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Android開發學習之使用ContentProvider實現數據共享

日期：2017/3/1 10:14:09 编辑：Linux編程

ContentProvider是我學習安卓這幾個月以來碰到最難理解的一塊，感覺很難掌握，不知道如何使用這一塊內容，有些方法的參數使用起來真的是令人發指，我也不打算一下子把全部內容都運用自如，那是不可能的事情，下面是學習ContentProvider所實現的一個實例：

實例：使用ContentProvider共享生詞本數據

這個實例可以簡單實現添加生詞和查詢生詞的功能，我原本想擴展一下這個應用程序的功能，但卻不知道從何做起，只是簡簡單單換了了界面背景就是了。

創建項目：DictProvider

項目運行效果：

下面只給出主要代碼布局文件和string資源文件均不給出

運行以上項目需要在Menifest文件注冊相關信息，和設置相關權限

<activity Android:name=".ResultActivity"
android:theme="@android:style/Theme.Dialog"
android:label="找到的單詞">
</activity>
<provider android:name=".DictProvider"
android:authorities="org.crazyit.providers.dictprovider"/>

定義的工具類：Words.java

package wwj.dictprovider;
import android.net.Uri;
import android.provider.BaseColumns;
public final class Words
{
// 定義該ContentProvider的Authority
public static final String AUTHORITY
= "org.crazyit.providers.dictprovider";
//定義一個靜態內部類
public static final class Word implements BaseColumns
{
// 定義Content所允許操作的3個數據列
public final static String _ID = "_id";
public final static String WORD = "word";
public final static String DETAIL = "detail";
// 定義該Content提供服務的兩個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");
}
}

因為要用到SQLite數據庫，所以需要繼承SQLiteOpenHelper類

==>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)
{
// 第一個使用數據庫時自動建表
db.execSQL(CREATE_TABLE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
System.out.println("--------onUpdate Called--------"
+ oldVersion + "--->" + newVersion);
}
}

實現ContentProvider類：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
{
// 為UriMatcher注冊兩個Uri
matcher.addURI(Words.AUTHORITY, "words", WORDS);
matcher.addURI(Words.AUTHORITY, "word/#", WORD);
}
// 第一次調用該DictProvider時，系統先創建DictProvider對象，並回調該方法
@Override
public boolean onCreate()
{
dbOpenHelper = new MyDatabaseHelper(this.getContext(), "myDict.db3", 1);
return true;
}
// 插入數據方法
@Override
public Uri insert(Uri uri, ContentValues values)
{
// 獲得數據庫實例
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
// 插入數據，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的後面追加ID數據
Uri wordUri = ContentUris.withAppendedId(uri, rowId);
// 通知數據已經改變
getContext().getContentResolver().notifyChange(wordUri, null);
return wordUri;
}
return null;
}
// 刪除數據的方法
@Override
public int delete(Uri uri, String selection, String[] selectionArgs)
{
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
// 記錄所刪除的記錄數
int num = 0;
// 對於uri進行匹配。
switch (matcher.match(uri))
{
case WORDS:
num = db.delete("dict", selection, selectionArgs);
break;
case WORD:
// 解析出所需要刪除的記錄ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原來的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);
}
// 通知數據已經改變
getContext().getContentResolver().notifyChange(uri, null);
return num;
}
// 修改數據的方法
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
// 記錄所修改的記錄數
int num = 0;
switch (matcher.match(uri))
{
case WORDS:
num = db.update("dict", values, selection, selectionArgs);
break;
case WORD:
// 解析出想修改的記錄ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原來的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);
}
// 通知數據已經改變
getContext().getContentResolver().notifyChange(uri, null);
return num;
}
// 查詢數據的方法
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
switch (matcher.match(uri))
{
case WORDS:
// 執行查詢
return db.query("dict", projection, selection, selectionArgs,
null, null, sortOrder);
case WORD:
// 解析出想查詢的記錄ID
long id = ContentUris.parseId(uri);
String where = Words.Word._ID + "=" + id;
// 如果原來的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參數對應的數據的MIME類型
@Override
public String getType(Uri uri)
{
switch(matcher.match(uri))
{
// 如果操作的數據是多項記錄
case WORDS:
return "vnd.android.cursor.dir/org.crazyit.dict";
// 如果操作的數據是單項記錄
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);
// 獲取系統的ContentResolver對象
contentResolver = getContentResolver();
insert = (Button)findViewById(R.id.insert);
search = (Button)findViewById(R.id.search);
// 為insert按鈕的單擊事件綁定事件監聽器
insert.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View source)
{
//獲取用戶輸入
String word = ((EditText)findViewById(R.id.word))
.getText().toString();
String detail = ((EditText)findViewById(R.id.detail))
.getText().toString();
//插入生詞記錄
ContentValues values = new ContentValues();
values.put(Words.Word.WORD , word);
values.put(Words.Word.DETAIL , detail);
contentResolver.insert(Words.Word.DICT_CONTENT_URI, values);
//顯示提示信息
Toast.makeText(DictResolver.this, "添加生詞成功！" , 8000)
.show();
}
});
// 為search按鈕的單擊事件綁定事件監聽器
search.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View source)
{
// 獲取用戶輸入
String key = ((EditText) findViewById(R.id.key)).getText()
.toString();
// 執行查詢
Cursor cursor = contentResolver.query(
Words.Word.DICT_CONTENT_URI, null
, "word like ? or detail like ?"
, new String[]{"%" + key + "%" , "%" + key + "%"}
, null);
//創建一個Bundle對象
Bundle data = new Bundle();
data.putSerializable("data", converCursorToList(cursor));
//創建一個Intent
Intent intent = new Intent(DictResolver.this
, ResultActivity.class);
intent.putExtras(data);
//啟動Activity
startActivity(intent);
}
});
}
private ArrayList<Map<String, String>> converCursorToList(
Cursor cursor)
{
ArrayList<Map<String, String>> result
= new ArrayList<Map<String, String>>();
// 遍歷Cursor結果集
while (cursor.moveToNext())
{
// 將結果集中的數據存入ArrayList中
Map<String, String> map = new HashMap<String, String>();
// 取出查詢記錄中第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();
//獲取該intent所攜帶的數據
Bundle data = intent.getExtras();
//從Bundle數據包中取出數據
@SuppressWarnings("unchecked")
List<Map<String, String>> list =
(List<Map<String, String>>)data.getSerializable("data");
//將List封裝成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);
}
}