一、排坑
二、内容提供者
- 应用的数据库是不允许其他应用访问的
- 内容提供者的作用就是让别的应用访问到你的数据库
-
自定义内容提供者,继承ContentProvider类,重写增删改查方法,在方法中写增删改查数据库的代码,
- 在清单文件中定义内容提供者的标签,注意必须要有authorities属性,这是内容提供者的主机名,功能类似地址
- 创建一个其他应用,访问自定义的内容提供者,实现对数据库的插入操作
提供者
public class PersonProvider extends ContentProvider { private MyOpenHelper oh; SQLiteDatabase db; //创建uri匹配器对象 static UriMatcher um = new UriMatcher(UriMatcher.NO_MATCH); //检测其他用户传入的uri与匹配器定义好的uri中,哪条匹配 static { um.addURI("com.itheima.people", "person", 1);//content://com.itheima.people/person um.addURI("com.itheima.people", "teacher", 2);//content://com.itheima.people/teacher um.addURI("com.itheima.people", "person/#", 3);//content://com.itheima.people/person/4 } //内容提供者创建时调用 @Override public boolean onCreate() { oh = new MyOpenHelper(getContext()); db = oh.getWritableDatabase(); return false; } @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { Cursor cursor = null; if(um.match(uri) == 1){ cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder, null); } else if(um.match(uri) == 2){ cursor = db.query("teacher", projection, selection, selectionArgs, null, null, sortOrder, null); } else if(um.match(uri) == 3){ //把uri末尾携带的数字取出来 long id = ContentUris.parseId(uri); cursor = db.query("person", projection, "_id = ?", new String[]{id + ""}, null, null, sortOrder, null); } else{ throw new IllegalArgumentException("uri又有问题哟亲么么哒"); } return cursor; } @Override public String getType(Uri uri) { if(um.match(uri) == 1){ return "vnd.android.cursor.dir/person"; } else if(um.match(uri) == 3){ return "vnd.android.cursor.item/person"; } return null; } //此方法供其他应用调用,用于往people数据库里插数据 //values:由其他应用传入,用于封装要插入的数据 //uri:内容提供者的主机名,也就是地址 @Override public Uri insert(Uri uri, ContentValues values) { //使用uri匹配器匹配传入的uri if(um.match(uri) == 1){ db.insert("person", null, values); //发送数据改变的通知 //uri:通知发送到哪一个uri上,所有注册在这个uri上的内容观察者都可以收到这个通知 getContext().getContentResolver().notifyChange(uri, null); } else if(um.match(uri) == 2){ db.insert("teacher", null, values); getContext().getContentResolver().notifyChange(uri, null); } else{ throw new IllegalArgumentException("uri有问题哟亲么么哒"); } return uri; } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { int i = db.delete("person", selection, selectionArgs); return i; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { int i = db.update("person", values, selection, selectionArgs); return i; } }
public class MyOpenHelper extends SQLiteOpenHelper { public MyOpenHelper(Context context) { super(context, "people.db", null, 2); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { db.execSQL("create table person(_id integer primary key autoincrement, name varchar(10), money integer(20))"); db.execSQL("create table teacher(_id integer primary key autoincrement, name varchar(10))"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub db.execSQL("create table teacher(_id integer primary key autoincrement, name varchar(10))"); } }
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.index42.customcontentprovider"> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <provider android:name=".provider.PersonProvider" android:authorities="com.itheima.people" android:exported="true" ></provider> </application> </manifest>