移动应用开发程序演练——ContentProvider(内容提供者)

工具：Android Studio

查看短信的猫（内容提供者的创建和查看）

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/bg"/>
    <TextView
        android:id="@+id/tv_des"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="18dp"
        android:paddingLeft="20dp"
        android:text="读取到的系统短信信息如下："
        android:textSize="20sp"
        android:visibility="invisible"/>
    <TextView
        android:id="@+id/tv_sms"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tv_des"
        android:lines="20"
        android:paddingLeft="20dp"
        android:paddingTop="10dp"
        android:textSize="16sp"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="28dp"
        android:layout_marginLeft="26dp"
        android:layout_marginStart="26dp"
        android:background="#D9D1FA"
        android:onClick="readSMS"
        android:text="查看短信"
        android:textSize="30sp"/>

</RelativeLayout>

SmsInfo.java

package com.example.readsms;

public class SmsInfo {
    private int _id;//短信的主键
    private String address;//发送地址
    private int type;//类型
    private String body;//短信内容
    private long date;//时间
    //构造方法
    public SmsInfo(int _id,String address,int type,String body,long date){
        this._id=_id;
        this.address=address;
        this.type=type;
        this.body=body;
        this.date=date;
    }
    public int get_id(){
        return _id;
    }
    public void set_id(int _id){
        this._id=_id;
    }
    public String getAddress(){
        return address;
    }
    public void setAddress(String address){
        this.address=address;
    }
    public int getType(){
        return type;
    }
    public void setType(int type){
        this.type=type;
    }
    public String getBody(){
        return body;
    }
    public void setBody(String body){
        this.body=body;
    }
    public long getDate(){
        return date;
    }
    public void setDate(long date){
        this.date=date;
    }
}
 

MainActivity.java

> package com.example.readsms;
> 
> import androidx.appcompat.app.AppCompatActivity; import
> android.content.ContentResolver; import android.database.Cursor;
> import android.net.Uri; import android.view.View; import
> android.widget.TextView; import java.util.ArrayList; import
> java.util.List;
> 
> import android.os.Bundle;
> 
> public class MainActivity extends AppCompatActivity {
>     private TextView tvSms;
>     private TextView tvDes;
>     private String text = "";
> 
>     @Override
>     protected void onCreate(Bundle savedInstanceState) {
>         super.onCreate(savedInstanceState);
>         setContentView(R.layout.activity_main);
>         tvSms = (TextView) findViewById(R.id.tv_sms);
>         tvDes = (TextView) findViewById(R.id.tv_des);
>     }
>     //单击Button时触发的方法
>     public void readSMS(View view){
>         //查询系统信息的Uri
>         Uri uri = Uri.parse("content://sms/");
>         //获取ContentResolver对象
>         ContentResolver resolver = getContentResolver();
>         //通过ContentResolver对象查询系统短信
>         Cursor cursor = resolver.query(uri,new String[]{"_id","address","type","body","date"},null,null,null);
>         List<SmsInfo> smsInfos = new ArrayList<SmsInfo>();
>         if(cursor != null && cursor.getCount() > 0){
>             tvDes.setVisibility(View.VISIBLE);
>             while (cursor.moveToNext()){
>                 int _id = cursor.getInt(0);
>                 String address = cursor.getString(1);
>                 int type = cursor.getInt(2);
>                 String body = cursor.getString(3);
>                 long date = cursor.getLong(4);
>                 SmsInfo smsInfo = new SmsInfo(_id,address,type,body,date);
>                 smsInfos.add(smsInfo);
>             }
>             cursor.close();
>         }
>         //将查询到的短信内容显示到界面上
>         for(int i = 0;i < smsInfos.size();i++){
>             text += "手机号码：" + smsInfos.get(i).getAddress() + "\n";
>             text += "短信内容：" + smsInfos.get(i).getBody() + "\n\n";
>             tvSms.setText(text);
>         }
>     } }

AndroidManifest.xml

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

    <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/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>
<uses-permission android:name="android.permission.READ_SMS"/>
</manifest>

界面效果：

监测数据的猫（内容观察者的创建和查看）

源代码：
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/bg"
    android:orientation="vertical" tools:context=".MainActivity">
    <Button
        android:id="@+id/btn_insert"
        android:layout_width="120dp"
        android:layout_height="40dp"
        android:layout_marginLeft="40dp"
        android:layout_marginStart="40dp"
        android:layout_marginTop="50dp"
        android:backgroundTint="@drawable/btn_bg"
        android:text="添加"
        android:textColor="#006000"
        android:textSize="20dp"/>
    <Button
        android:id="@+id/btn_update"
        android:layout_width="120dp"
        android:layout_height="40dp"
        android:layout_marginLeft="80dp"
        android:layout_marginStart="80dp"
        android:layout_marginTop="120dp"
        android:backgroundTint="@drawable/btn_bg"
        android:text="更新"
        android:textColor="#006000"
        android:textSize="20dp"/>
    <Button
        android:id="@+id/btn_delete"
        android:layout_width="120dp"
        android:layout_height="40dp"
        android:layout_marginLeft="120dp"
        android:layout_marginStart="120dp"
        android:layout_marginTop="190dp"
        android:backgroundTint="@drawable/btn_bg"
        android:text="删除"
        android:textColor="#006000"
        android:textSize="20dp"/>
    <Button
        android:id="@+id/btn_select"
        android:layout_width="120dp"
        android:layout_height="40dp"
        android:layout_marginLeft="160dp"
        android:layout_marginStart="160dp"
        android:layout_marginTop="260dp"
        android:backgroundTint="@drawable/btn_bg"
        android:text="查询"
        android:textColor="#006000"
        android:textSize="20dp"/>

</RelativeLayout>

PersonDBOpenHelper.java

package cn.itcast.contentobserverdb;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabaseLockedException;
import android.database.sqlite.SQLiteOpenHelper;
public class PersonDBOpenHelper extends SQLiteOpenHelper
{
    public PersonDBOpenHelper(Context context)
    {
        super(context,"person.db",null,1);
    }
    public void onCreate(SQLiteDatabase db)
    {
        db.execSQL("create table info (_id integer primary key autoincrement,name varchar(20))");
    }
    public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion)
    {

    }
}

PersonProvider.java

package cn.itcast.contentobserverdb;
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 PersonProvider extends ContentProvider{
    private static UriMatcher mUriMatcher=new UriMatcher(-1);
    private static final int SUCCESS=1;
    private PersonDBOpenHelper helper;
    static {
        mUriMatcher.addURI("cn.itcast.service","info",SUCCESS);
    }
    public boolean onCreate()
    {
        helper=new PersonDBOpenHelper(getContext());
        return false;
    }
    public Cursor query(Uri uri,String[] projection,String selection,String[] selectionArgs,String sortOrder)
    {
        int code=mUriMatcher.match(uri);
        if(code==SUCCESS)
        {
            SQLiteDatabase db=helper.getReadableDatabase();
            return db.query("info",projection,selection,selectionArgs,null,null,sortOrder);
        }else {
            throw new IllegalArgumentException("路径不正确，我是不会给你提供数据的!");
        }
    }
    public Uri insert(Uri uri,ContentValues values)
    {
        int code=mUriMatcher.match(uri);
        if(code==SUCCESS)
        {
            SQLiteDatabase db=helper.getReadableDatabase();
            long rowId=db.insert("info",null,values);
            if(rowId>0)
            {
                Uri insertedUri=ContentUris.withAppendedId(uri,rowId);
                getContext().getContentResolver().notifyChange(insertedUri,null);
                return insertedUri;
            }
            db.close();
            return uri;
        }else {
            throw new IllegalArgumentException("路径不正确，我是不会给你插入数据的！");
        }
    }
    public int delete(Uri uri,String selection,String[] selectionArgs)
    {
        int code=mUriMatcher.match(uri);
        if(code==SUCCESS)
        {
            SQLiteDatabase db=helper.getWritableDatabase();
            int count=db.delete("info",selection,selectionArgs);

            if(count>0)
            {
                getContext().getContentResolver().notifyChange(uri,null);
            }
            db.close();
            return count;
        }else {
            throw new IllegalArgumentException("路径不正确，我是不会给你删除数据的！");
        }
    }
    public int update(Uri uri,ContentValues values,String selection,String[] selectionArgs)
    {
        int code=mUriMatcher.match(uri);
        if(code==SUCCESS)
        {
            SQLiteDatabase db=helper.getReadableDatabase();
            int count=db.update("info",values,selection,selectionArgs);
            if(count>0)
            {
                getContext().getContentResolver().notifyChange(uri,null);
            }
            db.close();
            return count;
        }else {
            throw new IllegalArgumentException("路径不正确，我是不会给你更新数据的！");
        }
    }
    public String getType(Uri uri)
    {
        return null;
    }

}

MainActivity.java（ContentObserverDB）

package cn.itcast.contentobserverdb;
import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private ContentResolver resolver;
    private Uri uri;
    private ContentValues values;
    private Button btnInsert;
    private Button btnUpdate;
    private Button btnDelete;
    private Button btnSelect;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();//初始化界面
        createDB();//创建数据库
    }
    private void initView(){
        btnInsert = (Button) findViewById(R.id.btn_insert);
        btnUpdate = (Button) findViewById(R.id.btn_update);
        btnDelete = (Button) findViewById(R.id.btn_delete);
        btnSelect = (Button) findViewById(R.id.btn_select);
        btnInsert.setOnClickListener(this);
        btnUpdate.setOnClickListener(this);
        btnDelete.setOnClickListener(this);
        btnSelect.setOnClickListener(this);
    }
    @Override
    public void onClick(View v){
        //得到一个内容提供者的解析对象
        resolver = getContentResolver();
        //新加一个Uri路径，参数是string类型
        uri = Uri.parse("content://cn.itcast.contentobserverdb/info");
        //新建一个ContentValues对象，该对象以key-values的形式添加记录到数据库表中
        values = new ContentValues();
        switch (v.getId()){
            case R.id.btn_insert:
                Random random = new Random();
                values.put("name","add_itcast" + random.nextInt(10));
                Uri newuri = resolver.insert(uri,values);
                Toast.makeText(this,"添加成功",Toast.LENGTH_SHORT).show();
                Log.i("数据库应用：","添加");
                break;
            case R.id.btn_delete:
                //返回删除数据的条目数
                int deleteCount = resolver.delete(uri,"name=?",new String[]{"itcast0"});
                Toast.makeText(this,"成功删除了"+deleteCount+"行",Toast.LENGTH_SHORT).show();
                Log.i("数据库应用：","删除");
                break;
            case R.id.btn_select:
                List<Map<String,String>> data = new ArrayList<Map<String,String>>();
                //返回查询结果，是一个指向结果集的游标
                Cursor cursor = resolver.query(uri,new String[]{"_id","name"},null,null,null);
                //遍历结果集中的数据，将每一条遍历的结果存储在一个List的集合中
                while (cursor.moveToNext()){
                    Map<String,String> map = new HashMap<String, String>();
                    map.put("_id",cursor.getString(0));
                    map.put("name",cursor.getString(1));
                    data.add(map);
                }
                //关闭游标，释放资源
                cursor.close();
                Log.i("数据库应用：","查询结果：" + data.toString());
                break;
            case R.id.btn_update:
                //将数据库info表中name为itcast1的这条记录更改为name是update_itcast
                values.put("name","update_itcast");
                int updateCount = resolver.update(uri,values,"name=?",new String[]{"itcast1"});
                Toast.makeText(this,"成功更新了" + updateCount + "行",Toast.LENGTH_SHORT).show();
                Log.i("数据库应用：","更新");
                break;
        }
    }
    private void createDB(){
        //创建数据库并向info表中添加3条数据
        PersonDBOpenHelper helper = new PersonDBOpenHelper(this);
        SQLiteDatabase db = helper.getWritableDatabase();
        for(int i = 0; i < 3; i++){
            ContentValues values = new ContentValues();
            values.put("name","itcast" + i);
            db.insert("info",null,values);
        }
        db.close();
    }
}

MainActivity.java(MonitorData)

package cn.itcast.monitordata;

import androidx.appcompat.app.AppCompatActivity;
import android.database.ContentObserver;
import android.net.Uri;
import android.os.Handler;
import android.util.Log;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //该Uri路径指向数据库应用中的数据库info表
        Uri uri = Uri.parse("content://cn.itcast.contentobserverdb/info");
        //注册内容观察者，参数uri指向要监测是数据库info表
        //参数true定义了监测的范围，最后一个参数是一个内容观察者对象
        getContentResolver().registerContentObserver(uri,true,new MyObserver(new Handler()));
    }
    private class MyObserver extends ContentObserver{
        public MyObserver(Handler handler){//handler是一个消息处理器
            super(handler);
        }
        @Override
        //当info表中的数据发生变化时执行该方法
        public void onChange(boolean selfChange){
            Log.i("监测数据变化","有人动了你的数据库！");
            super.onChange(selfChange);
        }
    }
}

界面效果：