在应用之间共享数据

通过ContentProvider封装数据

ContentProvider使用的Uri语法结构如下：

content://authority/data_path/id

content：通用前缀，表示该uri用于ContentProvider定位资源

authority：是授权者名称，用来确定具体由哪一个ContentProvider提供资源。因此一般anthority都由类小写的全程组成，以保证唯一性。

data_path：是数据路径，用来确定请求的是哪一个数据集

id：是数据编号，用来请求单条数据。如果是多条，这个字段请忽略。

通过ContentResolver访问数据

使用内容组件获取通信信息

运行时，动态申请权限

利用ContentResolver读写联系人

利用ContentObserver监听短信

使用Servet和Client进行通信实例

server-UserDBHelper.java

package com.example.server.database;import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;public class UserDBHelper extends SQLiteOpenHelper {public static final String DB_NAME = "user.db";public static final String TABLE_NAME = "user_info";public static final int DB_VERSION = 1;public static UserDBHelper mHelper = null;private SQLiteDatabase mRDB = null;private SQLiteDatabase mWDB = null;public static UserDBHelper getInstance(Context context) {if (mHelper == null) {mHelper = new UserDBHelper(context);}return mHelper;}public UserDBHelper(Context context) {super(context, DB_NAME, null, DB_VERSION);}public SQLiteDatabase openReadLink() {if (mRDB == null || !mRDB.isOpen()) {mRDB = mHelper.getReadableDatabase();}return mRDB;}public SQLiteDatabase openWriteLink() {if (mWDB == null || !mWDB.isOpen()) {mWDB = mHelper.getWritableDatabase();}return mWDB;}public void closeDBLink() {if (mRDB != null && mRDB.isOpen()) {mRDB.close();mRDB = null;}if (mWDB != null && mWDB.isOpen()) {mWDB.close();mWDB = null;}}//创建数据库，执行建表语句@Overridepublic void onCreate(SQLiteDatabase db) {String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +"_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," +"name VARCHAR NOT NULL," +"age INTEGER NOT NULL," +"height LONG NOT NULL," +"weight FLOAT NOT NULL," +"married INTEGER NOT NULL);";db.execSQL(sql);}//    public void insert(User user) {
//        ContentValues values = new ContentValues();
//        mWDB.insert(TABLE_NAME,null,values);
//    }@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
}

server-UserContentProvider.java

package com.example.server.provider;import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;
import android.util.Log;import com.example.server.database.UserDBHelper;public class UserContentProvider extends ContentProvider {private UserDBHelper dbHelper;private static String TAG = "pansd-UserContentProvider";@Overridepublic boolean onCreate() {Log.d(TAG, "onCreate: UserContentProvider");dbHelper = UserDBHelper.getInstance(getContext());return true;}public UserContentProvider() {}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {// Implement this to handle requests to delete one or more rows.throw new UnsupportedOperationException("Not yet implemented");}@Overridepublic String getType(Uri uri) {// TODO: Implement this to handle requests for the MIME type of the data// at the given URI.throw new UnsupportedOperationException("Not yet implemented");}// content://com.example.server.provider.UserContentProvider/user@Overridepublic Uri insert(Uri uri, ContentValues values) {// TODO: Implement this to handle requests to insert a new row.Log.d(TAG, "insert: 开始插入");SQLiteDatabase writableDatabase = dbHelper.getWritableDatabase();writableDatabase.insert(UserDBHelper.TABLE_NAME,null,values);
//        throw new UnsupportedOperationException("Not yet implemented");Log.d(TAG, "insert: 插入成功");return uri;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {// TODO: Implement this to handle query requests from clients.Log.d(TAG, "query: UserContentProvider");SQLiteDatabase db = dbHelper.getReadableDatabase();Cursor query = db.query(UserDBHelper.TABLE_NAME, projection, selection, selectionArgs, null, null, null);//        throw new UnsupportedOperationException("Not yet implemented");return query;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {// TODO: Implement this to handle requests to update one or more rows.throw new UnsupportedOperationException("Not yet implemented");}
}

server-清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.server"><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/Theme.Demo1"><providerandroid:name=".provider.UserContentProvider"android:authorities="com.example.server.provider.usercontentprovider"android:enabled="true"android:exported="true"></provider><activity android:name=".MainActivity"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity></application></manifest>

Client-avtivity

package com.example.client;import androidx.appcompat.app.AppCompatActivity;import android.content.ContentValues;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;public class ContentWriteActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_content_write);}public void contentProviderWrite(View view) {ContentValues values = new ContentValues();values.put("name", "pshdhx");values.put("age", 22);values.put("height", 183);values.put("weight", Float.parseFloat("164"));values.put("married", true);getContentResolver().insert(UserInfoContent.CONTENT_URI, values);
//        Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();System.out.println("values = " + values);}public void contentProviderQuery(View view) {Cursor query = getContentResolver().query(UserInfoContent.CONTENT_URI, null, null, null, null);int userId = 999;String name = "";if (query != null) {while (query.moveToNext()) {userId = query.getInt(query.getColumnIndex("_id"));name = query.getString(query.getColumnIndex("name"));}query.close();}Toast.makeText(this, "userId="+userId+"=name="+name, Toast.LENGTH_SHORT).show();
//        System.out.println("name = " + name);}
}

Client-清单文件

    <queries><package android:name="com.example.server"/>
<!--        <provider android:authorities="com.example.server.provider.UserContentProvider"/>--></queries>