接着上文《Android 内容提供者简介》进一步实现内容提供者。
每个Content Provider类都使用URI（Universal Resource Identifier，通用资源标识符）作为独立的标识，格式如：content://com.example.app.provider/table1。其他应用程序通过不同的uri访问不同的内容提供者，并获取/操作里面的数据。
例如在本项目中对应如下URI：
content://com.wuyudong.db.personprovider/insert 添加的操作
content://com.wuyudong.db.personprovider/delete 删除的操作
content://com.wuyudong.db.personprovider/update 更新的操作
content://com.wuyudong.db.personprovider/query 查询的操作
在PersonDBProvider.java中添加代码：
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 { // 定义一个URI的匹配器用于匹配uri， 如果路径不满足条件 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 { // 添加一组匹配规则 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) { // 返回查询的结果集 SQLiteDatabase db = helper.getReadableDatabase(); Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder); return cursor; } else { throw new IllegalArgumentException("路径不匹配，不能执行查询操作"); } } @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; } }
新建一个名为other的项目，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="读取DB的数据" /> </RelativeLayout>
点击下图的按钮，kill掉 com.wuyudong.db进程
点击Button按钮后，com.wuyudong.db进程重新运行，而且打印数据库中person表中的数据
进一步完善其他操作，修改布局
<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="读取DB的数据" /> <Button android:onClick="delete" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="删除DB的数据" /> <Button android:onClick="update" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="修改DB的数据" /> <Button android:onClick="insert" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="添加DB的数据" /> </LinearLayout>
接下来实现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 { // 定义一个URI的匹配器用于匹配uri， 如果路径不满足条件 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 { // 添加一组匹配规则 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) { // 返回查询的结果集 SQLiteDatabase db = helper.getReadableDatabase(); Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder); return cursor; } else { throw new IllegalArgumentException("路径不匹配，不能执行查询操作"); } } @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) { // 返回查询的结果集 SQLiteDatabase db = helper.getWritableDatabase(); db.insert("person", null, values); } else { throw new IllegalArgumentException("路径不匹配，不能执行插入操作"); } return null; } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { if (matcher.match(uri) == DELETE) { // 返回查询的结果集 SQLiteDatabase db = helper.getWritableDatabase(); db.delete("person", selection, selectionArgs); } else { throw new IllegalArgumentException("路径不匹配，不能执行删除操作"); } return 0; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { if (matcher.match(uri) == UPDATE) { // 返回查询的结果集 SQLiteDatabase db = helper.getWritableDatabase(); db.update("person", values, selection, selectionArgs); } else { throw new IllegalArgumentException("路径不匹配，不能执行修改操作"); } return 0; } }