我們這里先假設先有一個A應用程序，這個程序中存在一個BookStore數據庫和一張Book表，

然后還有一個B應用程序，跨程序實現數據共享的意思就是，通過B程序，我們可以對A程序中Book表中的數據進行CRUD（增刪改查）操作。

下面我們就一一來實現A應用程序和B應用程序。

A應用程序：DatabaseSave

B應用程序：ProviderTest

我們需要實現ProviderTest應用程序對DatabaseSave應用程序的CRUD操作。

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Database項目GitHub地址：

https://github.com/Skymqq/DatabaseSave.git

ProviderTest項目GitHub地址：

https://github.com/Skymqq/ProvidertTest.git

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應用程序A(DatabaseSave項目)

我們就直接引用之前創建的DatabaseSave項目文件來繼續學習。

如果你沒有看過之前的數據庫存儲項目，可以去GitHub下載一下，項目地址：

https://github.com/Skymqq/DatabaseSave.git

下載之后導入到AS中后，新建一個ContentProvider，步驟如下：

new---》other---》ContentProvider

可以看到，我們將

內容提供器命名為DatabaseProvider

authority指定為com.example.databasesave.provider

Exported屬性表示是否允許外部程序訪問我們的內容提供器

Enabled屬性表示是否啟用這個內容提供器。

將兩個屬性都勾上，點擊Finish完成創建。

DatabaseProvider.java代碼：

package com.example.administrator.databasesave;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 DatabaseProvider extends ContentProvider {public static final int BOOK_DIR = 0;public static final int BOOK_ITEM = 1;public static final int CATEGORY_DIR = 2;public static final int CATEGORY_ITEM = 3;public static final String AUTHORITY = "com.example.databasesave.provider";private static UriMatcher uriMatcher;private MyDatabaseHelper helper;static {//在靜態代碼塊中對UriMatcher進行初始化操作，并將期望匹配的幾種URI格式添加進去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);}@Overridepublic boolean onCreate() {//完成創建、升級 BookStore數據庫helper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);return true;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {//查詢數據SQLiteDatabase db = helper.getWritableDatabase();Cursor cursor = null;switch (uriMatcher.match(uri)) {case BOOK_DIR:cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);break;case BOOK_ITEM: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("Category", 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;}@Overridepublic Uri insert(Uri uri, ContentValues values) {//添加數據SQLiteDatabase db = helper.getWritableDatabase();Uri uriReturn = null;switch (uriMatcher.match(uri)) {case BOOK_DIR:case BOOK_ITEM: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;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {//更新數據SQLiteDatabase db = helper.getWritableDatabase();int updateRows = 0;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;}return updateRows;}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {//刪除數據SQLiteDatabase db = helper.getWritableDatabase();int deleteRows = 0;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;}return deleteRows;}@Overridepublic String getType(Uri uri) {switch (uriMatcher.match(uri)) {case BOOK_DIR:return "vnd.android.cursor.dir/vnd.com.example.databasesave.provider.book";case BOOK_ITEM:return "vnd.android.cursor.item/vnd.com.example.databasesave.provider.book";case CATEGORY_DIR:return "vnd.android.cursor.dir/vnd.com.example.databasesave.provider.category";case CATEGORY_ITEM:return "vnd.android.cursor.item/vnd.com.example.databasesave.provider.category";}return null;}}

MyDatabaseHelper.java代碼：

package com.example.administrator.databasesave;import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.widget.Toast;public class MyDatabaseHelper extends SQLiteOpenHelper {private Context context;public static final String CREATE_BOOK = "create table Book(" +"id integer primary key autoincrement," +"author text," +"price real," +"pages integer," +"name text)";public static final String CREATE_CATEGORY = "create table Category(" +"id integer primary key autoincrement," +"category_name text," +"category_code integer)";public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {super(context, name, factory, version);this.context = context;}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(CREATE_BOOK);//執行sql語句創建Book表db.execSQL(CREATE_CATEGORY);//執行sql語句創建Category表}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("drop table if exists Book");db.execSQL("drop table if exists Category");onCreate(db);} }

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AndroidManifest.xml代碼：

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.administrator.databasesave"><uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /><applicationandroid:allowBackup="true"android:icon="@mipmap/ic_launcher"android:label="@string/app_name"android:roundIcon="@mipmap/ic_launcher_round"android:supportsRtl="true"android:theme="@style/AppTheme"><activity android:name=".MainActivity"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity><providerandroid:name=".DatabaseProvider"android:authorities="com.example.databasesave.provider"android:enabled="true"android:exported="true"></provider></application></manifest>

現在這個DatabaseSave項目已經擁有了跨程序共享數據的功能了，再此，我們先將之前運行在模擬器上的DatabaseSave應用卸載，再重新安裝應用，以防止之前的項目文件對我們造成干擾。

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應用程序B(ProviderTest項目)

下面我們再新建一個ProviderTest項目，我們希望通過這個新建的項目去訪問DatabaseSave項目中的數據，從而實現跨程序共享數據的功能。

activity_main.xml代碼：

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><Buttonandroid:id="@+id/btn_add"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Add Data To Book"android:textAllCaps="false"android:textSize="18sp"android:textStyle="bold" /><Buttonandroid:id="@+id/btn_query"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Query Data From Book"android:textAllCaps="false"android:textSize="18sp"android:textStyle="bold" /><Buttonandroid:id="@+id/btn_update"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Update Book"android:textAllCaps="false"android:textSize="18sp"android:textStyle="bold" /><Buttonandroid:id="@+id/btn_delete"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="Delete Data From Book"android:textAllCaps="false"android:textSize="18sp"android:textStyle="bold" /></LinearLayout>

MainActivity.java代碼：

package com.example.administrator.providertest;import android.content.ContentValues; import android.database.Cursor; import android.net.Uri; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.Toast;public class MainActivity extends AppCompatActivity implements View.OnClickListener {private static final String TAG = "MainActivity";private Button btn_add, btn_query, btn_update, btn_delete;private String newId;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initView();//初始化UI控件}private void initView() {btn_add = (Button) findViewById(R.id.btn_add);btn_query = (Button) findViewById(R.id.btn_query);btn_update = (Button) findViewById(R.id.btn_query);btn_delete = (Button) findViewById(R.id.btn_delete);btn_add.setOnClickListener(this);btn_query.setOnClickListener(this);btn_update.setOnClickListener(this);btn_delete.setOnClickListener(this);}@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.btn_add:add();//添加數據Toast.makeText(this, "add successfully", Toast.LENGTH_SHORT).show();break;case R.id.btn_query:query();//查詢數據Toast.makeText(this, "query successfully", Toast.LENGTH_SHORT).show();break;case R.id.btn_update:update();//更新數據Toast.makeText(this, "update successfully", Toast.LENGTH_SHORT).show();break;case R.id.btn_delete:delete();//刪除數據Toast.makeText(this, "delete successfully", Toast.LENGTH_SHORT).show();break;default:break;}}private void add() {Uri uri = Uri.parse("content://com.example.databasesave.provider/book");ContentValues cv = new ContentValues();cv.put("name", "A Clash of Kings");cv.put("author", "George Martin");cv.put("pages", 1040);cv.put("price", 22.85);Uri newUri = getContentResolver().insert(uri, cv);newId = newUri.getPathSegments().get(1);}private void query() {Uri uri = Uri.parse("content://com.example.databasesave.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.e(TAG, "book name is " + name);Log.e(TAG, "book author is " + author);Log.e(TAG, "book pages are " + pages);Log.e(TAG, "book price is " + price);}cursor.close();}}private void update() {Uri uri = Uri.parse("content://com.example.databasesave.provider/book/" + newId);ContentValues cv = new ContentValues();cv.put("name", "A Storm of Swords");cv.put("pages", 1216);cv.put("price", 24.05);getContentResolver().update(uri, cv, null, null);}private void delete() {Uri uri = Uri.parse("content://com.example.databasesave.provider/book/" + newId);getContentResolver().delete(uri, null, null);} }

運行ProviderTest應用程序：

1.添加數據

在PrioviderTest中點擊Add Data To Book按鈕向Book表中添加數據

使用adb shell查看Book表中的數據如下：

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2.查詢數據：

在PrioviderTest中點擊Query Data From Book按鈕從Book表中查詢數據：

ProviderTest中的Logcat將Book表中查詢出來的數據打印：

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3.更新數據：

在PrioviderTest中點擊Update Data 按鈕更新Book表中的數據：

Logcat打印：

未更新前的數據：

更新后的數據：

4.刪除數據：

在PrioviderTest中點擊Delete Data From Book按鈕刪除Book表中的數據：

adb shell查看Book表中是否還有數據：

說明我們的刪除功能也是可以使用的。

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跨程序共享數據的CRUD操作，基本上就這些。

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