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;
} }