跨程序内容提供器ContentProvider
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MainActivity.java
package test.example.com.datasavetest;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.net.Uri;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;public class MainActivity extends Activity{ private Button addData,queryData,updateData,deleteData,replaceData; private MyDatabaseHelper dbHelper; private SQLiteDatabase db; private String newId; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); init(); } private void init() { addData = (Button) findViewById(R.id.add_data); queryData = (Button) findViewById(R.id.query_data); updateData = (Button) findViewById(R.id.update_data); deleteData = (Button) findViewById(R.id.delete_data); addData.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //添加数据 //先调用了Uri.parse()方法将一个内容URI 解析成Uri 对象 Uri uri = Uri.parse("content://test.example.com.datasavetest.provider/book"); //把要添加的数据都存放到ContentValues 对象中 ContentValues values = new ContentValues(); values.put("name","A Clash of Kings"); values.put("author","George Martin"); values.put("pages",1040); values.put("price",22.85); //着调用ContentResolver 的insert()方法执行添加操作 //insert()方法会返回一个Uri 对象，这个对象中包含了新增数据的id Uri newUri = getContentResolver().insert(uri,values); //通过getPathSegments()方法将这个id取出 newId = newUri.getPathSegments().get(1); } }); queryData.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //查询数据 //调用了Uri.parse()方法将一个内容URI 解析成Uri 对象 Uri uri = Uri.parse("content://test.example.com.datasavetest.provider/book"); Cursor cursor = getContentResolver().query(uri, null, null, null, null); if (cursor != null) { while (cursor.moveToNext()) { String name = cursor.getString(cursor.getColumnIndex("name")); String author = cursor.getString(cursor.getColumnIndex("author")); int pages = cursor.getInt(cursor.getColumnIndex("pages")); double price = cursor.getDouble(cursor.getColumnIndex("price")); Log.d("test","----------------------------"); Log.d("test", "book name is " + name); Log.d("test", "book author is " + author); Log.d("test", "book pages is " + pages); Log.d("test", "book price is " + price); } cursor.close(); } } }); updateData.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //更新数据 Uri uri = Uri.parse("content://test.example.com.datasavetest.provider/book/" +newId); ContentValues values = new ContentValues(); values.put("name","A Storm of Swords"); values.put("pages",1216); values.put("price",24.05); getContentResolver().update(uri,values,null,null); } }); deleteData.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //删除数据 Uri uri = Uri.parse("content://test.example.com.datasavetest.provider/book/"+newId); getContentResolver().delete(uri,null,null); } }); }}MyDatabaseHelper
package test.example.com.datasavetest;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;import android.widget.Toast;/** * Created by fengq on 2015/8/25 0025. */public class MyDatabaseHelper extends SQLiteOpenHelper { /** public static final String CREATE_BOOK = "create table book (" + "id integer primary key autoincrement," + //integer表示整形，primary key表示主键，autoincrement表示自增长 "author text," + //text表示文本类型 "price real," + //real表示浮点型 "pages integer," + "name text)"; */ public static final String CREATE_BOOK = "create table Book (" + "id integer primary key autoincrement, " + "author text, " + "price real, " + "pages integer, " + "name text" + "category_id integer)"; //Category表，用于记录书籍的分类 public static final String CREATE_CATEGORY = "create table Category (" + "id integer primary key autoincrement," + "category_name text," + "category_code integer)"; private Context mContext; public MyDatabaseHelper(Context context,String name,SQLiteDatabase.CursorFactory factory,int version) { super(context,name,factory,version); mContext = context; } @Override public void onCreate(SQLiteDatabase db) { /** * 当程序中没有BookStore.db时会创建数据库并调用onCreate函数 */ //通过db.execSQL(SQLCommand)来执行没有返回值的SQL语言 db.execSQL(CREATE_BOOK); db.execSQL(CREATE_CATEGORY); Toast.makeText(mContext,"Create succeeded", Toast.LENGTH_SHORT).show(); Log.d("test","Create succeeded"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { /** //如果数据库中存在这两张表就将这两张表删除，再调用onCreate方法去重新创建 db.execSQL("drop table if exists Book"); db.execSQL("drop table if exists Category"); Toast.makeText(mContext,"Delete succeeded", Toast.LENGTH_SHORT).show(); onCreate(db); */ switch (oldVersion) { //如果用户当前数据库的版本号是1，就只会创建一张Category表 case 1: db.execSQL(CREATE_CATEGORY); //如果当前数据库的版本号是2，就会执行alter命令来为Book表新增一个category_id列 case 2: db.execSQL("alter table Book add column category_id integer"); default: /** * switch中的每一个case的最后都是没有使用break的， * 保证在跨版本升级的时候，每一次的数据库修改都能被全部执行到 * */ } }}main_activity.xml
<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:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity" android:orientation="vertical"> <Button android:id="@+id/add_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Add To Book" /> <Button android:id="@+id/query_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Query From Book" /> <Button android:id="@+id/update_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Update Book" /> <Button android:id="@+id/delete_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Delete From Book" /></LinearLayout>
DatabaseProvider.java
package test.example.com.datasavetest;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;/** * Created by fengq on 2015/8/28 0028. */public class DatabaseProvider extends ContentProvider { //访问Book中的所有数据 public static final int BOOK_DIR = 0; //访问Book中的单条数据 public static final int BOOK_ITEM = 1; //访问Category中的所有数据 public static final int CATEGORY_DIR = 2; //访问Category中的单条数据 public static final int CATEGORY_ITEM = 3; public static final String AUTHORITY = "test.example.com.datasavetest.provider"; public static UriMatcher uriMatcher; private MyDatabaseHelper dbHelper; //在静态代码块中对UriMatcher进行初始化操作 static { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI(AUTHORITY,"book",BOOK_DIR); uriMatcher.addURI(AUTHORITY,"book/#",BOOK_ITEM); uriMatcher.addURI(AUTHORITY,"category",CATEGORY_DIR); uriMatcher.addURI(AUTHORITY,"category/#",CATEGORY_ITEM); } @Override public boolean onCreate() { //创建MyDatabaseHelper的实例 dbHelper = new MyDatabaseHelper(getContext(),"BookStore.db",null,2); //返回true表示内容提供器初始化成功，这时数据库就完成了创建或升级操作 return true; } @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { //查询数据 //获取SQLiteDatabase的实例 SQLiteDatabase db = dbHelper.getReadableDatabase(); Cursor cursor = null; //根据传入的Uri参数判断出用户想要访问哪张表 switch (uriMatcher.match(uri)) { case BOOK_DIR: //调用SQLiteDatabase的query()进行查询，并返回Cursor对象 cursor = db.query("Book",projection,selection,selectionArgs,null,null,sortOrder); break; case BOOK_ITEM: /** * 访问单条数据时，调用getPathSegments()方法 * 将内容URI权限之后的部分以"/"符号进行分割，并把分割后的结果放入到一个字符串列表中， * 这个列表的第0个位置存放的是路径 * 第1个位置存放的是id * 得到id之后，通过selection和selectionArgs参数进行约束，实现了查询单条数据的功能 * */ String bookId = uri.getPathSegments().get(1); cursor = db.query("Book",projection,"id = ?",new String[]{bookId},null,null,sortOrder); break; case CATEGORY_DIR: cursor = db.query("Book",projection,selection,selectionArgs,null,null,sortOrder); break; case CATEGORY_ITEM: String categoryId = uri.getPathSegments().get(1); cursor = db.query("Category",projection,"id = ?",new String[]{categoryId},null,null,sortOrder); break; default: break; } return cursor; } @Override public String getType(Uri uri) { switch (uriMatcher.match(uri)) { case BOOK_DIR: return "vnd.android.cursor.dir/vnd.test.example.com.datasavetest.provider.book"; case BOOK_ITEM: return "vnd.android.cursor.item/vnd.test.example.com.datasavetest.provider.book"; case CATEGORY_DIR: return "vnd.android.cursor.dir/vnd.test.example.com.datasavetest.provider.category"; case CATEGORY_ITEM: return "vnd.android.cursor.item/vnd.test.example.com.datasavetest.provider.category"; } return null; } @Override public Uri insert(Uri uri, ContentValues values) { //添加数据 //获取SQLiteDatabase实例 SQLiteDatabase db = dbHelper.getWritableDatabase(); Uri uriReturn = null; //根据Uri参数判断用户想往哪张表添加数据 switch (uriMatcher.match(uri)) { case BOOK_DIR: case BOOK_ITEM: /** * insert()方法要求返回一个能够表示这条新增数据的URI， * 调用Uri.parse()方法将一个内容URI解析成Uri对象 * 这个内容URI是以新增数据的id结尾 * */ long newBookId = db.insert("Book",null,values); uriReturn = Uri.parse("content://"+AUTHORITY+"/book/"+newBookId); break; case CATEGORY_DIR: case CATEGORY_ITEM: long newCategoryId = db.insert("Category",null,values); uriReturn = Uri.parse("content://"+AUTHORITY+"/category/"+newCategoryId); break; default: break; } return uriReturn; } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { //删除数据 //先获取到SQLiteDatabase 的实例 SQLiteDatabase db = dbHelper.getWritableDatabase(); int deleteRows = 0; //根据传入的Uri 参数判断出用户想要删除哪张表里的数据 switch (uriMatcher.match(uri)) { case BOOK_DIR: deleteRows = db.delete("Book",selection,selectionArgs); break; case BOOK_ITEM: String bookId = uri.getPathSegments().get(1); deleteRows = db.delete("Book","id = ?",new String[]{bookId}); break; case CATEGORY_DIR: deleteRows = db.delete("Category",selection,selectionArgs); break; case CATEGORY_ITEM: String categoryId = uri.getPathSegments().get(1); deleteRows = db.delete("Category","id = ?",new String[]{ categoryId}); break; default: break; } //被删除的行数将作为返回值返回 return deleteRows; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { //更新数据 //获取SQLiteDatabase的实例 SQLiteDatabase db = dbHelper.getWritableDatabase(); int updateRows = 0; //根据传入的Uri 参数判断出用户想要更新哪张表里的数据 switch (uriMatcher.match(uri)) { case BOOK_DIR: updateRows = db.update("Book",values,selection,selectionArgs); break; case BOOK_ITEM: String bookId = uri.getPathSegments().get(1); updateRows = db.update("Book",values,"id = ?",new String[]{ bookId}); break; case CATEGORY_DIR: updateRows = db.update("Category",values,selection,selectionArgs); break; case CATEGORY_ITEM: String categoryId = uri.getPathSegments().get(1); updateRows = db.update("Category",values,"id = ?",new String[]{ categoryId}); break; default: break; } //受影响的行数将作为返回值返回 return updateRows; }}AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="test.example.com.datasavetest" > <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name=".MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <!-- 在android:name属性中指定了该类的全名， 在android:authorities属性中指定了该内容提供器的权限 --> <provider android:authorities="test.example.com.datasavetest.provider" android:name="test.example.com.datasavetest.DatabaseProvider"> </provider> </application></manifest>
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