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ContentProvider和ContentResolver演示

作者:互联网

(1)概述

这里来模拟应用是如何访问ContentProvider,所以此处的ContentProvider也是自定义的,后通过ContentResolver来访问,具体源码可访问如下:

(2)部分源码

(A)ContentProvider

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

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <permission
        android:name="com.demo.contentProvider"
        android:label="provider permission"
        android:protectionLevel="normal" />

    <permission
        android:name="com.demo.contentProvider.read"
        android:label="provider read permission"
        android:protectionLevel="normal" />

    <permission
        android:name="com.demo.contentProvider.write"
        android:label="provider write permission"
        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:theme="@style/Theme.Provider">
        <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=".PersonContentProvider"
            android:authorities="com.example.provider"
            android:exported="true"
            android:enabled="true"
            android:grantUriPermissions="true"
            android:permission="com.demo.contentProvider"
            android:readPermission="com.demo.contentProvider.read"
            android:writePermission="com.demo.contentProvider.write" />
    </application>

</manifest>
package com.example.provider;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.util.Log;

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

import java.io.File;

public class PersonContentProvider extends ContentProvider {

    private static final UriMatcher sUriMatcher;
    private static final int MATCH_FIRST = 1;
    private static final int MATCH_SECOND = 2;
    public static final String AUTHORITY = "com.example.provider";
    public static final Uri CONTENT_URI_FIRST = Uri.parse("content://" + AUTHORITY +
            File.separator + DatabaseHelper.TABLE_FIRST_NAME);
    public static final Uri CONTENT_URI_SECOND = Uri.parse("content://" + AUTHORITY +
            File.separator + DatabaseHelper.TABLE_SECOND_NAME);

    public static final String CONTENT_FIRST_TYPE = "vnd.android.cursor.dir/demo.first";
    public static final String CONTENT_SECOND_TYPE = "vnd.android.cursor.item/demo.second";

    static {
        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        sUriMatcher.addURI(AUTHORITY, DatabaseHelper.TABLE_FIRST_NAME, MATCH_FIRST);
        sUriMatcher.addURI(AUTHORITY, DatabaseHelper.TABLE_SECOND_NAME, MATCH_SECOND);
    }

    private DatabaseHelper mDbHelper;

    @Override
    public boolean onCreate() {
        mDbHelper = new DatabaseHelper(getContext());
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s, @Nullable String[] strings1, @Nullable String s1) {
        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
        switch (sUriMatcher.match(uri)) {
            case MATCH_FIRST:
                queryBuilder.setTables(DatabaseHelper.TABLE_FIRST_NAME);
                break;
            case MATCH_SECOND:
                queryBuilder.setTables(DatabaseHelper.TABLE_SECOND_NAME);
                break;
            default:
                throw new IllegalArgumentException("Unknow URI: " + uri);
        }
        SQLiteDatabase db = mDbHelper.getReadableDatabase();
        Cursor cursor = queryBuilder.query(db, strings, s, strings1, null, null, null);
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        switch (sUriMatcher.match(uri)) {
            case MATCH_FIRST: {
                return CONTENT_FIRST_TYPE;
            }
            case MATCH_SECOND: {
                return CONTENT_SECOND_TYPE;
            }
        }
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
        SQLiteDatabase db = mDbHelper.getWritableDatabase();
        Uri retUri = null;
        long rowID = 0;
        switch (sUriMatcher.match(uri)) {
            case MATCH_FIRST:
                rowID = db.insert(DatabaseHelper.TABLE_FIRST_NAME, null, contentValues);
                if (rowID > 0) {
                    retUri = ContentUris.withAppendedId(uri, rowID);
                }
                break;
            case MATCH_SECOND:
                rowID = db.insert(DatabaseHelper.TABLE_SECOND_NAME, null, contentValues);
                if (rowID > 0) {
                    retUri = ContentUris.withAppendedId(uri, rowID);
                }
                break;
            default:
                throw new IllegalArgumentException("Unknow URI: " + uri);
        }
        return retUri;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String s, @Nullable String[] strings) {
        SQLiteDatabase db = mDbHelper.getWritableDatabase();
        int count = 0;
        switch (sUriMatcher.match(uri)) {
            case MATCH_FIRST:
                count = db.delete(DatabaseHelper.TABLE_FIRST_NAME, s, strings);
                break;

            case MATCH_SECOND:
                count = db.delete(DatabaseHelper.TABLE_SECOND_NAME, s, strings);
                break;
            default:
                throw new IllegalArgumentException("Unknow URI :" + uri);

        }
        this.getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s, @Nullable String[] strings) {
        SQLiteDatabase db = mDbHelper.getWritableDatabase();
        int count = 0;
        switch (sUriMatcher.match(uri)) {
            case MATCH_FIRST:
                count = db.update(DatabaseHelper.TABLE_FIRST_NAME, contentValues, s, strings);
                break;
            case MATCH_SECOND:
                count = db.update(DatabaseHelper.TABLE_SECOND_NAME, contentValues, s, strings);
                break;

            default:
                throw new IllegalArgumentException("Unknow URI : " + uri);
        }
        this.getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }
}

(B)ContentResolver

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

    <queries>
        <provider android:authorities="com.example.provider"/>
    </queries>

    <uses-permission android:name="com.demo.contentProvider.read" />
    <uses-permission android:name="com.demo.contentProvider.write" />

    <application
        android: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.Resolver">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name=".SecondActivity">
            <intent-filter>
                <action android:name="com.example.second"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:mimeType="vnd.android.cursor.item/demo.second" />
            </intent-filter>
        </activity>
    </application>

</manifest>
package com.example.resolver;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;
import android.content.Intent;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private static final String TABLE_FIRST_NAME = "first";
    private static final String TABLE_SECOND_NAME = "second";
    public static final String AUTHORITY = "com.example.provider";
    public static final Uri CONTENT_URI_FIRST = Uri.parse("content://" + AUTHORITY + File.separator + TABLE_FIRST_NAME);
    public static final Uri CONTENT_URI_SECOND = Uri.parse("content://" + AUTHORITY + File.separator + TABLE_SECOND_NAME);
    
    public Uri mCurrentURI = getUri(TABLE_FIRST_NAME);

    private DataBaseObserver mObserver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mObserver = new DataBaseObserver(new Handler());
        getContentResolver().registerContentObserver(getUri(null), true, mObserver);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        getContentResolver().unregisterContentObserver(mObserver);
    }

    public class DataBaseObserver extends ContentObserver {

        public DataBaseObserver(Handler handler) {
            super(handler);
        }

        @Override
        public void onChange(boolean selfChange) {
            super.onChange(selfChange);
            Log.e("MainActivity", "selfChange = " + selfChange);
        }
    }

    private Uri getUri(String path) {
        return new Uri.Builder().authority(AUTHORITY)
                .path(path)
                .scheme("content")
                .build();
    }

    private void secondPart() {
        Intent intent = new Intent();
        intent.setAction("com.example.second");
        intent.setData(mCurrentURI);
        try {
            startActivity(intent);
        } catch (Exception e) {
            Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
        }
    }

    private void insert() {
        ContentValues values = new ContentValues();
        values.put("name", "hello");
        values.put("detail", "my name is demo");
        Uri uri = this.getContentResolver().insert(mCurrentURI, values);
        Log.e("MainActivity", "insert : " + uri.toString());
    }

    private void query() {
        Cursor cursor = this.getContentResolver().query(mCurrentURI, null, null, null, null);
        Log.e("MainActivity", "query : count = " + cursor.getCount());
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            String table = cursor.getString(cursor.getColumnIndex("table_name"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String detail = cursor.getString(cursor.getColumnIndex("detail"));
            Log.e("MainActivity", "query : table_name = " + table + ", name = " + name + ", detail = " + detail);
            cursor.moveToNext();
        }
        cursor.close();
    }

    private void update() {
        ContentValues values = new ContentValues();
        values.put("detail", "my name is update");
        int count = this.getContentResolver().update(mCurrentURI, values, "_id = 1", null);
        Log.e("MainActivity", "update : count = " + count);
        query();
    }

    private void delete() {
        int count = this.getContentResolver().delete(mCurrentURI, "_id = 1", null);
        Log.e("MainActivity", "delete : count = " + count);
        query();
    }

    private void switchURI(Uri uri) {
        mCurrentURI = uri;
        mtv.setText("switch URI = " + mCurrentURI.toString());
    }
}

(3)注意事项

(A)Android R平台,将软件的TargetApi提升到30后,原来用的好好的自定义的ContentProvider找不到了,或者直接报 Unknow Uri 问题。

//需要在使用Uri的客户端的AndroidManifest.xml下加上标签

<queries>
        <provider android:authorities="com.example.provider"/>
</queries>

否则在进行registerContentObserver会出现如下Error:

getContentResolver().registerContentObserver(getUri(null), true, mObserver);

//error
Failed to find provider com.demo.provider.PersonContentProvider for user 0

(B)Provider权限问题

ContentProvider:

<permission
        android:name="com.demo.contentProvider"
        android:label="provider permission"
        android:protectionLevel="normal" />

    <permission
        android:name="com.demo.contentProvider.read"
        android:label="provider read permission"
        android:protectionLevel="normal" />

    <permission
        android:name="com.demo.contentProvider.write"
        android:label="provider write permission"
        android:protectionLevel="normal" />

<provider
            android:name=".PersonContentProvider"
            android:authorities="com.example.provider"
            android:exported="true"
            android:enabled="true"
            android:grantUriPermissions="true"
            android:permission="com.demo.contentProvider"
            android:readPermission="com.demo.contentProvider.read"
            android:writePermission="com.demo.contentProvider.write" />

ContentResolver:

<uses-permission android:name="com.demo.contentProvider.read" />
<uses-permission android:name="com.demo.contentProvider.write" />

标签:演示,Uri,ContentResolver,uri,import,android,ContentProvider,public,FIRST
来源: https://blog.csdn.net/dongxianfei/article/details/122088208