自定义ContentProvider内容提供者

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一、自定义的内容提供者

1. 继承 ContentProvider

2. 实现增删改查方法以及 onCreate 方法

3. 制定 Uri 的网址规则，形成特定的功能

4. 四大组件都需要在清单文件注册，来确认内容提供者是否可以被其他程序访问

5. 内部需要进行数据的操作，增删改查

5.1 确认使用哪种数据类型：SQLite, File, SharedPreferences

5.2 onCreate 方法，需要初始化通常 DbHelper

5.3 每一个操作的方法，第一个参数都代表了需要操作的哪一张表。通过Uri来标示；

5.4 使用 UriMatcher 类对象，来进行网址匹配，判断访问那个表

关于 Uri 与 authorities 说明

Uri 就是一个网址

规则： content://<authority>/path

authority 代表的就是 Android 系统中内容提供者的唯一标示，就像服务器的IP地址

清单文件里面声明内容提供者的authority

http://www.baidu.com/images

http://www.baidu.com/news

二、创建自定义内容提供者

public class MyProvider extends ContentProvider {    private MyDbHelper mMyDbHelper;    public static final int CODES_CODE = 1;    public static final UriMatcher uriMatcher;    static {        uriMatcher = new UriMatcher(0);        uriMatcher.addURI("*","codes",CODES_CODE);    }    public MyProvider() {    }    @Override    public boolean onCreate() {        mMyDbHelper = new MyDbHelper(getContext());        return true;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection,                        String[] selectionArgs, String sortOrder) {        Cursor ret = null;        SQLiteDatabase database = mMyDbHelper.getWritableDatabase();        int code = uriMatcher.match(uri);        switch (code) {            case CODES_CODE:                ret = database.query("codes",projection,selection,selectionArgs,null,null,sortOrder);                break;        }        return ret;    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        int index = 0;        SQLiteDatabase database = mMyDbHelper.getWritableDatabase();        int code = uriMatcher.match(uri);        switch (code) {            case CODES_CODE:                index = database.delete("codes",selection,selectionArgs);                break;        }        database.close();        return index;    }    @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) {       Uri ret = null;        SQLiteDatabase database = mMyDbHelper.getWritableDatabase();        int codes = uriMatcher.match(uri);        switch (codes) {            case CODES_CODE:                long index = database.insert("codes", null, values);                ret = ContentUris.withAppendedId(uri,index);                break;        }        database.close();        return ret;    }    @Override    public int update(Uri uri, ContentValues values, String selection,                      String[] selectionArgs) {       int index = 0;        SQLiteDatabase database = mMyDbHelper.getWritableDatabase();        int code = uriMatcher.match(uri);        switch (code) {            case CODES_CODE:                index = database.update("codes", values, selection, selectionArgs);                break;        }        database.close();        return index;    }}

2.创建数据库

MyDbHelper.java

public class MyDbHelper extends SQLiteOpenHelper {    public static final String CODE_MANGER ="create table codes (" +            "_id integer primary key autoincrement," +            "title varchar," +            "webView varchar," +            "user varchar," +            "pass varchar," +            "remark long," +            "update_t long)";    public MyDbHelper(Context context){        super(context,"manger",null,1);    }    @Override    public void onCreate(SQLiteDatabase db) {                db.execSQL(CODE_MANGER);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        //db.execSQL("alter table income add column type integer default 0");        if (newVersion ==2){            db.execSQL("alter table codes add column update_t long default 0");        }    }}

3.Activity调用数据库的数据

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemLongClickListener, AdapterView.OnItemClickListener {    private TextView mTitle;    private TextView mUser;    private SimpleCursorAdapter mAdapter;    private ListView mListView;    private Cursor cursor;    private SQLiteDatabase mDatabase;    private ContentResolver mResolver;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);//        MyDbHelper helper = new MyDbHelper(this);//        mDatabase = helper.getWritableDatabase();        mTitle = (TextView) findViewById(R.id.db_title);        mUser = (TextView) findViewById(R.id.db_username);        mResolver = getContentResolver();        Uri uri = Uri.parse("content://abc/codes");        cursor = mResolver.query(uri, null, null, null, "remark desc");        if (cursor != null){            mAdapter = new SimpleCursorAdapter(this,                    R.layout.db_item,cursor,                    new String[]{"title","user"},                    new int[]{R.id.db_title,R.id.db_username},                    CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);            mListView = (ListView) findViewById(R.id.main_list);            RequeryData();            mListView.setAdapter(mAdapter);            mListView.setOnItemLongClickListener(this);            mListView.setOnItemClickListener(this);        }    }//    @Override//    protected void onStart() {//        super.onStart();//        RequeryData();//    }    @Override    protected void onResume() {        super.onResume();        RequeryData();    }    private void RequeryData() {        Uri uri = Uri.parse("content://abc/codes");        cursor = mResolver.query(uri, null, null, null, "remark desc");        mAdapter.changeCursor(cursor);        //mAdapter.notifyDataSetChanged();    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        getMenuInflater().inflate(R.menu.menu_item,menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        switch (item.getItemId()) {            case R.id.action_edit:                Toast.makeText(MainActivity.this, "edit被点击", Toast.LENGTH_SHORT).show();                int id = cursor.getColumnIndex("_id");                break;            case R.id.action_add:                Toast.makeText(MainActivity.this, "add被点击了", Toast.LENGTH_SHORT).show();                Intent intent = new Intent(this, EditActivity.class);                startActivity(intent);                break;        }        return true;    }    @Override    public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {        Intent intent = new Intent(this,EditActivity.class);        intent.putExtra("_id",id);        startActivity(intent);        return true;    }    @Override    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        Intent intent = new Intent(this, InfoActivity.class);        intent.putExtra("_id", id);        startActivity(intent);    }}

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