目 录

PersonCp

PersonCp.java

insert()

ContentObserver

音乐播放器

1、添加读写权限

1.1、动态权限授予（调用封装好的方法）

2、获取音乐文件（MainActivity.java）

2、Music.java（实体类）

申请访问SD卡的权限

设置适配器

下拉刷新

PersonCp

PersonCp.java

package cn.wangzg.personcp;

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.net.Uri;

import java.util.Objects;


public class PersonCp extends ContentProvider { //数据库作为数据源，将数据保存到数据库中。
    private MyHelper mHelper;
    private final static String AUTHORITY = "cn.wangzg.personprovider";
    private static UriMatcher mUriMatcher;
    private static final int PERSON_DIR = 0;
    private static final int PERSON = 1;

    
    static {
        mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 该URI表示返回所有的person,其中PERSONS为该特定Uri的标识码
        mUriMatcher.addURI(AUTHORITY, "person", PERSON_DIR);
        // 该URI表示返回某一个person,其中PERSON为该特定Uri的标识码
        mUriMatcher.addURI(AUTHORITY, "person/#", PERSON);
    }


    
    @Override
    public String getType(Uri uri) {
        switch (mUriMatcher.match(uri)) {
            case PERSON_DIR:
                return "vnd.android.cursor.dir/" + AUTHORITY + ".persons";
            case PERSON:
                return "vnd.android.cursor.item/" + AUTHORITY + ".person";
            default:
                throw new IllegalArgumentException("unknown uri" + uri.toString());
        }
    }


    @Override
    public boolean onCreate() {
        mHelper = new MyHelper(getContext());
        return true;
    }


    
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = mHelper.getWritableDatabase();
        switch (mUriMatcher.match(uri)) {
            case PERSON_DIR:
                long newId = db.insert("person", "name,phone,salary", values);
                //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应
                getContext().getContentResolver().notifyChange(uri, null);
                return ContentUris.withAppendedId(uri, newId);
            default:
                throw new IllegalArgumentException("unknown uri" + uri.toString());
        }
    }

    
    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        SQLiteDatabase db = mHelper.getWritableDatabase();
        int updatedNum = 0;
        switch (mUriMatcher.match(uri)) {
            // 更新表
            case PERSON_DIR:
                updatedNum = db.update("person", values, selection, selectionArgs);
                break;
            // 按照id更新某条数据
            case PERSON:
                long id = ContentUris.parseId(uri);
                String where = "id=" + id;
                if (selection != null && !"".equals(selection.trim())) {
                    where = selection + " and " + where;
                }
                updatedNum = db.update("person", values, where, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("unknown uri" + uri.toString());
        }
        //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应
        Objects.requireNonNull(getContext()).getContentResolver().notifyChange(uri, null);
        return updatedNum;
    }

    
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase db = mHelper.getWritableDatabase();
        int deletedNum = 0;
        switch (mUriMatcher.match(uri)) {
            // 删除表
            case PERSON_DIR:
                deletedNum = db.delete("person", selection, selectionArgs);
                break;
            // 按照id删除某条数据
            case PERSON:
                long id = ContentUris.parseId(uri);
                String where = "id=" + id;
                if (selection != null && !"".equals(selection.trim())) {
                    where = selection + " and " + where;
                }
                deletedNum = db.delete("person", where, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("unknown uri" + uri.toString());
        }
        //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应
        Objects.requireNonNull(getContext()).getContentResolver().notifyChange(uri, null);
        return deletedNum;
    }

    
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        SQLiteDatabase db = mHelper.getWritableDatabase();
        Cursor cursor = null;
        switch (mUriMatcher.match(uri)) {
            // 查询表
            case PERSON_DIR:
                cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            // 按照id查询某条数据
            case PERSON:
                // 第一步:
                long id = ContentUris.parseId(uri);
                String where = "id=" + id;
                // 第二步:
                if (selection != null && !"".equals(selection.trim())) {
                    where = selection + " and " + where;
                }
                cursor = db.query("person", projection, where, selectionArgs, null, null, sortOrder);
                break;
            default:
                throw new IllegalArgumentException("unknown uri" + uri.toString());
        }
        return cursor;
    }
}

insert()

ContentObserver

菜鸟教程 【4.4.1 ContentProvider初探】 

https://www.runoob.com/w3cnote/android-tutorial-contentprovider.html

音乐播放器

1、添加读写权限

1.1、动态权限授予（调用封装好的方法）

2、获取音乐文件（MainActivity.java）

2、Music.java（实体类）

申请访问SD卡的权限

设置适配器

下拉刷新

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