概況

定義：contentProvider是android中提供專門進(jìn)行不同程序數(shù)據(jù)共享的方式，其底層實現(xiàn)是Binder，contentProvider以表格的形式組織數(shù)據(jù)，而且包含多個表。
作用：訪問系統(tǒng)預(yù)置的ContentProvider，如通訊錄，自定義contentProvider暴露給外界，方便調(diào)用。

ContentProvider的工作過程

首先給一張大圖（反應(yīng)了ContentProvider的工作流程）

ContentProvider工作流程

簡單介紹：

• 一個應(yīng)用啟動入口方法是ActivityThread的main方法，main方法中會創(chuàng)建ActivityThread的實例和主線程的消息隊列，然后通過attch方法遠(yuǎn)程調(diào)用遠(yuǎn)程的Ams的attachApplication，并把ApplicationThread對象給Ams。ams的attachApplication方法會調(diào)用ApplicationThread的bindApplication，經(jīng)過handler傳回ActivityThread中處理，即交給handleBindApplication方法，此方法會創(chuàng)建Application對象，和加載ContentProvider。
• 所以Application的onCreate的執(zhí)行在加載ContentProvider之后。
• ApplicationThread是Binder對象，它的Binder接口是IApplicationThread，主要用于Ams和ActivityThread的之間通信。

聊聊之后發(fā)生的事：

• contentProvider開始后，外界無法直接訪問，必須通過AMS根據(jù)uri獲取對應(yīng)的ContentProvider的binder接口（IcontentProvider），來訪問數(shù)據(jù)。
• 通過android：multiprocess設(shè)置ContentProvider是單實例還是多實例。
• 訪問ContentProvider通過ContentResolver，實際上就是ApplicationContentProvider，第一次觸發(fā)ContentProvider方法，伴隨著啟動其所在進(jìn)程。

選query方法，來仔細(xì)介紹：（具體參見開發(fā)藝術(shù)探索）

1、首先獲取IContentProvider對象，（通過acquireProvider方法獲取ContentProvider）。
2、發(fā)送一個進(jìn)程間請求給AMS讓其啟動目標(biāo)ContentProvider，最后通過installProvider修改引用次數(shù)。
3、AMS首先啟動進(jìn)程，然后啟動ContentProvider，具體啟動進(jìn)程的方法是startProcessLocked方法，內(nèi)部通過Process的start方法完成進(jìn)程的啟動。
4、ActivityThread的attach方法會將Application對象通過AMS的attachApplication方法跨進(jìn)程傳遞給AMS，最終會完成ContentProvider創(chuàng)建過程。
5、一個流程：
attachApplication（ams）--》 attachApplicationLocked（ams）--》 bindApplication（ApplicationThread） -（發(fā)送消息）-》Handler--》handleBindApplication
6、四個步驟：

• 創(chuàng)建ContextImpl和Instrumentation
• 創(chuàng)建Application對象
• 啟動當(dāng)前進(jìn)程的ContentProvider并調(diào)用其OnCreate
• 調(diào)用Application的onCreate方法

上例子

首先是讀取系統(tǒng)的一些信息：

package com.example.contentprovider;

import android.Manifest;
import android.content.ContentProvider;
import android.content.ContentProviderOperation;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Intent;
import android.content.OperationApplicationException;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.net.Uri;
import android.os.RemoteException;
import android.provider.ContactsContract;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    private TextView text_content;
    private Button change_text;
    private Button intent_second;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
    }

    //初始化
    private void init(){
    //三組權(quán)限
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED) {
            //沒有授權(quán)，則申請授權(quán)
            //ActivityCompat.requestPermissions() 參數(shù)一：context 參數(shù)二：申請的權(quán)限名數(shù)組 參數(shù)三：請求碼，要求唯一值
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_CONTACTS}, 2);
        } else {
            getContacts();
        }
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_CONTACTS) != PackageManager.PERMISSION_GRANTED) {
           
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_CONTACTS}, 2);
        }
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_SMS) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_SMS}, 1);
        } else {
            getMsgs();
        }
//        insertMsg();
        initView();
    }


    //初始化頁面和設(shè)置點擊事件
    private void initView(){
        text_content = (TextView)findViewById(R.id.text_content);
        change_text = (Button)findViewById(R.id.add_contacts);
        intent_second = (Button)findViewById(R.id.intent_to_second);
        intent_second.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                intent.setClass(MainActivity.this,SecondActivity.class);
                startActivity(intent);
            }
        });
        change_text.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try{
                    //添加聯(lián)系人，因為原方法拋出了異常，所以調(diào)用的時候需要try-catch語句
                    AddContact();
                }catch (Exception e){
                    e.printStackTrace();
                }

            }
        });
    }

    //查詢短信一些信息
    private void getMsgs(){
    //短信的uri
        Uri uri = Uri.parse("content://sms/");
        ContentResolver resolver = getContentResolver();
        //獲取的是哪些列的信息
        Cursor cursor = resolver.query(uri, new String[]{"address","date","type","body"}, null, null, null);
        while(cursor.moveToNext())
        {
            String address = cursor.getString(0);
            String date = cursor.getString(1);
            String type = cursor.getString(2);
            String body = cursor.getString(3);
            System.out.println("地址:" + address);
            System.out.println("時間:" + date);
            System.out.println("類型:" + type);
            System.out.println("內(nèi)容:" + body);
            System.out.println("======================");
        }
        cursor.close();
    }

    //添加聯(lián)系人
    private void AddContact() throws RemoteException,OperationApplicationException{
        Uri uri = Uri.parse("content://com.android.contacts/raw_contacts");
        Uri dataUri = Uri.parse("content://com.android.contacts/data");

        ContentResolver resolver = getContentResolver();
        ArrayList<ContentProviderOperation> operations = new ArrayList<>();
        ContentProviderOperation op1 = ContentProviderOperation.newInsert(uri)
                .withValue("account_name",null)
                .build();
        operations.add(op1);

        ContentProviderOperation op2 = ContentProviderOperation.newInsert(dataUri)
                .withValueBackReference("raw_contact_id",0)
                .withValue("mimetype","vnd.android.cursor.item/name")
                .withValue("data2","Coder_pig")
                .build();
        operations.add(op2);

        ContentProviderOperation op3 = ContentProviderOperation.newInsert(dataUri)
                .withValueBackReference("raw_contact_id", 0)
                .withValue("mimetype", "vnd.android.cursor.item/phone_v2")
                .withValue("data1", "13798988888")
                .withValue("data2", "2")
                .build();
        operations.add(op3);

        ContentProviderOperation op4 = ContentProviderOperation.newInsert(dataUri)
                .withValueBackReference("raw_contact_id", 0)
                .withValue("mimetype", "vnd.android.cursor.item/email_v2")
                .withValue("data1", "1825273284@qq.com")
                .withValue("data2", "2")
                .build();
        operations.add(op4);
        //將上述內(nèi)容添加到手機聯(lián)系人中~
        resolver.applyBatch("com.android.contacts", operations);
        Toast.makeText(getApplicationContext(), "添加成功", Toast.LENGTH_SHORT).show();
    }

    //獲取聯(lián)系人信息
    private void getContacts(){
        ContentResolver resolver = getContentResolver();
        Uri uri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;
        Cursor cursor = resolver.query(uri,null,null,null,null);
        while (cursor.moveToNext()){
            String cName = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
            String cNum = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
            System.out.print("姓名："+cName);
            System.out.println("號碼："+cNum);
            System.out.println("++++++++++++++++++++++");
        }
        cursor.close();
    }

    //動態(tài)權(quán)限申請
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    getContacts();
                } else {
                    Toast.makeText(MainActivity.this, "read sms denied", Toast.LENGTH_SHORT).show();
                }
                break;
            case 2:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    getMsgs();
                } else {
                    Toast.makeText(MainActivity.this, "read call denied", Toast.LENGTH_SHORT).show();
                }
                break;

        }
    }
}

運行結(jié)果：

聯(lián)系人

短信

新添加的聯(lián)系人

然后是自定義ContentProvider
目錄結(jié)構(gòu)：

目錄結(jié)構(gòu)

DBOpenHelper是關(guān)于數(shù)據(jù)庫的一個類：

package com.example.contentprovider.util;

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

public class DBOpenHelper extends SQLiteOpenHelper {

    final String CREATE_SQL = "CREATE TABLE test(_id INTEGER PRIMARY KEY AUTOINCREMENT,name)";

    public DBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version){
        super(context,name,null,1);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_SQL);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

}

內(nèi)容提供器：（ContentProvider）

package com.example.contentprovider.util;

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;

public class NameContentProvider extends ContentProvider {

    //初始化一些常量
    private static UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
    private DBOpenHelper dbOpenHelper;

    static {
        matcher.addURI("com.example.contentprovider.myprovider","test",1);
    }

    @Override
    public boolean onCreate() {
        //實例化對象
        dbOpenHelper = new DBOpenHelper(this.getContext(),"test.db",null,1);
        return true;
    }

    @Override
    public Cursor query( Uri uri,String[] projection,String selection, String[] selectionArgs, String sortOrder) {
        return null;
    }


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

    @Override
    public Uri insert(Uri uri , ContentValues values) {
        switch (matcher.match(uri)){
            //證明uri是否匹配成功
            case 1:
                SQLiteDatabase db = dbOpenHelper.getReadableDatabase();
                long rowId = db.insert("test",null,values);
                if(rowId > 0){
                    // 在前面已有的uri后面追加id
                    Uri nameUri = ContentUris.withAppendedId(uri,rowId);
                    //通知內(nèi)容提供器，內(nèi)容發(fā)生改變了
                    getContext().getContentResolver().notifyChange(nameUri,null);;
                    return  nameUri;
                }
        }
        return null;
    }

    @Override
    public int delete(Uri uri, String selection,String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update( Uri uri,  ContentValues values,  String selection, String[] selectionArgs) {
        return 0;
    }
}

AsyncTask(用于更新ui)

package com.example.contentprovider.util;

import android.os.AsyncTask;
import android.widget.TextView;

public class MyAsyncTask extends AsyncTask<Integer,Integer,String> {
    private TextView txt;
    private String str;
    public  MyAsyncTask(TextView txt,String str){
        super();
        this.txt = txt;
        this.str = str;
    }
    @Override
    protected String doInBackground(Integer... integers) {
        return null;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        txt.setText(str);
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
    }
}

SecondActivity:

package com.example.contentprovider;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import com.example.contentprovider.util.DBOpenHelper;
import com.example.contentprovider.util.MyAsyncTask;

public class SecondActivity extends AppCompatActivity {
    private DBOpenHelper dbOpenHelper;
    private String name = null;
    private TextView text_show;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        text_show = (TextView)findViewById(R.id.txt_show_data);
    }
    public void onClick(View view){
        if(view.getId() == R.id.cursor_data){
            watch();
        }
    }
    private void watch(){
        dbOpenHelper = new DBOpenHelper(this,"test.db",null,1);
        SQLiteDatabase sqLiteDatabase = dbOpenHelper.getReadableDatabase();
        Cursor cursor = sqLiteDatabase.query("test",new String[]{"name"},"name=?",new String[] { "測試" },null,null,null);
        while (cursor.moveToNext()) {
            name = cursor.getString(cursor.getColumnIndex("name"));
            //輸出查詢結(jié)果
            System.out.println("查詢到的數(shù)據(jù)是:\n"+"name: "+name);

        }
        if(name != null){
            MyAsyncTask myAsyncTask = new MyAsyncTask(text_show,name);
            myAsyncTask.execute();
        }
        //關(guān)閉數(shù)據(jù)庫
        sqLiteDatabase.close();
    }
}

在其他程序的調(diào)用：（ProviderTeminate的MainActivity）

package com.example.providerterminate;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button btninsert;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btninsert = (Button) findViewById(R.id.btn_insert);

        //讀取contentprovider 數(shù)據(jù)
        final ContentResolver resolver = this.getContentResolver();


        btninsert.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                ContentValues values = new ContentValues();
                values.put("name", "測試");
                Uri uri = Uri.parse("content://com.example.contentprovider.myprovider/test");
                resolver.insert(uri, values);
                Toast.makeText(getApplicationContext(), "數(shù)據(jù)插入成功", Toast.LENGTH_SHORT).show();

            }
        });

    }
}

運行結(jié)果

建立數(shù)據(jù)庫和插入元素