android ContentProvider實現資源共享實例

ContentProvider為存儲和讀取數據提供了統一的接口，使用ContentProvider，應用程序可以實現數據共享，android內置的許多數據都是使用ContentProvider形式，供開發者調用的(如視頻，音頻，圖片，通訊錄等)。

本實例將SQLite作為存儲數據的方式。

Activity代碼：<喎?/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+CjwvcD4KPHByZSBjbGFzcz0="brush:java;">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 { @Override public 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); // 插入單條數據 // Uri uri = // getContentResolver().insert(CPMetadata.users.CONTENT_URI, values); // Log.d("ContentProvider", "uri : " + uri); Log.d("ContentProvider", "count : " + count); } } class UpdateListener implements OnClickListener { @Override public void onClick(View v) { //要更新的數據 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1 Uri 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 { @Override public void onClick(View v) { //根據ID刪除，ContentUris.withAppendedId() 方法在URI的結尾追加一個2 Uri 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 { @Override public 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); //更新和刪除數據使用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"); //根據游標打印查詢結果 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
	}

	@Override
	public 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());
	}

	@Override
	public 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);
	}

	@Override
	public boolean onCreate() {
		helper = new DBHelper(getContext());
		db = helper.getWritableDatabase();
		return true;
	}

	@Override
	public 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;
	}

	@Override
	public 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);
	}

	@Override
	public 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;
	}

	@Override
	public 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;
	}

	@Override
	public 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;
	}

注冊ContentProvider，

android:exported="true"

表示是否允許外部應用訪問，必須設置

新建一個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() {
			
			@Override
			public 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();
				//根據游標打印查詢結果
				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());
			}
		});
    }

完整代碼下載地址：

點我下載實例