android文件权限简述

内容提供者（ContentProvider）

内容解析者（ContentResolver）

综合实例-联系人信息管理

关键代码

MyContentProvider.java

package com.example.contentproviderdemo;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.util.Log;
public class MyContentProvider extends ContentProvider {
    public MyContentProvider() {
    }
    @Override
    public 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");
    }
    @Override
    public 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");
    }
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // TODO: Implement this to handle requests to insert a new row.
        throw new UnsupportedOperationException("Not yet implemented");
    }
    @Override
    public boolean onCreate() {
        // TODO: Implement this to initialize your content provider on startup.
        return false;
    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        // TODO: Implement this to handle query requests from clients.
        Log.d("15pb","MyContentProvider::query");
        return null;
    }
    @Override
    public 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");
    }
}

MainActivity.java

package com.example.contentproviderdemo;
import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void btnClick(View view) {
        // 1. 获取内容解析者
        ContentResolver resolver = getContentResolver();
        // 2. 创建URI
        Uri uri = Uri.parse("content://"+"MyContentProvider");
        // 3. 查询
        Cursor cursor = resolver.query(uri,null,null,null,null,null);
        Log.d("15pb","cursor:"+cursor);
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <Button
        android:id="@+id/btn1"
        android:onClick="btnClick"
        android:text="访问内容提供者"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"></Button>
</LinearLayout>