ContentProvider，Android四大元件之一，主要用於不同程式間的資料互動功能 Uri（通用資源識別符號 Universal Resource Identifer），代表資料操作的地址，每一個ContentProvider釋出資料時都會有唯一的地址。 建立自定義ContentProvider： 1.使用SQLite技術，建立好資料庫和資料表 2.新建類繼承ContentProvider

public class DatabaseProvider extends ContentProvider {
3.重寫6個抽象方法 
    private MyDBHelpter myDBHelpter;
    private static final String TAG = "DatabaseProvider";

    //新增整形常亮
    public static final int USER_DIR = 0;
    public static final int USER_ITEM = 1;
    //建立authority
    public static final String AUTHORITY = "com.example.administrator.databasetest.provider";
      4.建立UriMatcher，定義Uri規則 
    //建立UriMatcher物件
    private static UriMatcher uriMatcher;

    //建立靜態程式碼塊
    static {
        //例項化UriMatcher物件
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        //可以實現匹配URI的功能
        //引數1：authority 引數2：路徑 引數3：自定義程式碼
        uriMatcher.addURI(AUTHORITY, "userdemo", USER_DIR);
        uriMatcher.addURI(AUTHORITY, "userdemo/#", USER_ITEM);
    }

    public DatabaseProvider() {
        Log.e(TAG, "DatabaseProvider: ");
    }
    //onCreate()方法
    @Override
    public boolean onCreate() {
        //實現建立MyDBHelpter物件
        myDBHelpter = new MyDBHelpter(getContext(), "userdbdemo", null, 1);
        return true;
    }

    //刪除資料表資料
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        //建立SQLiteDatabase物件
        SQLiteDatabase db = myDBHelpter.getWritableDatabase();
        int deleteInt = 0;
        //匹配uri
        switch (uriMatcher.match(uri)) {
            case USER_DIR:
                //引數1：表名   引數2：約束刪除列的名字   引數3：具體行的值
                deleteInt = db.delete("userdemo", selection, selectionArgs);
                break;
            case USER_ITEM:
                String deleteId = uri.getPathSegments().get(1);
                deleteInt = db.delete("userdemo", "id=?", new String[]{deleteId});
                break;
            default:
        }

        return deleteInt;
    }

    //插入資料
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = myDBHelpter.getWritableDatabase();
        switch (uriMatcher.match(uri)) {
            case USER_DIR:
            case USER_ITEM:
                //引數1：表名  引數2：沒有賦值的設為空   引數3：插入值
                long newUserId = db.insert("userdemo", null, values);
                break;
            default:
                break;
        }
        return null;
    }

    //查詢資料
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        SQLiteDatabase db = myDBHelpter.getWritableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
            case USER_DIR:
                //引數1：表名  其他引數可借鑑上面的介紹
                cursor = db.query("userdemo", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            case USER_ITEM:
                String queryId = uri.getPathSegments().get(1);
                cursor = db.query("userdemo", projection, "id=?", new String[]{queryId}, null, null, sortOrder);
                break;
            default:
        }
        return cursor;

    }

    //更新資料
    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {

        SQLiteDatabase db = myDBHelpter.getWritableDatabase();
        int updateRow = 0;
        switch (uriMatcher.match(uri)) {
            case USER_DIR:
                updateRow = db.update("userdemo",values,selection,selectionArgs);
                break;
            case USER_ITEM:
                String updateId = uri.getPathSegments().get(1);
                updateRow = db.update("userdemo",values,"id=?",new String[]{updateId});

                break;
            default:
        }
        return updateRow;
    }

    @Override
    public String getType(Uri uri) {
        throw new UnsupportedOperationException("Not yet implemented");
    }
}


  5.在Manifest中註冊provider 
  

 

6.ContentResolver對ContentProvider中共享的資料進行增刪改查操作

public class MainActivity extends AppCompatActivity implements View.OnClickListener{


    private Button insertBtn;
    private EditText editText;
    private Button deleteBtn;
    private  Button queryBtn;
    private Button updateBtn;

    private  String newId;

    private static final String TAG = "MainActivity";


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

        bangID();
    }

    private void bangID() {
        insertBtn = findViewById(R.id.main_insert_btn);
        editText = findViewById(R.id.main_et);
        deleteBtn = findViewById(R.id.main_delete_btn);
        queryBtn = findViewById(R.id.main_query_btn);
        updateBtn = findViewById(R.id.main_update_btn);


        insertBtn.setOnClickListener(this);
        deleteBtn.setOnClickListener(this);
        queryBtn.setOnClickListener(this);
        updateBtn.setOnClickListener(this);


    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.main_insert_btn:
                String name = editText.getText().toString();
                //建立期待匹配的uri
                Uri uri1 = Uri.parse("content://com.example.administrator.databasetest.provider/userdemo");
                ContentValues values = new ContentValues();
                values.put("name",name);
                //獲得ContentResolver物件，呼叫方法
                getContentResolver().insert(uri1,values);
                break;
            case R.id.main_delete_btn:
                String name1 = editText.getText().toString();
                Uri uri2 = Uri.parse("content://com.example.administrator.databasetest.provider/userdemo");
                getContentResolver().delete(uri2,"name=?",new String[]{name1});
                break;
            case R.id.main_query_btn:
                Uri uri = Uri.parse("content://com.example.administrator.databasetest.provider/userdemo");
                Cursor cursor = getContentResolver().query(uri,null,null,null,null);
                cursor.moveToFirst();
                do{
                    String name2 = cursor.getString(cursor.getColumnIndex("name"));
                    Log.e(TAG, "onClick: "+name2 );

                }while(cursor.moveToNext());
                cursor.close();
                break;
            case R.id.main_update_btn:
                String updateStr = editText.getText().toString();
                Uri uri3 =Uri.parse("content://com.example.administrator.databasetest.provider/userdemo");
                ContentValues values1 = new ContentValues();
                values1.put("name",updateStr);
                getContentResolver().update(uri3,values1,"name=?",new String[]{""});
                break;
            default:
        }

    }
}