来的where子句存在，拼接where子句
if (selection != null && !selection.equals(""))
{
where = where + " and " + selection;
}
num = db.delete("dict", where, selectionArgs);
break;
default:
throw new IllegalArgumentException("未知Uri:" + uri);
}
// 通知数据已经改变
getContext().getContentResolver().notifyChange(uri, null);
return num;
}
// 修改数据的方法
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
// 记录所修改的记录数
int num = 0;
switch (matcher.match(uri))
{
case WORDS:
num = db.update("dict", values, selection, selectionArgs);
break;
case WORD:
// 解析出想修改的记录ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原来的where子句存在，拼接where子句
if (selection != null && !selection.equals(""))
{
where = where + " and " + selection;
}
num = db.update("dict", values, where, selectionArgs);
break;
default:
throw new IllegalArgumentException("未知Uri:" + uri);
}
// 通知数据已经改变
getContext().getContentResolver().notifyChange(uri, null);
return num;
}
// 查询数据的方法
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
switch (matcher.match(uri))
{
case WORDS:
// 执行查询
return db.query("dict", projection, selection, selectionArgs,
null, null, sortOrder);
case WORD:
// 解析出想查询的记录ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原来的where子句存在，拼接where子句
if (selection != null && !"".equals(selection))
{
where = where + " and " + selection;
}
return db.query("dict", projection, where, selectionArgs, null,
null, sortOrder);
default:
throw new IllegalArgumentException("未知Uri:" + uri);
}
}
// 返回指定uri参数对应的数据的MIME类型
@Override
public String getType(Uri uri)
{
switch(matcher.match(uri))
{
// 如果操作的数据是多项记录
case WORDS:
return "vnd.android.cursor.dir/org.crazyit.dict";
// 如果操作的数据是单项记录
case WORD:
return "vnd.android.cursor.item/org.crazyit.dict";
default:
throw new IllegalArgumentException("未知Uri:" + uri);
}
}
}
主Activity文件：DictResolver.java
package wwj.dictprovider;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class DictResolver extends Activity
{
ContentResolver contentResolver;
Button insert = null;
Button search = null;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// 获取系统的ContentResolver对象
contentResolver = getContentResolver();
insert = (Button)findViewById(R.id.insert);
search = (Button)findViewById(R.id.search);
// 为insert按钮的单击事件绑定事件监听器
insert.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View source)
{
//获取用户输入
String word = ((EditText)findViewById(R.id.word))
.getText().toString();
String detail = ((EditText)findViewById(R.id.detail))
.getText().toString();
//插入生词记录
ContentValues values = new ContentValues();
values.put(Words.Word.WORD , word);
values.put(Words.Word.DETAIL , detail);
contentResolver.insert(Words.Word.DICT_CONTENT_URI, values);
//显示提示信息
Toast.makeText(DictResolver.this, "添加生词成功！" , 8000)
.show();
}
});
// 为search按钮的单击事件绑定事件监听器
search.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View source)
{
// 获取用户输入
String key = ((EditText) findViewById(R.id.key)).getText()
.toString();
// 执行查询
Cursor cursor = contentResolver.query(
Words.Word.DICT_CONTENT_URI, null
, "word like ? or detail like ?"
, new String[]{"%" + key + "%" , "%" + key + "%"}
, null);
//创建一个Bundle对象
Bundle data = new Bundle();
data.putSerializable("data", converCursorToList(cursor));
//创建一个Intent
Intent intent = new Intent(DictResolver.this
, ResultActivity.class);
intent.putExtras(data);
//启动Activity
startActivity(intent);
}
});
}
private ArrayList<Map<String, String>> converCursorToList(
Cursor cursor)
{
ArrayList<Map<String, String>> result
= new ArrayList<Map<String, String>>();
// 遍历Cursor结果集
while (cursor.moveToNext())
{
// 将结果集中的数据存入ArrayList中
Map<String, String> map = new HashMap<String, String>();
// 取出查询记录中第2列、第3列的值
map.put(Words.Word.WORD, cursor.getString(1));
map.put(Words.Word.DETAIL, cursor.getString(2));
result.add(map);
}
return result;
}
}
ResultActivity.java
package wwj.dictprovider;
import java.util.List;
import java.util.Map;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class ResultActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.popup);
ListView listView = (ListView)findViewById(R.id.show);
Intent intent = getIntent();
//获取该intent所携带的数据
Bundle data = intent.getExtras();
//从Bundle数据包中取出数据
@SuppressWarnings("unchecked")
List<Map<String, String>> list =
(List<Map<String, String>>)data.getSerializable("data");
//将List封装成SimpleAdapter
SimpleAdapter adapter = new SimpleAdapter(ResultActivity.this, list, R.layout.line
, new String[]{"word", "detail"}
, new int[]{R.id.word, R.id.detail});
//填充ListView
listView.setAdapter(adapter);
}
}
