android ContentProvider實現資源共用執行個體

標籤：android   contentprovider   

ContentProvider為儲存和讀取資料提供了統一的介面，使用ContentProvider，應用程式可以實現資料共用，android內建的許多資料都是使用ContentProvider形式，供開發人員調用的(如視頻，音頻，圖片，通訊錄等)。

本執行個體將SQLite作為儲存資料的方式。

Activity代碼：

protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_content_provider);insertButton = (Button) findViewById(R.id.insertButton);updateButton = (Button) findViewById(R.id.updateButton);deleteButton = (Button) findViewById(R.id.deleteButton);queryButton = (Button) findViewById(R.id.queryButton);insertButton.setOnClickListener(new InsertListener());updateButton.setOnClickListener(new UpdateListener());deleteButton.setOnClickListener(new DeleteListener());queryButton.setOnClickListener(new QueryListener());}class InsertListener implements OnClickListener {@Overridepublic void onClick(View v) {ContentValues[] values = new ContentValues[2];ContentValues value = new ContentValues();value.put(CPMetadata.users.NAME, "張三");value.put(CPMetadata.users.AGE, 12);values[0] = value;value = new ContentValues();value.put(CPMetadata.users.NAME, "李四");value.put(CPMetadata.users.AGE, 11);values[1] = value;//多條插入，調用DemoProvider的insert()，每條調用一次，結果返回成功行數int count = getContentResolver().bulkInsert(CPMetadata.users.CONTENT_URI, values);// 插入單條資料// Uri uri =// getContentResolver().insert(CPMetadata.users.CONTENT_URI, values);// Log.d("ContentProvider", "uri : " + uri);Log.d("ContentProvider", "count : " + count);}}class UpdateListener implements OnClickListener {@Overridepublic void onClick(View v) {//要更新的資料ContentValues values = new ContentValues();values.put(CPMetadata.users.NAME, "趙六");values.put(CPMetadata.users.AGE, 22);//根據ID更新，ContentUris.withAppendedId() 方法在URI的結尾追加一個1Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 1);int count = getContentResolver().update(uri, values, null, null);Log.d("ContentProvider", "update rows : " + count);}}class DeleteListener implements OnClickListener {@Overridepublic void onClick(View v) {//根據ID刪除，ContentUris.withAppendedId() 方法在URI的結尾追加一個2Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 2);int count = getContentResolver().delete(uri, null, null);Log.d("ContentProvider", "delete rows : " + count);}}class QueryListener implements OnClickListener {@Overridepublic void onClick(View v) {//根據ID查詢使用此uri，ContentUris.withAppendedId() 方法在URI的結尾追加一個1//Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 1);//更新和刪除資料使用where子句方法同理Cursor cursor = getContentResolver().query(CPMetadata.users.CONTENT_URI, null, CPMetadata.users.NAME + "=?", new String[]{"張三"}, CPMetadata.users._ID + " desc");//根據遊標列印查詢結果while (cursor.moveToNext()) {String id = cursor.getString(cursor.getColumnIndex(CPMetadata.users._ID));String name = cursor.getString(cursor.getColumnIndex(CPMetadata.users.NAME));String age = cursor.getString(cursor.getColumnIndex(CPMetadata.users.AGE));Log.d("ContentProvider", "ID : " + id + "  NAME : " + name + "  AGE : " + age);}cursor.close();}}

CPMetadata代碼：

public class CPMetadata {public static final String AUTHORITY = "com.example.olds1_contentprovider.DemoProvider";public static final String DATABASE_NAME = "DemoProviderDB";public static final int DATABASE_VERSION = 1;public static final int CONTENT = 1;public static final int CONTENT_ITEM = 2;public static final class users implements BaseColumns {public static final String TABLE_NAME = "users";public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/users");public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.demoprovider.user";public static final String CONTENT_TYPE_ITEM = "vnd.android.cursor.item/vnd.demoprovider.user";public static final String NAME = "name";public static final String AGE = "age";}}

DBHelper代碼：

public class DBHelper extends SQLiteOpenHelper{public DBHelper(Context context) {super(context, CPMetadata.DATABASE_NAME, null, CPMetadata.DATABASE_VERSION);// TODO Auto-generated constructor stub}@Overridepublic void onCreate(SQLiteDatabase db) {StringBuffer sql = new StringBuffer();sql.append("create table " + CPMetadata.users.TABLE_NAME + "(");sql.append(CPMetadata.users._ID + " integer primary key autoincrement,");sql.append(CPMetadata.users.NAME + " varchar(20),");sql.append(CPMetadata.users.AGE + " integer);");db.execSQL(sql.toString());}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stub}}

public class DemoProvider extends ContentProvider {private DBHelper helper;private SQLiteDatabase db;private static final UriMatcher uriMatcher;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(CPMetadata.AUTHORITY, CPMetadata.users.TABLE_NAME, CPMetadata.CONTENT);uriMatcher.addURI(CPMetadata.AUTHORITY, CPMetadata.users.TABLE_NAME + "/#",CPMetadata.CONTENT_ITEM);}@Overridepublic boolean onCreate() {helper = new DBHelper(getContext());db = helper.getWritableDatabase();return true;}@Overridepublic String getType(Uri uri) {switch (uriMatcher.match(uri)) {case CPMetadata.CONTENT:return CPMetadata.users.CONTENT_TYPE;case CPMetadata.CONTENT_ITEM:return CPMetadata.users.CONTENT_TYPE_ITEM;default:throw new IllegalArgumentException("unknown URI:" + uri);}}/** * 整理where子句 * 條件分為有ID和無ID兩種，ID為主鍵具有唯一性，不用添加其他條件 * 無ID則使用傳入的條件處理 * @param uri * @param selection * @return */public String getWhereStr(Uri uri, String selection){String whereStr;switch (uriMatcher.match(uri)) {case CPMetadata.CONTENT:whereStr = selection;break;case CPMetadata.CONTENT_ITEM:whereStr = CPMetadata.users._ID + "=" + uri.getPathSegments().get(1);break;default:throw new IllegalArgumentException("unknown URI :" + uri);}return whereStr;}@Overridepublic Uri insert(Uri uri, ContentValues values) {long rowid = db.insert(CPMetadata.users.TABLE_NAME, null, values);if (rowid > 0) {Uri insertUri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, rowid);getContext().getContentResolver().notifyChange(insertUri, null);Log.d("ContentProvider", "Insert Success  :" + insertUri);return insertUri;}throw new IllegalArgumentException("unknown URI: " + uri);}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {int count = 0;String  whereStr = getWhereStr(uri, selection);Log.d("ContentProvider", "Delete Where  :" + whereStr);count = db.delete(CPMetadata.users.TABLE_NAME, whereStr, selectionArgs);getContext().getContentResolver().notifyChange(uri, null);return count;}@Overridepublic int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {int count = 0;String  whereStr = getWhereStr(uri, selection);Log.d("ContentProvider", "Update Where  :" + whereStr);count = db.update(CPMetadata.users.TABLE_NAME, values, whereStr, selectionArgs);getContext().getContentResolver().notifyChange(uri, null);return count;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,String sortOrder) {Cursor cursor;String  whereStr = getWhereStr(uri, selection);Log.d("ContentProvider", "Query Where  :" + whereStr);cursor = db.query(CPMetadata.users.TABLE_NAME, projection, whereStr, selectionArgs, null, null, sortOrder);cursor.setNotificationUri(getContext().getContentResolver(), uri);return cursor;}

註冊ContentProvider，紅色部分表示是否允許外部應用訪問，必須設定

<span style="color:#4b4b4b;"><provider            android:name="DemoProvider"            android:authorities="com.example.olds1_contentprovider.DemoProvider"             </span><span style="color:#ff0000;">android:exported="true"</span><span style="color:#4b4b4b;">>        </provider></span>

建立一個test工程，

效果：

Activity代碼如下：

private Button button;private TextView textView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.button);        textView = (TextView)findViewById(R.id.textView);        button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {String uriStr = "content://com.example.olds1_contentprovider.DemoProvider/users";Uri uri = Uri.parse(uriStr);Cursor cursor = getContentResolver().query(uri, null, "name=?", new String[]{"張三"}, null);StringBuffer show = new StringBuffer();//根據遊標列印查詢結果while (cursor.moveToNext()) {String id = cursor.getString(cursor.getColumnIndex("_id"));String name = cursor.getString(cursor.getColumnIndex("name"));String age = cursor.getString(cursor.getColumnIndex("age"));show.append("ID : " + id + "  NAME : " + name + "  AGE : " + age + "\n");}cursor.close();textView.setText(show.toString());}});    }

完整代碼：

點我下載執行個體

android ContentProvider實現資源共用執行個體