ContentProvider使用例子

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ContentProvider的简单例子

public class FirewallManagerProvider extends ContentProvider {    private final static UriMatcher mUriMatcher;    private static final int MATCH_CODE_MOBILE = 1;    private static final int MATCH_CODE_WIFI = 2;    public static final String AUTHORITY = "com.example.contentproviderdemo.provider.FirewallManagerProvider";    public static final Uri CONTENT_URI_FIREWALL_MOBILE = Uri            .parse("content://" + AUTHORITY + "/"                    + FirewallDatabaseHelper.MOBILE_TABLE);    public static final Uri CONTENT_URI_FIREWALL_WIFI = Uri.parse("content://"            + AUTHORITY + "/" + FirewallDatabaseHelper.WIFI_TABLE);    static {        mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        mUriMatcher.addURI(AUTHORITY, FirewallDatabaseHelper.MOBILE_TABLE,                MATCH_CODE_MOBILE);        mUriMatcher.addURI(AUTHORITY, FirewallDatabaseHelper.WIFI_TABLE,                MATCH_CODE_WIFI);    }    private FirewallDatabaseHelper mHelper;    @Override    public boolean onCreate() {        mHelper = FirewallDatabaseHelper.getInstance(getContext()                .getApplicationContext());        return false;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection,            String[] selectionArgs, String sortOrder) {        return null;    }    @Override    public String getType(Uri uri) {        return null;    }    @Override    public Uri insert(Uri uri, ContentValues values) {        SQLiteDatabase db = mHelper.getWritableDatabase();        long rowId;        Uri result = null;        switch (mUriMatcher.match(uri)) {        case MATCH_CODE_MOBILE:            // 插入后返回的是当前所在的行号            rowId = db.insert(FirewallDatabaseHelper.MOBILE_TABLE, null, values);            if (rowId > 0) {                // 将行号添加到URI的末尾，做为结果返回                result = ContentUris.withAppendedId(CONTENT_URI_FIREWALL_MOBILE, rowId);                getContext().getContentResolver().notifyChange(uri, null);            }            break;        case MATCH_CODE_WIFI:            rowId = db.insert(FirewallDatabaseHelper.WIFI_TABLE, null, values);            if (rowId > 0) {                result = ContentUris.withAppendedId(CONTENT_URI_FIREWALL_WIFI, rowId);                getContext().getContentResolver().notifyChange(uri, null);            }            break;        default:            throw new IllegalArgumentException("Unknown URI " + uri);        }        return result;    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        return 0;    }    @Override    public int update(Uri uri, ContentValues values, String selection,            String[] selectionArgs) {        return 0;    }}

FirewallDatabaseHellper：

public class FirewallDatabaseHelper extends SQLiteOpenHelper {    private static final String DATABASE_NAME = "firewall.db";    private static final int DATABASE_VERSION = 1;    public static final String MOBILE_TABLE = "mobile";    public static final String WIFI_TABLE = "wifi";    private static FirewallDatabaseHelper mInstance;    public static synchronized FirewallDatabaseHelper getInstance(Context context) {        if (mInstance == null) {            mInstance = new FirewallDatabaseHelper(context);        }        return mInstance;    }    private FirewallDatabaseHelper(Context context) {        super(context, DATABASE_NAME, null, DATABASE_VERSION);    }    public FirewallDatabaseHelper(Context context, String name,            CursorFactory factory, int version) {        super(context, name, factory, version);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("create table if not exists mobile ("                + " _id integer primary key autoincrement ,"                + " pkg_name text unique not null ,"                + " uid int " + ");");        db.execSQL("create table if not exists wifi ("                + " _id integer primary key autoincrement ,"                + " pkg_name text unique not null ,"                + " uid int " + ");");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

provider在Manifest中的注册：

添加自定义权限，注意是permission：

<permission    android:name="com.example.contentproviderdemo.provider.FirewallManagerProvider"    android:protectionLevel="normal" ></permission>

<provider    android:name="com.example.contentproviderdemo.provider.FirewallManagerProvider"    android:authorities="com.example.contentproviderdemo.provider.FirewallManagerProvider"    android:exported="true"    android:permission="com.example.contentproviderdemo.provider.FirewallManagerProvider" ></provider>

第三方应用调用以及监听数据库变化：

public class MainActivity extends Activity {    public static final String AUTHORITY = "com.example.contentproviderdemo.provider.FirewallManagerProvider";    public static final Uri CONTENT_URI_FIREWALL_MOBILE = Uri            .parse("content://" + AUTHORITY + "/mobile");    public static final Uri CONTENT_URI_FIREWALL_WIFI = Uri.parse("content://"            + AUTHORITY + "/wifi");    private MyContentObserver myContentObserver;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button button1 = (Button) findViewById(R.id.button1);        button1.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                insertData();            }        });        ContentResolver resolver = getContentResolver();        myContentObserver = new MyContentObserver(new Handler());        // notifyForDescendents: 为false时，表示精确匹配，为true时，表示可以同时匹配其派生的URI        resolver.registerContentObserver(CONTENT_URI_FIREWALL_MOBILE, false,                myContentObserver);    }    private class MyContentObserver extends ContentObserver {        public MyContentObserver(Handler handler) {            super(handler);        }        @Override        public void onChange(boolean selfChange) {            super.onChange(selfChange);            System.out.println("数据库发生了变化");        }    }    private void insertData() {        ContentValues values = new ContentValues();        values.put("pkg_name", "cn.hehe");        values.put("uid", 10013);        try {            Uri insertUri = getContentResolver().insert(                    CONTENT_URI_FIREWALL_MOBILE, values);            long rowId = ContentUris.parseId(insertUri);            if (rowId > 0) {                System.out.println("插入成功");            }        } catch (Exception e) {            e.printStackTrace();        }    }    @Override    protected void onDestroy() {        super.onDestroy();        getContentResolver().unregisterContentObserver(myContentObserver);    }}

Manifest中需要添加权限，注意是uses-permission：

<uses-permission android:name="com.example.contentproviderdemo.provider.FirewallManagerProvider" />

provider节点下exported属性的说明：

这个属性用于指示该provider算法能被其他应用程序调用或进行交互。设置为true，则能够被调用或交互；设置为false时，只有同一个应用程序的组件或者带有相同用户ID的应用程序才能调用。

provider节点下可以声明的权限相关属性有：readPermission、writePermission、permission。

readPermission:使用Content Provider的查询功能所必需的权限，即调用ContentProvider里面的query()方法的权限。

writePermission:使用Content Provider的修改功能所必需的权限，即调用insert()、delete()、update()方法的权限。

permission:客户端读、写Content Provider中数据所必需的权限名称。本属性为一次性设置读和写权限提供了快捷途径。不过，readPermission和writePermission属性优先于本属性。即如果同时设置了readPermission属性和permission权限，则声明readPermission权限的应用才能读取。

SQLiteQueryBuilder中的setProjectionMap,

这里的ProjectionMap必须是一个hashmap,更重要的是：

If a projection map is set it must contain all column names the user may request, even if the key and value are the same

qb.setProjectionMap(sCallsProjectionMap);

这个函数的作用是在qb里设置数据库字段的别名，即用户定义列名->数据库列名，在执行qb.query时可以使用用户定义列名设置projection、selection等。

如果不需要对列名进行映射，可以不调用这个函数。但是如果调用，必须对所有列都进行映射，映射中key和value可以完全相同。

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