Android 內容提供者的實現，android內容提供

Android 內容提供者的實現，android內容提供

接著上文《Android 內容提供者簡介》進一步實現內容提供者。

每個Content Provider類都使用URI（Universal Resource Identifier，通用資源標識符）作為獨立的標識，格式如：content://com.example.app.provider/table1。其他應用程序通過不同的uri訪問不同的內容提供者，並獲取/操作裡面的數據。

例如在本項目中對應如下URI：

content://com.wuyudong.db.personprovider/insert 添加的操作
content://com.wuyudong.db.personprovider/delete 刪除的操作
content://com.wuyudong.db.personprovider/update 更新的操作
content://com.wuyudong.db.personprovider/query 查詢的操作

在PersonDBProvider.java中添加代碼：

package com.wuyudong.db;


import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class PersonDBProvider extends ContentProvider {

    // 定義一個URI的匹配器用於匹配uri， 如果路徑不滿足條件 返回-1
    private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int INSERT = 1;
    private static final int DELETE = 2;
    private static final int UPDATE = 3;
    private static final int QUERY = 4;
    private PersonSQLiteOpenHelper helper; 

    static {
        // 添加一組匹配規則 com.wuyudong.db.personprovider
        matcher.addURI("com.wuyudong.db.personprovider", "insert",
                INSERT);
        matcher.addURI("com.wuyudong.db.personprovider", "delete",
                DELETE);
        matcher.addURI("com.wuyudong.db.personprovider", "update",
                UPDATE);
        matcher.addURI("com.wuyudong.db.personprovider", "query", QUERY);
    }

    @Override
    public boolean onCreate() {

        helper = new PersonSQLiteOpenHelper(getContext());
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        if (matcher.match(uri) == QUERY) {
            // 返回查詢的結果集
            SQLiteDatabase db = helper.getReadableDatabase();
            Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder);
            return cursor;
        } else {
            throw new IllegalArgumentException("路徑不匹配，不能執行查詢操作");
        }
    }

    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        // TODO Auto-generated method stub
        return 0;
    }

}

新建一個名為other的項目，布局如下：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <Button
        android:onClick="click"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="讀取DB的數據" />

</RelativeLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity" > <Button android:onClick="click" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="讀取DB的數據" /> <Button android:onClick="delete" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="刪除DB的數據" /> <Button android:onClick="update" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="修改DB的數據" /> <Button android:onClick="insert" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="添加DB的數據" /> </LinearLayout>

接下來實現PersonDBProvider中的其他方法

package com.wuyudong.db;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class PersonDBProvider extends ContentProvider {

    // 定義一個URI的匹配器用於匹配uri， 如果路徑不滿足條件 返回-1
    private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int INSERT = 1;
    private static final int DELETE = 2;
    private static final int UPDATE = 3;
    private static final int QUERY = 4;
    private PersonSQLiteOpenHelper helper;

    static {
        // 添加一組匹配規則 com.wuyudong.db.personprovider
        matcher.addURI("com.wuyudong.db.personprovider", "insert", INSERT);
        matcher.addURI("com.wuyudong.db.personprovider", "delete", DELETE);
        matcher.addURI("com.wuyudong.db.personprovider", "update", UPDATE);
        matcher.addURI("com.wuyudong.db.personprovider", "query", QUERY);
    }

    @Override
    public boolean onCreate() {

        helper = new PersonSQLiteOpenHelper(getContext());
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        if (matcher.match(uri) == QUERY) {
            // 返回查詢的結果集
            SQLiteDatabase db = helper.getReadableDatabase();
            Cursor cursor = db.query("person", projection, selection,
                    selectionArgs, null, null, sortOrder);
            return cursor;
        } else {
            throw new IllegalArgumentException("路徑不匹配，不能執行查詢操作");
        }
    }

    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        if (matcher.match(uri) == INSERT) {
            // 返回查詢的結果集
            SQLiteDatabase db = helper.getWritableDatabase();
            db.insert("person", null, values);
        } else {
            throw new IllegalArgumentException("路徑不匹配，不能執行插入操作");
        }
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        if (matcher.match(uri) == DELETE) {
            // 返回查詢的結果集
            SQLiteDatabase db = helper.getWritableDatabase();
            db.delete("person", selection, selectionArgs);
        } else {
            throw new IllegalArgumentException("路徑不匹配，不能執行刪除操作");
        }
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        if (matcher.match(uri) == UPDATE) {
            // 返回查詢的結果集
            SQLiteDatabase db = helper.getWritableDatabase();
            db.update("person", values, selection, selectionArgs);
        } else {
            throw new IllegalArgumentException("路徑不匹配，不能執行修改操作");
        }
        return 0;
    }

}