郑州app开发android内容提供者访问其他应用的数据库。整个思路是这样的，一共需要建立两个项目，第一个是内容提供者自己的数据，另外一个项目是访问刚才内容提供者的数据。因为两个项目中，布局都是button按钮，所以在这里就不展示了。

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第一个内容提供者

MainActivity.java

package cn.xhhkj.cyd;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ComponentName;

import android.content.Intent;

import android.content.ServiceConnection;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.bundle;

import android.os.Ibinder;

import android.util.Log;

import android.view.View;

public class MainActivity extends AppCompatActivity {

    private SQLiteDatabase database;

    private static final String TAG = "结果是";

    @Override

    protected void onCreate(bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        MyOpenHelper helper = new MyOpenHelper(this);

        database = helper.getReadableDatabase();

    }

    public void insert(View view) {

        database.execSQL("insert into info(name,phone) values('王小明','13777777')");

        database.execSQL("insert into info(name,phone) values('赵小明','13888888')");

        database.execSQL("insert into info(name,phone) values('李大明','13666666')");

    }

    public void query(View view) {

        Cursor cursor = database.rawQuery("select * from info", null);

        while(cursor.moveToNext()){

            String name = cursor.getString(cursor.getColumnIndex("name"));

            String phone = cursor.getString(cursor.getColumnIndex("phone"));

            Log.d(TAG,"name="+name+"phone="+phone);

        }

        cursor.close();

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        database.close();

    }

}

MyOpenHelper.java 这个类是提供数据的类。

package cn.xhhkj.cyd;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

public class MyOpenHelper extends SQLiteOpenHelper {

    public MyOpenHelper(Context context) {

        super(context, "xhhkj.db", null, 1);

    }

    @Override

    public void onCreate(SQLiteDatabase db) {

        db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),phone varchar(20))");

        db.execSQL("alter table info add age integer");

    }

    @Override

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

    }

}

Myprovider.java

package cn.xhhkj.cyd;

import android.content.Contentprovider;

import android.content.ContentValues;

import android.content.UriMatcher;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.net.Uri;

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

public class Myprovider extends Contentprovider {

    private MyOpenHelper openHelper;

    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);

    private static final int QUERY_SUCESS = 0;

    private static final int INSERT_MATCHED = 1;

    private static final int UpDATE_MATCHED = 2;

    private static final int DELETE_MATCHED = 3;

    static

    {

        sURIMatcher.addURI("cn.xhhkj.provider", "query", QUERY_SUCESS);

        sURIMatcher.addURI("cn.xhhkj.provider", "insert", INSERT_MATCHED);

        sURIMatcher.addURI("cn.xhhkj.provider", "update", UpDATE_MATCHED);

        sURIMatcher.addURI("cn.xhhkj.provider", "delete", DELETE_MATCHED);

        //sURIMatcher.addURI("com.itheima.provider", "student", 5);

    }

    @Override

    public boolean onCreate() {

        openHelper = new MyOpenHelper(getContext());

        return false;

    }

    @Nullable

    @Override

    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {

        int result = sURIMatcher.match(uri);

        if(result == QUERY_SUCESS){

            SQLiteDatabase db = openHelper.getReadableDatabase();

            Cursor cursor = db.query("info", projection, selection, selectionArgs, null, null, sortOrder);

            return cursor;

        }else{

            throw new IllegalStateException("异常");

        }

    }

    @Nullable

    @Override

    public String getType(@NonNull Uri uri) {

        return null;

    }

    @Nullable

    @Override

    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {

        int result = sURIMatcher.match(uri);

        if(result==INSERT_MATCHED){

            SQLiteDatabase db = openHelper.getReadableDatabase();

            long insert = db.insert("info", null, values);

            getContext().getContentResolver().notifyChange(uri, null);

            return Uri.parse(String.valueOf(insert));

        }else{

            return null;

        }

    }

    @Override

    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {

        int result = sURIMatcher.match(uri);

        if(result==DELETE_MATCHED){

            SQLiteDatabase db = openHelper.getReadableDatabase();

            int delete = db.delete("info", selection, selectionArgs);

            return delete;

        }else{

            return -1;

        }

    }

    @Override

    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {

        int result = sURIMatcher.match(uri);

        if (result == UpDATE_MATCHED) {

            SQLiteDatabase db = openHelper.getReadableDatabase();

            int update = db.update("info", values, selection, selectionArgs);

            db.close();

            return update;

        } else {

            return -1;

        }

    }

}

这个类是真正的内容提供者。

另外一个项目，只是通过getContentResolver来查询内容提供者。

MainActivity.java

package cn.xhhkj.xhhkjtest;

import android.app.Activity;

import android.content.ContentResolver;

import android.database.Cursor;

import android.net.Uri;

import android.os.bundle;

import android.util.Log;

import android.view.View;

public class MainActivity extends Activity {

    private static final String TAG = "结果是";

    @Override

    protected void onCreate(bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

    public void query(View view) {

        ContentResolver contentResolver = getContentResolver();

        Uri uri =Uri.parse("content://cn.xhhkj.provider/query");

        Cursor cursor = contentResolver.query(uri, null, null, null, null);

        while(cursor.moveToNext()){

            String name = cursor.getString(cursor.getColumnIndex("name"));

            String phone = cursor.getString(cursor.getColumnIndex("phone"));

            Log.d(TAG,"name="+name+"phone="+phone);

        }

    }

}