Android之ContentProvider共享数据(解决了Android11上的适配问题)

本文链接：https://blog.youkuaiyun.com/Llearn1202/article/details/115494318

本文展示了如何在Android中使用ContentProvider实现进程间数据共享。通过创建SQLite数据库和ContentProvider，分别在本地和远程进程中进行数据的插入、查询和删除操作，实现了不同应用之间的数据交互。

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一、共享进程

SQLite数据库代码

package com.ly.provider.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

/**
 * create people ly
 * <p>
 * create datatime 2021-4-7 14:25
 */
public class DBHelper extends SQLiteOpenHelper {


    // 数据库名
    private static final String DATABASE_NAME = "liudb.db";

    // 表名
    public static final String USER_TABLE_NAME = "user";
    //创建表
    private final String SQL_CREATE_TABLE="CREATE TABLE IF NOT EXISTS " + USER_TABLE_NAME + "(_id INTEGER PRIMARY KEY AUTOINCREMENT," + " name TEXT)";
    //删除表
    private final String SQL_DROP_TABLE="DROP TABLE IF EXISTS "+USER_TABLE_NAME;


    private static final int DATABASE_VERSION = 1;
    //数据库版本号

    public DBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(SQL_DROP_TABLE);
        onCreate(db);
    }
}

ContentProvider代码

package com.ly.provider.db;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

/**
 * create people ly
 * <p>
 * create datatime 2021-4-7 14:34
 */
public class LProvider extends ContentProvider {

    private Context mContext;
    DBHelper mDbHelper = null;
    SQLiteDatabase db = null;

    public static final String AUTOHORITY = "cn.scu.myprovider";
    // 设置ContentProvider的唯一标识

    public static final int User_Code = 1;

    // UriMatcher类使用:在ContentProvider 中注册URI
    private static final UriMatcher mMatcher;
    static{
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 初始化
        mMatcher.addURI(AUTOHORITY,"user", User_Code);
        // 若URI资源路径 = content://cn.scu.myprovider/user ，则返回注册码User_Code
    }
    @Override
    public boolean onCreate() {
        mContext = getContext();
        // 在ContentProvider创建时对数据库进行初始化
        // 运行在主线程，故不能做耗时操作,此处仅作展示
        mDbHelper = new DBHelper(getContext());
        db = mDbHelper.getWritableDatabase();

        // 初始化两个表的数据(先清空两个表,再各加入一个记录)
        db.execSQL("delete from user");
        db.execSQL("insert into user values(1,'Carson');");
        db.execSQL("insert into user values(2,'Kobe');");
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        // 根据URI匹配 URI_CODE，从而匹配ContentProvider中相应的表名
        // 该方法在最下面
        String table = getTableName(uri);

//        // 通过ContentUris类从URL中获取ID
//        long personid = ContentUris.parseId(uri);
//        System.out.println(personid);

        // 查询数据
        return db.query(table,projection,selection,selectionArgs,null,null,sortOrder,null);
    }
    /**
     * 根据URI匹配 URI_CODE，从而匹配ContentProvider中相应的表名
     */
    private String getTableName(Uri uri){
        String tableName = null;
        switch (mMatcher.match(uri)) {
            case User_Code:
                tableName = DBHelper.USER_TABLE_NAME;
                break;

        }
        return tableName;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        String table = getTableName(uri);
        db.insert(table,null,values);
        mContext.getContentResolver().notifyChange(uri, null);
        return uri;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        String table = getTableName(uri);
        int delete = db.delete(table, selection, selectionArgs);
        return delete;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        String table = getTableName(uri);
        return db.update(table,values,selection,selectionArgs);
    }
}

清单文件配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ly.provider">

    <!--// 声明本应用 可允许通信的权限-->
    <permission android:name="scut.carson_ho.Write" android:protectionLevel="normal"/>
    <permission android:name="scut.carson_ho.Read" android:protectionLevel="normal"/>
    <!--// 细分读 & 写权限如下，但本Demo直接采用全权限
    // <permission android:name="scut.carson_ho.Write" android:protectionLevel="normal"/>
    <permission android:name="scut.carson_ho.Read" android:protectionLevel="normal"/>
    // -->
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:requestLegacyExternalStorage="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>
        <provider android:name=".db.LProvider"
            android:authorities="cn.scu.myprovider"
            android:grantUriPermissions="true"
            android:exported="true"
            android:enabled="true"
            android:writePermission="scut.carson_ho.Write"
            android:readPermission="scut.carson_ho.Read"
            />
        <!--
        // 声明外界进程可访问该Provider的权限（读 & 写）
        android:permission="scut.carson_ho.PROVIDER"

        // 权限可细分为读 & 写的权限
        // 外界需要声明同样的读 & 写的权限才可进行相应操作，否则会报错
        // android:readPermisson = "scut.carson_ho.Read"
        // android:writePermisson = "scut.carson_ho.Write"

        // 设置此provider是否可以被其他进程使用
        android:exported="true"
        -->
    </application>

</manifest>

本地访问

package com.ly.provider;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        /**
         * 对user表进行操作
         */

        // 设置URI
        Uri uri_user = Uri.parse("content://cn.scu.myprovider/user");

        // 插入表中数据
        ContentValues values = new ContentValues();
        values.put("_id", 3);
        values.put("name", "Iverson");


        // 获取ContentResolver
        ContentResolver resolver =  getContentResolver();
        // 通过ContentResolver 根据URI 向ContentProvider中插入数据
        resolver.insert(uri_user,values);

        // 通过ContentResolver 向ContentProvider中查询数据
        Cursor cursor = resolver.query(uri_user, new String[]{"_id","name"}, null, null, null);
        while (cursor.moveToNext()){
            System.out.println("query book:" + cursor.getInt(0) +" "+ cursor.getString(1));
            // 将表中数据全部输出
        }
        resolver.delete(uri_user,"name=?",new String[]{"Iverson"});
        Cursor cursor1 = resolver.query(uri_user, new String[]{"_id","name"}, null, null, null);
        while (cursor1.moveToNext()){
            System.out.println("query book:" + cursor1.getInt(0) +" "+ cursor1.getString(1));
            // 将表中数据全部输出
        }
        cursor.close();
        cursor1.close();
        // 关闭游标
    }
}

build.gradle版本

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.ly.provider"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

}

二、访问进程

Activity访问代码

package com.ly.lydemo;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.DocumentsContract;
import android.provider.Settings;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 设置URI
        Uri uri_user = Uri.parse("content://cn.scu.myprovider/user");
        // 插入表中数据
        ContentValues values = new ContentValues();
        values.put("_id", 3);
        values.put("name", "Jordan");


        // 获取ContentResolver
        ContentResolver resolver =  getContentResolver();
        // 通过ContentResolver 根据URI 向ContentProvider中插入数据
        resolver.insert(uri_user,values);

        // 通过ContentResolver 向ContentProvider中查询数据
        Cursor cursor = resolver.query(uri_user, new String[]{"_id","name"}, null, null, null);
        while (cursor.moveToNext()){
            System.out.println("query book:" + cursor.getInt(0) +" "+ cursor.getString(1));
            // 将表中数据全部输出
        }
        cursor.close();
    }
}

清单文件配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ly.lydemo">
    <uses-permission android:name="scut.carson_ho.Write"/>
    <uses-permission android:name="scut.carson_ho.Read" />
 <queries>
        <package android:name="com.ly.provider" />

    </queries>
    <!-- android:requestLegacyExternalStorage="true"-->
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:requestLegacyExternalStorage="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>

    </application>

</manifest>

build.gradle版本

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.ly.lydemo"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

}

注意：
Android11版本上必须加上以下配置才可访问：

 <queries>
        <package android:name="com.ly.provider" />

    </queries>