ep3 Content Provider

1.作业内容

1、contentprovider是安卓四大组件之一，请使用其方法类进行数据获取；
2、请自建一个provider，然后在另一个app中使用resolver调用这个provider。
3、本次作业请启用新项目，理论上需要两个APP进行实验。

2.作业目标

1、ContentProvider可以帮助应用程序管理对自己存储的数据的访问，由其他应用存储，并提供与其他应用共享数据的方法。它们封装了数据，并提供定义数据安全性的机制。内容提供商是标准将一个进程中的数据与另一个进程中运行的代码连接起来的接口。
2、在本次实验中实现resolver中调用调用provider的insert方法，在provider中创建的数据库中进行增操作。

3.核心代码

provider中实现数据库的创建和基本操作，并定义

1.provider app

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

        MyDAO myDAO=new MyDAO(this);
    }
}

数据库部分

Mydbhelper.java:定义数据库，创建学生表

public class Mydbhelper extends SQLiteOpenHelper {
    public Mydbhelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL("create table student(" +
                "id integer primary key autoincrement,name varchar,age integer)");
        Log.d("dolly","onCreate...");
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        Log.d("dolly","onUpgrade...");
    }
}

MyDAO.java:数据库操作类

public class MyDAO {
    private Context context;
    private SQLiteDatabase database;
    public MyDAO(Context context){
        this.context=context;

        Mydbhelper dBhelper =new Mydbhelper(context,"dollyDB",null,1);
        database=dBhelper.getReadableDatabase();
    }

    public Uri DAOinsert(ContentValues contentValues) {
        long rowid = database.insert("student", null, contentValues);

        Uri uri = Uri.parse("content://dolly.provider2/student");
        Uri inserturi = ContentUris.withAppendedId(uri, rowid);
        context.getContentResolver().notifyChange(inserturi, null);
        return inserturi;

        }
    }

MyContentProvider.java: 提供insert方法供resovler使用

public class MyContentProvider extends ContentProvider {
    private MyDAO myDAO;
    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.
        return  myDAO.DAOinsert(values);
    }

    @Override
    public boolean onCreate() {
        // TODO: Implement this to initialize your content provider on startup.
        Context context=getContext();
        myDAO=new MyDAO(context);
        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.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @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");
    }
}

2.resovler app

** MainActivity.java**

public class MainActivity extends AppCompatActivity {

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

        ContentResolver resolver=getContentResolver();

        ContentValues values=new ContentValues();
        values.put("name","dolly");
        values.put("age",20);

        Uri uri=Uri.parse("content://dolly.provider2/student");

        Button button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                resolver.insert(uri,values);
            }
        });

    }
}