设计目标

contentprovider是安卓四大组件之一，使用其方法类进行数据获取

通过contentprovider实现在不同软件之间的数据传输

通过uri来标识其它应用要访问的数据，通过ContentResolver的增、删、改、查方法实现对共享数据的操作。

还可以通过注册ContentObserver来监听数据是否发生了变化来对应的刷新页面。

URI（Universal Resource Identifier）统一资源定位符

代码

provider

MyDAO

 1 package com.example.provider;
 2 
 3 import android.content.ContentUris;
 4 import android.content.ContentValues;
 5 import android.content.Context;
 6 import android.database.sqlite.SQLiteDatabase;
 7 import android.net.Uri;
 8 
 9 public class MyDAO {
10     private Context context;
11     private SQLiteDatabase database;
12 
13     public MyDAO(Context context) {
14         this.context = context;
15         MyDBhelper dBhelper = new MyDBhelper(context, "testDB", null, 1);
16         database = dBhelper.getWritableDatabase();
17     }
18 
19     public Uri DAOinsert(ContentValues contentValues) {
20         long rowid=database.insert("student", null, contentValues);
21 //        Uri uri=Uri.parse("content://test.provider2/student/10");//取第10行
22         Uri uri=Uri.parse("content://test.provider2");
23         Uri inserturi=ContentUris.withAppendedId(uri,rowid);
24         context.getContentResolver().notifyChange(inserturi,null);
25         return inserturi;
26     }
27 
28 }

MyDBhelper

 1 package com.example.provider;
 2 
 3 import android.content.Context;
 4 import android.database.sqlite.SQLiteDatabase;
 5 import android.database.sqlite.SQLiteOpenHelper;
 6 import android.util.Log;
 7 
 8 import androidx.annotation.Nullable;
 9 
10 public class MyDBhelper extends SQLiteOpenHelper {
11     public MyDBhelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
12         super(context, name, factory, version);
13     }
14 
15     @Override
16     public void onCreate(SQLiteDatabase sqLiteDatebase) {
17 //        SQLiteDatabase sqLiteDatebase = null;
18         sqLiteDatebase.execSQL("create table student(" +
19                 "id integer primary key autoincrement,name varchar(20),age integer)");
20     }
21     @Override
22     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
23 
24     }
25 }

MainActivity

 1 package com.example.provider;
 2 
 3 import androidx.appcompat.app.AppCompatActivity;
 4 
 5 import android.os.Bundle;
 6 
 7 public class MainActivity extends AppCompatActivity {
 8 
 9     @Override
10     protected void onCreate(Bundle savedInstanceState) {
11         super.onCreate(savedInstanceState);
12         setContentView(R.layout.activity_main);
13 
14 
15         MyDAO myDAO=new MyDAO(this);
16     }
17 }

MyContentProvider

 1 package com.example.provider;
 2 
 3 import android.content.ContentProvider;
 4 import android.content.ContentValues;
 5 import android.content.Context;
 6 import android.database.Cursor;
 7 import android.net.Uri;
 8 
 9 public class MyContentProvider extends ContentProvider {
10     private MyDAO myDAO;
11 
12     public MyContentProvider() {
13 
14 
15     }
16 
17     @Override
18     public int delete(Uri uri, String selection, String[] selectionArgs) {
19         // Implement this to handle requests to delete one or more rows.
20         throw new UnsupportedOperationException("Not yet implemented");
21     }
22 
23     @Override
24     public String getType(Uri uri) {
25 
26         // TODO: Implement this to handle requests for the MIME type of the data
27         // at the given URI.
28         throw new UnsupportedOperationException("Not yet implemented");
29     }
30 
31     @Override
32     public Uri insert(Uri uri, ContentValues values) {
33 
34         return myDAO.DAOinsert(values);
35         // TODO: Implement this to handle requests to insert a new row.
36 //        throw new UnsupportedOperationException("Not yet implemented");
37     }
38 
39     @Override
40     public boolean onCreate() {
41 
42         Context context=getContext();
43         myDAO=new MyDAO(context);
44         // TODO: Implement this to initialize your content provider on startup.
45         return false;
46     }
47 
48     @Override
49     public Cursor query(Uri uri, String[] projection, String selection,
50                         String[] selectionArgs, String sortOrder) {
51         // TODO: Implement this to handle query requests from clients.
52         throw new UnsupportedOperationException("Not yet implemented");
53     }
54 
55     @Override
56     public int update(Uri uri, ContentValues values, String selection,
57                       String[] selectionArgs) {
58         // TODO: Implement this to handle requests to update one or more rows.
59         throw new UnsupportedOperationException("Not yet implemented");
60     }
61 }

resolver

MainActivity

 1 package com.example.resolver;
 2 
 3 import androidx.appcompat.app.AppCompatActivity;
 4 
 5 import android.content.ContentResolver;
 6 import android.content.ContentValues;
 7 import android.net.Uri;
 8 import android.os.Bundle;
 9 import android.view.View;
10 import android.widget.Button;
11 
12 public class MainActivity extends AppCompatActivity {
13 
14     @Override
15     protected void onCreate(Bundle savedInstanceState) {
16         super.onCreate(savedInstanceState);
17         setContentView(R.layout.activity_main);
18         ContentResolver resolver=getContentResolver();
19         Button button=findViewById(R.id.button);
20 
21         ContentValues values=new ContentValues();
22         values.put("name","myinsert");
23         values.put("age",99);
24 
25         Uri uri=Uri.parse("content://test.provider2/student");
26 
27         button.setOnClickListener(new View.OnClickListener() {
28             @Override
29             public void onClick(View v) {
30                 resolver.insert(uri,values);
31 
32             }
33         });
34     }
35 }

运行结果

项目地址

https://github.com/yoyo-sanchez/yoyo/tree/main/contentProvider